--- /dev/null
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
+ * Copyright 2014 Nexenta Systems, Inc. All rights reserved.
+ */
+
+/*
+ * DVA-based Adjustable Replacement Cache
+ *
+ * While much of the theory of operation used here is
+ * based on the self-tuning, low overhead replacement cache
+ * presented by Megiddo and Modha at FAST 2003, there are some
+ * significant differences:
+ *
+ * 1. The Megiddo and Modha model assumes any page is evictable.
+ * Pages in its cache cannot be "locked" into memory. This makes
+ * the eviction algorithm simple: evict the last page in the list.
+ * This also make the performance characteristics easy to reason
+ * about. Our cache is not so simple. At any given moment, some
+ * subset of the blocks in the cache are un-evictable because we
+ * have handed out a reference to them. Blocks are only evictable
+ * when there are no external references active. This makes
+ * eviction far more problematic: we choose to evict the evictable
+ * blocks that are the "lowest" in the list.
+ *
+ * There are times when it is not possible to evict the requested
+ * space. In these circumstances we are unable to adjust the cache
+ * size. To prevent the cache growing unbounded at these times we
+ * implement a "cache throttle" that slows the flow of new data
+ * into the cache until we can make space available.
+ *
+ * 2. The Megiddo and Modha model assumes a fixed cache size.
+ * Pages are evicted when the cache is full and there is a cache
+ * miss. Our model has a variable sized cache. It grows with
+ * high use, but also tries to react to memory pressure from the
+ * operating system: decreasing its size when system memory is
+ * tight.
+ *
+ * 3. The Megiddo and Modha model assumes a fixed page size. All
+ * elements of the cache are therefore exactly the same size. So
+ * when adjusting the cache size following a cache miss, its simply
+ * a matter of choosing a single page to evict. In our model, we
+ * have variable sized cache blocks (rangeing from 512 bytes to
+ * 128K bytes). We therefore choose a set of blocks to evict to make
+ * space for a cache miss that approximates as closely as possible
+ * the space used by the new block.
+ *
+ * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
+ * by N. Megiddo & D. Modha, FAST 2003
+ */
+
+/*
+ * The locking model:
+ *
+ * A new reference to a cache buffer can be obtained in two
+ * ways: 1) via a hash table lookup using the DVA as a key,
+ * or 2) via one of the ARC lists. The arc_read() interface
+ * uses method 1, while the internal arc algorithms for
+ * adjusting the cache use method 2. We therefore provide two
+ * types of locks: 1) the hash table lock array, and 2) the
+ * arc list locks.
+ *
+ * Buffers do not have their own mutexes, rather they rely on the
+ * hash table mutexes for the bulk of their protection (i.e. most
+ * fields in the arc_buf_hdr_t are protected by these mutexes).
+ *
+ * buf_hash_find() returns the appropriate mutex (held) when it
+ * locates the requested buffer in the hash table. It returns
+ * NULL for the mutex if the buffer was not in the table.
+ *
+ * buf_hash_remove() expects the appropriate hash mutex to be
+ * already held before it is invoked.
+ *
+ * Each arc state also has a mutex which is used to protect the
+ * buffer list associated with the state. When attempting to
+ * obtain a hash table lock while holding an arc list lock you
+ * must use: mutex_tryenter() to avoid deadlock. Also note that
+ * the active state mutex must be held before the ghost state mutex.
+ *
+ * Arc buffers may have an associated eviction callback function.
+ * This function will be invoked prior to removing the buffer (e.g.
+ * in arc_do_user_evicts()). Note however that the data associated
+ * with the buffer may be evicted prior to the callback. The callback
+ * must be made with *no locks held* (to prevent deadlock). Additionally,
+ * the users of callbacks must ensure that their private data is
+ * protected from simultaneous callbacks from arc_clear_callback()
+ * and arc_do_user_evicts().
+ *
+ * It as also possible to register a callback which is run when the
+ * arc_meta_limit is reached and no buffers can be safely evicted. In
+ * this case the arc user should drop a reference on some arc buffers so
+ * they can be reclaimed and the arc_meta_limit honored. For example,
+ * when using the ZPL each dentry holds a references on a znode. These
+ * dentries must be pruned before the arc buffer holding the znode can
+ * be safely evicted.
+ *
+ * Note that the majority of the performance stats are manipulated
+ * with atomic operations.
+ *
+ * The L2ARC uses the l2ad_mtx on each vdev for the following:
+ *
+ * - L2ARC buflist creation
+ * - L2ARC buflist eviction
+ * - L2ARC write completion, which walks L2ARC buflists
+ * - ARC header destruction, as it removes from L2ARC buflists
+ * - ARC header release, as it removes from L2ARC buflists
+ */
+
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/zio_compress.h>
+#include <sys/zfs_context.h>
+#include <sys/arc.h>
+#include <sys/refcount.h>
+#include <sys/vdev.h>
+#include <sys/vdev_impl.h>
+#include <sys/dsl_pool.h>
+#include <sys/multilist.h>
+#ifdef _KERNEL
+#include <sys/vmsystm.h>
+#include <vm/anon.h>
+#include <sys/fs/swapnode.h>
+#include <sys/zpl.h>
+#include <linux/mm_compat.h>
+#endif
+#include <sys/callb.h>
+#include <sys/kstat.h>
+#include <sys/dmu_tx.h>
+#include <zfs_fletcher.h>
+#include <sys/arc_impl.h>
+#include <sys/trace_arc.h>
+
+#ifndef _KERNEL
+/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
+boolean_t arc_watch = B_FALSE;
+#endif
+
+static kmutex_t arc_reclaim_lock;
+static kcondvar_t arc_reclaim_thread_cv;
+static boolean_t arc_reclaim_thread_exit;
+static kcondvar_t arc_reclaim_waiters_cv;
+
+static kmutex_t arc_user_evicts_lock;
+static kcondvar_t arc_user_evicts_cv;
+static boolean_t arc_user_evicts_thread_exit;
+
+/*
+ * The number of headers to evict in arc_evict_state_impl() before
+ * dropping the sublist lock and evicting from another sublist. A lower
+ * value means we're more likely to evict the "correct" header (i.e. the
+ * oldest header in the arc state), but comes with higher overhead
+ * (i.e. more invocations of arc_evict_state_impl()).
+ */
+int zfs_arc_evict_batch_limit = 10;
+
+/*
+ * The number of sublists used for each of the arc state lists. If this
+ * is not set to a suitable value by the user, it will be configured to
+ * the number of CPUs on the system in arc_init().
+ */
+int zfs_arc_num_sublists_per_state = 0;
+
+/* number of seconds before growing cache again */
+static int arc_grow_retry = 5;
+
+/* shift of arc_c for calculating overflow limit in arc_get_data_buf */
+int zfs_arc_overflow_shift = 8;
+
+/* shift of arc_c for calculating both min and max arc_p */
+static int arc_p_min_shift = 4;
+
+/* log2(fraction of arc to reclaim) */
+static int arc_shrink_shift = 7;
+
+/*
+ * log2(fraction of ARC which must be free to allow growing).
+ * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
+ * when reading a new block into the ARC, we will evict an equal-sized block
+ * from the ARC.
+ *
+ * This must be less than arc_shrink_shift, so that when we shrink the ARC,
+ * we will still not allow it to grow.
+ */
+int arc_no_grow_shift = 5;
+
+
+/*
+ * minimum lifespan of a prefetch block in clock ticks
+ * (initialized in arc_init())
+ */
+static int arc_min_prefetch_lifespan;
+
+/*
+ * If this percent of memory is free, don't throttle.
+ */
+int arc_lotsfree_percent = 10;
+
+static int arc_dead;
+
+/*
+ * The arc has filled available memory and has now warmed up.
+ */
+static boolean_t arc_warm;
+
+/*
+ * These tunables are for performance analysis.
+ */
+unsigned long zfs_arc_max = 0;
+unsigned long zfs_arc_min = 0;
+unsigned long zfs_arc_meta_limit = 0;
+unsigned long zfs_arc_meta_min = 0;
+int zfs_arc_grow_retry = 0;
+int zfs_arc_shrink_shift = 0;
+int zfs_arc_p_min_shift = 0;
+int zfs_disable_dup_eviction = 0;
+int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
+
+/*
+ * These tunables are Linux specific
+ */
+unsigned long zfs_arc_sys_free = 0;
+int zfs_arc_min_prefetch_lifespan = 0;
+int zfs_arc_p_aggressive_disable = 1;
+int zfs_arc_p_dampener_disable = 1;
+int zfs_arc_meta_prune = 10000;
+int zfs_arc_meta_strategy = ARC_STRATEGY_META_BALANCED;
+int zfs_arc_meta_adjust_restarts = 4096;
+int zfs_arc_lotsfree_percent = 10;
+
+/* The 6 states: */
+static arc_state_t ARC_anon;
+static arc_state_t ARC_mru;
+static arc_state_t ARC_mru_ghost;
+static arc_state_t ARC_mfu;
+static arc_state_t ARC_mfu_ghost;
+static arc_state_t ARC_l2c_only;
+
+typedef struct arc_stats {
+ kstat_named_t arcstat_hits;
+ kstat_named_t arcstat_misses;
+ kstat_named_t arcstat_demand_data_hits;
+ kstat_named_t arcstat_demand_data_misses;
+ kstat_named_t arcstat_demand_metadata_hits;
+ kstat_named_t arcstat_demand_metadata_misses;
+ kstat_named_t arcstat_prefetch_data_hits;
+ kstat_named_t arcstat_prefetch_data_misses;
+ kstat_named_t arcstat_prefetch_metadata_hits;
+ kstat_named_t arcstat_prefetch_metadata_misses;
+ kstat_named_t arcstat_mru_hits;
+ kstat_named_t arcstat_mru_ghost_hits;
+ kstat_named_t arcstat_mfu_hits;
+ kstat_named_t arcstat_mfu_ghost_hits;
+ kstat_named_t arcstat_deleted;
+ /*
+ * Number of buffers that could not be evicted because the hash lock
+ * was held by another thread. The lock may not necessarily be held
+ * by something using the same buffer, since hash locks are shared
+ * by multiple buffers.
+ */
+ kstat_named_t arcstat_mutex_miss;
+ /*
+ * Number of buffers skipped because they have I/O in progress, are
+ * indrect prefetch buffers that have not lived long enough, or are
+ * not from the spa we're trying to evict from.
+ */
+ kstat_named_t arcstat_evict_skip;
+ /*
+ * Number of times arc_evict_state() was unable to evict enough
+ * buffers to reach its target amount.
+ */
+ kstat_named_t arcstat_evict_not_enough;
+ kstat_named_t arcstat_evict_l2_cached;
+ kstat_named_t arcstat_evict_l2_eligible;
+ kstat_named_t arcstat_evict_l2_ineligible;
+ kstat_named_t arcstat_evict_l2_skip;
+ kstat_named_t arcstat_hash_elements;
+ kstat_named_t arcstat_hash_elements_max;
+ kstat_named_t arcstat_hash_collisions;
+ kstat_named_t arcstat_hash_chains;
+ kstat_named_t arcstat_hash_chain_max;
+ kstat_named_t arcstat_p;
+ kstat_named_t arcstat_c;
+ kstat_named_t arcstat_c_min;
+ kstat_named_t arcstat_c_max;
+ kstat_named_t arcstat_size;
+ /*
+ * Number of bytes consumed by internal ARC structures necessary
+ * for tracking purposes; these structures are not actually
+ * backed by ARC buffers. This includes arc_buf_hdr_t structures
+ * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
+ * caches), and arc_buf_t structures (allocated via arc_buf_t
+ * cache).
+ */
+ kstat_named_t arcstat_hdr_size;
+ /*
+ * Number of bytes consumed by ARC buffers of type equal to
+ * ARC_BUFC_DATA. This is generally consumed by buffers backing
+ * on disk user data (e.g. plain file contents).
+ */
+ kstat_named_t arcstat_data_size;
+ /*
+ * Number of bytes consumed by ARC buffers of type equal to
+ * ARC_BUFC_METADATA. This is generally consumed by buffers
+ * backing on disk data that is used for internal ZFS
+ * structures (e.g. ZAP, dnode, indirect blocks, etc).
+ */
+ kstat_named_t arcstat_metadata_size;
+ /*
+ * Number of bytes consumed by various buffers and structures
+ * not actually backed with ARC buffers. This includes bonus
+ * buffers (allocated directly via zio_buf_* functions),
+ * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
+ * cache), and dnode_t structures (allocated via dnode_t cache).
+ */
+ kstat_named_t arcstat_other_size;
+ /*
+ * Total number of bytes consumed by ARC buffers residing in the
+ * arc_anon state. This includes *all* buffers in the arc_anon
+ * state; e.g. data, metadata, evictable, and unevictable buffers
+ * are all included in this value.
+ */
+ kstat_named_t arcstat_anon_size;
+ /*
+ * Number of bytes consumed by ARC buffers that meet the
+ * following criteria: backing buffers of type ARC_BUFC_DATA,
+ * residing in the arc_anon state, and are eligible for eviction
+ * (e.g. have no outstanding holds on the buffer).
+ */
+ kstat_named_t arcstat_anon_evictable_data;
+ /*
+ * Number of bytes consumed by ARC buffers that meet the
+ * following criteria: backing buffers of type ARC_BUFC_METADATA,
+ * residing in the arc_anon state, and are eligible for eviction
+ * (e.g. have no outstanding holds on the buffer).
+ */
+ kstat_named_t arcstat_anon_evictable_metadata;
+ /*
+ * Total number of bytes consumed by ARC buffers residing in the
+ * arc_mru state. This includes *all* buffers in the arc_mru
+ * state; e.g. data, metadata, evictable, and unevictable buffers
+ * are all included in this value.
+ */
+ kstat_named_t arcstat_mru_size;
+ /*
+ * Number of bytes consumed by ARC buffers that meet the
+ * following criteria: backing buffers of type ARC_BUFC_DATA,
+ * residing in the arc_mru state, and are eligible for eviction
+ * (e.g. have no outstanding holds on the buffer).
+ */
+ kstat_named_t arcstat_mru_evictable_data;
+ /*
+ * Number of bytes consumed by ARC buffers that meet the
+ * following criteria: backing buffers of type ARC_BUFC_METADATA,
+ * residing in the arc_mru state, and are eligible for eviction
+ * (e.g. have no outstanding holds on the buffer).
+ */
+ kstat_named_t arcstat_mru_evictable_metadata;
+ /*
+ * Total number of bytes that *would have been* consumed by ARC
+ * buffers in the arc_mru_ghost state. The key thing to note
+ * here, is the fact that this size doesn't actually indicate
+ * RAM consumption. The ghost lists only consist of headers and
+ * don't actually have ARC buffers linked off of these headers.
+ * Thus, *if* the headers had associated ARC buffers, these
+ * buffers *would have* consumed this number of bytes.
+ */
+ kstat_named_t arcstat_mru_ghost_size;
+ /*
+ * Number of bytes that *would have been* consumed by ARC
+ * buffers that are eligible for eviction, of type
+ * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
+ */
+ kstat_named_t arcstat_mru_ghost_evictable_data;
+ /*
+ * Number of bytes that *would have been* consumed by ARC
+ * buffers that are eligible for eviction, of type
+ * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
+ */
+ kstat_named_t arcstat_mru_ghost_evictable_metadata;
+ /*
+ * Total number of bytes consumed by ARC buffers residing in the
+ * arc_mfu state. This includes *all* buffers in the arc_mfu
+ * state; e.g. data, metadata, evictable, and unevictable buffers
+ * are all included in this value.
+ */
+ kstat_named_t arcstat_mfu_size;
+ /*
+ * Number of bytes consumed by ARC buffers that are eligible for
+ * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
+ * state.
+ */
+ kstat_named_t arcstat_mfu_evictable_data;
+ /*
+ * Number of bytes consumed by ARC buffers that are eligible for
+ * eviction, of type ARC_BUFC_METADATA, and reside in the
+ * arc_mfu state.
+ */
+ kstat_named_t arcstat_mfu_evictable_metadata;
+ /*
+ * Total number of bytes that *would have been* consumed by ARC
+ * buffers in the arc_mfu_ghost state. See the comment above
+ * arcstat_mru_ghost_size for more details.
+ */
+ kstat_named_t arcstat_mfu_ghost_size;
+ /*
+ * Number of bytes that *would have been* consumed by ARC
+ * buffers that are eligible for eviction, of type
+ * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
+ */
+ kstat_named_t arcstat_mfu_ghost_evictable_data;
+ /*
+ * Number of bytes that *would have been* consumed by ARC
+ * buffers that are eligible for eviction, of type
+ * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
+ */
+ kstat_named_t arcstat_mfu_ghost_evictable_metadata;
+ kstat_named_t arcstat_l2_hits;
+ kstat_named_t arcstat_l2_misses;
+ kstat_named_t arcstat_l2_feeds;
+ kstat_named_t arcstat_l2_rw_clash;
+ kstat_named_t arcstat_l2_read_bytes;
+ kstat_named_t arcstat_l2_write_bytes;
+ kstat_named_t arcstat_l2_writes_sent;
+ kstat_named_t arcstat_l2_writes_done;
+ kstat_named_t arcstat_l2_writes_error;
+ kstat_named_t arcstat_l2_writes_lock_retry;
+ kstat_named_t arcstat_l2_evict_lock_retry;
+ kstat_named_t arcstat_l2_evict_reading;
+ kstat_named_t arcstat_l2_evict_l1cached;
+ kstat_named_t arcstat_l2_free_on_write;
+ kstat_named_t arcstat_l2_cdata_free_on_write;
+ kstat_named_t arcstat_l2_abort_lowmem;
+ kstat_named_t arcstat_l2_cksum_bad;
+ kstat_named_t arcstat_l2_io_error;
+ kstat_named_t arcstat_l2_size;
+ kstat_named_t arcstat_l2_asize;
+ kstat_named_t arcstat_l2_hdr_size;
+ kstat_named_t arcstat_l2_compress_successes;
+ kstat_named_t arcstat_l2_compress_zeros;
+ kstat_named_t arcstat_l2_compress_failures;
+ kstat_named_t arcstat_memory_throttle_count;
+ kstat_named_t arcstat_duplicate_buffers;
+ kstat_named_t arcstat_duplicate_buffers_size;
+ kstat_named_t arcstat_duplicate_reads;
+ kstat_named_t arcstat_memory_direct_count;
+ kstat_named_t arcstat_memory_indirect_count;
+ kstat_named_t arcstat_no_grow;
+ kstat_named_t arcstat_tempreserve;
+ kstat_named_t arcstat_loaned_bytes;
+ kstat_named_t arcstat_prune;
+ kstat_named_t arcstat_meta_used;
+ kstat_named_t arcstat_meta_limit;
+ kstat_named_t arcstat_meta_max;
+ kstat_named_t arcstat_meta_min;
+ kstat_named_t arcstat_need_free;
+ kstat_named_t arcstat_sys_free;
+} arc_stats_t;
+
+static arc_stats_t arc_stats = {
+ { "hits", KSTAT_DATA_UINT64 },
+ { "misses", KSTAT_DATA_UINT64 },
+ { "demand_data_hits", KSTAT_DATA_UINT64 },
+ { "demand_data_misses", KSTAT_DATA_UINT64 },
+ { "demand_metadata_hits", KSTAT_DATA_UINT64 },
+ { "demand_metadata_misses", KSTAT_DATA_UINT64 },
+ { "prefetch_data_hits", KSTAT_DATA_UINT64 },
+ { "prefetch_data_misses", KSTAT_DATA_UINT64 },
+ { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
+ { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
+ { "mru_hits", KSTAT_DATA_UINT64 },
+ { "mru_ghost_hits", KSTAT_DATA_UINT64 },
+ { "mfu_hits", KSTAT_DATA_UINT64 },
+ { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
+ { "deleted", KSTAT_DATA_UINT64 },
+ { "mutex_miss", KSTAT_DATA_UINT64 },
+ { "evict_skip", KSTAT_DATA_UINT64 },
+ { "evict_not_enough", KSTAT_DATA_UINT64 },
+ { "evict_l2_cached", KSTAT_DATA_UINT64 },
+ { "evict_l2_eligible", KSTAT_DATA_UINT64 },
+ { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
+ { "evict_l2_skip", KSTAT_DATA_UINT64 },
+ { "hash_elements", KSTAT_DATA_UINT64 },
+ { "hash_elements_max", KSTAT_DATA_UINT64 },
+ { "hash_collisions", KSTAT_DATA_UINT64 },
+ { "hash_chains", KSTAT_DATA_UINT64 },
+ { "hash_chain_max", KSTAT_DATA_UINT64 },
+ { "p", KSTAT_DATA_UINT64 },
+ { "c", KSTAT_DATA_UINT64 },
+ { "c_min", KSTAT_DATA_UINT64 },
+ { "c_max", KSTAT_DATA_UINT64 },
+ { "size", KSTAT_DATA_UINT64 },
+ { "hdr_size", KSTAT_DATA_UINT64 },
+ { "data_size", KSTAT_DATA_UINT64 },
+ { "metadata_size", KSTAT_DATA_UINT64 },
+ { "other_size", KSTAT_DATA_UINT64 },
+ { "anon_size", KSTAT_DATA_UINT64 },
+ { "anon_evictable_data", KSTAT_DATA_UINT64 },
+ { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
+ { "mru_size", KSTAT_DATA_UINT64 },
+ { "mru_evictable_data", KSTAT_DATA_UINT64 },
+ { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
+ { "mru_ghost_size", KSTAT_DATA_UINT64 },
+ { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
+ { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
+ { "mfu_size", KSTAT_DATA_UINT64 },
+ { "mfu_evictable_data", KSTAT_DATA_UINT64 },
+ { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
+ { "mfu_ghost_size", KSTAT_DATA_UINT64 },
+ { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
+ { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
+ { "l2_hits", KSTAT_DATA_UINT64 },
+ { "l2_misses", KSTAT_DATA_UINT64 },
+ { "l2_feeds", KSTAT_DATA_UINT64 },
+ { "l2_rw_clash", KSTAT_DATA_UINT64 },
+ { "l2_read_bytes", KSTAT_DATA_UINT64 },
+ { "l2_write_bytes", KSTAT_DATA_UINT64 },
+ { "l2_writes_sent", KSTAT_DATA_UINT64 },
+ { "l2_writes_done", KSTAT_DATA_UINT64 },
+ { "l2_writes_error", KSTAT_DATA_UINT64 },
+ { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
+ { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
+ { "l2_evict_reading", KSTAT_DATA_UINT64 },
+ { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
+ { "l2_free_on_write", KSTAT_DATA_UINT64 },
+ { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 },
+ { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
+ { "l2_cksum_bad", KSTAT_DATA_UINT64 },
+ { "l2_io_error", KSTAT_DATA_UINT64 },
+ { "l2_size", KSTAT_DATA_UINT64 },
+ { "l2_asize", KSTAT_DATA_UINT64 },
+ { "l2_hdr_size", KSTAT_DATA_UINT64 },
+ { "l2_compress_successes", KSTAT_DATA_UINT64 },
+ { "l2_compress_zeros", KSTAT_DATA_UINT64 },
+ { "l2_compress_failures", KSTAT_DATA_UINT64 },
+ { "memory_throttle_count", KSTAT_DATA_UINT64 },
+ { "duplicate_buffers", KSTAT_DATA_UINT64 },
+ { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
+ { "duplicate_reads", KSTAT_DATA_UINT64 },
+ { "memory_direct_count", KSTAT_DATA_UINT64 },
+ { "memory_indirect_count", KSTAT_DATA_UINT64 },
+ { "arc_no_grow", KSTAT_DATA_UINT64 },
+ { "arc_tempreserve", KSTAT_DATA_UINT64 },
+ { "arc_loaned_bytes", KSTAT_DATA_UINT64 },
+ { "arc_prune", KSTAT_DATA_UINT64 },
+ { "arc_meta_used", KSTAT_DATA_UINT64 },
+ { "arc_meta_limit", KSTAT_DATA_UINT64 },
+ { "arc_meta_max", KSTAT_DATA_UINT64 },
+ { "arc_meta_min", KSTAT_DATA_UINT64 },
+ { "arc_need_free", KSTAT_DATA_UINT64 },
+ { "arc_sys_free", KSTAT_DATA_UINT64 }
+};
+
+#define ARCSTAT(stat) (arc_stats.stat.value.ui64)
+
+#define ARCSTAT_INCR(stat, val) \
+ atomic_add_64(&arc_stats.stat.value.ui64, (val))
+
+#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
+#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
+
+#define ARCSTAT_MAX(stat, val) { \
+ uint64_t m; \
+ while ((val) > (m = arc_stats.stat.value.ui64) && \
+ (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
+ continue; \
+}
+
+#define ARCSTAT_MAXSTAT(stat) \
+ ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
+
+/*
+ * We define a macro to allow ARC hits/misses to be easily broken down by
+ * two separate conditions, giving a total of four different subtypes for
+ * each of hits and misses (so eight statistics total).
+ */
+#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
+ if (cond1) { \
+ if (cond2) { \
+ ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
+ } else { \
+ ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
+ } \
+ } else { \
+ if (cond2) { \
+ ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
+ } else { \
+ ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
+ } \
+ }
+
+kstat_t *arc_ksp;
+static arc_state_t *arc_anon;
+static arc_state_t *arc_mru;
+static arc_state_t *arc_mru_ghost;
+static arc_state_t *arc_mfu;
+static arc_state_t *arc_mfu_ghost;
+static arc_state_t *arc_l2c_only;
+
+/*
+ * There are several ARC variables that are critical to export as kstats --
+ * but we don't want to have to grovel around in the kstat whenever we wish to
+ * manipulate them. For these variables, we therefore define them to be in
+ * terms of the statistic variable. This assures that we are not introducing
+ * the possibility of inconsistency by having shadow copies of the variables,
+ * while still allowing the code to be readable.
+ */
+#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
+#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
+#define arc_c ARCSTAT(arcstat_c) /* target size of cache */
+#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
+#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
+#define arc_no_grow ARCSTAT(arcstat_no_grow)
+#define arc_tempreserve ARCSTAT(arcstat_tempreserve)
+#define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
+#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
+#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
+#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
+#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
+#define arc_need_free ARCSTAT(arcstat_need_free) /* bytes to be freed */
+#define arc_sys_free ARCSTAT(arcstat_sys_free) /* target system free bytes */
+
+#define L2ARC_IS_VALID_COMPRESS(_c_) \
+ ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
+
+static list_t arc_prune_list;
+static kmutex_t arc_prune_mtx;
+static taskq_t *arc_prune_taskq;
+static arc_buf_t *arc_eviction_list;
+static arc_buf_hdr_t arc_eviction_hdr;
+
+#define GHOST_STATE(state) \
+ ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
+ (state) == arc_l2c_only)
+
+#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
+#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
+#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
+#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
+#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ)
+#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE)
+
+#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
+#define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS)
+#define HDR_L2_READING(hdr) \
+ (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
+ ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
+#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
+#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
+#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
+
+#define HDR_ISTYPE_METADATA(hdr) \
+ ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
+#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
+
+#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
+#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
+
+/*
+ * Other sizes
+ */
+
+#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
+#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
+
+/*
+ * Hash table routines
+ */
+
+#define HT_LOCK_ALIGN 64
+#define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))
+
+struct ht_lock {
+ kmutex_t ht_lock;
+#ifdef _KERNEL
+ unsigned char pad[HT_LOCK_PAD];
+#endif
+};
+
+#define BUF_LOCKS 8192
+typedef struct buf_hash_table {
+ uint64_t ht_mask;
+ arc_buf_hdr_t **ht_table;
+ struct ht_lock ht_locks[BUF_LOCKS];
+} buf_hash_table_t;
+
+static buf_hash_table_t buf_hash_table;
+
+#define BUF_HASH_INDEX(spa, dva, birth) \
+ (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
+#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
+#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
+#define HDR_LOCK(hdr) \
+ (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
+
+uint64_t zfs_crc64_table[256];
+
+/*
+ * Level 2 ARC
+ */
+
+#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
+#define L2ARC_HEADROOM 2 /* num of writes */
+/*
+ * If we discover during ARC scan any buffers to be compressed, we boost
+ * our headroom for the next scanning cycle by this percentage multiple.
+ */
+#define L2ARC_HEADROOM_BOOST 200
+#define L2ARC_FEED_SECS 1 /* caching interval secs */
+#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
+
+/*
+ * Used to distinguish headers that are being process by
+ * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk
+ * address. This can happen when the header is added to the l2arc's list
+ * of buffers to write in the first stage of l2arc_write_buffers(), but
+ * has not yet been written out which happens in the second stage of
+ * l2arc_write_buffers().
+ */
+#define L2ARC_ADDR_UNSET ((uint64_t)(-1))
+
+#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
+#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
+
+/* L2ARC Performance Tunables */
+unsigned long l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */
+unsigned long l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */
+unsigned long l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */
+unsigned long l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
+unsigned long l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
+unsigned long l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */
+int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
+int l2arc_nocompress = B_FALSE; /* don't compress bufs */
+int l2arc_feed_again = B_TRUE; /* turbo warmup */
+int l2arc_norw = B_FALSE; /* no reads during writes */
+
+/*
+ * L2ARC Internals
+ */
+static list_t L2ARC_dev_list; /* device list */
+static list_t *l2arc_dev_list; /* device list pointer */
+static kmutex_t l2arc_dev_mtx; /* device list mutex */
+static l2arc_dev_t *l2arc_dev_last; /* last device used */
+static list_t L2ARC_free_on_write; /* free after write buf list */
+static list_t *l2arc_free_on_write; /* free after write list ptr */
+static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
+static uint64_t l2arc_ndev; /* number of devices */
+
+typedef struct l2arc_read_callback {
+ arc_buf_t *l2rcb_buf; /* read buffer */
+ spa_t *l2rcb_spa; /* spa */
+ blkptr_t l2rcb_bp; /* original blkptr */
+ zbookmark_phys_t l2rcb_zb; /* original bookmark */
+ int l2rcb_flags; /* original flags */
+ enum zio_compress l2rcb_compress; /* applied compress */
+} l2arc_read_callback_t;
+
+typedef struct l2arc_data_free {
+ /* protected by l2arc_free_on_write_mtx */
+ void *l2df_data;
+ size_t l2df_size;
+ void (*l2df_func)(void *, size_t);
+ list_node_t l2df_list_node;
+} l2arc_data_free_t;
+
+static kmutex_t l2arc_feed_thr_lock;
+static kcondvar_t l2arc_feed_thr_cv;
+static uint8_t l2arc_thread_exit;
+
+static void arc_get_data_buf(arc_buf_t *);
+static void arc_access(arc_buf_hdr_t *, kmutex_t *);
+static boolean_t arc_is_overflowing(void);
+static void arc_buf_watch(arc_buf_t *);
+static void arc_tuning_update(void);
+
+static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
+static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
+
+static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
+static void l2arc_read_done(zio_t *);
+
+static boolean_t l2arc_compress_buf(arc_buf_hdr_t *);
+static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress);
+static void l2arc_release_cdata_buf(arc_buf_hdr_t *);
+
+static uint64_t
+buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
+{
+ uint8_t *vdva = (uint8_t *)dva;
+ uint64_t crc = -1ULL;
+ int i;
+
+ ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
+
+ for (i = 0; i < sizeof (dva_t); i++)
+ crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
+
+ crc ^= (spa>>8) ^ birth;
+
+ return (crc);
+}
+
+#define BUF_EMPTY(buf) \
+ ((buf)->b_dva.dva_word[0] == 0 && \
+ (buf)->b_dva.dva_word[1] == 0)
+
+#define BUF_EQUAL(spa, dva, birth, buf) \
+ ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
+ ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
+ ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
+
+static void
+buf_discard_identity(arc_buf_hdr_t *hdr)
+{
+ hdr->b_dva.dva_word[0] = 0;
+ hdr->b_dva.dva_word[1] = 0;
+ hdr->b_birth = 0;
+}
+
+static arc_buf_hdr_t *
+buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
+{
+ const dva_t *dva = BP_IDENTITY(bp);
+ uint64_t birth = BP_PHYSICAL_BIRTH(bp);
+ uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
+ kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
+ arc_buf_hdr_t *hdr;
+
+ mutex_enter(hash_lock);
+ for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
+ hdr = hdr->b_hash_next) {
+ if (BUF_EQUAL(spa, dva, birth, hdr)) {
+ *lockp = hash_lock;
+ return (hdr);
+ }
+ }
+ mutex_exit(hash_lock);
+ *lockp = NULL;
+ return (NULL);
+}
+
+/*
+ * Insert an entry into the hash table. If there is already an element
+ * equal to elem in the hash table, then the already existing element
+ * will be returned and the new element will not be inserted.
+ * Otherwise returns NULL.
+ * If lockp == NULL, the caller is assumed to already hold the hash lock.
+ */
+static arc_buf_hdr_t *
+buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
+{
+ uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
+ kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
+ arc_buf_hdr_t *fhdr;
+ uint32_t i;
+
+ ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
+ ASSERT(hdr->b_birth != 0);
+ ASSERT(!HDR_IN_HASH_TABLE(hdr));
+
+ if (lockp != NULL) {
+ *lockp = hash_lock;
+ mutex_enter(hash_lock);
+ } else {
+ ASSERT(MUTEX_HELD(hash_lock));
+ }
+
+ for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
+ fhdr = fhdr->b_hash_next, i++) {
+ if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
+ return (fhdr);
+ }
+
+ hdr->b_hash_next = buf_hash_table.ht_table[idx];
+ buf_hash_table.ht_table[idx] = hdr;
+ hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
+
+ /* collect some hash table performance data */
+ if (i > 0) {
+ ARCSTAT_BUMP(arcstat_hash_collisions);
+ if (i == 1)
+ ARCSTAT_BUMP(arcstat_hash_chains);
+
+ ARCSTAT_MAX(arcstat_hash_chain_max, i);
+ }
+
+ ARCSTAT_BUMP(arcstat_hash_elements);
+ ARCSTAT_MAXSTAT(arcstat_hash_elements);
+
+ return (NULL);
+}
+
+static void
+buf_hash_remove(arc_buf_hdr_t *hdr)
+{
+ arc_buf_hdr_t *fhdr, **hdrp;
+ uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
+
+ ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
+ ASSERT(HDR_IN_HASH_TABLE(hdr));
+
+ hdrp = &buf_hash_table.ht_table[idx];
+ while ((fhdr = *hdrp) != hdr) {
+ ASSERT(fhdr != NULL);
+ hdrp = &fhdr->b_hash_next;
+ }
+ *hdrp = hdr->b_hash_next;
+ hdr->b_hash_next = NULL;
+ hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE;
+
+ /* collect some hash table performance data */
+ ARCSTAT_BUMPDOWN(arcstat_hash_elements);
+
+ if (buf_hash_table.ht_table[idx] &&
+ buf_hash_table.ht_table[idx]->b_hash_next == NULL)
+ ARCSTAT_BUMPDOWN(arcstat_hash_chains);
+}
+
+/*
+ * Global data structures and functions for the buf kmem cache.
+ */
+static kmem_cache_t *hdr_full_cache;
+static kmem_cache_t *hdr_l2only_cache;
+static kmem_cache_t *buf_cache;
+
+static void
+buf_fini(void)
+{
+ int i;
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+ /*
+ * Large allocations which do not require contiguous pages
+ * should be using vmem_free() in the linux kernel\
+ */
+ vmem_free(buf_hash_table.ht_table,
+ (buf_hash_table.ht_mask + 1) * sizeof (void *));
+#else
+ kmem_free(buf_hash_table.ht_table,
+ (buf_hash_table.ht_mask + 1) * sizeof (void *));
+#endif
+ for (i = 0; i < BUF_LOCKS; i++)
+ mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
+ kmem_cache_destroy(hdr_full_cache);
+ kmem_cache_destroy(hdr_l2only_cache);
+ kmem_cache_destroy(buf_cache);
+}
+
+/*
+ * Constructor callback - called when the cache is empty
+ * and a new buf is requested.
+ */
+/* ARGSUSED */
+static int
+hdr_full_cons(void *vbuf, void *unused, int kmflag)
+{
+ arc_buf_hdr_t *hdr = vbuf;
+
+ bzero(hdr, HDR_FULL_SIZE);
+ cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
+ refcount_create(&hdr->b_l1hdr.b_refcnt);
+ mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
+ list_link_init(&hdr->b_l1hdr.b_arc_node);
+ list_link_init(&hdr->b_l2hdr.b_l2node);
+ multilist_link_init(&hdr->b_l1hdr.b_arc_node);
+ arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
+
+ return (0);
+}
+
+/* ARGSUSED */
+static int
+hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
+{
+ arc_buf_hdr_t *hdr = vbuf;
+
+ bzero(hdr, HDR_L2ONLY_SIZE);
+ arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
+
+ return (0);
+}
+
+/* ARGSUSED */
+static int
+buf_cons(void *vbuf, void *unused, int kmflag)
+{
+ arc_buf_t *buf = vbuf;
+
+ bzero(buf, sizeof (arc_buf_t));
+ mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
+ arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
+
+ return (0);
+}
+
+/*
+ * Destructor callback - called when a cached buf is
+ * no longer required.
+ */
+/* ARGSUSED */
+static void
+hdr_full_dest(void *vbuf, void *unused)
+{
+ arc_buf_hdr_t *hdr = vbuf;
+
+ ASSERT(BUF_EMPTY(hdr));
+ cv_destroy(&hdr->b_l1hdr.b_cv);
+ refcount_destroy(&hdr->b_l1hdr.b_refcnt);
+ mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
+ ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
+ arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
+}
+
+/* ARGSUSED */
+static void
+hdr_l2only_dest(void *vbuf, void *unused)
+{
+ ASSERTV(arc_buf_hdr_t *hdr = vbuf);
+
+ ASSERT(BUF_EMPTY(hdr));
+ arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
+}
+
+/* ARGSUSED */
+static void
+buf_dest(void *vbuf, void *unused)
+{
+ arc_buf_t *buf = vbuf;
+
+ mutex_destroy(&buf->b_evict_lock);
+ arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
+}
+
+/*
+ * Reclaim callback -- invoked when memory is low.
+ */
+/* ARGSUSED */
+static void
+hdr_recl(void *unused)
+{
+ dprintf("hdr_recl called\n");
+ /*
+ * umem calls the reclaim func when we destroy the buf cache,
+ * which is after we do arc_fini().
+ */
+ if (!arc_dead)
+ cv_signal(&arc_reclaim_thread_cv);
+}
+
+static void
+buf_init(void)
+{
+ uint64_t *ct;
+ uint64_t hsize = 1ULL << 12;
+ int i, j;
+
+ /*
+ * The hash table is big enough to fill all of physical memory
+ * with an average block size of zfs_arc_average_blocksize (default 8K).
+ * By default, the table will take up
+ * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
+ */
+ while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
+ hsize <<= 1;
+retry:
+ buf_hash_table.ht_mask = hsize - 1;
+#if defined(_KERNEL) && defined(HAVE_SPL)
+ /*
+ * Large allocations which do not require contiguous pages
+ * should be using vmem_alloc() in the linux kernel
+ */
+ buf_hash_table.ht_table =
+ vmem_zalloc(hsize * sizeof (void*), KM_SLEEP);
+#else
+ buf_hash_table.ht_table =
+ kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
+#endif
+ if (buf_hash_table.ht_table == NULL) {
+ ASSERT(hsize > (1ULL << 8));
+ hsize >>= 1;
+ goto retry;
+ }
+
+ hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
+ 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
+ hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
+ HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
+ NULL, NULL, 0);
+ buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
+ 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
+
+ for (i = 0; i < 256; i++)
+ for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
+ *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
+
+ for (i = 0; i < BUF_LOCKS; i++) {
+ mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
+ NULL, MUTEX_DEFAULT, NULL);
+ }
+}
+
+/*
+ * Transition between the two allocation states for the arc_buf_hdr struct.
+ * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
+ * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
+ * version is used when a cache buffer is only in the L2ARC in order to reduce
+ * memory usage.
+ */
+static arc_buf_hdr_t *
+arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
+{
+ arc_buf_hdr_t *nhdr;
+ l2arc_dev_t *dev;
+
+ ASSERT(HDR_HAS_L2HDR(hdr));
+ ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
+ (old == hdr_l2only_cache && new == hdr_full_cache));
+
+ dev = hdr->b_l2hdr.b_dev;
+ nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
+
+ ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
+ buf_hash_remove(hdr);
+
+ bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
+
+ if (new == hdr_full_cache) {
+ nhdr->b_flags |= ARC_FLAG_HAS_L1HDR;
+ /*
+ * arc_access and arc_change_state need to be aware that a
+ * header has just come out of L2ARC, so we set its state to
+ * l2c_only even though it's about to change.
+ */
+ nhdr->b_l1hdr.b_state = arc_l2c_only;
+
+ /* Verify previous threads set to NULL before freeing */
+ ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL);
+ } else {
+ ASSERT(hdr->b_l1hdr.b_buf == NULL);
+ ASSERT0(hdr->b_l1hdr.b_datacnt);
+
+ /*
+ * If we've reached here, We must have been called from
+ * arc_evict_hdr(), as such we should have already been
+ * removed from any ghost list we were previously on
+ * (which protects us from racing with arc_evict_state),
+ * thus no locking is needed during this check.
+ */
+ ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
+
+ /*
+ * A buffer must not be moved into the arc_l2c_only
+ * state if it's not finished being written out to the
+ * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field
+ * might try to be accessed, even though it was removed.
+ */
+ VERIFY(!HDR_L2_WRITING(hdr));
+ VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
+
+ nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR;
+ }
+ /*
+ * The header has been reallocated so we need to re-insert it into any
+ * lists it was on.
+ */
+ (void) buf_hash_insert(nhdr, NULL);
+
+ ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
+
+ mutex_enter(&dev->l2ad_mtx);
+
+ /*
+ * We must place the realloc'ed header back into the list at
+ * the same spot. Otherwise, if it's placed earlier in the list,
+ * l2arc_write_buffers() could find it during the function's
+ * write phase, and try to write it out to the l2arc.
+ */
+ list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
+ list_remove(&dev->l2ad_buflist, hdr);
+
+ mutex_exit(&dev->l2ad_mtx);
+
+ /*
+ * Since we're using the pointer address as the tag when
+ * incrementing and decrementing the l2ad_alloc refcount, we
+ * must remove the old pointer (that we're about to destroy) and
+ * add the new pointer to the refcount. Otherwise we'd remove
+ * the wrong pointer address when calling arc_hdr_destroy() later.
+ */
+
+ (void) refcount_remove_many(&dev->l2ad_alloc,
+ hdr->b_l2hdr.b_asize, hdr);
+
+ (void) refcount_add_many(&dev->l2ad_alloc,
+ nhdr->b_l2hdr.b_asize, nhdr);
+
+ buf_discard_identity(hdr);
+ hdr->b_freeze_cksum = NULL;
+ kmem_cache_free(old, hdr);
+
+ return (nhdr);
+}
+
+
+#define ARC_MINTIME (hz>>4) /* 62 ms */
+
+static void
+arc_cksum_verify(arc_buf_t *buf)
+{
+ zio_cksum_t zc;
+
+ if (!(zfs_flags & ZFS_DEBUG_MODIFY))
+ return;
+
+ mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) {
+ mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ return;
+ }
+ fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
+ if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
+ panic("buffer modified while frozen!");
+ mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+}
+
+static int
+arc_cksum_equal(arc_buf_t *buf)
+{
+ zio_cksum_t zc;
+ int equal;
+
+ mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
+ equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
+ mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+
+ return (equal);
+}
+
+static void
+arc_cksum_compute(arc_buf_t *buf, boolean_t force)
+{
+ if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
+ return;
+
+ mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ if (buf->b_hdr->b_freeze_cksum != NULL) {
+ mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ return;
+ }
+ buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
+ fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
+ buf->b_hdr->b_freeze_cksum);
+ mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ arc_buf_watch(buf);
+}
+
+#ifndef _KERNEL
+void
+arc_buf_sigsegv(int sig, siginfo_t *si, void *unused)
+{
+ panic("Got SIGSEGV at address: 0x%lx\n", (long) si->si_addr);
+}
+#endif
+
+/* ARGSUSED */
+static void
+arc_buf_unwatch(arc_buf_t *buf)
+{
+#ifndef _KERNEL
+ if (arc_watch) {
+ ASSERT0(mprotect(buf->b_data, buf->b_hdr->b_size,
+ PROT_READ | PROT_WRITE));
+ }
+#endif
+}
+
+/* ARGSUSED */
+static void
+arc_buf_watch(arc_buf_t *buf)
+{
+#ifndef _KERNEL
+ if (arc_watch)
+ ASSERT0(mprotect(buf->b_data, buf->b_hdr->b_size, PROT_READ));
+#endif
+}
+
+static arc_buf_contents_t
+arc_buf_type(arc_buf_hdr_t *hdr)
+{
+ if (HDR_ISTYPE_METADATA(hdr)) {
+ return (ARC_BUFC_METADATA);
+ } else {
+ return (ARC_BUFC_DATA);
+ }
+}
+
+static uint32_t
+arc_bufc_to_flags(arc_buf_contents_t type)
+{
+ switch (type) {
+ case ARC_BUFC_DATA:
+ /* metadata field is 0 if buffer contains normal data */
+ return (0);
+ case ARC_BUFC_METADATA:
+ return (ARC_FLAG_BUFC_METADATA);
+ default:
+ break;
+ }
+ panic("undefined ARC buffer type!");
+ return ((uint32_t)-1);
+}
+
+void
+arc_buf_thaw(arc_buf_t *buf)
+{
+ if (zfs_flags & ZFS_DEBUG_MODIFY) {
+ if (buf->b_hdr->b_l1hdr.b_state != arc_anon)
+ panic("modifying non-anon buffer!");
+ if (HDR_IO_IN_PROGRESS(buf->b_hdr))
+ panic("modifying buffer while i/o in progress!");
+ arc_cksum_verify(buf);
+ }
+
+ mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+ if (buf->b_hdr->b_freeze_cksum != NULL) {
+ kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
+ buf->b_hdr->b_freeze_cksum = NULL;
+ }
+
+ mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
+
+ arc_buf_unwatch(buf);
+}
+
+void
+arc_buf_freeze(arc_buf_t *buf)
+{
+ kmutex_t *hash_lock;
+
+ if (!(zfs_flags & ZFS_DEBUG_MODIFY))
+ return;
+
+ hash_lock = HDR_LOCK(buf->b_hdr);
+ mutex_enter(hash_lock);
+
+ ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
+ buf->b_hdr->b_l1hdr.b_state == arc_anon);
+ arc_cksum_compute(buf, B_FALSE);
+ mutex_exit(hash_lock);
+
+}
+
+static void
+add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
+{
+ arc_state_t *state;
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT(MUTEX_HELD(hash_lock));
+
+ state = hdr->b_l1hdr.b_state;
+
+ if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
+ (state != arc_anon)) {
+ /* We don't use the L2-only state list. */
+ if (state != arc_l2c_only) {
+ arc_buf_contents_t type = arc_buf_type(hdr);
+ uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt;
+ multilist_t *list = &state->arcs_list[type];
+ uint64_t *size = &state->arcs_lsize[type];
+
+ multilist_remove(list, hdr);
+
+ if (GHOST_STATE(state)) {
+ ASSERT0(hdr->b_l1hdr.b_datacnt);
+ ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
+ delta = hdr->b_size;
+ }
+ ASSERT(delta > 0);
+ ASSERT3U(*size, >=, delta);
+ atomic_add_64(size, -delta);
+ }
+ /* remove the prefetch flag if we get a reference */
+ hdr->b_flags &= ~ARC_FLAG_PREFETCH;
+ }
+}
+
+static int
+remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
+{
+ int cnt;
+ arc_state_t *state = hdr->b_l1hdr.b_state;
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
+ ASSERT(!GHOST_STATE(state));
+
+ /*
+ * arc_l2c_only counts as a ghost state so we don't need to explicitly
+ * check to prevent usage of the arc_l2c_only list.
+ */
+ if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
+ (state != arc_anon)) {
+ arc_buf_contents_t type = arc_buf_type(hdr);
+ multilist_t *list = &state->arcs_list[type];
+ uint64_t *size = &state->arcs_lsize[type];
+
+ multilist_insert(list, hdr);
+
+ ASSERT(hdr->b_l1hdr.b_datacnt > 0);
+ atomic_add_64(size, hdr->b_size *
+ hdr->b_l1hdr.b_datacnt);
+ }
+ return (cnt);
+}
+
+/*
+ * Returns detailed information about a specific arc buffer. When the
+ * state_index argument is set the function will calculate the arc header
+ * list position for its arc state. Since this requires a linear traversal
+ * callers are strongly encourage not to do this. However, it can be helpful
+ * for targeted analysis so the functionality is provided.
+ */
+void
+arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
+{
+ arc_buf_hdr_t *hdr = ab->b_hdr;
+ l1arc_buf_hdr_t *l1hdr = NULL;
+ l2arc_buf_hdr_t *l2hdr = NULL;
+ arc_state_t *state = NULL;
+
+ memset(abi, 0, sizeof (arc_buf_info_t));
+
+ if (hdr == NULL)
+ return;
+
+ abi->abi_flags = hdr->b_flags;
+
+ if (HDR_HAS_L1HDR(hdr)) {
+ l1hdr = &hdr->b_l1hdr;
+ state = l1hdr->b_state;
+ }
+ if (HDR_HAS_L2HDR(hdr))
+ l2hdr = &hdr->b_l2hdr;
+
+ if (l1hdr) {
+ abi->abi_datacnt = l1hdr->b_datacnt;
+ abi->abi_access = l1hdr->b_arc_access;
+ abi->abi_mru_hits = l1hdr->b_mru_hits;
+ abi->abi_mru_ghost_hits = l1hdr->b_mru_ghost_hits;
+ abi->abi_mfu_hits = l1hdr->b_mfu_hits;
+ abi->abi_mfu_ghost_hits = l1hdr->b_mfu_ghost_hits;
+ abi->abi_holds = refcount_count(&l1hdr->b_refcnt);
+ }
+
+ if (l2hdr) {
+ abi->abi_l2arc_dattr = l2hdr->b_daddr;
+ abi->abi_l2arc_asize = l2hdr->b_asize;
+ abi->abi_l2arc_compress = l2hdr->b_compress;
+ abi->abi_l2arc_hits = l2hdr->b_hits;
+ }
+
+ abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON;
+ abi->abi_state_contents = arc_buf_type(hdr);
+ abi->abi_size = hdr->b_size;
+}
+
+/*
+ * Move the supplied buffer to the indicated state. The hash lock
+ * for the buffer must be held by the caller.
+ */
+static void
+arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
+ kmutex_t *hash_lock)
+{
+ arc_state_t *old_state;
+ int64_t refcnt;
+ uint32_t datacnt;
+ uint64_t from_delta, to_delta;
+ arc_buf_contents_t buftype = arc_buf_type(hdr);
+
+ /*
+ * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
+ * in arc_read() when bringing a buffer out of the L2ARC. However, the
+ * L1 hdr doesn't always exist when we change state to arc_anon before
+ * destroying a header, in which case reallocating to add the L1 hdr is
+ * pointless.
+ */
+ if (HDR_HAS_L1HDR(hdr)) {
+ old_state = hdr->b_l1hdr.b_state;
+ refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
+ datacnt = hdr->b_l1hdr.b_datacnt;
+ } else {
+ old_state = arc_l2c_only;
+ refcnt = 0;
+ datacnt = 0;
+ }
+
+ ASSERT(MUTEX_HELD(hash_lock));
+ ASSERT3P(new_state, !=, old_state);
+ ASSERT(refcnt == 0 || datacnt > 0);
+ ASSERT(!GHOST_STATE(new_state) || datacnt == 0);
+ ASSERT(old_state != arc_anon || datacnt <= 1);
+
+ from_delta = to_delta = datacnt * hdr->b_size;
+
+ /*
+ * If this buffer is evictable, transfer it from the
+ * old state list to the new state list.
+ */
+ if (refcnt == 0) {
+ if (old_state != arc_anon && old_state != arc_l2c_only) {
+ uint64_t *size = &old_state->arcs_lsize[buftype];
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ multilist_remove(&old_state->arcs_list[buftype], hdr);
+
+ /*
+ * If prefetching out of the ghost cache,
+ * we will have a non-zero datacnt.
+ */
+ if (GHOST_STATE(old_state) && datacnt == 0) {
+ /* ghost elements have a ghost size */
+ ASSERT(hdr->b_l1hdr.b_buf == NULL);
+ from_delta = hdr->b_size;
+ }
+ ASSERT3U(*size, >=, from_delta);
+ atomic_add_64(size, -from_delta);
+ }
+ if (new_state != arc_anon && new_state != arc_l2c_only) {
+ uint64_t *size = &new_state->arcs_lsize[buftype];
+
+ /*
+ * An L1 header always exists here, since if we're
+ * moving to some L1-cached state (i.e. not l2c_only or
+ * anonymous), we realloc the header to add an L1hdr
+ * beforehand.
+ */
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ multilist_insert(&new_state->arcs_list[buftype], hdr);
+
+ /* ghost elements have a ghost size */
+ if (GHOST_STATE(new_state)) {
+ ASSERT0(datacnt);
+ ASSERT(hdr->b_l1hdr.b_buf == NULL);
+ to_delta = hdr->b_size;
+ }
+ atomic_add_64(size, to_delta);
+ }
+ }
+
+ ASSERT(!BUF_EMPTY(hdr));
+ if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
+ buf_hash_remove(hdr);
+
+ /* adjust state sizes (ignore arc_l2c_only) */
+
+ if (to_delta && new_state != arc_l2c_only) {
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ if (GHOST_STATE(new_state)) {
+ ASSERT0(datacnt);
+
+ /*
+ * We moving a header to a ghost state, we first
+ * remove all arc buffers. Thus, we'll have a
+ * datacnt of zero, and no arc buffer to use for
+ * the reference. As a result, we use the arc
+ * header pointer for the reference.
+ */
+ (void) refcount_add_many(&new_state->arcs_size,
+ hdr->b_size, hdr);
+ } else {
+ arc_buf_t *buf;
+ ASSERT3U(datacnt, !=, 0);
+
+ /*
+ * Each individual buffer holds a unique reference,
+ * thus we must remove each of these references one
+ * at a time.
+ */
+ for (buf = hdr->b_l1hdr.b_buf; buf != NULL;
+ buf = buf->b_next) {
+ (void) refcount_add_many(&new_state->arcs_size,
+ hdr->b_size, buf);
+ }
+ }
+ }
+
+ if (from_delta && old_state != arc_l2c_only) {
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ if (GHOST_STATE(old_state)) {
+ /*
+ * When moving a header off of a ghost state,
+ * there's the possibility for datacnt to be
+ * non-zero. This is because we first add the
+ * arc buffer to the header prior to changing
+ * the header's state. Since we used the header
+ * for the reference when putting the header on
+ * the ghost state, we must balance that and use
+ * the header when removing off the ghost state
+ * (even though datacnt is non zero).
+ */
+
+ IMPLY(datacnt == 0, new_state == arc_anon ||
+ new_state == arc_l2c_only);
+
+ (void) refcount_remove_many(&old_state->arcs_size,
+ hdr->b_size, hdr);
+ } else {
+ arc_buf_t *buf;
+ ASSERT3U(datacnt, !=, 0);
+
+ /*
+ * Each individual buffer holds a unique reference,
+ * thus we must remove each of these references one
+ * at a time.
+ */
+ for (buf = hdr->b_l1hdr.b_buf; buf != NULL;
+ buf = buf->b_next) {
+ (void) refcount_remove_many(
+ &old_state->arcs_size, hdr->b_size, buf);
+ }
+ }
+ }
+
+ if (HDR_HAS_L1HDR(hdr))
+ hdr->b_l1hdr.b_state = new_state;
+
+ /*
+ * L2 headers should never be on the L2 state list since they don't
+ * have L1 headers allocated.
+ */
+ ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
+ multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
+}
+
+void
+arc_space_consume(uint64_t space, arc_space_type_t type)
+{
+ ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
+
+ switch (type) {
+ default:
+ break;
+ case ARC_SPACE_DATA:
+ ARCSTAT_INCR(arcstat_data_size, space);
+ break;
+ case ARC_SPACE_META:
+ ARCSTAT_INCR(arcstat_metadata_size, space);
+ break;
+ case ARC_SPACE_OTHER:
+ ARCSTAT_INCR(arcstat_other_size, space);
+ break;
+ case ARC_SPACE_HDRS:
+ ARCSTAT_INCR(arcstat_hdr_size, space);
+ break;
+ case ARC_SPACE_L2HDRS:
+ ARCSTAT_INCR(arcstat_l2_hdr_size, space);
+ break;
+ }
+
+ if (type != ARC_SPACE_DATA)
+ ARCSTAT_INCR(arcstat_meta_used, space);
+
+ atomic_add_64(&arc_size, space);
+}
+
+void
+arc_space_return(uint64_t space, arc_space_type_t type)
+{
+ ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
+
+ switch (type) {
+ default:
+ break;
+ case ARC_SPACE_DATA:
+ ARCSTAT_INCR(arcstat_data_size, -space);
+ break;
+ case ARC_SPACE_META:
+ ARCSTAT_INCR(arcstat_metadata_size, -space);
+ break;
+ case ARC_SPACE_OTHER:
+ ARCSTAT_INCR(arcstat_other_size, -space);
+ break;
+ case ARC_SPACE_HDRS:
+ ARCSTAT_INCR(arcstat_hdr_size, -space);
+ break;
+ case ARC_SPACE_L2HDRS:
+ ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
+ break;
+ }
+
+ if (type != ARC_SPACE_DATA) {
+ ASSERT(arc_meta_used >= space);
+ if (arc_meta_max < arc_meta_used)
+ arc_meta_max = arc_meta_used;
+ ARCSTAT_INCR(arcstat_meta_used, -space);
+ }
+
+ ASSERT(arc_size >= space);
+ atomic_add_64(&arc_size, -space);
+}
+
+arc_buf_t *
+arc_buf_alloc(spa_t *spa, uint64_t size, void *tag, arc_buf_contents_t type)
+{
+ arc_buf_hdr_t *hdr;
+ arc_buf_t *buf;
+
+ VERIFY3U(size, <=, spa_maxblocksize(spa));
+ hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
+ ASSERT(BUF_EMPTY(hdr));
+ ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
+ hdr->b_size = size;
+ hdr->b_spa = spa_load_guid(spa);
+ hdr->b_l1hdr.b_mru_hits = 0;
+ hdr->b_l1hdr.b_mru_ghost_hits = 0;
+ hdr->b_l1hdr.b_mfu_hits = 0;
+ hdr->b_l1hdr.b_mfu_ghost_hits = 0;
+ hdr->b_l1hdr.b_l2_hits = 0;
+
+ buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
+ buf->b_hdr = hdr;
+ buf->b_data = NULL;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_next = NULL;
+
+ hdr->b_flags = arc_bufc_to_flags(type);
+ hdr->b_flags |= ARC_FLAG_HAS_L1HDR;
+
+ hdr->b_l1hdr.b_buf = buf;
+ hdr->b_l1hdr.b_state = arc_anon;
+ hdr->b_l1hdr.b_arc_access = 0;
+ hdr->b_l1hdr.b_datacnt = 1;
+ hdr->b_l1hdr.b_tmp_cdata = NULL;
+
+ arc_get_data_buf(buf);
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
+
+ return (buf);
+}
+
+static char *arc_onloan_tag = "onloan";
+
+/*
+ * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
+ * flight data by arc_tempreserve_space() until they are "returned". Loaned
+ * buffers must be returned to the arc before they can be used by the DMU or
+ * freed.
+ */
+arc_buf_t *
+arc_loan_buf(spa_t *spa, uint64_t size)
+{
+ arc_buf_t *buf;
+
+ buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
+
+ atomic_add_64(&arc_loaned_bytes, size);
+ return (buf);
+}
+
+/*
+ * Return a loaned arc buffer to the arc.
+ */
+void
+arc_return_buf(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(buf->b_data != NULL);
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
+ (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
+
+ atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
+}
+
+/* Detach an arc_buf from a dbuf (tag) */
+void
+arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(buf->b_data != NULL);
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
+ (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+
+ atomic_add_64(&arc_loaned_bytes, hdr->b_size);
+}
+
+static arc_buf_t *
+arc_buf_clone(arc_buf_t *from)
+{
+ arc_buf_t *buf;
+ arc_buf_hdr_t *hdr = from->b_hdr;
+ uint64_t size = hdr->b_size;
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT(hdr->b_l1hdr.b_state != arc_anon);
+
+ buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
+ buf->b_hdr = hdr;
+ buf->b_data = NULL;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_next = hdr->b_l1hdr.b_buf;
+ hdr->b_l1hdr.b_buf = buf;
+ arc_get_data_buf(buf);
+ bcopy(from->b_data, buf->b_data, size);
+
+ /*
+ * This buffer already exists in the arc so create a duplicate
+ * copy for the caller. If the buffer is associated with user data
+ * then track the size and number of duplicates. These stats will be
+ * updated as duplicate buffers are created and destroyed.
+ */
+ if (HDR_ISTYPE_DATA(hdr)) {
+ ARCSTAT_BUMP(arcstat_duplicate_buffers);
+ ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
+ }
+ hdr->b_l1hdr.b_datacnt += 1;
+ return (buf);
+}
+
+void
+arc_buf_add_ref(arc_buf_t *buf, void* tag)
+{
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock;
+
+ /*
+ * Check to see if this buffer is evicted. Callers
+ * must verify b_data != NULL to know if the add_ref
+ * was successful.
+ */
+ mutex_enter(&buf->b_evict_lock);
+ if (buf->b_data == NULL) {
+ mutex_exit(&buf->b_evict_lock);
+ return;
+ }
+ hash_lock = HDR_LOCK(buf->b_hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+ mutex_exit(&buf->b_evict_lock);
+
+ ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
+ hdr->b_l1hdr.b_state == arc_mfu);
+
+ add_reference(hdr, hash_lock, tag);
+ DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
+ arc_access(hdr, hash_lock);
+ mutex_exit(hash_lock);
+ ARCSTAT_BUMP(arcstat_hits);
+ ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
+ demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
+ data, metadata, hits);
+}
+
+static void
+arc_buf_free_on_write(void *data, size_t size,
+ void (*free_func)(void *, size_t))
+{
+ l2arc_data_free_t *df;
+
+ df = kmem_alloc(sizeof (*df), KM_SLEEP);
+ df->l2df_data = data;
+ df->l2df_size = size;
+ df->l2df_func = free_func;
+ mutex_enter(&l2arc_free_on_write_mtx);
+ list_insert_head(l2arc_free_on_write, df);
+ mutex_exit(&l2arc_free_on_write_mtx);
+}
+
+/*
+ * Free the arc data buffer. If it is an l2arc write in progress,
+ * the buffer is placed on l2arc_free_on_write to be freed later.
+ */
+static void
+arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ if (HDR_L2_WRITING(hdr)) {
+ arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func);
+ ARCSTAT_BUMP(arcstat_l2_free_on_write);
+ } else {
+ free_func(buf->b_data, hdr->b_size);
+ }
+}
+
+static void
+arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
+{
+ ASSERT(HDR_HAS_L2HDR(hdr));
+ ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx));
+
+ /*
+ * The b_tmp_cdata field is linked off of the b_l1hdr, so if
+ * that doesn't exist, the header is in the arc_l2c_only state,
+ * and there isn't anything to free (it's already been freed).
+ */
+ if (!HDR_HAS_L1HDR(hdr))
+ return;
+
+ /*
+ * The header isn't being written to the l2arc device, thus it
+ * shouldn't have a b_tmp_cdata to free.
+ */
+ if (!HDR_L2_WRITING(hdr)) {
+ ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
+ return;
+ }
+
+ /*
+ * The header does not have compression enabled. This can be due
+ * to the buffer not being compressible, or because we're
+ * freeing the buffer before the second phase of
+ * l2arc_write_buffer() has started (which does the compression
+ * step). In either case, b_tmp_cdata does not point to a
+ * separately compressed buffer, so there's nothing to free (it
+ * points to the same buffer as the arc_buf_t's b_data field).
+ */
+ if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_OFF) {
+ hdr->b_l1hdr.b_tmp_cdata = NULL;
+ return;
+ }
+
+ /*
+ * There's nothing to free since the buffer was all zero's and
+ * compressed to a zero length buffer.
+ */
+ if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) {
+ ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
+ return;
+ }
+
+ ASSERT(L2ARC_IS_VALID_COMPRESS(hdr->b_l2hdr.b_compress));
+
+ arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata,
+ hdr->b_size, zio_data_buf_free);
+
+ ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write);
+ hdr->b_l1hdr.b_tmp_cdata = NULL;
+}
+
+/*
+ * Free up buf->b_data and if 'remove' is set, then pull the
+ * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
+ */
+static void
+arc_buf_destroy(arc_buf_t *buf, boolean_t remove)
+{
+ arc_buf_t **bufp;
+
+ /* free up data associated with the buf */
+ if (buf->b_data != NULL) {
+ arc_state_t *state = buf->b_hdr->b_l1hdr.b_state;
+ uint64_t size = buf->b_hdr->b_size;
+ arc_buf_contents_t type = arc_buf_type(buf->b_hdr);
+
+ arc_cksum_verify(buf);
+ arc_buf_unwatch(buf);
+
+ if (type == ARC_BUFC_METADATA) {
+ arc_buf_data_free(buf, zio_buf_free);
+ arc_space_return(size, ARC_SPACE_META);
+ } else {
+ ASSERT(type == ARC_BUFC_DATA);
+ arc_buf_data_free(buf, zio_data_buf_free);
+ arc_space_return(size, ARC_SPACE_DATA);
+ }
+
+ /* protected by hash lock, if in the hash table */
+ if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) {
+ uint64_t *cnt = &state->arcs_lsize[type];
+
+ ASSERT(refcount_is_zero(
+ &buf->b_hdr->b_l1hdr.b_refcnt));
+ ASSERT(state != arc_anon && state != arc_l2c_only);
+
+ ASSERT3U(*cnt, >=, size);
+ atomic_add_64(cnt, -size);
+ }
+
+ (void) refcount_remove_many(&state->arcs_size, size, buf);
+ buf->b_data = NULL;
+
+ /*
+ * If we're destroying a duplicate buffer make sure
+ * that the appropriate statistics are updated.
+ */
+ if (buf->b_hdr->b_l1hdr.b_datacnt > 1 &&
+ HDR_ISTYPE_DATA(buf->b_hdr)) {
+ ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
+ ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
+ }
+ ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0);
+ buf->b_hdr->b_l1hdr.b_datacnt -= 1;
+ }
+
+ /* only remove the buf if requested */
+ if (!remove)
+ return;
+
+ /* remove the buf from the hdr list */
+ for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf;
+ bufp = &(*bufp)->b_next)
+ continue;
+ *bufp = buf->b_next;
+ buf->b_next = NULL;
+
+ ASSERT(buf->b_efunc == NULL);
+
+ /* clean up the buf */
+ buf->b_hdr = NULL;
+ kmem_cache_free(buf_cache, buf);
+}
+
+static void
+arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
+{
+ l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
+ l2arc_dev_t *dev = l2hdr->b_dev;
+
+ ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
+ ASSERT(HDR_HAS_L2HDR(hdr));
+
+ list_remove(&dev->l2ad_buflist, hdr);
+
+ /*
+ * We don't want to leak the b_tmp_cdata buffer that was
+ * allocated in l2arc_write_buffers()
+ */
+ arc_buf_l2_cdata_free(hdr);
+
+ /*
+ * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then
+ * this header is being processed by l2arc_write_buffers() (i.e.
+ * it's in the first stage of l2arc_write_buffers()).
+ * Re-affirming that truth here, just to serve as a reminder. If
+ * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or
+ * may not have its HDR_L2_WRITING flag set. (the write may have
+ * completed, in which case HDR_L2_WRITING will be false and the
+ * b_daddr field will point to the address of the buffer on disk).
+ */
+ IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr));
+
+ /*
+ * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with
+ * l2arc_write_buffers(). Since we've just removed this header
+ * from the l2arc buffer list, this header will never reach the
+ * second stage of l2arc_write_buffers(), which increments the
+ * accounting stats for this header. Thus, we must be careful
+ * not to decrement them for this header either.
+ */
+ if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) {
+ ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
+ ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
+
+ vdev_space_update(dev->l2ad_vdev,
+ -l2hdr->b_asize, 0, 0);
+
+ (void) refcount_remove_many(&dev->l2ad_alloc,
+ l2hdr->b_asize, hdr);
+ }
+
+ hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
+}
+
+static void
+arc_hdr_destroy(arc_buf_hdr_t *hdr)
+{
+ if (HDR_HAS_L1HDR(hdr)) {
+ ASSERT(hdr->b_l1hdr.b_buf == NULL ||
+ hdr->b_l1hdr.b_datacnt > 0);
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
+ }
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ ASSERT(!HDR_IN_HASH_TABLE(hdr));
+
+ if (HDR_HAS_L2HDR(hdr)) {
+ l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
+ boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
+
+ if (!buflist_held)
+ mutex_enter(&dev->l2ad_mtx);
+
+ /*
+ * Even though we checked this conditional above, we
+ * need to check this again now that we have the
+ * l2ad_mtx. This is because we could be racing with
+ * another thread calling l2arc_evict() which might have
+ * destroyed this header's L2 portion as we were waiting
+ * to acquire the l2ad_mtx. If that happens, we don't
+ * want to re-destroy the header's L2 portion.
+ */
+ if (HDR_HAS_L2HDR(hdr))
+ arc_hdr_l2hdr_destroy(hdr);
+
+ if (!buflist_held)
+ mutex_exit(&dev->l2ad_mtx);
+ }
+
+ if (!BUF_EMPTY(hdr))
+ buf_discard_identity(hdr);
+
+ if (hdr->b_freeze_cksum != NULL) {
+ kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
+ hdr->b_freeze_cksum = NULL;
+ }
+
+ if (HDR_HAS_L1HDR(hdr)) {
+ while (hdr->b_l1hdr.b_buf) {
+ arc_buf_t *buf = hdr->b_l1hdr.b_buf;
+
+ if (buf->b_efunc != NULL) {
+ mutex_enter(&arc_user_evicts_lock);
+ mutex_enter(&buf->b_evict_lock);
+ ASSERT(buf->b_hdr != NULL);
+ arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE);
+ hdr->b_l1hdr.b_buf = buf->b_next;
+ buf->b_hdr = &arc_eviction_hdr;
+ buf->b_next = arc_eviction_list;
+ arc_eviction_list = buf;
+ mutex_exit(&buf->b_evict_lock);
+ cv_signal(&arc_user_evicts_cv);
+ mutex_exit(&arc_user_evicts_lock);
+ } else {
+ arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE);
+ }
+ }
+ }
+
+ ASSERT3P(hdr->b_hash_next, ==, NULL);
+ if (HDR_HAS_L1HDR(hdr)) {
+ ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
+ ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
+ kmem_cache_free(hdr_full_cache, hdr);
+ } else {
+ kmem_cache_free(hdr_l2only_cache, hdr);
+ }
+}
+
+void
+arc_buf_free(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ int hashed = hdr->b_l1hdr.b_state != arc_anon;
+
+ ASSERT(buf->b_efunc == NULL);
+ ASSERT(buf->b_data != NULL);
+
+ if (hashed) {
+ kmutex_t *hash_lock = HDR_LOCK(hdr);
+
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+
+ (void) remove_reference(hdr, hash_lock, tag);
+ if (hdr->b_l1hdr.b_datacnt > 1) {
+ arc_buf_destroy(buf, TRUE);
+ } else {
+ ASSERT(buf == hdr->b_l1hdr.b_buf);
+ ASSERT(buf->b_efunc == NULL);
+ hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
+ }
+ mutex_exit(hash_lock);
+ } else if (HDR_IO_IN_PROGRESS(hdr)) {
+ int destroy_hdr;
+ /*
+ * We are in the middle of an async write. Don't destroy
+ * this buffer unless the write completes before we finish
+ * decrementing the reference count.
+ */
+ mutex_enter(&arc_user_evicts_lock);
+ (void) remove_reference(hdr, NULL, tag);
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
+ mutex_exit(&arc_user_evicts_lock);
+ if (destroy_hdr)
+ arc_hdr_destroy(hdr);
+ } else {
+ if (remove_reference(hdr, NULL, tag) > 0)
+ arc_buf_destroy(buf, TRUE);
+ else
+ arc_hdr_destroy(hdr);
+ }
+}
+
+boolean_t
+arc_buf_remove_ref(arc_buf_t *buf, void* tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ kmutex_t *hash_lock = HDR_LOCK(hdr);
+ boolean_t no_callback = (buf->b_efunc == NULL);
+
+ if (hdr->b_l1hdr.b_state == arc_anon) {
+ ASSERT(hdr->b_l1hdr.b_datacnt == 1);
+ arc_buf_free(buf, tag);
+ return (no_callback);
+ }
+
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT(hdr->b_l1hdr.b_datacnt > 0);
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+ ASSERT(hdr->b_l1hdr.b_state != arc_anon);
+ ASSERT(buf->b_data != NULL);
+
+ (void) remove_reference(hdr, hash_lock, tag);
+ if (hdr->b_l1hdr.b_datacnt > 1) {
+ if (no_callback)
+ arc_buf_destroy(buf, TRUE);
+ } else if (no_callback) {
+ ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL);
+ ASSERT(buf->b_efunc == NULL);
+ hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
+ }
+ ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 ||
+ refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ mutex_exit(hash_lock);
+ return (no_callback);
+}
+
+uint64_t
+arc_buf_size(arc_buf_t *buf)
+{
+ return (buf->b_hdr->b_size);
+}
+
+/*
+ * Called from the DMU to determine if the current buffer should be
+ * evicted. In order to ensure proper locking, the eviction must be initiated
+ * from the DMU. Return true if the buffer is associated with user data and
+ * duplicate buffers still exist.
+ */
+boolean_t
+arc_buf_eviction_needed(arc_buf_t *buf)
+{
+ arc_buf_hdr_t *hdr;
+ boolean_t evict_needed = B_FALSE;
+
+ if (zfs_disable_dup_eviction)
+ return (B_FALSE);
+
+ mutex_enter(&buf->b_evict_lock);
+ hdr = buf->b_hdr;
+ if (hdr == NULL) {
+ /*
+ * We are in arc_do_user_evicts(); let that function
+ * perform the eviction.
+ */
+ ASSERT(buf->b_data == NULL);
+ mutex_exit(&buf->b_evict_lock);
+ return (B_FALSE);
+ } else if (buf->b_data == NULL) {
+ /*
+ * We have already been added to the arc eviction list;
+ * recommend eviction.
+ */
+ ASSERT3P(hdr, ==, &arc_eviction_hdr);
+ mutex_exit(&buf->b_evict_lock);
+ return (B_TRUE);
+ }
+
+ if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr))
+ evict_needed = B_TRUE;
+
+ mutex_exit(&buf->b_evict_lock);
+ return (evict_needed);
+}
+
+/*
+ * Evict the arc_buf_hdr that is provided as a parameter. The resultant
+ * state of the header is dependent on its state prior to entering this
+ * function. The following transitions are possible:
+ *
+ * - arc_mru -> arc_mru_ghost
+ * - arc_mfu -> arc_mfu_ghost
+ * - arc_mru_ghost -> arc_l2c_only
+ * - arc_mru_ghost -> deleted
+ * - arc_mfu_ghost -> arc_l2c_only
+ * - arc_mfu_ghost -> deleted
+ */
+static int64_t
+arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
+{
+ arc_state_t *evicted_state, *state;
+ int64_t bytes_evicted = 0;
+
+ ASSERT(MUTEX_HELD(hash_lock));
+ ASSERT(HDR_HAS_L1HDR(hdr));
+
+ state = hdr->b_l1hdr.b_state;
+ if (GHOST_STATE(state)) {
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ ASSERT(hdr->b_l1hdr.b_buf == NULL);
+
+ /*
+ * l2arc_write_buffers() relies on a header's L1 portion
+ * (i.e. its b_tmp_cdata field) during its write phase.
+ * Thus, we cannot push a header onto the arc_l2c_only
+ * state (removing its L1 piece) until the header is
+ * done being written to the l2arc.
+ */
+ if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
+ ARCSTAT_BUMP(arcstat_evict_l2_skip);
+ return (bytes_evicted);
+ }
+
+ ARCSTAT_BUMP(arcstat_deleted);
+ bytes_evicted += hdr->b_size;
+
+ DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
+
+ if (HDR_HAS_L2HDR(hdr)) {
+ /*
+ * This buffer is cached on the 2nd Level ARC;
+ * don't destroy the header.
+ */
+ arc_change_state(arc_l2c_only, hdr, hash_lock);
+ /*
+ * dropping from L1+L2 cached to L2-only,
+ * realloc to remove the L1 header.
+ */
+ hdr = arc_hdr_realloc(hdr, hdr_full_cache,
+ hdr_l2only_cache);
+ } else {
+ arc_change_state(arc_anon, hdr, hash_lock);
+ arc_hdr_destroy(hdr);
+ }
+ return (bytes_evicted);
+ }
+
+ ASSERT(state == arc_mru || state == arc_mfu);
+ evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
+
+ /* prefetch buffers have a minimum lifespan */
+ if (HDR_IO_IN_PROGRESS(hdr) ||
+ ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
+ ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
+ arc_min_prefetch_lifespan)) {
+ ARCSTAT_BUMP(arcstat_evict_skip);
+ return (bytes_evicted);
+ }
+
+ ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
+ ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0);
+ while (hdr->b_l1hdr.b_buf) {
+ arc_buf_t *buf = hdr->b_l1hdr.b_buf;
+ if (!mutex_tryenter(&buf->b_evict_lock)) {
+ ARCSTAT_BUMP(arcstat_mutex_miss);
+ break;
+ }
+ if (buf->b_data != NULL)
+ bytes_evicted += hdr->b_size;
+ if (buf->b_efunc != NULL) {
+ mutex_enter(&arc_user_evicts_lock);
+ arc_buf_destroy(buf, FALSE);
+ hdr->b_l1hdr.b_buf = buf->b_next;
+ buf->b_hdr = &arc_eviction_hdr;
+ buf->b_next = arc_eviction_list;
+ arc_eviction_list = buf;
+ cv_signal(&arc_user_evicts_cv);
+ mutex_exit(&arc_user_evicts_lock);
+ mutex_exit(&buf->b_evict_lock);
+ } else {
+ mutex_exit(&buf->b_evict_lock);
+ arc_buf_destroy(buf, TRUE);
+ }
+ }
+
+ if (HDR_HAS_L2HDR(hdr)) {
+ ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size);
+ } else {
+ if (l2arc_write_eligible(hdr->b_spa, hdr))
+ ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size);
+ else
+ ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size);
+ }
+
+ if (hdr->b_l1hdr.b_datacnt == 0) {
+ arc_change_state(evicted_state, hdr, hash_lock);
+ ASSERT(HDR_IN_HASH_TABLE(hdr));
+ hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
+ hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
+ DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
+ }
+
+ return (bytes_evicted);
+}
+
+static uint64_t
+arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
+ uint64_t spa, int64_t bytes)
+{
+ multilist_sublist_t *mls;
+ uint64_t bytes_evicted = 0;
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock;
+ int evict_count = 0;
+
+ ASSERT3P(marker, !=, NULL);
+ IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
+
+ mls = multilist_sublist_lock(ml, idx);
+
+ for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
+ hdr = multilist_sublist_prev(mls, marker)) {
+ if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
+ (evict_count >= zfs_arc_evict_batch_limit))
+ break;
+
+ /*
+ * To keep our iteration location, move the marker
+ * forward. Since we're not holding hdr's hash lock, we
+ * must be very careful and not remove 'hdr' from the
+ * sublist. Otherwise, other consumers might mistake the
+ * 'hdr' as not being on a sublist when they call the
+ * multilist_link_active() function (they all rely on
+ * the hash lock protecting concurrent insertions and
+ * removals). multilist_sublist_move_forward() was
+ * specifically implemented to ensure this is the case
+ * (only 'marker' will be removed and re-inserted).
+ */
+ multilist_sublist_move_forward(mls, marker);
+
+ /*
+ * The only case where the b_spa field should ever be
+ * zero, is the marker headers inserted by
+ * arc_evict_state(). It's possible for multiple threads
+ * to be calling arc_evict_state() concurrently (e.g.
+ * dsl_pool_close() and zio_inject_fault()), so we must
+ * skip any markers we see from these other threads.
+ */
+ if (hdr->b_spa == 0)
+ continue;
+
+ /* we're only interested in evicting buffers of a certain spa */
+ if (spa != 0 && hdr->b_spa != spa) {
+ ARCSTAT_BUMP(arcstat_evict_skip);
+ continue;
+ }
+
+ hash_lock = HDR_LOCK(hdr);
+
+ /*
+ * We aren't calling this function from any code path
+ * that would already be holding a hash lock, so we're
+ * asserting on this assumption to be defensive in case
+ * this ever changes. Without this check, it would be
+ * possible to incorrectly increment arcstat_mutex_miss
+ * below (e.g. if the code changed such that we called
+ * this function with a hash lock held).
+ */
+ ASSERT(!MUTEX_HELD(hash_lock));
+
+ if (mutex_tryenter(hash_lock)) {
+ uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
+ mutex_exit(hash_lock);
+
+ bytes_evicted += evicted;
+
+ /*
+ * If evicted is zero, arc_evict_hdr() must have
+ * decided to skip this header, don't increment
+ * evict_count in this case.
+ */
+ if (evicted != 0)
+ evict_count++;
+
+ /*
+ * If arc_size isn't overflowing, signal any
+ * threads that might happen to be waiting.
+ *
+ * For each header evicted, we wake up a single
+ * thread. If we used cv_broadcast, we could
+ * wake up "too many" threads causing arc_size
+ * to significantly overflow arc_c; since
+ * arc_get_data_buf() doesn't check for overflow
+ * when it's woken up (it doesn't because it's
+ * possible for the ARC to be overflowing while
+ * full of un-evictable buffers, and the
+ * function should proceed in this case).
+ *
+ * If threads are left sleeping, due to not
+ * using cv_broadcast, they will be woken up
+ * just before arc_reclaim_thread() sleeps.
+ */
+ mutex_enter(&arc_reclaim_lock);
+ if (!arc_is_overflowing())
+ cv_signal(&arc_reclaim_waiters_cv);
+ mutex_exit(&arc_reclaim_lock);
+ } else {
+ ARCSTAT_BUMP(arcstat_mutex_miss);
+ }
+ }
+
+ multilist_sublist_unlock(mls);
+
+ return (bytes_evicted);
+}
+
+/*
+ * Evict buffers from the given arc state, until we've removed the
+ * specified number of bytes. Move the removed buffers to the
+ * appropriate evict state.
+ *
+ * This function makes a "best effort". It skips over any buffers
+ * it can't get a hash_lock on, and so, may not catch all candidates.
+ * It may also return without evicting as much space as requested.
+ *
+ * If bytes is specified using the special value ARC_EVICT_ALL, this
+ * will evict all available (i.e. unlocked and evictable) buffers from
+ * the given arc state; which is used by arc_flush().
+ */
+static uint64_t
+arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
+ arc_buf_contents_t type)
+{
+ uint64_t total_evicted = 0;
+ multilist_t *ml = &state->arcs_list[type];
+ int num_sublists;
+ arc_buf_hdr_t **markers;
+ int i;
+
+ IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
+
+ num_sublists = multilist_get_num_sublists(ml);
+
+ /*
+ * If we've tried to evict from each sublist, made some
+ * progress, but still have not hit the target number of bytes
+ * to evict, we want to keep trying. The markers allow us to
+ * pick up where we left off for each individual sublist, rather
+ * than starting from the tail each time.
+ */
+ markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
+ for (i = 0; i < num_sublists; i++) {
+ multilist_sublist_t *mls;
+
+ markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
+
+ /*
+ * A b_spa of 0 is used to indicate that this header is
+ * a marker. This fact is used in arc_adjust_type() and
+ * arc_evict_state_impl().
+ */
+ markers[i]->b_spa = 0;
+
+ mls = multilist_sublist_lock(ml, i);
+ multilist_sublist_insert_tail(mls, markers[i]);
+ multilist_sublist_unlock(mls);
+ }
+
+ /*
+ * While we haven't hit our target number of bytes to evict, or
+ * we're evicting all available buffers.
+ */
+ while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
+ /*
+ * Start eviction using a randomly selected sublist,
+ * this is to try and evenly balance eviction across all
+ * sublists. Always starting at the same sublist
+ * (e.g. index 0) would cause evictions to favor certain
+ * sublists over others.
+ */
+ int sublist_idx = multilist_get_random_index(ml);
+ uint64_t scan_evicted = 0;
+
+ for (i = 0; i < num_sublists; i++) {
+ uint64_t bytes_remaining;
+ uint64_t bytes_evicted;
+
+ if (bytes == ARC_EVICT_ALL)
+ bytes_remaining = ARC_EVICT_ALL;
+ else if (total_evicted < bytes)
+ bytes_remaining = bytes - total_evicted;
+ else
+ break;
+
+ bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
+ markers[sublist_idx], spa, bytes_remaining);
+
+ scan_evicted += bytes_evicted;
+ total_evicted += bytes_evicted;
+
+ /* we've reached the end, wrap to the beginning */
+ if (++sublist_idx >= num_sublists)
+ sublist_idx = 0;
+ }
+
+ /*
+ * If we didn't evict anything during this scan, we have
+ * no reason to believe we'll evict more during another
+ * scan, so break the loop.
+ */
+ if (scan_evicted == 0) {
+ /* This isn't possible, let's make that obvious */
+ ASSERT3S(bytes, !=, 0);
+
+ /*
+ * When bytes is ARC_EVICT_ALL, the only way to
+ * break the loop is when scan_evicted is zero.
+ * In that case, we actually have evicted enough,
+ * so we don't want to increment the kstat.
+ */
+ if (bytes != ARC_EVICT_ALL) {
+ ASSERT3S(total_evicted, <, bytes);
+ ARCSTAT_BUMP(arcstat_evict_not_enough);
+ }
+
+ break;
+ }
+ }
+
+ for (i = 0; i < num_sublists; i++) {
+ multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
+ multilist_sublist_remove(mls, markers[i]);
+ multilist_sublist_unlock(mls);
+
+ kmem_cache_free(hdr_full_cache, markers[i]);
+ }
+ kmem_free(markers, sizeof (*markers) * num_sublists);
+
+ return (total_evicted);
+}
+
+/*
+ * Flush all "evictable" data of the given type from the arc state
+ * specified. This will not evict any "active" buffers (i.e. referenced).
+ *
+ * When 'retry' is set to FALSE, the function will make a single pass
+ * over the state and evict any buffers that it can. Since it doesn't
+ * continually retry the eviction, it might end up leaving some buffers
+ * in the ARC due to lock misses.
+ *
+ * When 'retry' is set to TRUE, the function will continually retry the
+ * eviction until *all* evictable buffers have been removed from the
+ * state. As a result, if concurrent insertions into the state are
+ * allowed (e.g. if the ARC isn't shutting down), this function might
+ * wind up in an infinite loop, continually trying to evict buffers.
+ */
+static uint64_t
+arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
+ boolean_t retry)
+{
+ uint64_t evicted = 0;
+
+ while (state->arcs_lsize[type] != 0) {
+ evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
+
+ if (!retry)
+ break;
+ }
+
+ return (evicted);
+}
+
+/*
+ * Helper function for arc_prune_async() it is responsible for safely
+ * handling the execution of a registered arc_prune_func_t.
+ */
+static void
+arc_prune_task(void *ptr)
+{
+ arc_prune_t *ap = (arc_prune_t *)ptr;
+ arc_prune_func_t *func = ap->p_pfunc;
+
+ if (func != NULL)
+ func(ap->p_adjust, ap->p_private);
+
+ refcount_remove(&ap->p_refcnt, func);
+}
+
+/*
+ * Notify registered consumers they must drop holds on a portion of the ARC
+ * buffered they reference. This provides a mechanism to ensure the ARC can
+ * honor the arc_meta_limit and reclaim otherwise pinned ARC buffers. This
+ * is analogous to dnlc_reduce_cache() but more generic.
+ *
+ * This operation is performed asynchronously so it may be safely called
+ * in the context of the arc_reclaim_thread(). A reference is taken here
+ * for each registered arc_prune_t and the arc_prune_task() is responsible
+ * for releasing it once the registered arc_prune_func_t has completed.
+ */
+static void
+arc_prune_async(int64_t adjust)
+{
+ arc_prune_t *ap;
+
+ mutex_enter(&arc_prune_mtx);
+ for (ap = list_head(&arc_prune_list); ap != NULL;
+ ap = list_next(&arc_prune_list, ap)) {
+
+ if (refcount_count(&ap->p_refcnt) >= 2)
+ continue;
+
+ refcount_add(&ap->p_refcnt, ap->p_pfunc);
+ ap->p_adjust = adjust;
+ taskq_dispatch(arc_prune_taskq, arc_prune_task, ap, TQ_SLEEP);
+ ARCSTAT_BUMP(arcstat_prune);
+ }
+ mutex_exit(&arc_prune_mtx);
+}
+
+/*
+ * Evict the specified number of bytes from the state specified,
+ * restricting eviction to the spa and type given. This function
+ * prevents us from trying to evict more from a state's list than
+ * is "evictable", and to skip evicting altogether when passed a
+ * negative value for "bytes". In contrast, arc_evict_state() will
+ * evict everything it can, when passed a negative value for "bytes".
+ */
+static uint64_t
+arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
+ arc_buf_contents_t type)
+{
+ int64_t delta;
+
+ if (bytes > 0 && state->arcs_lsize[type] > 0) {
+ delta = MIN(state->arcs_lsize[type], bytes);
+ return (arc_evict_state(state, spa, delta, type));
+ }
+
+ return (0);
+}
+
+/*
+ * The goal of this function is to evict enough meta data buffers from the
+ * ARC in order to enforce the arc_meta_limit. Achieving this is slightly
+ * more complicated than it appears because it is common for data buffers
+ * to have holds on meta data buffers. In addition, dnode meta data buffers
+ * will be held by the dnodes in the block preventing them from being freed.
+ * This means we can't simply traverse the ARC and expect to always find
+ * enough unheld meta data buffer to release.
+ *
+ * Therefore, this function has been updated to make alternating passes
+ * over the ARC releasing data buffers and then newly unheld meta data
+ * buffers. This ensures forward progress is maintained and arc_meta_used
+ * will decrease. Normally this is sufficient, but if required the ARC
+ * will call the registered prune callbacks causing dentry and inodes to
+ * be dropped from the VFS cache. This will make dnode meta data buffers
+ * available for reclaim.
+ */
+static uint64_t
+arc_adjust_meta_balanced(void)
+{
+ int64_t adjustmnt, delta, prune = 0;
+ uint64_t total_evicted = 0;
+ arc_buf_contents_t type = ARC_BUFC_DATA;
+ int restarts = MAX(zfs_arc_meta_adjust_restarts, 0);
+
+restart:
+ /*
+ * This slightly differs than the way we evict from the mru in
+ * arc_adjust because we don't have a "target" value (i.e. no
+ * "meta" arc_p). As a result, I think we can completely
+ * cannibalize the metadata in the MRU before we evict the
+ * metadata from the MFU. I think we probably need to implement a
+ * "metadata arc_p" value to do this properly.
+ */
+ adjustmnt = arc_meta_used - arc_meta_limit;
+
+ if (adjustmnt > 0 && arc_mru->arcs_lsize[type] > 0) {
+ delta = MIN(arc_mru->arcs_lsize[type], adjustmnt);
+ total_evicted += arc_adjust_impl(arc_mru, 0, delta, type);
+ adjustmnt -= delta;
+ }
+
+ /*
+ * We can't afford to recalculate adjustmnt here. If we do,
+ * new metadata buffers can sneak into the MRU or ANON lists,
+ * thus penalize the MFU metadata. Although the fudge factor is
+ * small, it has been empirically shown to be significant for
+ * certain workloads (e.g. creating many empty directories). As
+ * such, we use the original calculation for adjustmnt, and
+ * simply decrement the amount of data evicted from the MRU.
+ */
+
+ if (adjustmnt > 0 && arc_mfu->arcs_lsize[type] > 0) {
+ delta = MIN(arc_mfu->arcs_lsize[type], adjustmnt);
+ total_evicted += arc_adjust_impl(arc_mfu, 0, delta, type);
+ }
+
+ adjustmnt = arc_meta_used - arc_meta_limit;
+
+ if (adjustmnt > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
+ delta = MIN(adjustmnt,
+ arc_mru_ghost->arcs_lsize[type]);
+ total_evicted += arc_adjust_impl(arc_mru_ghost, 0, delta, type);
+ adjustmnt -= delta;
+ }
+
+ if (adjustmnt > 0 && arc_mfu_ghost->arcs_lsize[type] > 0) {
+ delta = MIN(adjustmnt,
+ arc_mfu_ghost->arcs_lsize[type]);
+ total_evicted += arc_adjust_impl(arc_mfu_ghost, 0, delta, type);
+ }
+
+ /*
+ * If after attempting to make the requested adjustment to the ARC
+ * the meta limit is still being exceeded then request that the
+ * higher layers drop some cached objects which have holds on ARC
+ * meta buffers. Requests to the upper layers will be made with
+ * increasingly large scan sizes until the ARC is below the limit.
+ */
+ if (arc_meta_used > arc_meta_limit) {
+ if (type == ARC_BUFC_DATA) {
+ type = ARC_BUFC_METADATA;
+ } else {
+ type = ARC_BUFC_DATA;
+
+ if (zfs_arc_meta_prune) {
+ prune += zfs_arc_meta_prune;
+ arc_prune_async(prune);
+ }
+ }
+
+ if (restarts > 0) {
+ restarts--;
+ goto restart;
+ }
+ }
+ return (total_evicted);
+}
+
+/*
+ * Evict metadata buffers from the cache, such that arc_meta_used is
+ * capped by the arc_meta_limit tunable.
+ */
+static uint64_t
+arc_adjust_meta_only(void)
+{
+ uint64_t total_evicted = 0;
+ int64_t target;
+
+ /*
+ * If we're over the meta limit, we want to evict enough
+ * metadata to get back under the meta limit. We don't want to
+ * evict so much that we drop the MRU below arc_p, though. If
+ * we're over the meta limit more than we're over arc_p, we
+ * evict some from the MRU here, and some from the MFU below.
+ */
+ target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
+ (int64_t)(refcount_count(&arc_anon->arcs_size) +
+ refcount_count(&arc_mru->arcs_size) - arc_p));
+
+ total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
+
+ /*
+ * Similar to the above, we want to evict enough bytes to get us
+ * below the meta limit, but not so much as to drop us below the
+ * space alloted to the MFU (which is defined as arc_c - arc_p).
+ */
+ target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
+ (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
+
+ total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
+
+ return (total_evicted);
+}
+
+static uint64_t
+arc_adjust_meta(void)
+{
+ if (zfs_arc_meta_strategy == ARC_STRATEGY_META_ONLY)
+ return (arc_adjust_meta_only());
+ else
+ return (arc_adjust_meta_balanced());
+}
+
+/*
+ * Return the type of the oldest buffer in the given arc state
+ *
+ * This function will select a random sublist of type ARC_BUFC_DATA and
+ * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
+ * is compared, and the type which contains the "older" buffer will be
+ * returned.
+ */
+static arc_buf_contents_t
+arc_adjust_type(arc_state_t *state)
+{
+ multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA];
+ multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA];
+ int data_idx = multilist_get_random_index(data_ml);
+ int meta_idx = multilist_get_random_index(meta_ml);
+ multilist_sublist_t *data_mls;
+ multilist_sublist_t *meta_mls;
+ arc_buf_contents_t type;
+ arc_buf_hdr_t *data_hdr;
+ arc_buf_hdr_t *meta_hdr;
+
+ /*
+ * We keep the sublist lock until we're finished, to prevent
+ * the headers from being destroyed via arc_evict_state().
+ */
+ data_mls = multilist_sublist_lock(data_ml, data_idx);
+ meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
+
+ /*
+ * These two loops are to ensure we skip any markers that
+ * might be at the tail of the lists due to arc_evict_state().
+ */
+
+ for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
+ data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
+ if (data_hdr->b_spa != 0)
+ break;
+ }
+
+ for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
+ meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
+ if (meta_hdr->b_spa != 0)
+ break;
+ }
+
+ if (data_hdr == NULL && meta_hdr == NULL) {
+ type = ARC_BUFC_DATA;
+ } else if (data_hdr == NULL) {
+ ASSERT3P(meta_hdr, !=, NULL);
+ type = ARC_BUFC_METADATA;
+ } else if (meta_hdr == NULL) {
+ ASSERT3P(data_hdr, !=, NULL);
+ type = ARC_BUFC_DATA;
+ } else {
+ ASSERT3P(data_hdr, !=, NULL);
+ ASSERT3P(meta_hdr, !=, NULL);
+
+ /* The headers can't be on the sublist without an L1 header */
+ ASSERT(HDR_HAS_L1HDR(data_hdr));
+ ASSERT(HDR_HAS_L1HDR(meta_hdr));
+
+ if (data_hdr->b_l1hdr.b_arc_access <
+ meta_hdr->b_l1hdr.b_arc_access) {
+ type = ARC_BUFC_DATA;
+ } else {
+ type = ARC_BUFC_METADATA;
+ }
+ }
+
+ multilist_sublist_unlock(meta_mls);
+ multilist_sublist_unlock(data_mls);
+
+ return (type);
+}
+
+/*
+ * Evict buffers from the cache, such that arc_size is capped by arc_c.
+ */
+static uint64_t
+arc_adjust(void)
+{
+ uint64_t total_evicted = 0;
+ uint64_t bytes;
+ int64_t target;
+
+ /*
+ * If we're over arc_meta_limit, we want to correct that before
+ * potentially evicting data buffers below.
+ */
+ total_evicted += arc_adjust_meta();
+
+ /*
+ * Adjust MRU size
+ *
+ * If we're over the target cache size, we want to evict enough
+ * from the list to get back to our target size. We don't want
+ * to evict too much from the MRU, such that it drops below
+ * arc_p. So, if we're over our target cache size more than
+ * the MRU is over arc_p, we'll evict enough to get back to
+ * arc_p here, and then evict more from the MFU below.
+ */
+ target = MIN((int64_t)(arc_size - arc_c),
+ (int64_t)(refcount_count(&arc_anon->arcs_size) +
+ refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
+
+ /*
+ * If we're below arc_meta_min, always prefer to evict data.
+ * Otherwise, try to satisfy the requested number of bytes to
+ * evict from the type which contains older buffers; in an
+ * effort to keep newer buffers in the cache regardless of their
+ * type. If we cannot satisfy the number of bytes from this
+ * type, spill over into the next type.
+ */
+ if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
+ arc_meta_used > arc_meta_min) {
+ bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
+ total_evicted += bytes;
+
+ /*
+ * If we couldn't evict our target number of bytes from
+ * metadata, we try to get the rest from data.
+ */
+ target -= bytes;
+
+ total_evicted +=
+ arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
+ } else {
+ bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
+ total_evicted += bytes;
+
+ /*
+ * If we couldn't evict our target number of bytes from
+ * data, we try to get the rest from metadata.
+ */
+ target -= bytes;
+
+ total_evicted +=
+ arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
+ }
+
+ /*
+ * Adjust MFU size
+ *
+ * Now that we've tried to evict enough from the MRU to get its
+ * size back to arc_p, if we're still above the target cache
+ * size, we evict the rest from the MFU.
+ */
+ target = arc_size - arc_c;
+
+ if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
+ arc_meta_used > arc_meta_min) {
+ bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
+ total_evicted += bytes;
+
+ /*
+ * If we couldn't evict our target number of bytes from
+ * metadata, we try to get the rest from data.
+ */
+ target -= bytes;
+
+ total_evicted +=
+ arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
+ } else {
+ bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
+ total_evicted += bytes;
+
+ /*
+ * If we couldn't evict our target number of bytes from
+ * data, we try to get the rest from data.
+ */
+ target -= bytes;
+
+ total_evicted +=
+ arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
+ }
+
+ /*
+ * Adjust ghost lists
+ *
+ * In addition to the above, the ARC also defines target values
+ * for the ghost lists. The sum of the mru list and mru ghost
+ * list should never exceed the target size of the cache, and
+ * the sum of the mru list, mfu list, mru ghost list, and mfu
+ * ghost list should never exceed twice the target size of the
+ * cache. The following logic enforces these limits on the ghost
+ * caches, and evicts from them as needed.
+ */
+ target = refcount_count(&arc_mru->arcs_size) +
+ refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
+
+ bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
+ total_evicted += bytes;
+
+ target -= bytes;
+
+ total_evicted +=
+ arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
+
+ /*
+ * We assume the sum of the mru list and mfu list is less than
+ * or equal to arc_c (we enforced this above), which means we
+ * can use the simpler of the two equations below:
+ *
+ * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
+ * mru ghost + mfu ghost <= arc_c
+ */
+ target = refcount_count(&arc_mru_ghost->arcs_size) +
+ refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
+
+ bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
+ total_evicted += bytes;
+
+ target -= bytes;
+
+ total_evicted +=
+ arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
+
+ return (total_evicted);
+}
+
+static void
+arc_do_user_evicts(void)
+{
+ mutex_enter(&arc_user_evicts_lock);
+ while (arc_eviction_list != NULL) {
+ arc_buf_t *buf = arc_eviction_list;
+ arc_eviction_list = buf->b_next;
+ mutex_enter(&buf->b_evict_lock);
+ buf->b_hdr = NULL;
+ mutex_exit(&buf->b_evict_lock);
+ mutex_exit(&arc_user_evicts_lock);
+
+ if (buf->b_efunc != NULL)
+ VERIFY0(buf->b_efunc(buf->b_private));
+
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ kmem_cache_free(buf_cache, buf);
+ mutex_enter(&arc_user_evicts_lock);
+ }
+ mutex_exit(&arc_user_evicts_lock);
+}
+
+void
+arc_flush(spa_t *spa, boolean_t retry)
+{
+ uint64_t guid = 0;
+
+ /*
+ * If retry is TRUE, a spa must not be specified since we have
+ * no good way to determine if all of a spa's buffers have been
+ * evicted from an arc state.
+ */
+ ASSERT(!retry || spa == 0);
+
+ if (spa != NULL)
+ guid = spa_load_guid(spa);
+
+ (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
+ (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
+
+ (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
+ (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
+
+ (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
+ (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
+
+ (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
+ (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
+
+ arc_do_user_evicts();
+ ASSERT(spa || arc_eviction_list == NULL);
+}
+
+void
+arc_shrink(int64_t to_free)
+{
+ uint64_t c = arc_c;
+
+ if (c > to_free && c - to_free > arc_c_min) {
+ arc_c = c - to_free;
+ atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
+ if (arc_c > arc_size)
+ arc_c = MAX(arc_size, arc_c_min);
+ if (arc_p > arc_c)
+ arc_p = (arc_c >> 1);
+ ASSERT(arc_c >= arc_c_min);
+ ASSERT((int64_t)arc_p >= 0);
+ } else {
+ arc_c = arc_c_min;
+ }
+
+ if (arc_size > arc_c)
+ (void) arc_adjust();
+}
+
+typedef enum free_memory_reason_t {
+ FMR_UNKNOWN,
+ FMR_NEEDFREE,
+ FMR_LOTSFREE,
+ FMR_SWAPFS_MINFREE,
+ FMR_PAGES_PP_MAXIMUM,
+ FMR_HEAP_ARENA,
+ FMR_ZIO_ARENA,
+} free_memory_reason_t;
+
+int64_t last_free_memory;
+free_memory_reason_t last_free_reason;
+
+#ifdef _KERNEL
+/*
+ * Additional reserve of pages for pp_reserve.
+ */
+int64_t arc_pages_pp_reserve = 64;
+
+/*
+ * Additional reserve of pages for swapfs.
+ */
+int64_t arc_swapfs_reserve = 64;
+#endif /* _KERNEL */
+
+/*
+ * Return the amount of memory that can be consumed before reclaim will be
+ * needed. Positive if there is sufficient free memory, negative indicates
+ * the amount of memory that needs to be freed up.
+ */
+static int64_t
+arc_available_memory(void)
+{
+ int64_t lowest = INT64_MAX;
+ free_memory_reason_t r = FMR_UNKNOWN;
+#ifdef _KERNEL
+ int64_t n;
+#ifdef __linux__
+ pgcnt_t needfree = btop(arc_need_free);
+ pgcnt_t lotsfree = btop(arc_sys_free);
+ pgcnt_t desfree = 0;
+#endif
+
+ if (needfree > 0) {
+ n = PAGESIZE * (-needfree);
+ if (n < lowest) {
+ lowest = n;
+ r = FMR_NEEDFREE;
+ }
+ }
+
+ /*
+ * check that we're out of range of the pageout scanner. It starts to
+ * schedule paging if freemem is less than lotsfree and needfree.
+ * lotsfree is the high-water mark for pageout, and needfree is the
+ * number of needed free pages. We add extra pages here to make sure
+ * the scanner doesn't start up while we're freeing memory.
+ */
+ n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
+ if (n < lowest) {
+ lowest = n;
+ r = FMR_LOTSFREE;
+ }
+
+#ifndef __linux__
+ /*
+ * check to make sure that swapfs has enough space so that anon
+ * reservations can still succeed. anon_resvmem() checks that the
+ * availrmem is greater than swapfs_minfree, and the number of reserved
+ * swap pages. We also add a bit of extra here just to prevent
+ * circumstances from getting really dire.
+ */
+ n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
+ desfree - arc_swapfs_reserve);
+ if (n < lowest) {
+ lowest = n;
+ r = FMR_SWAPFS_MINFREE;
+ }
+
+
+ /*
+ * Check that we have enough availrmem that memory locking (e.g., via
+ * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
+ * stores the number of pages that cannot be locked; when availrmem
+ * drops below pages_pp_maximum, page locking mechanisms such as
+ * page_pp_lock() will fail.)
+ */
+ n = PAGESIZE * (availrmem - pages_pp_maximum -
+ arc_pages_pp_reserve);
+ if (n < lowest) {
+ lowest = n;
+ r = FMR_PAGES_PP_MAXIMUM;
+ }
+#endif
+
+#if defined(__i386)
+ /*
+ * If we're on an i386 platform, it's possible that we'll exhaust the
+ * kernel heap space before we ever run out of available physical
+ * memory. Most checks of the size of the heap_area compare against
+ * tune.t_minarmem, which is the minimum available real memory that we
+ * can have in the system. However, this is generally fixed at 25 pages
+ * which is so low that it's useless. In this comparison, we seek to
+ * calculate the total heap-size, and reclaim if more than 3/4ths of the
+ * heap is allocated. (Or, in the calculation, if less than 1/4th is
+ * free)
+ */
+ n = vmem_size(heap_arena, VMEM_FREE) -
+ (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
+ if (n < lowest) {
+ lowest = n;
+ r = FMR_HEAP_ARENA;
+ }
+#endif
+
+ /*
+ * If zio data pages are being allocated out of a separate heap segment,
+ * then enforce that the size of available vmem for this arena remains
+ * above about 1/16th free.
+ *
+ * Note: The 1/16th arena free requirement was put in place
+ * to aggressively evict memory from the arc in order to avoid
+ * memory fragmentation issues.
+ */
+ if (zio_arena != NULL) {
+ n = vmem_size(zio_arena, VMEM_FREE) -
+ (vmem_size(zio_arena, VMEM_ALLOC) >> 4);
+ if (n < lowest) {
+ lowest = n;
+ r = FMR_ZIO_ARENA;
+ }
+ }
+#else /* _KERNEL */
+ /* Every 100 calls, free a small amount */
+ if (spa_get_random(100) == 0)
+ lowest = -1024;
+#endif /* _KERNEL */
+
+ last_free_memory = lowest;
+ last_free_reason = r;
+
+ return (lowest);
+}
+
+/*
+ * Determine if the system is under memory pressure and is asking
+ * to reclaim memory. A return value of TRUE indicates that the system
+ * is under memory pressure and that the arc should adjust accordingly.
+ */
+static boolean_t
+arc_reclaim_needed(void)
+{
+ return (arc_available_memory() < 0);
+}
+
+static void
+arc_kmem_reap_now(void)
+{
+ size_t i;
+ kmem_cache_t *prev_cache = NULL;
+ kmem_cache_t *prev_data_cache = NULL;
+ extern kmem_cache_t *zio_buf_cache[];
+ extern kmem_cache_t *zio_data_buf_cache[];
+ extern kmem_cache_t *range_seg_cache;
+
+ if ((arc_meta_used >= arc_meta_limit) && zfs_arc_meta_prune) {
+ /*
+ * We are exceeding our meta-data cache limit.
+ * Prune some entries to release holds on meta-data.
+ */
+ arc_prune_async(zfs_arc_meta_prune);
+ }
+
+ for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
+#ifdef _ILP32
+ /* reach upper limit of cache size on 32-bit */
+ if (zio_buf_cache[i] == NULL)
+ break;
+#endif
+ if (zio_buf_cache[i] != prev_cache) {
+ prev_cache = zio_buf_cache[i];
+ kmem_cache_reap_now(zio_buf_cache[i]);
+ }
+ if (zio_data_buf_cache[i] != prev_data_cache) {
+ prev_data_cache = zio_data_buf_cache[i];
+ kmem_cache_reap_now(zio_data_buf_cache[i]);
+ }
+ }
+ kmem_cache_reap_now(buf_cache);
+ kmem_cache_reap_now(hdr_full_cache);
+ kmem_cache_reap_now(hdr_l2only_cache);
+ kmem_cache_reap_now(range_seg_cache);
+
+ if (zio_arena != NULL) {
+ /*
+ * Ask the vmem arena to reclaim unused memory from its
+ * quantum caches.
+ */
+ vmem_qcache_reap(zio_arena);
+ }
+}
+
+/*
+ * Threads can block in arc_get_data_buf() waiting for this thread to evict
+ * enough data and signal them to proceed. When this happens, the threads in
+ * arc_get_data_buf() are sleeping while holding the hash lock for their
+ * particular arc header. Thus, we must be careful to never sleep on a
+ * hash lock in this thread. This is to prevent the following deadlock:
+ *
+ * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L",
+ * waiting for the reclaim thread to signal it.
+ *
+ * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
+ * fails, and goes to sleep forever.
+ *
+ * This possible deadlock is avoided by always acquiring a hash lock
+ * using mutex_tryenter() from arc_reclaim_thread().
+ */
+static void
+arc_reclaim_thread(void)
+{
+ fstrans_cookie_t cookie = spl_fstrans_mark();
+ clock_t growtime = 0;
+ callb_cpr_t cpr;
+
+ CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
+
+ mutex_enter(&arc_reclaim_lock);
+ while (!arc_reclaim_thread_exit) {
+ int64_t to_free;
+ int64_t free_memory = arc_available_memory();
+ uint64_t evicted = 0;
+
+ arc_tuning_update();
+
+ mutex_exit(&arc_reclaim_lock);
+
+ if (free_memory < 0) {
+
+ arc_no_grow = B_TRUE;
+ arc_warm = B_TRUE;
+
+ /*
+ * Wait at least zfs_grow_retry (default 5) seconds
+ * before considering growing.
+ */
+ growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
+
+ arc_kmem_reap_now();
+
+ /*
+ * If we are still low on memory, shrink the ARC
+ * so that we have arc_shrink_min free space.
+ */
+ free_memory = arc_available_memory();
+
+ to_free = (arc_c >> arc_shrink_shift) - free_memory;
+ if (to_free > 0) {
+#ifdef _KERNEL
+ to_free = MAX(to_free, arc_need_free);
+#endif
+ arc_shrink(to_free);
+ }
+ } else if (free_memory < arc_c >> arc_no_grow_shift) {
+ arc_no_grow = B_TRUE;
+ } else if (ddi_get_lbolt() >= growtime) {
+ arc_no_grow = B_FALSE;
+ }
+
+ evicted = arc_adjust();
+
+ mutex_enter(&arc_reclaim_lock);
+
+ /*
+ * If evicted is zero, we couldn't evict anything via
+ * arc_adjust(). This could be due to hash lock
+ * collisions, but more likely due to the majority of
+ * arc buffers being unevictable. Therefore, even if
+ * arc_size is above arc_c, another pass is unlikely to
+ * be helpful and could potentially cause us to enter an
+ * infinite loop.
+ */
+ if (arc_size <= arc_c || evicted == 0) {
+ /*
+ * We're either no longer overflowing, or we
+ * can't evict anything more, so we should wake
+ * up any threads before we go to sleep and clear
+ * arc_need_free since nothing more can be done.
+ */
+ cv_broadcast(&arc_reclaim_waiters_cv);
+ arc_need_free = 0;
+
+ /*
+ * Block until signaled, or after one second (we
+ * might need to perform arc_kmem_reap_now()
+ * even if we aren't being signalled)
+ */
+ CALLB_CPR_SAFE_BEGIN(&cpr);
+ (void) cv_timedwait_sig(&arc_reclaim_thread_cv,
+ &arc_reclaim_lock, ddi_get_lbolt() + hz);
+ CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
+ }
+ }
+
+ arc_reclaim_thread_exit = FALSE;
+ cv_broadcast(&arc_reclaim_thread_cv);
+ CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
+ spl_fstrans_unmark(cookie);
+ thread_exit();
+}
+
+static void
+arc_user_evicts_thread(void)
+{
+ fstrans_cookie_t cookie = spl_fstrans_mark();
+ callb_cpr_t cpr;
+
+ CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG);
+
+ mutex_enter(&arc_user_evicts_lock);
+ while (!arc_user_evicts_thread_exit) {
+ mutex_exit(&arc_user_evicts_lock);
+
+ arc_do_user_evicts();
+
+ /*
+ * This is necessary in order for the mdb ::arc dcmd to
+ * show up to date information. Since the ::arc command
+ * does not call the kstat's update function, without
+ * this call, the command may show stale stats for the
+ * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
+ * with this change, the data might be up to 1 second
+ * out of date; but that should suffice. The arc_state_t
+ * structures can be queried directly if more accurate
+ * information is needed.
+ */
+ if (arc_ksp != NULL)
+ arc_ksp->ks_update(arc_ksp, KSTAT_READ);
+
+ mutex_enter(&arc_user_evicts_lock);
+
+ /*
+ * Block until signaled, or after one second (we need to
+ * call the arc's kstat update function regularly).
+ */
+ CALLB_CPR_SAFE_BEGIN(&cpr);
+ (void) cv_timedwait_sig(&arc_user_evicts_cv,
+ &arc_user_evicts_lock, ddi_get_lbolt() + hz);
+ CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock);
+ }
+
+ arc_user_evicts_thread_exit = FALSE;
+ cv_broadcast(&arc_user_evicts_cv);
+ CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */
+ spl_fstrans_unmark(cookie);
+ thread_exit();
+}
+
+#ifdef _KERNEL
+/*
+ * Determine the amount of memory eligible for eviction contained in the
+ * ARC. All clean data reported by the ghost lists can always be safely
+ * evicted. Due to arc_c_min, the same does not hold for all clean data
+ * contained by the regular mru and mfu lists.
+ *
+ * In the case of the regular mru and mfu lists, we need to report as
+ * much clean data as possible, such that evicting that same reported
+ * data will not bring arc_size below arc_c_min. Thus, in certain
+ * circumstances, the total amount of clean data in the mru and mfu
+ * lists might not actually be evictable.
+ *
+ * The following two distinct cases are accounted for:
+ *
+ * 1. The sum of the amount of dirty data contained by both the mru and
+ * mfu lists, plus the ARC's other accounting (e.g. the anon list),
+ * is greater than or equal to arc_c_min.
+ * (i.e. amount of dirty data >= arc_c_min)
+ *
+ * This is the easy case; all clean data contained by the mru and mfu
+ * lists is evictable. Evicting all clean data can only drop arc_size
+ * to the amount of dirty data, which is greater than arc_c_min.
+ *
+ * 2. The sum of the amount of dirty data contained by both the mru and
+ * mfu lists, plus the ARC's other accounting (e.g. the anon list),
+ * is less than arc_c_min.
+ * (i.e. arc_c_min > amount of dirty data)
+ *
+ * 2.1. arc_size is greater than or equal arc_c_min.
+ * (i.e. arc_size >= arc_c_min > amount of dirty data)
+ *
+ * In this case, not all clean data from the regular mru and mfu
+ * lists is actually evictable; we must leave enough clean data
+ * to keep arc_size above arc_c_min. Thus, the maximum amount of
+ * evictable data from the two lists combined, is exactly the
+ * difference between arc_size and arc_c_min.
+ *
+ * 2.2. arc_size is less than arc_c_min
+ * (i.e. arc_c_min > arc_size > amount of dirty data)
+ *
+ * In this case, none of the data contained in the mru and mfu
+ * lists is evictable, even if it's clean. Since arc_size is
+ * already below arc_c_min, evicting any more would only
+ * increase this negative difference.
+ */
+static uint64_t
+arc_evictable_memory(void) {
+ uint64_t arc_clean =
+ arc_mru->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
+ arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
+ uint64_t ghost_clean =
+ arc_mru_ghost->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mru_ghost->arcs_lsize[ARC_BUFC_METADATA] +
+ arc_mfu_ghost->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mfu_ghost->arcs_lsize[ARC_BUFC_METADATA];
+ uint64_t arc_dirty = MAX((int64_t)arc_size - (int64_t)arc_clean, 0);
+
+ if (arc_dirty >= arc_c_min)
+ return (ghost_clean + arc_clean);
+
+ return (ghost_clean + MAX((int64_t)arc_size - (int64_t)arc_c_min, 0));
+}
+
+/*
+ * If sc->nr_to_scan is zero, the caller is requesting a query of the
+ * number of objects which can potentially be freed. If it is nonzero,
+ * the request is to free that many objects.
+ *
+ * Linux kernels >= 3.12 have the count_objects and scan_objects callbacks
+ * in struct shrinker and also require the shrinker to return the number
+ * of objects freed.
+ *
+ * Older kernels require the shrinker to return the number of freeable
+ * objects following the freeing of nr_to_free.
+ */
+static spl_shrinker_t
+__arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
+{
+ int64_t pages;
+
+ /* The arc is considered warm once reclaim has occurred */
+ if (unlikely(arc_warm == B_FALSE))
+ arc_warm = B_TRUE;
+
+ /* Return the potential number of reclaimable pages */
+ pages = btop((int64_t)arc_evictable_memory());
+ if (sc->nr_to_scan == 0)
+ return (pages);
+
+ /* Not allowed to perform filesystem reclaim */
+ if (!(sc->gfp_mask & __GFP_FS))
+ return (SHRINK_STOP);
+
+ /* Reclaim in progress */
+ if (mutex_tryenter(&arc_reclaim_lock) == 0)
+ return (SHRINK_STOP);
+
+ mutex_exit(&arc_reclaim_lock);
+
+ /*
+ * Evict the requested number of pages by shrinking arc_c the
+ * requested amount. If there is nothing left to evict just
+ * reap whatever we can from the various arc slabs.
+ */
+ if (pages > 0) {
+ arc_shrink(ptob(sc->nr_to_scan));
+ arc_kmem_reap_now();
+#ifdef HAVE_SPLIT_SHRINKER_CALLBACK
+ pages = MAX(pages - btop(arc_evictable_memory()), 0);
+#else
+ pages = btop(arc_evictable_memory());
+#endif
+ } else {
+ arc_kmem_reap_now();
+ pages = SHRINK_STOP;
+ }
+
+ /*
+ * We've reaped what we can, wake up threads.
+ */
+ cv_broadcast(&arc_reclaim_waiters_cv);
+
+ /*
+ * When direct reclaim is observed it usually indicates a rapid
+ * increase in memory pressure. This occurs because the kswapd
+ * threads were unable to asynchronously keep enough free memory
+ * available. In this case set arc_no_grow to briefly pause arc
+ * growth to avoid compounding the memory pressure.
+ */
+ if (current_is_kswapd()) {
+ ARCSTAT_BUMP(arcstat_memory_indirect_count);
+ } else {
+ arc_no_grow = B_TRUE;
+ arc_need_free = ptob(sc->nr_to_scan);
+ ARCSTAT_BUMP(arcstat_memory_direct_count);
+ }
+
+ return (pages);
+}
+SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func);
+
+SPL_SHRINKER_DECLARE(arc_shrinker, arc_shrinker_func, DEFAULT_SEEKS);
+#endif /* _KERNEL */
+
+/*
+ * Adapt arc info given the number of bytes we are trying to add and
+ * the state that we are comming from. This function is only called
+ * when we are adding new content to the cache.
+ */
+static void
+arc_adapt(int bytes, arc_state_t *state)
+{
+ int mult;
+ uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
+ int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
+ int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
+
+ if (state == arc_l2c_only)
+ return;
+
+ ASSERT(bytes > 0);
+ /*
+ * Adapt the target size of the MRU list:
+ * - if we just hit in the MRU ghost list, then increase
+ * the target size of the MRU list.
+ * - if we just hit in the MFU ghost list, then increase
+ * the target size of the MFU list by decreasing the
+ * target size of the MRU list.
+ */
+ if (state == arc_mru_ghost) {
+ mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
+ if (!zfs_arc_p_dampener_disable)
+ mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
+
+ arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
+ } else if (state == arc_mfu_ghost) {
+ uint64_t delta;
+
+ mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
+ if (!zfs_arc_p_dampener_disable)
+ mult = MIN(mult, 10);
+
+ delta = MIN(bytes * mult, arc_p);
+ arc_p = MAX(arc_p_min, arc_p - delta);
+ }
+ ASSERT((int64_t)arc_p >= 0);
+
+ if (arc_reclaim_needed()) {
+ cv_signal(&arc_reclaim_thread_cv);
+ return;
+ }
+
+ if (arc_no_grow)
+ return;
+
+ if (arc_c >= arc_c_max)
+ return;
+
+ /*
+ * If we're within (2 * maxblocksize) bytes of the target
+ * cache size, increment the target cache size
+ */
+ ASSERT3U(arc_c, >=, 2ULL << SPA_MAXBLOCKSHIFT);
+ if (arc_size >= arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
+ atomic_add_64(&arc_c, (int64_t)bytes);
+ if (arc_c > arc_c_max)
+ arc_c = arc_c_max;
+ else if (state == arc_anon)
+ atomic_add_64(&arc_p, (int64_t)bytes);
+ if (arc_p > arc_c)
+ arc_p = arc_c;
+ }
+ ASSERT((int64_t)arc_p >= 0);
+}
+
+/*
+ * Check if arc_size has grown past our upper threshold, determined by
+ * zfs_arc_overflow_shift.
+ */
+static boolean_t
+arc_is_overflowing(void)
+{
+ /* Always allow at least one block of overflow */
+ uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
+ arc_c >> zfs_arc_overflow_shift);
+
+ return (arc_size >= arc_c + overflow);
+}
+
+/*
+ * The buffer, supplied as the first argument, needs a data block. If we
+ * are hitting the hard limit for the cache size, we must sleep, waiting
+ * for the eviction thread to catch up. If we're past the target size
+ * but below the hard limit, we'll only signal the reclaim thread and
+ * continue on.
+ */
+static void
+arc_get_data_buf(arc_buf_t *buf)
+{
+ arc_state_t *state = buf->b_hdr->b_l1hdr.b_state;
+ uint64_t size = buf->b_hdr->b_size;
+ arc_buf_contents_t type = arc_buf_type(buf->b_hdr);
+
+ arc_adapt(size, state);
+
+ /*
+ * If arc_size is currently overflowing, and has grown past our
+ * upper limit, we must be adding data faster than the evict
+ * thread can evict. Thus, to ensure we don't compound the
+ * problem by adding more data and forcing arc_size to grow even
+ * further past it's target size, we halt and wait for the
+ * eviction thread to catch up.
+ *
+ * It's also possible that the reclaim thread is unable to evict
+ * enough buffers to get arc_size below the overflow limit (e.g.
+ * due to buffers being un-evictable, or hash lock collisions).
+ * In this case, we want to proceed regardless if we're
+ * overflowing; thus we don't use a while loop here.
+ */
+ if (arc_is_overflowing()) {
+ mutex_enter(&arc_reclaim_lock);
+
+ /*
+ * Now that we've acquired the lock, we may no longer be
+ * over the overflow limit, lets check.
+ *
+ * We're ignoring the case of spurious wake ups. If that
+ * were to happen, it'd let this thread consume an ARC
+ * buffer before it should have (i.e. before we're under
+ * the overflow limit and were signalled by the reclaim
+ * thread). As long as that is a rare occurrence, it
+ * shouldn't cause any harm.
+ */
+ if (arc_is_overflowing()) {
+ cv_signal(&arc_reclaim_thread_cv);
+ cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
+ }
+
+ mutex_exit(&arc_reclaim_lock);
+ }
+
+ if (type == ARC_BUFC_METADATA) {
+ buf->b_data = zio_buf_alloc(size);
+ arc_space_consume(size, ARC_SPACE_META);
+ } else {
+ ASSERT(type == ARC_BUFC_DATA);
+ buf->b_data = zio_data_buf_alloc(size);
+ arc_space_consume(size, ARC_SPACE_DATA);
+ }
+
+ /*
+ * Update the state size. Note that ghost states have a
+ * "ghost size" and so don't need to be updated.
+ */
+ if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) {
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ arc_state_t *state = hdr->b_l1hdr.b_state;
+
+ (void) refcount_add_many(&state->arcs_size, size, buf);
+
+ /*
+ * If this is reached via arc_read, the link is
+ * protected by the hash lock. If reached via
+ * arc_buf_alloc, the header should not be accessed by
+ * any other thread. And, if reached via arc_read_done,
+ * the hash lock will protect it if it's found in the
+ * hash table; otherwise no other thread should be
+ * trying to [add|remove]_reference it.
+ */
+ if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type],
+ size);
+ }
+ /*
+ * If we are growing the cache, and we are adding anonymous
+ * data, and we have outgrown arc_p, update arc_p
+ */
+ if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
+ (refcount_count(&arc_anon->arcs_size) +
+ refcount_count(&arc_mru->arcs_size) > arc_p))
+ arc_p = MIN(arc_c, arc_p + size);
+ }
+}
+
+/*
+ * This routine is called whenever a buffer is accessed.
+ * NOTE: the hash lock is dropped in this function.
+ */
+static void
+arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
+{
+ clock_t now;
+
+ ASSERT(MUTEX_HELD(hash_lock));
+ ASSERT(HDR_HAS_L1HDR(hdr));
+
+ if (hdr->b_l1hdr.b_state == arc_anon) {
+ /*
+ * This buffer is not in the cache, and does not
+ * appear in our "ghost" list. Add the new buffer
+ * to the MRU state.
+ */
+
+ ASSERT0(hdr->b_l1hdr.b_arc_access);
+ hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
+ DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
+ arc_change_state(arc_mru, hdr, hash_lock);
+
+ } else if (hdr->b_l1hdr.b_state == arc_mru) {
+ now = ddi_get_lbolt();
+
+ /*
+ * If this buffer is here because of a prefetch, then either:
+ * - clear the flag if this is a "referencing" read
+ * (any subsequent access will bump this into the MFU state).
+ * or
+ * - move the buffer to the head of the list if this is
+ * another prefetch (to make it less likely to be evicted).
+ */
+ if (HDR_PREFETCH(hdr)) {
+ if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
+ /* link protected by hash lock */
+ ASSERT(multilist_link_active(
+ &hdr->b_l1hdr.b_arc_node));
+ } else {
+ hdr->b_flags &= ~ARC_FLAG_PREFETCH;
+ atomic_inc_32(&hdr->b_l1hdr.b_mru_hits);
+ ARCSTAT_BUMP(arcstat_mru_hits);
+ }
+ hdr->b_l1hdr.b_arc_access = now;
+ return;
+ }
+
+ /*
+ * This buffer has been "accessed" only once so far,
+ * but it is still in the cache. Move it to the MFU
+ * state.
+ */
+ if (ddi_time_after(now, hdr->b_l1hdr.b_arc_access +
+ ARC_MINTIME)) {
+ /*
+ * More than 125ms have passed since we
+ * instantiated this buffer. Move it to the
+ * most frequently used state.
+ */
+ hdr->b_l1hdr.b_arc_access = now;
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+ arc_change_state(arc_mfu, hdr, hash_lock);
+ }
+ atomic_inc_32(&hdr->b_l1hdr.b_mru_hits);
+ ARCSTAT_BUMP(arcstat_mru_hits);
+ } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
+ arc_state_t *new_state;
+ /*
+ * This buffer has been "accessed" recently, but
+ * was evicted from the cache. Move it to the
+ * MFU state.
+ */
+
+ if (HDR_PREFETCH(hdr)) {
+ new_state = arc_mru;
+ if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
+ hdr->b_flags &= ~ARC_FLAG_PREFETCH;
+ DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
+ } else {
+ new_state = arc_mfu;
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+ }
+
+ hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
+ arc_change_state(new_state, hdr, hash_lock);
+
+ atomic_inc_32(&hdr->b_l1hdr.b_mru_ghost_hits);
+ ARCSTAT_BUMP(arcstat_mru_ghost_hits);
+ } else if (hdr->b_l1hdr.b_state == arc_mfu) {
+ /*
+ * This buffer has been accessed more than once and is
+ * still in the cache. Keep it in the MFU state.
+ *
+ * NOTE: an add_reference() that occurred when we did
+ * the arc_read() will have kicked this off the list.
+ * If it was a prefetch, we will explicitly move it to
+ * the head of the list now.
+ */
+ if ((HDR_PREFETCH(hdr)) != 0) {
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ /* link protected by hash_lock */
+ ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
+ }
+ atomic_inc_32(&hdr->b_l1hdr.b_mfu_hits);
+ ARCSTAT_BUMP(arcstat_mfu_hits);
+ hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
+ } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
+ arc_state_t *new_state = arc_mfu;
+ /*
+ * This buffer has been accessed more than once but has
+ * been evicted from the cache. Move it back to the
+ * MFU state.
+ */
+
+ if (HDR_PREFETCH(hdr)) {
+ /*
+ * This is a prefetch access...
+ * move this block back to the MRU state.
+ */
+ ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
+ new_state = arc_mru;
+ }
+
+ hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+ arc_change_state(new_state, hdr, hash_lock);
+
+ atomic_inc_32(&hdr->b_l1hdr.b_mfu_ghost_hits);
+ ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
+ } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
+ /*
+ * This buffer is on the 2nd Level ARC.
+ */
+
+ hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+ arc_change_state(arc_mfu, hdr, hash_lock);
+ } else {
+ cmn_err(CE_PANIC, "invalid arc state 0x%p",
+ hdr->b_l1hdr.b_state);
+ }
+}
+
+/* a generic arc_done_func_t which you can use */
+/* ARGSUSED */
+void
+arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
+{
+ if (zio == NULL || zio->io_error == 0)
+ bcopy(buf->b_data, arg, buf->b_hdr->b_size);
+ VERIFY(arc_buf_remove_ref(buf, arg));
+}
+
+/* a generic arc_done_func_t */
+void
+arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
+{
+ arc_buf_t **bufp = arg;
+ if (zio && zio->io_error) {
+ VERIFY(arc_buf_remove_ref(buf, arg));
+ *bufp = NULL;
+ } else {
+ *bufp = buf;
+ ASSERT(buf->b_data);
+ }
+}
+
+static void
+arc_read_done(zio_t *zio)
+{
+ arc_buf_hdr_t *hdr;
+ arc_buf_t *buf;
+ arc_buf_t *abuf; /* buffer we're assigning to callback */
+ kmutex_t *hash_lock = NULL;
+ arc_callback_t *callback_list, *acb;
+ int freeable = FALSE;
+
+ buf = zio->io_private;
+ hdr = buf->b_hdr;
+
+ /*
+ * The hdr was inserted into hash-table and removed from lists
+ * prior to starting I/O. We should find this header, since
+ * it's in the hash table, and it should be legit since it's
+ * not possible to evict it during the I/O. The only possible
+ * reason for it not to be found is if we were freed during the
+ * read.
+ */
+ if (HDR_IN_HASH_TABLE(hdr)) {
+ arc_buf_hdr_t *found;
+
+ ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
+ ASSERT3U(hdr->b_dva.dva_word[0], ==,
+ BP_IDENTITY(zio->io_bp)->dva_word[0]);
+ ASSERT3U(hdr->b_dva.dva_word[1], ==,
+ BP_IDENTITY(zio->io_bp)->dva_word[1]);
+
+ found = buf_hash_find(hdr->b_spa, zio->io_bp,
+ &hash_lock);
+
+ ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
+ hash_lock == NULL) ||
+ (found == hdr &&
+ DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
+ (found == hdr && HDR_L2_READING(hdr)));
+ }
+
+ hdr->b_flags &= ~ARC_FLAG_L2_EVICTED;
+ if (l2arc_noprefetch && HDR_PREFETCH(hdr))
+ hdr->b_flags &= ~ARC_FLAG_L2CACHE;
+
+ /* byteswap if necessary */
+ callback_list = hdr->b_l1hdr.b_acb;
+ ASSERT(callback_list != NULL);
+ if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
+ dmu_object_byteswap_t bswap =
+ DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
+ if (BP_GET_LEVEL(zio->io_bp) > 0)
+ byteswap_uint64_array(buf->b_data, hdr->b_size);
+ else
+ dmu_ot_byteswap[bswap].ob_func(buf->b_data, hdr->b_size);
+ }
+
+ arc_cksum_compute(buf, B_FALSE);
+ arc_buf_watch(buf);
+
+ if (hash_lock && zio->io_error == 0 &&
+ hdr->b_l1hdr.b_state == arc_anon) {
+ /*
+ * Only call arc_access on anonymous buffers. This is because
+ * if we've issued an I/O for an evicted buffer, we've already
+ * called arc_access (to prevent any simultaneous readers from
+ * getting confused).
+ */
+ arc_access(hdr, hash_lock);
+ }
+
+ /* create copies of the data buffer for the callers */
+ abuf = buf;
+ for (acb = callback_list; acb; acb = acb->acb_next) {
+ if (acb->acb_done) {
+ if (abuf == NULL) {
+ ARCSTAT_BUMP(arcstat_duplicate_reads);
+ abuf = arc_buf_clone(buf);
+ }
+ acb->acb_buf = abuf;
+ abuf = NULL;
+ }
+ }
+ hdr->b_l1hdr.b_acb = NULL;
+ hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
+ ASSERT(!HDR_BUF_AVAILABLE(hdr));
+ if (abuf == buf) {
+ ASSERT(buf->b_efunc == NULL);
+ ASSERT(hdr->b_l1hdr.b_datacnt == 1);
+ hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
+ }
+
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
+ callback_list != NULL);
+
+ if (zio->io_error != 0) {
+ hdr->b_flags |= ARC_FLAG_IO_ERROR;
+ if (hdr->b_l1hdr.b_state != arc_anon)
+ arc_change_state(arc_anon, hdr, hash_lock);
+ if (HDR_IN_HASH_TABLE(hdr))
+ buf_hash_remove(hdr);
+ freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
+ }
+
+ /*
+ * Broadcast before we drop the hash_lock to avoid the possibility
+ * that the hdr (and hence the cv) might be freed before we get to
+ * the cv_broadcast().
+ */
+ cv_broadcast(&hdr->b_l1hdr.b_cv);
+
+ if (hash_lock != NULL) {
+ mutex_exit(hash_lock);
+ } else {
+ /*
+ * This block was freed while we waited for the read to
+ * complete. It has been removed from the hash table and
+ * moved to the anonymous state (so that it won't show up
+ * in the cache).
+ */
+ ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
+ freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
+ }
+
+ /* execute each callback and free its structure */
+ while ((acb = callback_list) != NULL) {
+ if (acb->acb_done)
+ acb->acb_done(zio, acb->acb_buf, acb->acb_private);
+
+ if (acb->acb_zio_dummy != NULL) {
+ acb->acb_zio_dummy->io_error = zio->io_error;
+ zio_nowait(acb->acb_zio_dummy);
+ }
+
+ callback_list = acb->acb_next;
+ kmem_free(acb, sizeof (arc_callback_t));
+ }
+
+ if (freeable)
+ arc_hdr_destroy(hdr);
+}
+
+/*
+ * "Read" the block at the specified DVA (in bp) via the
+ * cache. If the block is found in the cache, invoke the provided
+ * callback immediately and return. Note that the `zio' parameter
+ * in the callback will be NULL in this case, since no IO was
+ * required. If the block is not in the cache pass the read request
+ * on to the spa with a substitute callback function, so that the
+ * requested block will be added to the cache.
+ *
+ * If a read request arrives for a block that has a read in-progress,
+ * either wait for the in-progress read to complete (and return the
+ * results); or, if this is a read with a "done" func, add a record
+ * to the read to invoke the "done" func when the read completes,
+ * and return; or just return.
+ *
+ * arc_read_done() will invoke all the requested "done" functions
+ * for readers of this block.
+ */
+int
+arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
+ void *private, zio_priority_t priority, int zio_flags,
+ arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
+{
+ arc_buf_hdr_t *hdr = NULL;
+ arc_buf_t *buf = NULL;
+ kmutex_t *hash_lock = NULL;
+ zio_t *rzio;
+ uint64_t guid = spa_load_guid(spa);
+ int rc = 0;
+
+ ASSERT(!BP_IS_EMBEDDED(bp) ||
+ BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
+
+top:
+ if (!BP_IS_EMBEDDED(bp)) {
+ /*
+ * Embedded BP's have no DVA and require no I/O to "read".
+ * Create an anonymous arc buf to back it.
+ */
+ hdr = buf_hash_find(guid, bp, &hash_lock);
+ }
+
+ if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) {
+
+ *arc_flags |= ARC_FLAG_CACHED;
+
+ if (HDR_IO_IN_PROGRESS(hdr)) {
+
+ if (*arc_flags & ARC_FLAG_WAIT) {
+ cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
+ mutex_exit(hash_lock);
+ goto top;
+ }
+ ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
+
+ if (done) {
+ arc_callback_t *acb = NULL;
+
+ acb = kmem_zalloc(sizeof (arc_callback_t),
+ KM_SLEEP);
+ acb->acb_done = done;
+ acb->acb_private = private;
+ if (pio != NULL)
+ acb->acb_zio_dummy = zio_null(pio,
+ spa, NULL, NULL, NULL, zio_flags);
+
+ ASSERT(acb->acb_done != NULL);
+ acb->acb_next = hdr->b_l1hdr.b_acb;
+ hdr->b_l1hdr.b_acb = acb;
+ add_reference(hdr, hash_lock, private);
+ mutex_exit(hash_lock);
+ goto out;
+ }
+ mutex_exit(hash_lock);
+ goto out;
+ }
+
+ ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
+ hdr->b_l1hdr.b_state == arc_mfu);
+
+ if (done) {
+ add_reference(hdr, hash_lock, private);
+ /*
+ * If this block is already in use, create a new
+ * copy of the data so that we will be guaranteed
+ * that arc_release() will always succeed.
+ */
+ buf = hdr->b_l1hdr.b_buf;
+ ASSERT(buf);
+ ASSERT(buf->b_data);
+ if (HDR_BUF_AVAILABLE(hdr)) {
+ ASSERT(buf->b_efunc == NULL);
+ hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
+ } else {
+ buf = arc_buf_clone(buf);
+ }
+
+ } else if (*arc_flags & ARC_FLAG_PREFETCH &&
+ refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
+ hdr->b_flags |= ARC_FLAG_PREFETCH;
+ }
+ DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
+ arc_access(hdr, hash_lock);
+ if (*arc_flags & ARC_FLAG_L2CACHE)
+ hdr->b_flags |= ARC_FLAG_L2CACHE;
+ if (*arc_flags & ARC_FLAG_L2COMPRESS)
+ hdr->b_flags |= ARC_FLAG_L2COMPRESS;
+ mutex_exit(hash_lock);
+ ARCSTAT_BUMP(arcstat_hits);
+ ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
+ demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
+ data, metadata, hits);
+
+ if (done)
+ done(NULL, buf, private);
+ } else {
+ uint64_t size = BP_GET_LSIZE(bp);
+ arc_callback_t *acb;
+ vdev_t *vd = NULL;
+ uint64_t addr = 0;
+ boolean_t devw = B_FALSE;
+ enum zio_compress b_compress = ZIO_COMPRESS_OFF;
+ int32_t b_asize = 0;
+
+ /*
+ * Gracefully handle a damaged logical block size as a
+ * checksum error.
+ */
+ if (size > spa_maxblocksize(spa)) {
+ ASSERT3P(buf, ==, NULL);
+ rc = SET_ERROR(ECKSUM);
+ goto out;
+ }
+
+ if (hdr == NULL) {
+ /* this block is not in the cache */
+ arc_buf_hdr_t *exists = NULL;
+ arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
+ buf = arc_buf_alloc(spa, size, private, type);
+ hdr = buf->b_hdr;
+ if (!BP_IS_EMBEDDED(bp)) {
+ hdr->b_dva = *BP_IDENTITY(bp);
+ hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
+ exists = buf_hash_insert(hdr, &hash_lock);
+ }
+ if (exists != NULL) {
+ /* somebody beat us to the hash insert */
+ mutex_exit(hash_lock);
+ buf_discard_identity(hdr);
+ (void) arc_buf_remove_ref(buf, private);
+ goto top; /* restart the IO request */
+ }
+
+ /* if this is a prefetch, we don't have a reference */
+ if (*arc_flags & ARC_FLAG_PREFETCH) {
+ (void) remove_reference(hdr, hash_lock,
+ private);
+ hdr->b_flags |= ARC_FLAG_PREFETCH;
+ }
+ if (*arc_flags & ARC_FLAG_L2CACHE)
+ hdr->b_flags |= ARC_FLAG_L2CACHE;
+ if (*arc_flags & ARC_FLAG_L2COMPRESS)
+ hdr->b_flags |= ARC_FLAG_L2COMPRESS;
+ if (BP_GET_LEVEL(bp) > 0)
+ hdr->b_flags |= ARC_FLAG_INDIRECT;
+ } else {
+ /*
+ * This block is in the ghost cache. If it was L2-only
+ * (and thus didn't have an L1 hdr), we realloc the
+ * header to add an L1 hdr.
+ */
+ if (!HDR_HAS_L1HDR(hdr)) {
+ hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
+ hdr_full_cache);
+ }
+
+ ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
+
+ /* if this is a prefetch, we don't have a reference */
+ if (*arc_flags & ARC_FLAG_PREFETCH)
+ hdr->b_flags |= ARC_FLAG_PREFETCH;
+ else
+ add_reference(hdr, hash_lock, private);
+ if (*arc_flags & ARC_FLAG_L2CACHE)
+ hdr->b_flags |= ARC_FLAG_L2CACHE;
+ if (*arc_flags & ARC_FLAG_L2COMPRESS)
+ hdr->b_flags |= ARC_FLAG_L2COMPRESS;
+ buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
+ buf->b_hdr = hdr;
+ buf->b_data = NULL;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_next = NULL;
+ hdr->b_l1hdr.b_buf = buf;
+ ASSERT0(hdr->b_l1hdr.b_datacnt);
+ hdr->b_l1hdr.b_datacnt = 1;
+ arc_get_data_buf(buf);
+ arc_access(hdr, hash_lock);
+ }
+
+ ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
+
+ acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
+ acb->acb_done = done;
+ acb->acb_private = private;
+
+ ASSERT(hdr->b_l1hdr.b_acb == NULL);
+ hdr->b_l1hdr.b_acb = acb;
+ hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
+
+ if (HDR_HAS_L2HDR(hdr) &&
+ (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
+ devw = hdr->b_l2hdr.b_dev->l2ad_writing;
+ addr = hdr->b_l2hdr.b_daddr;
+ b_compress = hdr->b_l2hdr.b_compress;
+ b_asize = hdr->b_l2hdr.b_asize;
+ /*
+ * Lock out device removal.
+ */
+ if (vdev_is_dead(vd) ||
+ !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
+ vd = NULL;
+ }
+
+ if (hash_lock != NULL)
+ mutex_exit(hash_lock);
+
+ /*
+ * At this point, we have a level 1 cache miss. Try again in
+ * L2ARC if possible.
+ */
+ ASSERT3U(hdr->b_size, ==, size);
+ DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
+ uint64_t, size, zbookmark_phys_t *, zb);
+ ARCSTAT_BUMP(arcstat_misses);
+ ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
+ demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
+ data, metadata, misses);
+
+ if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
+ /*
+ * Read from the L2ARC if the following are true:
+ * 1. The L2ARC vdev was previously cached.
+ * 2. This buffer still has L2ARC metadata.
+ * 3. This buffer isn't currently writing to the L2ARC.
+ * 4. The L2ARC entry wasn't evicted, which may
+ * also have invalidated the vdev.
+ * 5. This isn't prefetch and l2arc_noprefetch is set.
+ */
+ if (HDR_HAS_L2HDR(hdr) &&
+ !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
+ !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
+ l2arc_read_callback_t *cb;
+
+ DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_l2_hits);
+ atomic_inc_32(&hdr->b_l2hdr.b_hits);
+
+ cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
+ KM_SLEEP);
+ cb->l2rcb_buf = buf;
+ cb->l2rcb_spa = spa;
+ cb->l2rcb_bp = *bp;
+ cb->l2rcb_zb = *zb;
+ cb->l2rcb_flags = zio_flags;
+ cb->l2rcb_compress = b_compress;
+
+ ASSERT(addr >= VDEV_LABEL_START_SIZE &&
+ addr + size < vd->vdev_psize -
+ VDEV_LABEL_END_SIZE);
+
+ /*
+ * l2arc read. The SCL_L2ARC lock will be
+ * released by l2arc_read_done().
+ * Issue a null zio if the underlying buffer
+ * was squashed to zero size by compression.
+ */
+ if (b_compress == ZIO_COMPRESS_EMPTY) {
+ rzio = zio_null(pio, spa, vd,
+ l2arc_read_done, cb,
+ zio_flags | ZIO_FLAG_DONT_CACHE |
+ ZIO_FLAG_CANFAIL |
+ ZIO_FLAG_DONT_PROPAGATE |
+ ZIO_FLAG_DONT_RETRY);
+ } else {
+ rzio = zio_read_phys(pio, vd, addr,
+ b_asize, buf->b_data,
+ ZIO_CHECKSUM_OFF,
+ l2arc_read_done, cb, priority,
+ zio_flags | ZIO_FLAG_DONT_CACHE |
+ ZIO_FLAG_CANFAIL |
+ ZIO_FLAG_DONT_PROPAGATE |
+ ZIO_FLAG_DONT_RETRY, B_FALSE);
+ }
+ DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
+ zio_t *, rzio);
+ ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
+
+ if (*arc_flags & ARC_FLAG_NOWAIT) {
+ zio_nowait(rzio);
+ goto out;
+ }
+
+ ASSERT(*arc_flags & ARC_FLAG_WAIT);
+ if (zio_wait(rzio) == 0)
+ goto out;
+
+ /* l2arc read error; goto zio_read() */
+ } else {
+ DTRACE_PROBE1(l2arc__miss,
+ arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_l2_misses);
+ if (HDR_L2_WRITING(hdr))
+ ARCSTAT_BUMP(arcstat_l2_rw_clash);
+ spa_config_exit(spa, SCL_L2ARC, vd);
+ }
+ } else {
+ if (vd != NULL)
+ spa_config_exit(spa, SCL_L2ARC, vd);
+ if (l2arc_ndev != 0) {
+ DTRACE_PROBE1(l2arc__miss,
+ arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_l2_misses);
+ }
+ }
+
+ rzio = zio_read(pio, spa, bp, buf->b_data, size,
+ arc_read_done, buf, priority, zio_flags, zb);
+
+ if (*arc_flags & ARC_FLAG_WAIT) {
+ rc = zio_wait(rzio);
+ goto out;
+ }
+
+ ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
+ zio_nowait(rzio);
+ }
+
+out:
+ spa_read_history_add(spa, zb, *arc_flags);
+ return (rc);
+}
+
+arc_prune_t *
+arc_add_prune_callback(arc_prune_func_t *func, void *private)
+{
+ arc_prune_t *p;
+
+ p = kmem_alloc(sizeof (*p), KM_SLEEP);
+ p->p_pfunc = func;
+ p->p_private = private;
+ list_link_init(&p->p_node);
+ refcount_create(&p->p_refcnt);
+
+ mutex_enter(&arc_prune_mtx);
+ refcount_add(&p->p_refcnt, &arc_prune_list);
+ list_insert_head(&arc_prune_list, p);
+ mutex_exit(&arc_prune_mtx);
+
+ return (p);
+}
+
+void
+arc_remove_prune_callback(arc_prune_t *p)
+{
+ boolean_t wait = B_FALSE;
+ mutex_enter(&arc_prune_mtx);
+ list_remove(&arc_prune_list, p);
+ if (refcount_remove(&p->p_refcnt, &arc_prune_list) > 0)
+ wait = B_TRUE;
+ mutex_exit(&arc_prune_mtx);
+
+ /* wait for arc_prune_task to finish */
+ if (wait)
+ taskq_wait_outstanding(arc_prune_taskq, 0);
+ ASSERT0(refcount_count(&p->p_refcnt));
+ refcount_destroy(&p->p_refcnt);
+ kmem_free(p, sizeof (*p));
+}
+
+void
+arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
+{
+ ASSERT(buf->b_hdr != NULL);
+ ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon);
+ ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) ||
+ func == NULL);
+ ASSERT(buf->b_efunc == NULL);
+ ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
+
+ buf->b_efunc = func;
+ buf->b_private = private;
+}
+
+/*
+ * Notify the arc that a block was freed, and thus will never be used again.
+ */
+void
+arc_freed(spa_t *spa, const blkptr_t *bp)
+{
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock;
+ uint64_t guid = spa_load_guid(spa);
+
+ ASSERT(!BP_IS_EMBEDDED(bp));
+
+ hdr = buf_hash_find(guid, bp, &hash_lock);
+ if (hdr == NULL)
+ return;
+ if (HDR_BUF_AVAILABLE(hdr)) {
+ arc_buf_t *buf = hdr->b_l1hdr.b_buf;
+ add_reference(hdr, hash_lock, FTAG);
+ hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
+ mutex_exit(hash_lock);
+
+ arc_release(buf, FTAG);
+ (void) arc_buf_remove_ref(buf, FTAG);
+ } else {
+ mutex_exit(hash_lock);
+ }
+
+}
+
+/*
+ * Clear the user eviction callback set by arc_set_callback(), first calling
+ * it if it exists. Because the presence of a callback keeps an arc_buf cached
+ * clearing the callback may result in the arc_buf being destroyed. However,
+ * it will not result in the *last* arc_buf being destroyed, hence the data
+ * will remain cached in the ARC. We make a copy of the arc buffer here so
+ * that we can process the callback without holding any locks.
+ *
+ * It's possible that the callback is already in the process of being cleared
+ * by another thread. In this case we can not clear the callback.
+ *
+ * Returns B_TRUE if the callback was successfully called and cleared.
+ */
+boolean_t
+arc_clear_callback(arc_buf_t *buf)
+{
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock;
+ arc_evict_func_t *efunc = buf->b_efunc;
+ void *private = buf->b_private;
+
+ mutex_enter(&buf->b_evict_lock);
+ hdr = buf->b_hdr;
+ if (hdr == NULL) {
+ /*
+ * We are in arc_do_user_evicts().
+ */
+ ASSERT(buf->b_data == NULL);
+ mutex_exit(&buf->b_evict_lock);
+ return (B_FALSE);
+ } else if (buf->b_data == NULL) {
+ /*
+ * We are on the eviction list; process this buffer now
+ * but let arc_do_user_evicts() do the reaping.
+ */
+ buf->b_efunc = NULL;
+ mutex_exit(&buf->b_evict_lock);
+ VERIFY0(efunc(private));
+ return (B_TRUE);
+ }
+ hash_lock = HDR_LOCK(hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+
+ ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <,
+ hdr->b_l1hdr.b_datacnt);
+ ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
+ hdr->b_l1hdr.b_state == arc_mfu);
+
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+
+ if (hdr->b_l1hdr.b_datacnt > 1) {
+ mutex_exit(&buf->b_evict_lock);
+ arc_buf_destroy(buf, TRUE);
+ } else {
+ ASSERT(buf == hdr->b_l1hdr.b_buf);
+ hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
+ mutex_exit(&buf->b_evict_lock);
+ }
+
+ mutex_exit(hash_lock);
+ VERIFY0(efunc(private));
+ return (B_TRUE);
+}
+
+/*
+ * Release this buffer from the cache, making it an anonymous buffer. This
+ * must be done after a read and prior to modifying the buffer contents.
+ * If the buffer has more than one reference, we must make
+ * a new hdr for the buffer.
+ */
+void
+arc_release(arc_buf_t *buf, void *tag)
+{
+ kmutex_t *hash_lock;
+ arc_state_t *state;
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ /*
+ * It would be nice to assert that if its DMU metadata (level >
+ * 0 || it's the dnode file), then it must be syncing context.
+ * But we don't know that information at this level.
+ */
+
+ mutex_enter(&buf->b_evict_lock);
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+
+ /*
+ * We don't grab the hash lock prior to this check, because if
+ * the buffer's header is in the arc_anon state, it won't be
+ * linked into the hash table.
+ */
+ if (hdr->b_l1hdr.b_state == arc_anon) {
+ mutex_exit(&buf->b_evict_lock);
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ ASSERT(!HDR_IN_HASH_TABLE(hdr));
+ ASSERT(!HDR_HAS_L2HDR(hdr));
+ ASSERT(BUF_EMPTY(hdr));
+
+ ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1);
+ ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
+ ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
+
+ ASSERT3P(buf->b_efunc, ==, NULL);
+ ASSERT3P(buf->b_private, ==, NULL);
+
+ hdr->b_l1hdr.b_arc_access = 0;
+ arc_buf_thaw(buf);
+
+ return;
+ }
+
+ hash_lock = HDR_LOCK(hdr);
+ mutex_enter(hash_lock);
+
+ /*
+ * This assignment is only valid as long as the hash_lock is
+ * held, we must be careful not to reference state or the
+ * b_state field after dropping the lock.
+ */
+ state = hdr->b_l1hdr.b_state;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+ ASSERT3P(state, !=, arc_anon);
+
+ /* this buffer is not on any list */
+ ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0);
+
+ if (HDR_HAS_L2HDR(hdr)) {
+ mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
+
+ /*
+ * We have to recheck this conditional again now that
+ * we're holding the l2ad_mtx to prevent a race with
+ * another thread which might be concurrently calling
+ * l2arc_evict(). In that case, l2arc_evict() might have
+ * destroyed the header's L2 portion as we were waiting
+ * to acquire the l2ad_mtx.
+ */
+ if (HDR_HAS_L2HDR(hdr))
+ arc_hdr_l2hdr_destroy(hdr);
+
+ mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
+ }
+
+ /*
+ * Do we have more than one buf?
+ */
+ if (hdr->b_l1hdr.b_datacnt > 1) {
+ arc_buf_hdr_t *nhdr;
+ arc_buf_t **bufp;
+ uint64_t blksz = hdr->b_size;
+ uint64_t spa = hdr->b_spa;
+ arc_buf_contents_t type = arc_buf_type(hdr);
+ uint32_t flags = hdr->b_flags;
+
+ ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
+ /*
+ * Pull the data off of this hdr and attach it to
+ * a new anonymous hdr.
+ */
+ (void) remove_reference(hdr, hash_lock, tag);
+ bufp = &hdr->b_l1hdr.b_buf;
+ while (*bufp != buf)
+ bufp = &(*bufp)->b_next;
+ *bufp = buf->b_next;
+ buf->b_next = NULL;
+
+ ASSERT3P(state, !=, arc_l2c_only);
+
+ (void) refcount_remove_many(
+ &state->arcs_size, hdr->b_size, buf);
+
+ if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
+ uint64_t *size;
+
+ ASSERT3P(state, !=, arc_l2c_only);
+ size = &state->arcs_lsize[type];
+ ASSERT3U(*size, >=, hdr->b_size);
+ atomic_add_64(size, -hdr->b_size);
+ }
+
+ /*
+ * We're releasing a duplicate user data buffer, update
+ * our statistics accordingly.
+ */
+ if (HDR_ISTYPE_DATA(hdr)) {
+ ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
+ ARCSTAT_INCR(arcstat_duplicate_buffers_size,
+ -hdr->b_size);
+ }
+ hdr->b_l1hdr.b_datacnt -= 1;
+ arc_cksum_verify(buf);
+ arc_buf_unwatch(buf);
+
+ mutex_exit(hash_lock);
+
+ nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
+ nhdr->b_size = blksz;
+ nhdr->b_spa = spa;
+
+ nhdr->b_l1hdr.b_mru_hits = 0;
+ nhdr->b_l1hdr.b_mru_ghost_hits = 0;
+ nhdr->b_l1hdr.b_mfu_hits = 0;
+ nhdr->b_l1hdr.b_mfu_ghost_hits = 0;
+ nhdr->b_l1hdr.b_l2_hits = 0;
+ nhdr->b_flags = flags & ARC_FLAG_L2_WRITING;
+ nhdr->b_flags |= arc_bufc_to_flags(type);
+ nhdr->b_flags |= ARC_FLAG_HAS_L1HDR;
+
+ nhdr->b_l1hdr.b_buf = buf;
+ nhdr->b_l1hdr.b_datacnt = 1;
+ nhdr->b_l1hdr.b_state = arc_anon;
+ nhdr->b_l1hdr.b_arc_access = 0;
+ nhdr->b_l1hdr.b_tmp_cdata = NULL;
+ nhdr->b_freeze_cksum = NULL;
+
+ (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
+ buf->b_hdr = nhdr;
+ mutex_exit(&buf->b_evict_lock);
+ (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf);
+ } else {
+ mutex_exit(&buf->b_evict_lock);
+ ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
+ /* protected by hash lock, or hdr is on arc_anon */
+ ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ hdr->b_l1hdr.b_mru_hits = 0;
+ hdr->b_l1hdr.b_mru_ghost_hits = 0;
+ hdr->b_l1hdr.b_mfu_hits = 0;
+ hdr->b_l1hdr.b_mfu_ghost_hits = 0;
+ hdr->b_l1hdr.b_l2_hits = 0;
+ arc_change_state(arc_anon, hdr, hash_lock);
+ hdr->b_l1hdr.b_arc_access = 0;
+ mutex_exit(hash_lock);
+
+ buf_discard_identity(hdr);
+ arc_buf_thaw(buf);
+ }
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+}
+
+int
+arc_released(arc_buf_t *buf)
+{
+ int released;
+
+ mutex_enter(&buf->b_evict_lock);
+ released = (buf->b_data != NULL &&
+ buf->b_hdr->b_l1hdr.b_state == arc_anon);
+ mutex_exit(&buf->b_evict_lock);
+ return (released);
+}
+
+#ifdef ZFS_DEBUG
+int
+arc_referenced(arc_buf_t *buf)
+{
+ int referenced;
+
+ mutex_enter(&buf->b_evict_lock);
+ referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
+ mutex_exit(&buf->b_evict_lock);
+ return (referenced);
+}
+#endif
+
+static void
+arc_write_ready(zio_t *zio)
+{
+ arc_write_callback_t *callback = zio->io_private;
+ arc_buf_t *buf = callback->awcb_buf;
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
+ ASSERT(hdr->b_l1hdr.b_datacnt > 0);
+ callback->awcb_ready(zio, buf, callback->awcb_private);
+
+ /*
+ * If the IO is already in progress, then this is a re-write
+ * attempt, so we need to thaw and re-compute the cksum.
+ * It is the responsibility of the callback to handle the
+ * accounting for any re-write attempt.
+ */
+ if (HDR_IO_IN_PROGRESS(hdr)) {
+ mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
+ if (hdr->b_freeze_cksum != NULL) {
+ kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
+ hdr->b_freeze_cksum = NULL;
+ }
+ mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
+ }
+ arc_cksum_compute(buf, B_FALSE);
+ hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
+}
+
+/*
+ * The SPA calls this callback for each physical write that happens on behalf
+ * of a logical write. See the comment in dbuf_write_physdone() for details.
+ */
+static void
+arc_write_physdone(zio_t *zio)
+{
+ arc_write_callback_t *cb = zio->io_private;
+ if (cb->awcb_physdone != NULL)
+ cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
+}
+
+static void
+arc_write_done(zio_t *zio)
+{
+ arc_write_callback_t *callback = zio->io_private;
+ arc_buf_t *buf = callback->awcb_buf;
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(hdr->b_l1hdr.b_acb == NULL);
+
+ if (zio->io_error == 0) {
+ if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
+ buf_discard_identity(hdr);
+ } else {
+ hdr->b_dva = *BP_IDENTITY(zio->io_bp);
+ hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
+ }
+ } else {
+ ASSERT(BUF_EMPTY(hdr));
+ }
+
+ /*
+ * If the block to be written was all-zero or compressed enough to be
+ * embedded in the BP, no write was performed so there will be no
+ * dva/birth/checksum. The buffer must therefore remain anonymous
+ * (and uncached).
+ */
+ if (!BUF_EMPTY(hdr)) {
+ arc_buf_hdr_t *exists;
+ kmutex_t *hash_lock;
+
+ ASSERT(zio->io_error == 0);
+
+ arc_cksum_verify(buf);
+
+ exists = buf_hash_insert(hdr, &hash_lock);
+ if (exists != NULL) {
+ /*
+ * This can only happen if we overwrite for
+ * sync-to-convergence, because we remove
+ * buffers from the hash table when we arc_free().
+ */
+ if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
+ if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
+ panic("bad overwrite, hdr=%p exists=%p",
+ (void *)hdr, (void *)exists);
+ ASSERT(refcount_is_zero(
+ &exists->b_l1hdr.b_refcnt));
+ arc_change_state(arc_anon, exists, hash_lock);
+ mutex_exit(hash_lock);
+ arc_hdr_destroy(exists);
+ exists = buf_hash_insert(hdr, &hash_lock);
+ ASSERT3P(exists, ==, NULL);
+ } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
+ /* nopwrite */
+ ASSERT(zio->io_prop.zp_nopwrite);
+ if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
+ panic("bad nopwrite, hdr=%p exists=%p",
+ (void *)hdr, (void *)exists);
+ } else {
+ /* Dedup */
+ ASSERT(hdr->b_l1hdr.b_datacnt == 1);
+ ASSERT(hdr->b_l1hdr.b_state == arc_anon);
+ ASSERT(BP_GET_DEDUP(zio->io_bp));
+ ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
+ }
+ }
+ hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
+ /* if it's not anon, we are doing a scrub */
+ if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
+ arc_access(hdr, hash_lock);
+ mutex_exit(hash_lock);
+ } else {
+ hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
+ }
+
+ ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
+ callback->awcb_done(zio, buf, callback->awcb_private);
+
+ kmem_free(callback, sizeof (arc_write_callback_t));
+}
+
+zio_t *
+arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
+ blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
+ const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
+ arc_done_func_t *done, void *private, zio_priority_t priority,
+ int zio_flags, const zbookmark_phys_t *zb)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ arc_write_callback_t *callback;
+ zio_t *zio;
+
+ ASSERT(ready != NULL);
+ ASSERT(done != NULL);
+ ASSERT(!HDR_IO_ERROR(hdr));
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ ASSERT(hdr->b_l1hdr.b_acb == NULL);
+ ASSERT(hdr->b_l1hdr.b_datacnt > 0);
+ if (l2arc)
+ hdr->b_flags |= ARC_FLAG_L2CACHE;
+ if (l2arc_compress)
+ hdr->b_flags |= ARC_FLAG_L2COMPRESS;
+ callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
+ callback->awcb_ready = ready;
+ callback->awcb_physdone = physdone;
+ callback->awcb_done = done;
+ callback->awcb_private = private;
+ callback->awcb_buf = buf;
+
+ zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
+ arc_write_ready, arc_write_physdone, arc_write_done, callback,
+ priority, zio_flags, zb);
+
+ return (zio);
+}
+
+static int
+arc_memory_throttle(uint64_t reserve, uint64_t txg)
+{
+#ifdef _KERNEL
+ uint64_t available_memory = ptob(freemem);
+ static uint64_t page_load = 0;
+ static uint64_t last_txg = 0;
+#ifdef __linux__
+ pgcnt_t minfree = btop(arc_sys_free / 4);
+#endif
+
+ if (freemem > physmem * arc_lotsfree_percent / 100)
+ return (0);
+
+ if (txg > last_txg) {
+ last_txg = txg;
+ page_load = 0;
+ }
+
+ /*
+ * If we are in pageout, we know that memory is already tight,
+ * the arc is already going to be evicting, so we just want to
+ * continue to let page writes occur as quickly as possible.
+ */
+ if (current_is_kswapd()) {
+ if (page_load > MAX(ptob(minfree), available_memory) / 4) {
+ DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
+ return (SET_ERROR(ERESTART));
+ }
+ /* Note: reserve is inflated, so we deflate */
+ page_load += reserve / 8;
+ return (0);
+ } else if (page_load > 0 && arc_reclaim_needed()) {
+ /* memory is low, delay before restarting */
+ ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
+ DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
+ return (SET_ERROR(EAGAIN));
+ }
+ page_load = 0;
+#endif
+ return (0);
+}
+
+void
+arc_tempreserve_clear(uint64_t reserve)
+{
+ atomic_add_64(&arc_tempreserve, -reserve);
+ ASSERT((int64_t)arc_tempreserve >= 0);
+}
+
+int
+arc_tempreserve_space(uint64_t reserve, uint64_t txg)
+{
+ int error;
+ uint64_t anon_size;
+
+ if (!arc_no_grow &&
+ reserve > arc_c/4 &&
+ reserve * 4 > (2ULL << SPA_MAXBLOCKSHIFT))
+ arc_c = MIN(arc_c_max, reserve * 4);
+
+ /*
+ * Throttle when the calculated memory footprint for the TXG
+ * exceeds the target ARC size.
+ */
+ if (reserve > arc_c) {
+ DMU_TX_STAT_BUMP(dmu_tx_memory_reserve);
+ return (SET_ERROR(ERESTART));
+ }
+
+ /*
+ * Don't count loaned bufs as in flight dirty data to prevent long
+ * network delays from blocking transactions that are ready to be
+ * assigned to a txg.
+ */
+ anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
+ arc_loaned_bytes), 0);
+
+ /*
+ * Writes will, almost always, require additional memory allocations
+ * in order to compress/encrypt/etc the data. We therefore need to
+ * make sure that there is sufficient available memory for this.
+ */
+ error = arc_memory_throttle(reserve, txg);
+ if (error != 0)
+ return (error);
+
+ /*
+ * Throttle writes when the amount of dirty data in the cache
+ * gets too large. We try to keep the cache less than half full
+ * of dirty blocks so that our sync times don't grow too large.
+ * Note: if two requests come in concurrently, we might let them
+ * both succeed, when one of them should fail. Not a huge deal.
+ */
+
+ if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
+ anon_size > arc_c / 4) {
+ dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
+ "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
+ arc_tempreserve>>10,
+ arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
+ arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
+ reserve>>10, arc_c>>10);
+ DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle);
+ return (SET_ERROR(ERESTART));
+ }
+ atomic_add_64(&arc_tempreserve, reserve);
+ return (0);
+}
+
+static void
+arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
+ kstat_named_t *evict_data, kstat_named_t *evict_metadata)
+{
+ size->value.ui64 = refcount_count(&state->arcs_size);
+ evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA];
+ evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA];
+}
+
+static int
+arc_kstat_update(kstat_t *ksp, int rw)
+{
+ arc_stats_t *as = ksp->ks_data;
+
+ if (rw == KSTAT_WRITE) {
+ return (EACCES);
+ } else {
+ arc_kstat_update_state(arc_anon,
+ &as->arcstat_anon_size,
+ &as->arcstat_anon_evictable_data,
+ &as->arcstat_anon_evictable_metadata);
+ arc_kstat_update_state(arc_mru,
+ &as->arcstat_mru_size,
+ &as->arcstat_mru_evictable_data,
+ &as->arcstat_mru_evictable_metadata);
+ arc_kstat_update_state(arc_mru_ghost,
+ &as->arcstat_mru_ghost_size,
+ &as->arcstat_mru_ghost_evictable_data,
+ &as->arcstat_mru_ghost_evictable_metadata);
+ arc_kstat_update_state(arc_mfu,
+ &as->arcstat_mfu_size,
+ &as->arcstat_mfu_evictable_data,
+ &as->arcstat_mfu_evictable_metadata);
+ arc_kstat_update_state(arc_mfu_ghost,
+ &as->arcstat_mfu_ghost_size,
+ &as->arcstat_mfu_ghost_evictable_data,
+ &as->arcstat_mfu_ghost_evictable_metadata);
+ }
+
+ return (0);
+}
+
+/*
+ * This function *must* return indices evenly distributed between all
+ * sublists of the multilist. This is needed due to how the ARC eviction
+ * code is laid out; arc_evict_state() assumes ARC buffers are evenly
+ * distributed between all sublists and uses this assumption when
+ * deciding which sublist to evict from and how much to evict from it.
+ */
+unsigned int
+arc_state_multilist_index_func(multilist_t *ml, void *obj)
+{
+ arc_buf_hdr_t *hdr = obj;
+
+ /*
+ * We rely on b_dva to generate evenly distributed index
+ * numbers using buf_hash below. So, as an added precaution,
+ * let's make sure we never add empty buffers to the arc lists.
+ */
+ ASSERT(!BUF_EMPTY(hdr));
+
+ /*
+ * The assumption here, is the hash value for a given
+ * arc_buf_hdr_t will remain constant throughout its lifetime
+ * (i.e. its b_spa, b_dva, and b_birth fields don't change).
+ * Thus, we don't need to store the header's sublist index
+ * on insertion, as this index can be recalculated on removal.
+ *
+ * Also, the low order bits of the hash value are thought to be
+ * distributed evenly. Otherwise, in the case that the multilist
+ * has a power of two number of sublists, each sublists' usage
+ * would not be evenly distributed.
+ */
+ return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
+ multilist_get_num_sublists(ml));
+}
+
+/*
+ * Called during module initialization and periodically thereafter to
+ * apply reasonable changes to the exposed performance tunings. Non-zero
+ * zfs_* values which differ from the currently set values will be applied.
+ */
+static void
+arc_tuning_update(void)
+{
+ /* Valid range: 64M - <all physical memory> */
+ if ((zfs_arc_max) && (zfs_arc_max != arc_c_max) &&
+ (zfs_arc_max > 64 << 20) && (zfs_arc_max < ptob(physmem)) &&
+ (zfs_arc_max > arc_c_min)) {
+ arc_c_max = zfs_arc_max;
+ arc_c = arc_c_max;
+ arc_p = (arc_c >> 1);
+ arc_meta_limit = MIN(arc_meta_limit, (3 * arc_c_max) / 4);
+ }
+
+ /* Valid range: 32M - <arc_c_max> */
+ if ((zfs_arc_min) && (zfs_arc_min != arc_c_min) &&
+ (zfs_arc_min >= 2ULL << SPA_MAXBLOCKSHIFT) &&
+ (zfs_arc_min <= arc_c_max)) {
+ arc_c_min = zfs_arc_min;
+ arc_c = MAX(arc_c, arc_c_min);
+ }
+
+ /* Valid range: 16M - <arc_c_max> */
+ if ((zfs_arc_meta_min) && (zfs_arc_meta_min != arc_meta_min) &&
+ (zfs_arc_meta_min >= 1ULL << SPA_MAXBLOCKSHIFT) &&
+ (zfs_arc_meta_min <= arc_c_max)) {
+ arc_meta_min = zfs_arc_meta_min;
+ arc_meta_limit = MAX(arc_meta_limit, arc_meta_min);
+ }
+
+ /* Valid range: <arc_meta_min> - <arc_c_max> */
+ if ((zfs_arc_meta_limit) && (zfs_arc_meta_limit != arc_meta_limit) &&
+ (zfs_arc_meta_limit >= zfs_arc_meta_min) &&
+ (zfs_arc_meta_limit <= arc_c_max))
+ arc_meta_limit = zfs_arc_meta_limit;
+
+ /* Valid range: 1 - N */
+ if (zfs_arc_grow_retry)
+ arc_grow_retry = zfs_arc_grow_retry;
+
+ /* Valid range: 1 - N */
+ if (zfs_arc_shrink_shift) {
+ arc_shrink_shift = zfs_arc_shrink_shift;
+ arc_no_grow_shift = MIN(arc_no_grow_shift, arc_shrink_shift -1);
+ }
+
+ /* Valid range: 1 - N */
+ if (zfs_arc_p_min_shift)
+ arc_p_min_shift = zfs_arc_p_min_shift;
+
+ /* Valid range: 1 - N ticks */
+ if (zfs_arc_min_prefetch_lifespan)
+ arc_min_prefetch_lifespan = zfs_arc_min_prefetch_lifespan;
+
+ /* Valid range: 0 - 100 */
+ if ((zfs_arc_lotsfree_percent >= 0) &&
+ (zfs_arc_lotsfree_percent <= 100))
+ arc_lotsfree_percent = zfs_arc_lotsfree_percent;
+
+ /* Valid range: 0 - <all physical memory> */
+ if ((zfs_arc_sys_free) && (zfs_arc_sys_free != arc_sys_free))
+ arc_sys_free = MIN(MAX(zfs_arc_sys_free, 0), ptob(physmem));
+
+}
+
+void
+arc_init(void)
+{
+ /*
+ * allmem is "all memory that we could possibly use".
+ */
+#ifdef _KERNEL
+ uint64_t allmem = ptob(physmem);
+#else
+ uint64_t allmem = (physmem * PAGESIZE) / 2;
+#endif
+
+ mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
+ cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
+ cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
+
+ mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
+ cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL);
+
+ /* Convert seconds to clock ticks */
+ arc_min_prefetch_lifespan = 1 * hz;
+
+ /* Start out with 1/8 of all memory */
+ arc_c = allmem / 8;
+
+#ifdef _KERNEL
+ /*
+ * On architectures where the physical memory can be larger
+ * than the addressable space (intel in 32-bit mode), we may
+ * need to limit the cache to 1/8 of VM size.
+ */
+ arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
+
+ /*
+ * Register a shrinker to support synchronous (direct) memory
+ * reclaim from the arc. This is done to prevent kswapd from
+ * swapping out pages when it is preferable to shrink the arc.
+ */
+ spl_register_shrinker(&arc_shrinker);
+
+ /* Set to 1/64 of all memory or a minimum of 512K */
+ arc_sys_free = MAX(ptob(physmem / 64), (512 * 1024));
+ arc_need_free = 0;
+#endif
+
+ /* Set min cache to allow safe operation of arc_adapt() */
+ arc_c_min = 2ULL << SPA_MAXBLOCKSHIFT;
+ /* Set max to 1/2 of all memory */
+ arc_c_max = allmem / 2;
+
+ arc_c = arc_c_max;
+ arc_p = (arc_c >> 1);
+
+ /* Set min to 1/2 of arc_c_min */
+ arc_meta_min = 1ULL << SPA_MAXBLOCKSHIFT;
+ /* Initialize maximum observed usage to zero */
+ arc_meta_max = 0;
+ /* Set limit to 3/4 of arc_c_max with a floor of arc_meta_min */
+ arc_meta_limit = MAX((3 * arc_c_max) / 4, arc_meta_min);
+
+ /* Apply user specified tunings */
+ arc_tuning_update();
+
+ if (zfs_arc_num_sublists_per_state < 1)
+ zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1);
+
+ /* if kmem_flags are set, lets try to use less memory */
+ if (kmem_debugging())
+ arc_c = arc_c / 2;
+ if (arc_c < arc_c_min)
+ arc_c = arc_c_min;
+
+ arc_anon = &ARC_anon;
+ arc_mru = &ARC_mru;
+ arc_mru_ghost = &ARC_mru_ghost;
+ arc_mfu = &ARC_mfu;
+ arc_mfu_ghost = &ARC_mfu_ghost;
+ arc_l2c_only = &ARC_l2c_only;
+ arc_size = 0;
+
+ multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+ multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
+ zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
+
+ arc_anon->arcs_state = ARC_STATE_ANON;
+ arc_mru->arcs_state = ARC_STATE_MRU;
+ arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
+ arc_mfu->arcs_state = ARC_STATE_MFU;
+ arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
+ arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
+
+ refcount_create(&arc_anon->arcs_size);
+ refcount_create(&arc_mru->arcs_size);
+ refcount_create(&arc_mru_ghost->arcs_size);
+ refcount_create(&arc_mfu->arcs_size);
+ refcount_create(&arc_mfu_ghost->arcs_size);
+ refcount_create(&arc_l2c_only->arcs_size);
+
+ buf_init();
+
+ arc_reclaim_thread_exit = FALSE;
+ arc_user_evicts_thread_exit = FALSE;
+ list_create(&arc_prune_list, sizeof (arc_prune_t),
+ offsetof(arc_prune_t, p_node));
+ arc_eviction_list = NULL;
+ mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
+ bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
+
+ arc_prune_taskq = taskq_create("arc_prune", max_ncpus, defclsyspri,
+ max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
+
+ arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
+ sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
+
+ if (arc_ksp != NULL) {
+ arc_ksp->ks_data = &arc_stats;
+ arc_ksp->ks_update = arc_kstat_update;
+ kstat_install(arc_ksp);
+ }
+
+ (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
+ TS_RUN, defclsyspri);
+
+ (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0,
+ TS_RUN, defclsyspri);
+
+ arc_dead = FALSE;
+ arc_warm = B_FALSE;
+
+ /*
+ * Calculate maximum amount of dirty data per pool.
+ *
+ * If it has been set by a module parameter, take that.
+ * Otherwise, use a percentage of physical memory defined by
+ * zfs_dirty_data_max_percent (default 10%) with a cap at
+ * zfs_dirty_data_max_max (default 25% of physical memory).
+ */
+ if (zfs_dirty_data_max_max == 0)
+ zfs_dirty_data_max_max = (uint64_t)physmem * PAGESIZE *
+ zfs_dirty_data_max_max_percent / 100;
+
+ if (zfs_dirty_data_max == 0) {
+ zfs_dirty_data_max = (uint64_t)physmem * PAGESIZE *
+ zfs_dirty_data_max_percent / 100;
+ zfs_dirty_data_max = MIN(zfs_dirty_data_max,
+ zfs_dirty_data_max_max);
+ }
+}
+
+void
+arc_fini(void)
+{
+ arc_prune_t *p;
+
+#ifdef _KERNEL
+ spl_unregister_shrinker(&arc_shrinker);
+#endif /* _KERNEL */
+
+ mutex_enter(&arc_reclaim_lock);
+ arc_reclaim_thread_exit = TRUE;
+ /*
+ * The reclaim thread will set arc_reclaim_thread_exit back to
+ * FALSE when it is finished exiting; we're waiting for that.
+ */
+ while (arc_reclaim_thread_exit) {
+ cv_signal(&arc_reclaim_thread_cv);
+ cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
+ }
+ mutex_exit(&arc_reclaim_lock);
+
+ mutex_enter(&arc_user_evicts_lock);
+ arc_user_evicts_thread_exit = TRUE;
+ /*
+ * The user evicts thread will set arc_user_evicts_thread_exit
+ * to FALSE when it is finished exiting; we're waiting for that.
+ */
+ while (arc_user_evicts_thread_exit) {
+ cv_signal(&arc_user_evicts_cv);
+ cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock);
+ }
+ mutex_exit(&arc_user_evicts_lock);
+
+ /* Use TRUE to ensure *all* buffers are evicted */
+ arc_flush(NULL, TRUE);
+
+ arc_dead = TRUE;
+
+ if (arc_ksp != NULL) {
+ kstat_delete(arc_ksp);
+ arc_ksp = NULL;
+ }
+
+ taskq_wait(arc_prune_taskq);
+ taskq_destroy(arc_prune_taskq);
+
+ mutex_enter(&arc_prune_mtx);
+ while ((p = list_head(&arc_prune_list)) != NULL) {
+ list_remove(&arc_prune_list, p);
+ refcount_remove(&p->p_refcnt, &arc_prune_list);
+ refcount_destroy(&p->p_refcnt);
+ kmem_free(p, sizeof (*p));
+ }
+ mutex_exit(&arc_prune_mtx);
+
+ list_destroy(&arc_prune_list);
+ mutex_destroy(&arc_prune_mtx);
+ mutex_destroy(&arc_reclaim_lock);
+ cv_destroy(&arc_reclaim_thread_cv);
+ cv_destroy(&arc_reclaim_waiters_cv);
+
+ mutex_destroy(&arc_user_evicts_lock);
+ cv_destroy(&arc_user_evicts_cv);
+
+ refcount_destroy(&arc_anon->arcs_size);
+ refcount_destroy(&arc_mru->arcs_size);
+ refcount_destroy(&arc_mru_ghost->arcs_size);
+ refcount_destroy(&arc_mfu->arcs_size);
+ refcount_destroy(&arc_mfu_ghost->arcs_size);
+ refcount_destroy(&arc_l2c_only->arcs_size);
+
+ multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
+ multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
+ multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
+ multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
+ multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
+ multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
+ multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
+ multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
+ multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]);
+ multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]);
+
+ buf_fini();
+
+ ASSERT0(arc_loaned_bytes);
+}
+
+/*
+ * Level 2 ARC
+ *
+ * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
+ * It uses dedicated storage devices to hold cached data, which are populated
+ * using large infrequent writes. The main role of this cache is to boost
+ * the performance of random read workloads. The intended L2ARC devices
+ * include short-stroked disks, solid state disks, and other media with
+ * substantially faster read latency than disk.
+ *
+ * +-----------------------+
+ * | ARC |
+ * +-----------------------+
+ * | ^ ^
+ * | | |
+ * l2arc_feed_thread() arc_read()
+ * | | |
+ * | l2arc read |
+ * V | |
+ * +---------------+ |
+ * | L2ARC | |
+ * +---------------+ |
+ * | ^ |
+ * l2arc_write() | |
+ * | | |
+ * V | |
+ * +-------+ +-------+
+ * | vdev | | vdev |
+ * | cache | | cache |
+ * +-------+ +-------+
+ * +=========+ .-----.
+ * : L2ARC : |-_____-|
+ * : devices : | Disks |
+ * +=========+ `-_____-'
+ *
+ * Read requests are satisfied from the following sources, in order:
+ *
+ * 1) ARC
+ * 2) vdev cache of L2ARC devices
+ * 3) L2ARC devices
+ * 4) vdev cache of disks
+ * 5) disks
+ *
+ * Some L2ARC device types exhibit extremely slow write performance.
+ * To accommodate for this there are some significant differences between
+ * the L2ARC and traditional cache design:
+ *
+ * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
+ * the ARC behave as usual, freeing buffers and placing headers on ghost
+ * lists. The ARC does not send buffers to the L2ARC during eviction as
+ * this would add inflated write latencies for all ARC memory pressure.
+ *
+ * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
+ * It does this by periodically scanning buffers from the eviction-end of
+ * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
+ * not already there. It scans until a headroom of buffers is satisfied,
+ * which itself is a buffer for ARC eviction. If a compressible buffer is
+ * found during scanning and selected for writing to an L2ARC device, we
+ * temporarily boost scanning headroom during the next scan cycle to make
+ * sure we adapt to compression effects (which might significantly reduce
+ * the data volume we write to L2ARC). The thread that does this is
+ * l2arc_feed_thread(), illustrated below; example sizes are included to
+ * provide a better sense of ratio than this diagram:
+ *
+ * head --> tail
+ * +---------------------+----------+
+ * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
+ * +---------------------+----------+ | o L2ARC eligible
+ * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
+ * +---------------------+----------+ |
+ * 15.9 Gbytes ^ 32 Mbytes |
+ * headroom |
+ * l2arc_feed_thread()
+ * |
+ * l2arc write hand <--[oooo]--'
+ * | 8 Mbyte
+ * | write max
+ * V
+ * +==============================+
+ * L2ARC dev |####|#|###|###| |####| ... |
+ * +==============================+
+ * 32 Gbytes
+ *
+ * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
+ * evicted, then the L2ARC has cached a buffer much sooner than it probably
+ * needed to, potentially wasting L2ARC device bandwidth and storage. It is
+ * safe to say that this is an uncommon case, since buffers at the end of
+ * the ARC lists have moved there due to inactivity.
+ *
+ * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
+ * then the L2ARC simply misses copying some buffers. This serves as a
+ * pressure valve to prevent heavy read workloads from both stalling the ARC
+ * with waits and clogging the L2ARC with writes. This also helps prevent
+ * the potential for the L2ARC to churn if it attempts to cache content too
+ * quickly, such as during backups of the entire pool.
+ *
+ * 5. After system boot and before the ARC has filled main memory, there are
+ * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
+ * lists can remain mostly static. Instead of searching from tail of these
+ * lists as pictured, the l2arc_feed_thread() will search from the list heads
+ * for eligible buffers, greatly increasing its chance of finding them.
+ *
+ * The L2ARC device write speed is also boosted during this time so that
+ * the L2ARC warms up faster. Since there have been no ARC evictions yet,
+ * there are no L2ARC reads, and no fear of degrading read performance
+ * through increased writes.
+ *
+ * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
+ * the vdev queue can aggregate them into larger and fewer writes. Each
+ * device is written to in a rotor fashion, sweeping writes through
+ * available space then repeating.
+ *
+ * 7. The L2ARC does not store dirty content. It never needs to flush
+ * write buffers back to disk based storage.
+ *
+ * 8. If an ARC buffer is written (and dirtied) which also exists in the
+ * L2ARC, the now stale L2ARC buffer is immediately dropped.
+ *
+ * The performance of the L2ARC can be tweaked by a number of tunables, which
+ * may be necessary for different workloads:
+ *
+ * l2arc_write_max max write bytes per interval
+ * l2arc_write_boost extra write bytes during device warmup
+ * l2arc_noprefetch skip caching prefetched buffers
+ * l2arc_nocompress skip compressing buffers
+ * l2arc_headroom number of max device writes to precache
+ * l2arc_headroom_boost when we find compressed buffers during ARC
+ * scanning, we multiply headroom by this
+ * percentage factor for the next scan cycle,
+ * since more compressed buffers are likely to
+ * be present
+ * l2arc_feed_secs seconds between L2ARC writing
+ *
+ * Tunables may be removed or added as future performance improvements are
+ * integrated, and also may become zpool properties.
+ *
+ * There are three key functions that control how the L2ARC warms up:
+ *
+ * l2arc_write_eligible() check if a buffer is eligible to cache
+ * l2arc_write_size() calculate how much to write
+ * l2arc_write_interval() calculate sleep delay between writes
+ *
+ * These three functions determine what to write, how much, and how quickly
+ * to send writes.
+ */
+
+static boolean_t
+l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
+{
+ /*
+ * A buffer is *not* eligible for the L2ARC if it:
+ * 1. belongs to a different spa.
+ * 2. is already cached on the L2ARC.
+ * 3. has an I/O in progress (it may be an incomplete read).
+ * 4. is flagged not eligible (zfs property).
+ */
+ if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
+ HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
+ return (B_FALSE);
+
+ return (B_TRUE);
+}
+
+static uint64_t
+l2arc_write_size(void)
+{
+ uint64_t size;
+
+ /*
+ * Make sure our globals have meaningful values in case the user
+ * altered them.
+ */
+ size = l2arc_write_max;
+ if (size == 0) {
+ cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
+ "be greater than zero, resetting it to the default (%d)",
+ L2ARC_WRITE_SIZE);
+ size = l2arc_write_max = L2ARC_WRITE_SIZE;
+ }
+
+ if (arc_warm == B_FALSE)
+ size += l2arc_write_boost;
+
+ return (size);
+
+}
+
+static clock_t
+l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
+{
+ clock_t interval, next, now;
+
+ /*
+ * If the ARC lists are busy, increase our write rate; if the
+ * lists are stale, idle back. This is achieved by checking
+ * how much we previously wrote - if it was more than half of
+ * what we wanted, schedule the next write much sooner.
+ */
+ if (l2arc_feed_again && wrote > (wanted / 2))
+ interval = (hz * l2arc_feed_min_ms) / 1000;
+ else
+ interval = hz * l2arc_feed_secs;
+
+ now = ddi_get_lbolt();
+ next = MAX(now, MIN(now + interval, began + interval));
+
+ return (next);
+}
+
+/*
+ * Cycle through L2ARC devices. This is how L2ARC load balances.
+ * If a device is returned, this also returns holding the spa config lock.
+ */
+static l2arc_dev_t *
+l2arc_dev_get_next(void)
+{
+ l2arc_dev_t *first, *next = NULL;
+
+ /*
+ * Lock out the removal of spas (spa_namespace_lock), then removal
+ * of cache devices (l2arc_dev_mtx). Once a device has been selected,
+ * both locks will be dropped and a spa config lock held instead.
+ */
+ mutex_enter(&spa_namespace_lock);
+ mutex_enter(&l2arc_dev_mtx);
+
+ /* if there are no vdevs, there is nothing to do */
+ if (l2arc_ndev == 0)
+ goto out;
+
+ first = NULL;
+ next = l2arc_dev_last;
+ do {
+ /* loop around the list looking for a non-faulted vdev */
+ if (next == NULL) {
+ next = list_head(l2arc_dev_list);
+ } else {
+ next = list_next(l2arc_dev_list, next);
+ if (next == NULL)
+ next = list_head(l2arc_dev_list);
+ }
+
+ /* if we have come back to the start, bail out */
+ if (first == NULL)
+ first = next;
+ else if (next == first)
+ break;
+
+ } while (vdev_is_dead(next->l2ad_vdev));
+
+ /* if we were unable to find any usable vdevs, return NULL */
+ if (vdev_is_dead(next->l2ad_vdev))
+ next = NULL;
+
+ l2arc_dev_last = next;
+
+out:
+ mutex_exit(&l2arc_dev_mtx);
+
+ /*
+ * Grab the config lock to prevent the 'next' device from being
+ * removed while we are writing to it.
+ */
+ if (next != NULL)
+ spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
+ mutex_exit(&spa_namespace_lock);
+
+ return (next);
+}
+
+/*
+ * Free buffers that were tagged for destruction.
+ */
+static void
+l2arc_do_free_on_write(void)
+{
+ list_t *buflist;
+ l2arc_data_free_t *df, *df_prev;
+
+ mutex_enter(&l2arc_free_on_write_mtx);
+ buflist = l2arc_free_on_write;
+
+ for (df = list_tail(buflist); df; df = df_prev) {
+ df_prev = list_prev(buflist, df);
+ ASSERT(df->l2df_data != NULL);
+ ASSERT(df->l2df_func != NULL);
+ df->l2df_func(df->l2df_data, df->l2df_size);
+ list_remove(buflist, df);
+ kmem_free(df, sizeof (l2arc_data_free_t));
+ }
+
+ mutex_exit(&l2arc_free_on_write_mtx);
+}
+
+/*
+ * A write to a cache device has completed. Update all headers to allow
+ * reads from these buffers to begin.
+ */
+static void
+l2arc_write_done(zio_t *zio)
+{
+ l2arc_write_callback_t *cb;
+ l2arc_dev_t *dev;
+ list_t *buflist;
+ arc_buf_hdr_t *head, *hdr, *hdr_prev;
+ kmutex_t *hash_lock;
+ int64_t bytes_dropped = 0;
+
+ cb = zio->io_private;
+ ASSERT(cb != NULL);
+ dev = cb->l2wcb_dev;
+ ASSERT(dev != NULL);
+ head = cb->l2wcb_head;
+ ASSERT(head != NULL);
+ buflist = &dev->l2ad_buflist;
+ ASSERT(buflist != NULL);
+ DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
+ l2arc_write_callback_t *, cb);
+
+ if (zio->io_error != 0)
+ ARCSTAT_BUMP(arcstat_l2_writes_error);
+
+ /*
+ * All writes completed, or an error was hit.
+ */
+top:
+ mutex_enter(&dev->l2ad_mtx);
+ for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
+ hdr_prev = list_prev(buflist, hdr);
+
+ hash_lock = HDR_LOCK(hdr);
+
+ /*
+ * We cannot use mutex_enter or else we can deadlock
+ * with l2arc_write_buffers (due to swapping the order
+ * the hash lock and l2ad_mtx are taken).
+ */
+ if (!mutex_tryenter(hash_lock)) {
+ /*
+ * Missed the hash lock. We must retry so we
+ * don't leave the ARC_FLAG_L2_WRITING bit set.
+ */
+ ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
+
+ /*
+ * We don't want to rescan the headers we've
+ * already marked as having been written out, so
+ * we reinsert the head node so we can pick up
+ * where we left off.
+ */
+ list_remove(buflist, head);
+ list_insert_after(buflist, hdr, head);
+
+ mutex_exit(&dev->l2ad_mtx);
+
+ /*
+ * We wait for the hash lock to become available
+ * to try and prevent busy waiting, and increase
+ * the chance we'll be able to acquire the lock
+ * the next time around.
+ */
+ mutex_enter(hash_lock);
+ mutex_exit(hash_lock);
+ goto top;
+ }
+
+ /*
+ * We could not have been moved into the arc_l2c_only
+ * state while in-flight due to our ARC_FLAG_L2_WRITING
+ * bit being set. Let's just ensure that's being enforced.
+ */
+ ASSERT(HDR_HAS_L1HDR(hdr));
+
+ /*
+ * We may have allocated a buffer for L2ARC compression,
+ * we must release it to avoid leaking this data.
+ */
+ l2arc_release_cdata_buf(hdr);
+
+ if (zio->io_error != 0) {
+ /*
+ * Error - drop L2ARC entry.
+ */
+ list_remove(buflist, hdr);
+ hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
+
+ ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize);
+ ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
+
+ bytes_dropped += hdr->b_l2hdr.b_asize;
+ (void) refcount_remove_many(&dev->l2ad_alloc,
+ hdr->b_l2hdr.b_asize, hdr);
+ }
+
+ /*
+ * Allow ARC to begin reads and ghost list evictions to
+ * this L2ARC entry.
+ */
+ hdr->b_flags &= ~ARC_FLAG_L2_WRITING;
+
+ mutex_exit(hash_lock);
+ }
+
+ atomic_inc_64(&l2arc_writes_done);
+ list_remove(buflist, head);
+ ASSERT(!HDR_HAS_L1HDR(head));
+ kmem_cache_free(hdr_l2only_cache, head);
+ mutex_exit(&dev->l2ad_mtx);
+
+ vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
+
+ l2arc_do_free_on_write();
+
+ kmem_free(cb, sizeof (l2arc_write_callback_t));
+}
+
+/*
+ * A read to a cache device completed. Validate buffer contents before
+ * handing over to the regular ARC routines.
+ */
+static void
+l2arc_read_done(zio_t *zio)
+{
+ l2arc_read_callback_t *cb;
+ arc_buf_hdr_t *hdr;
+ arc_buf_t *buf;
+ kmutex_t *hash_lock;
+ int equal;
+
+ ASSERT(zio->io_vd != NULL);
+ ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
+
+ spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
+
+ cb = zio->io_private;
+ ASSERT(cb != NULL);
+ buf = cb->l2rcb_buf;
+ ASSERT(buf != NULL);
+
+ hash_lock = HDR_LOCK(buf->b_hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+
+ /*
+ * If the buffer was compressed, decompress it first.
+ */
+ if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
+ l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
+ ASSERT(zio->io_data != NULL);
+ ASSERT3U(zio->io_size, ==, hdr->b_size);
+ ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size);
+
+ /*
+ * Check this survived the L2ARC journey.
+ */
+ equal = arc_cksum_equal(buf);
+ if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
+ mutex_exit(hash_lock);
+ zio->io_private = buf;
+ zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
+ zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
+ arc_read_done(zio);
+ } else {
+ mutex_exit(hash_lock);
+ /*
+ * Buffer didn't survive caching. Increment stats and
+ * reissue to the original storage device.
+ */
+ if (zio->io_error != 0) {
+ ARCSTAT_BUMP(arcstat_l2_io_error);
+ } else {
+ zio->io_error = SET_ERROR(EIO);
+ }
+ if (!equal)
+ ARCSTAT_BUMP(arcstat_l2_cksum_bad);
+
+ /*
+ * If there's no waiter, issue an async i/o to the primary
+ * storage now. If there *is* a waiter, the caller must
+ * issue the i/o in a context where it's OK to block.
+ */
+ if (zio->io_waiter == NULL) {
+ zio_t *pio = zio_unique_parent(zio);
+
+ ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
+
+ zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
+ buf->b_data, hdr->b_size, arc_read_done, buf,
+ zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
+ }
+ }
+
+ kmem_free(cb, sizeof (l2arc_read_callback_t));
+}
+
+/*
+ * This is the list priority from which the L2ARC will search for pages to
+ * cache. This is used within loops (0..3) to cycle through lists in the
+ * desired order. This order can have a significant effect on cache
+ * performance.
+ *
+ * Currently the metadata lists are hit first, MFU then MRU, followed by
+ * the data lists. This function returns a locked list, and also returns
+ * the lock pointer.
+ */
+static multilist_sublist_t *
+l2arc_sublist_lock(int list_num)
+{
+ multilist_t *ml = NULL;
+ unsigned int idx;
+
+ ASSERT(list_num >= 0 && list_num <= 3);
+
+ switch (list_num) {
+ case 0:
+ ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
+ break;
+ case 1:
+ ml = &arc_mru->arcs_list[ARC_BUFC_METADATA];
+ break;
+ case 2:
+ ml = &arc_mfu->arcs_list[ARC_BUFC_DATA];
+ break;
+ case 3:
+ ml = &arc_mru->arcs_list[ARC_BUFC_DATA];
+ break;
+ }
+
+ /*
+ * Return a randomly-selected sublist. This is acceptable
+ * because the caller feeds only a little bit of data for each
+ * call (8MB). Subsequent calls will result in different
+ * sublists being selected.
+ */
+ idx = multilist_get_random_index(ml);
+ return (multilist_sublist_lock(ml, idx));
+}
+
+/*
+ * Evict buffers from the device write hand to the distance specified in
+ * bytes. This distance may span populated buffers, it may span nothing.
+ * This is clearing a region on the L2ARC device ready for writing.
+ * If the 'all' boolean is set, every buffer is evicted.
+ */
+static void
+l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
+{
+ list_t *buflist;
+ arc_buf_hdr_t *hdr, *hdr_prev;
+ kmutex_t *hash_lock;
+ uint64_t taddr;
+
+ buflist = &dev->l2ad_buflist;
+
+ if (!all && dev->l2ad_first) {
+ /*
+ * This is the first sweep through the device. There is
+ * nothing to evict.
+ */
+ return;
+ }
+
+ if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
+ /*
+ * When nearing the end of the device, evict to the end
+ * before the device write hand jumps to the start.
+ */
+ taddr = dev->l2ad_end;
+ } else {
+ taddr = dev->l2ad_hand + distance;
+ }
+ DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
+ uint64_t, taddr, boolean_t, all);
+
+top:
+ mutex_enter(&dev->l2ad_mtx);
+ for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
+ hdr_prev = list_prev(buflist, hdr);
+
+ hash_lock = HDR_LOCK(hdr);
+
+ /*
+ * We cannot use mutex_enter or else we can deadlock
+ * with l2arc_write_buffers (due to swapping the order
+ * the hash lock and l2ad_mtx are taken).
+ */
+ if (!mutex_tryenter(hash_lock)) {
+ /*
+ * Missed the hash lock. Retry.
+ */
+ ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
+ mutex_exit(&dev->l2ad_mtx);
+ mutex_enter(hash_lock);
+ mutex_exit(hash_lock);
+ goto top;
+ }
+
+ if (HDR_L2_WRITE_HEAD(hdr)) {
+ /*
+ * We hit a write head node. Leave it for
+ * l2arc_write_done().
+ */
+ list_remove(buflist, hdr);
+ mutex_exit(hash_lock);
+ continue;
+ }
+
+ if (!all && HDR_HAS_L2HDR(hdr) &&
+ (hdr->b_l2hdr.b_daddr > taddr ||
+ hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
+ /*
+ * We've evicted to the target address,
+ * or the end of the device.
+ */
+ mutex_exit(hash_lock);
+ break;
+ }
+
+ ASSERT(HDR_HAS_L2HDR(hdr));
+ if (!HDR_HAS_L1HDR(hdr)) {
+ ASSERT(!HDR_L2_READING(hdr));
+ /*
+ * This doesn't exist in the ARC. Destroy.
+ * arc_hdr_destroy() will call list_remove()
+ * and decrement arcstat_l2_size.
+ */
+ arc_change_state(arc_anon, hdr, hash_lock);
+ arc_hdr_destroy(hdr);
+ } else {
+ ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
+ ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
+ /*
+ * Invalidate issued or about to be issued
+ * reads, since we may be about to write
+ * over this location.
+ */
+ if (HDR_L2_READING(hdr)) {
+ ARCSTAT_BUMP(arcstat_l2_evict_reading);
+ hdr->b_flags |= ARC_FLAG_L2_EVICTED;
+ }
+
+ /* Ensure this header has finished being written */
+ ASSERT(!HDR_L2_WRITING(hdr));
+ ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
+
+ arc_hdr_l2hdr_destroy(hdr);
+ }
+ mutex_exit(hash_lock);
+ }
+ mutex_exit(&dev->l2ad_mtx);
+}
+
+/*
+ * Find and write ARC buffers to the L2ARC device.
+ *
+ * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
+ * for reading until they have completed writing.
+ * The headroom_boost is an in-out parameter used to maintain headroom boost
+ * state between calls to this function.
+ *
+ * Returns the number of bytes actually written (which may be smaller than
+ * the delta by which the device hand has changed due to alignment).
+ */
+static uint64_t
+l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
+ boolean_t *headroom_boost)
+{
+ arc_buf_hdr_t *hdr, *hdr_prev, *head;
+ uint64_t write_asize, write_sz, headroom, buf_compress_minsz,
+ stats_size;
+ void *buf_data;
+ boolean_t full;
+ l2arc_write_callback_t *cb;
+ zio_t *pio, *wzio;
+ uint64_t guid = spa_load_guid(spa);
+ int try;
+ const boolean_t do_headroom_boost = *headroom_boost;
+
+ ASSERT(dev->l2ad_vdev != NULL);
+
+ /* Lower the flag now, we might want to raise it again later. */
+ *headroom_boost = B_FALSE;
+
+ pio = NULL;
+ write_sz = write_asize = 0;
+ full = B_FALSE;
+ head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
+ head->b_flags |= ARC_FLAG_L2_WRITE_HEAD;
+ head->b_flags |= ARC_FLAG_HAS_L2HDR;
+
+ /*
+ * We will want to try to compress buffers that are at least 2x the
+ * device sector size.
+ */
+ buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
+
+ /*
+ * Copy buffers for L2ARC writing.
+ */
+ for (try = 0; try <= 3; try++) {
+ multilist_sublist_t *mls = l2arc_sublist_lock(try);
+ uint64_t passed_sz = 0;
+
+ /*
+ * L2ARC fast warmup.
+ *
+ * Until the ARC is warm and starts to evict, read from the
+ * head of the ARC lists rather than the tail.
+ */
+ if (arc_warm == B_FALSE)
+ hdr = multilist_sublist_head(mls);
+ else
+ hdr = multilist_sublist_tail(mls);
+
+ headroom = target_sz * l2arc_headroom;
+ if (do_headroom_boost)
+ headroom = (headroom * l2arc_headroom_boost) / 100;
+
+ for (; hdr; hdr = hdr_prev) {
+ kmutex_t *hash_lock;
+ uint64_t buf_sz;
+ uint64_t buf_a_sz;
+
+ if (arc_warm == B_FALSE)
+ hdr_prev = multilist_sublist_next(mls, hdr);
+ else
+ hdr_prev = multilist_sublist_prev(mls, hdr);
+
+ hash_lock = HDR_LOCK(hdr);
+ if (!mutex_tryenter(hash_lock)) {
+ /*
+ * Skip this buffer rather than waiting.
+ */
+ continue;
+ }
+
+ passed_sz += hdr->b_size;
+ if (passed_sz > headroom) {
+ /*
+ * Searched too far.
+ */
+ mutex_exit(hash_lock);
+ break;
+ }
+
+ if (!l2arc_write_eligible(guid, hdr)) {
+ mutex_exit(hash_lock);
+ continue;
+ }
+
+ /*
+ * Assume that the buffer is not going to be compressed
+ * and could take more space on disk because of a larger
+ * disk block size.
+ */
+ buf_sz = hdr->b_size;
+ buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
+
+ if ((write_asize + buf_a_sz) > target_sz) {
+ full = B_TRUE;
+ mutex_exit(hash_lock);
+ break;
+ }
+
+ if (pio == NULL) {
+ /*
+ * Insert a dummy header on the buflist so
+ * l2arc_write_done() can find where the
+ * write buffers begin without searching.
+ */
+ mutex_enter(&dev->l2ad_mtx);
+ list_insert_head(&dev->l2ad_buflist, head);
+ mutex_exit(&dev->l2ad_mtx);
+
+ cb = kmem_alloc(
+ sizeof (l2arc_write_callback_t), KM_SLEEP);
+ cb->l2wcb_dev = dev;
+ cb->l2wcb_head = head;
+ pio = zio_root(spa, l2arc_write_done, cb,
+ ZIO_FLAG_CANFAIL);
+ }
+
+ /*
+ * Create and add a new L2ARC header.
+ */
+ hdr->b_l2hdr.b_dev = dev;
+ hdr->b_flags |= ARC_FLAG_L2_WRITING;
+ /*
+ * Temporarily stash the data buffer in b_tmp_cdata.
+ * The subsequent write step will pick it up from
+ * there. This is because can't access b_l1hdr.b_buf
+ * without holding the hash_lock, which we in turn
+ * can't access without holding the ARC list locks
+ * (which we want to avoid during compression/writing)
+ */
+ hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF;
+ hdr->b_l2hdr.b_asize = hdr->b_size;
+ hdr->b_l2hdr.b_hits = 0;
+ hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data;
+
+ /*
+ * Explicitly set the b_daddr field to a known
+ * value which means "invalid address". This
+ * enables us to differentiate which stage of
+ * l2arc_write_buffers() the particular header
+ * is in (e.g. this loop, or the one below).
+ * ARC_FLAG_L2_WRITING is not enough to make
+ * this distinction, and we need to know in
+ * order to do proper l2arc vdev accounting in
+ * arc_release() and arc_hdr_destroy().
+ *
+ * Note, we can't use a new flag to distinguish
+ * the two stages because we don't hold the
+ * header's hash_lock below, in the second stage
+ * of this function. Thus, we can't simply
+ * change the b_flags field to denote that the
+ * IO has been sent. We can change the b_daddr
+ * field of the L2 portion, though, since we'll
+ * be holding the l2ad_mtx; which is why we're
+ * using it to denote the header's state change.
+ */
+ hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET;
+ hdr->b_flags |= ARC_FLAG_HAS_L2HDR;
+
+ mutex_enter(&dev->l2ad_mtx);
+ list_insert_head(&dev->l2ad_buflist, hdr);
+ mutex_exit(&dev->l2ad_mtx);
+
+ /*
+ * Compute and store the buffer cksum before
+ * writing. On debug the cksum is verified first.
+ */
+ arc_cksum_verify(hdr->b_l1hdr.b_buf);
+ arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE);
+
+ mutex_exit(hash_lock);
+
+ write_sz += buf_sz;
+ write_asize += buf_a_sz;
+ }
+
+ multilist_sublist_unlock(mls);
+
+ if (full == B_TRUE)
+ break;
+ }
+
+ /* No buffers selected for writing? */
+ if (pio == NULL) {
+ ASSERT0(write_sz);
+ ASSERT(!HDR_HAS_L1HDR(head));
+ kmem_cache_free(hdr_l2only_cache, head);
+ return (0);
+ }
+
+ mutex_enter(&dev->l2ad_mtx);
+
+ /*
+ * Note that elsewhere in this file arcstat_l2_asize
+ * and the used space on l2ad_vdev are updated using b_asize,
+ * which is not necessarily rounded up to the device block size.
+ * Too keep accounting consistent we do the same here as well:
+ * stats_size accumulates the sum of b_asize of the written buffers,
+ * while write_asize accumulates the sum of b_asize rounded up
+ * to the device block size.
+ * The latter sum is used only to validate the corectness of the code.
+ */
+ stats_size = 0;
+ write_asize = 0;
+
+ /*
+ * Now start writing the buffers. We're starting at the write head
+ * and work backwards, retracing the course of the buffer selector
+ * loop above.
+ */
+ for (hdr = list_prev(&dev->l2ad_buflist, head); hdr;
+ hdr = list_prev(&dev->l2ad_buflist, hdr)) {
+ uint64_t buf_sz;
+
+ /*
+ * We rely on the L1 portion of the header below, so
+ * it's invalid for this header to have been evicted out
+ * of the ghost cache, prior to being written out. The
+ * ARC_FLAG_L2_WRITING bit ensures this won't happen.
+ */
+ ASSERT(HDR_HAS_L1HDR(hdr));
+
+ /*
+ * We shouldn't need to lock the buffer here, since we flagged
+ * it as ARC_FLAG_L2_WRITING in the previous step, but we must
+ * take care to only access its L2 cache parameters. In
+ * particular, hdr->l1hdr.b_buf may be invalid by now due to
+ * ARC eviction.
+ */
+ hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
+
+ if ((!l2arc_nocompress && HDR_L2COMPRESS(hdr)) &&
+ hdr->b_l2hdr.b_asize >= buf_compress_minsz) {
+ if (l2arc_compress_buf(hdr)) {
+ /*
+ * If compression succeeded, enable headroom
+ * boost on the next scan cycle.
+ */
+ *headroom_boost = B_TRUE;
+ }
+ }
+
+ /*
+ * Pick up the buffer data we had previously stashed away
+ * (and now potentially also compressed).
+ */
+ buf_data = hdr->b_l1hdr.b_tmp_cdata;
+ buf_sz = hdr->b_l2hdr.b_asize;
+
+ /*
+ * We need to do this regardless if buf_sz is zero or
+ * not, otherwise, when this l2hdr is evicted we'll
+ * remove a reference that was never added.
+ */
+ (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr);
+
+ /* Compression may have squashed the buffer to zero length. */
+ if (buf_sz != 0) {
+ uint64_t buf_a_sz;
+
+ wzio = zio_write_phys(pio, dev->l2ad_vdev,
+ dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
+ NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
+ ZIO_FLAG_CANFAIL, B_FALSE);
+
+ DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
+ zio_t *, wzio);
+ (void) zio_nowait(wzio);
+
+ stats_size += buf_sz;
+
+ /*
+ * Keep the clock hand suitably device-aligned.
+ */
+ buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
+ write_asize += buf_a_sz;
+ dev->l2ad_hand += buf_a_sz;
+ }
+ }
+
+ mutex_exit(&dev->l2ad_mtx);
+
+ ASSERT3U(write_asize, <=, target_sz);
+ ARCSTAT_BUMP(arcstat_l2_writes_sent);
+ ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
+ ARCSTAT_INCR(arcstat_l2_size, write_sz);
+ ARCSTAT_INCR(arcstat_l2_asize, stats_size);
+ vdev_space_update(dev->l2ad_vdev, stats_size, 0, 0);
+
+ /*
+ * Bump device hand to the device start if it is approaching the end.
+ * l2arc_evict() will already have evicted ahead for this case.
+ */
+ if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
+ dev->l2ad_hand = dev->l2ad_start;
+ dev->l2ad_first = B_FALSE;
+ }
+
+ dev->l2ad_writing = B_TRUE;
+ (void) zio_wait(pio);
+ dev->l2ad_writing = B_FALSE;
+
+ return (write_asize);
+}
+
+/*
+ * Compresses an L2ARC buffer.
+ * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its
+ * size in l2hdr->b_asize. This routine tries to compress the data and
+ * depending on the compression result there are three possible outcomes:
+ * *) The buffer was incompressible. The original l2hdr contents were left
+ * untouched and are ready for writing to an L2 device.
+ * *) The buffer was all-zeros, so there is no need to write it to an L2
+ * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
+ * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
+ * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
+ * data buffer which holds the compressed data to be written, and b_asize
+ * tells us how much data there is. b_compress is set to the appropriate
+ * compression algorithm. Once writing is done, invoke
+ * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
+ *
+ * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
+ * buffer was incompressible).
+ */
+static boolean_t
+l2arc_compress_buf(arc_buf_hdr_t *hdr)
+{
+ void *cdata;
+ size_t csize, len, rounded;
+ l2arc_buf_hdr_t *l2hdr;
+
+ ASSERT(HDR_HAS_L2HDR(hdr));
+
+ l2hdr = &hdr->b_l2hdr;
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT3U(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF);
+ ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);
+
+ len = l2hdr->b_asize;
+ cdata = zio_data_buf_alloc(len);
+ ASSERT3P(cdata, !=, NULL);
+ csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata,
+ cdata, l2hdr->b_asize);
+
+ rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
+ if (rounded > csize) {
+ bzero((char *)cdata + csize, rounded - csize);
+ csize = rounded;
+ }
+
+ if (csize == 0) {
+ /* zero block, indicate that there's nothing to write */
+ zio_data_buf_free(cdata, len);
+ l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
+ l2hdr->b_asize = 0;
+ hdr->b_l1hdr.b_tmp_cdata = NULL;
+ ARCSTAT_BUMP(arcstat_l2_compress_zeros);
+ return (B_TRUE);
+ } else if (csize > 0 && csize < len) {
+ /*
+ * Compression succeeded, we'll keep the cdata around for
+ * writing and release it afterwards.
+ */
+ l2hdr->b_compress = ZIO_COMPRESS_LZ4;
+ l2hdr->b_asize = csize;
+ hdr->b_l1hdr.b_tmp_cdata = cdata;
+ ARCSTAT_BUMP(arcstat_l2_compress_successes);
+ return (B_TRUE);
+ } else {
+ /*
+ * Compression failed, release the compressed buffer.
+ * l2hdr will be left unmodified.
+ */
+ zio_data_buf_free(cdata, len);
+ ARCSTAT_BUMP(arcstat_l2_compress_failures);
+ return (B_FALSE);
+ }
+}
+
+/*
+ * Decompresses a zio read back from an l2arc device. On success, the
+ * underlying zio's io_data buffer is overwritten by the uncompressed
+ * version. On decompression error (corrupt compressed stream), the
+ * zio->io_error value is set to signal an I/O error.
+ *
+ * Please note that the compressed data stream is not checksummed, so
+ * if the underlying device is experiencing data corruption, we may feed
+ * corrupt data to the decompressor, so the decompressor needs to be
+ * able to handle this situation (LZ4 does).
+ */
+static void
+l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
+{
+ uint64_t csize;
+ void *cdata;
+
+ ASSERT(L2ARC_IS_VALID_COMPRESS(c));
+
+ if (zio->io_error != 0) {
+ /*
+ * An io error has occured, just restore the original io
+ * size in preparation for a main pool read.
+ */
+ zio->io_orig_size = zio->io_size = hdr->b_size;
+ return;
+ }
+
+ if (c == ZIO_COMPRESS_EMPTY) {
+ /*
+ * An empty buffer results in a null zio, which means we
+ * need to fill its io_data after we're done restoring the
+ * buffer's contents.
+ */
+ ASSERT(hdr->b_l1hdr.b_buf != NULL);
+ bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size);
+ zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data;
+ } else {
+ ASSERT(zio->io_data != NULL);
+ /*
+ * We copy the compressed data from the start of the arc buffer
+ * (the zio_read will have pulled in only what we need, the
+ * rest is garbage which we will overwrite at decompression)
+ * and then decompress back to the ARC data buffer. This way we
+ * can minimize copying by simply decompressing back over the
+ * original compressed data (rather than decompressing to an
+ * aux buffer and then copying back the uncompressed buffer,
+ * which is likely to be much larger).
+ */
+ csize = zio->io_size;
+ cdata = zio_data_buf_alloc(csize);
+ bcopy(zio->io_data, cdata, csize);
+ if (zio_decompress_data(c, cdata, zio->io_data, csize,
+ hdr->b_size) != 0)
+ zio->io_error = EIO;
+ zio_data_buf_free(cdata, csize);
+ }
+
+ /* Restore the expected uncompressed IO size. */
+ zio->io_orig_size = zio->io_size = hdr->b_size;
+}
+
+/*
+ * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
+ * This buffer serves as a temporary holder of compressed data while
+ * the buffer entry is being written to an l2arc device. Once that is
+ * done, we can dispose of it.
+ */
+static void
+l2arc_release_cdata_buf(arc_buf_hdr_t *hdr)
+{
+ enum zio_compress comp;
+
+ ASSERT(HDR_HAS_L1HDR(hdr));
+ ASSERT(HDR_HAS_L2HDR(hdr));
+ comp = hdr->b_l2hdr.b_compress;
+ ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp));
+
+ if (comp == ZIO_COMPRESS_OFF) {
+ /*
+ * In this case, b_tmp_cdata points to the same buffer
+ * as the arc_buf_t's b_data field. We don't want to
+ * free it, since the arc_buf_t will handle that.
+ */
+ hdr->b_l1hdr.b_tmp_cdata = NULL;
+ } else if (comp == ZIO_COMPRESS_EMPTY) {
+ /*
+ * In this case, b_tmp_cdata was compressed to an empty
+ * buffer, thus there's nothing to free and b_tmp_cdata
+ * should have been set to NULL in l2arc_write_buffers().
+ */
+ ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
+ } else {
+ /*
+ * If the data was compressed, then we've allocated a
+ * temporary buffer for it, so now we need to release it.
+ */
+ ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);
+ zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata,
+ hdr->b_size);
+ hdr->b_l1hdr.b_tmp_cdata = NULL;
+ }
+
+}
+
+/*
+ * This thread feeds the L2ARC at regular intervals. This is the beating
+ * heart of the L2ARC.
+ */
+static void
+l2arc_feed_thread(void)
+{
+ callb_cpr_t cpr;
+ l2arc_dev_t *dev;
+ spa_t *spa;
+ uint64_t size, wrote;
+ clock_t begin, next = ddi_get_lbolt();
+ boolean_t headroom_boost = B_FALSE;
+ fstrans_cookie_t cookie;
+
+ CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
+
+ mutex_enter(&l2arc_feed_thr_lock);
+
+ cookie = spl_fstrans_mark();
+ while (l2arc_thread_exit == 0) {
+ CALLB_CPR_SAFE_BEGIN(&cpr);
+ (void) cv_timedwait_sig(&l2arc_feed_thr_cv,
+ &l2arc_feed_thr_lock, next);
+ CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
+ next = ddi_get_lbolt() + hz;
+
+ /*
+ * Quick check for L2ARC devices.
+ */
+ mutex_enter(&l2arc_dev_mtx);
+ if (l2arc_ndev == 0) {
+ mutex_exit(&l2arc_dev_mtx);
+ continue;
+ }
+ mutex_exit(&l2arc_dev_mtx);
+ begin = ddi_get_lbolt();
+
+ /*
+ * This selects the next l2arc device to write to, and in
+ * doing so the next spa to feed from: dev->l2ad_spa. This
+ * will return NULL if there are now no l2arc devices or if
+ * they are all faulted.
+ *
+ * If a device is returned, its spa's config lock is also
+ * held to prevent device removal. l2arc_dev_get_next()
+ * will grab and release l2arc_dev_mtx.
+ */
+ if ((dev = l2arc_dev_get_next()) == NULL)
+ continue;
+
+ spa = dev->l2ad_spa;
+ ASSERT(spa != NULL);
+
+ /*
+ * If the pool is read-only then force the feed thread to
+ * sleep a little longer.
+ */
+ if (!spa_writeable(spa)) {
+ next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
+ spa_config_exit(spa, SCL_L2ARC, dev);
+ continue;
+ }
+
+ /*
+ * Avoid contributing to memory pressure.
+ */
+ if (arc_reclaim_needed()) {
+ ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
+ spa_config_exit(spa, SCL_L2ARC, dev);
+ continue;
+ }
+
+ ARCSTAT_BUMP(arcstat_l2_feeds);
+
+ size = l2arc_write_size();
+
+ /*
+ * Evict L2ARC buffers that will be overwritten.
+ */
+ l2arc_evict(dev, size, B_FALSE);
+
+ /*
+ * Write ARC buffers.
+ */
+ wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
+
+ /*
+ * Calculate interval between writes.
+ */
+ next = l2arc_write_interval(begin, size, wrote);
+ spa_config_exit(spa, SCL_L2ARC, dev);
+ }
+ spl_fstrans_unmark(cookie);
+
+ l2arc_thread_exit = 0;
+ cv_broadcast(&l2arc_feed_thr_cv);
+ CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
+ thread_exit();
+}
+
+boolean_t
+l2arc_vdev_present(vdev_t *vd)
+{
+ l2arc_dev_t *dev;
+
+ mutex_enter(&l2arc_dev_mtx);
+ for (dev = list_head(l2arc_dev_list); dev != NULL;
+ dev = list_next(l2arc_dev_list, dev)) {
+ if (dev->l2ad_vdev == vd)
+ break;
+ }
+ mutex_exit(&l2arc_dev_mtx);
+
+ return (dev != NULL);
+}
+
+/*
+ * Add a vdev for use by the L2ARC. By this point the spa has already
+ * validated the vdev and opened it.
+ */
+void
+l2arc_add_vdev(spa_t *spa, vdev_t *vd)
+{
+ l2arc_dev_t *adddev;
+
+ ASSERT(!l2arc_vdev_present(vd));
+
+ /*
+ * Create a new l2arc device entry.
+ */
+ adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
+ adddev->l2ad_spa = spa;
+ adddev->l2ad_vdev = vd;
+ adddev->l2ad_start = VDEV_LABEL_START_SIZE;
+ adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
+ adddev->l2ad_hand = adddev->l2ad_start;
+ adddev->l2ad_first = B_TRUE;
+ adddev->l2ad_writing = B_FALSE;
+ list_link_init(&adddev->l2ad_node);
+
+ mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
+ /*
+ * This is a list of all ARC buffers that are still valid on the
+ * device.
+ */
+ list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
+
+ vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
+ refcount_create(&adddev->l2ad_alloc);
+
+ /*
+ * Add device to global list
+ */
+ mutex_enter(&l2arc_dev_mtx);
+ list_insert_head(l2arc_dev_list, adddev);
+ atomic_inc_64(&l2arc_ndev);
+ mutex_exit(&l2arc_dev_mtx);
+}
+
+/*
+ * Remove a vdev from the L2ARC.
+ */
+void
+l2arc_remove_vdev(vdev_t *vd)
+{
+ l2arc_dev_t *dev, *nextdev, *remdev = NULL;
+
+ /*
+ * Find the device by vdev
+ */
+ mutex_enter(&l2arc_dev_mtx);
+ for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
+ nextdev = list_next(l2arc_dev_list, dev);
+ if (vd == dev->l2ad_vdev) {
+ remdev = dev;
+ break;
+ }
+ }
+ ASSERT(remdev != NULL);
+
+ /*
+ * Remove device from global list
+ */
+ list_remove(l2arc_dev_list, remdev);
+ l2arc_dev_last = NULL; /* may have been invalidated */
+ atomic_dec_64(&l2arc_ndev);
+ mutex_exit(&l2arc_dev_mtx);
+
+ /*
+ * Clear all buflists and ARC references. L2ARC device flush.
+ */
+ l2arc_evict(remdev, 0, B_TRUE);
+ list_destroy(&remdev->l2ad_buflist);
+ mutex_destroy(&remdev->l2ad_mtx);
+ refcount_destroy(&remdev->l2ad_alloc);
+ kmem_free(remdev, sizeof (l2arc_dev_t));
+}
+
+void
+l2arc_init(void)
+{
+ l2arc_thread_exit = 0;
+ l2arc_ndev = 0;
+ l2arc_writes_sent = 0;
+ l2arc_writes_done = 0;
+
+ mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
+ cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
+ mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
+
+ l2arc_dev_list = &L2ARC_dev_list;
+ l2arc_free_on_write = &L2ARC_free_on_write;
+ list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
+ offsetof(l2arc_dev_t, l2ad_node));
+ list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
+ offsetof(l2arc_data_free_t, l2df_list_node));
+}
+
+void
+l2arc_fini(void)
+{
+ /*
+ * This is called from dmu_fini(), which is called from spa_fini();
+ * Because of this, we can assume that all l2arc devices have
+ * already been removed when the pools themselves were removed.
+ */
+
+ l2arc_do_free_on_write();
+
+ mutex_destroy(&l2arc_feed_thr_lock);
+ cv_destroy(&l2arc_feed_thr_cv);
+ mutex_destroy(&l2arc_dev_mtx);
+ mutex_destroy(&l2arc_free_on_write_mtx);
+
+ list_destroy(l2arc_dev_list);
+ list_destroy(l2arc_free_on_write);
+}
+
+void
+l2arc_start(void)
+{
+ if (!(spa_mode_global & FWRITE))
+ return;
+
+ (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
+ TS_RUN, defclsyspri);
+}
+
+void
+l2arc_stop(void)
+{
+ if (!(spa_mode_global & FWRITE))
+ return;
+
+ mutex_enter(&l2arc_feed_thr_lock);
+ cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
+ l2arc_thread_exit = 1;
+ while (l2arc_thread_exit != 0)
+ cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
+ mutex_exit(&l2arc_feed_thr_lock);
+}
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+EXPORT_SYMBOL(arc_buf_size);
+EXPORT_SYMBOL(arc_write);
+EXPORT_SYMBOL(arc_read);
+EXPORT_SYMBOL(arc_buf_remove_ref);
+EXPORT_SYMBOL(arc_buf_info);
+EXPORT_SYMBOL(arc_getbuf_func);
+EXPORT_SYMBOL(arc_add_prune_callback);
+EXPORT_SYMBOL(arc_remove_prune_callback);
+
+module_param(zfs_arc_min, ulong, 0644);
+MODULE_PARM_DESC(zfs_arc_min, "Min arc size");
+
+module_param(zfs_arc_max, ulong, 0644);
+MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
+
+module_param(zfs_arc_meta_limit, ulong, 0644);
+MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
+
+module_param(zfs_arc_meta_min, ulong, 0644);
+MODULE_PARM_DESC(zfs_arc_meta_min, "Min arc metadata");
+
+module_param(zfs_arc_meta_prune, int, 0644);
+MODULE_PARM_DESC(zfs_arc_meta_prune, "Meta objects to scan for prune");
+
+module_param(zfs_arc_meta_adjust_restarts, int, 0644);
+MODULE_PARM_DESC(zfs_arc_meta_adjust_restarts,
+ "Limit number of restarts in arc_adjust_meta");
+
+module_param(zfs_arc_meta_strategy, int, 0644);
+MODULE_PARM_DESC(zfs_arc_meta_strategy, "Meta reclaim strategy");
+
+module_param(zfs_arc_grow_retry, int, 0644);
+MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size");
+
+module_param(zfs_arc_p_aggressive_disable, int, 0644);
+MODULE_PARM_DESC(zfs_arc_p_aggressive_disable, "disable aggressive arc_p grow");
+
+module_param(zfs_arc_p_dampener_disable, int, 0644);
+MODULE_PARM_DESC(zfs_arc_p_dampener_disable, "disable arc_p adapt dampener");
+
+module_param(zfs_arc_shrink_shift, int, 0644);
+MODULE_PARM_DESC(zfs_arc_shrink_shift, "log2(fraction of arc to reclaim)");
+
+module_param(zfs_arc_p_min_shift, int, 0644);
+MODULE_PARM_DESC(zfs_arc_p_min_shift, "arc_c shift to calc min/max arc_p");
+
+module_param(zfs_disable_dup_eviction, int, 0644);
+MODULE_PARM_DESC(zfs_disable_dup_eviction, "disable duplicate buffer eviction");
+
+module_param(zfs_arc_average_blocksize, int, 0444);
+MODULE_PARM_DESC(zfs_arc_average_blocksize, "Target average block size");
+
+module_param(zfs_arc_min_prefetch_lifespan, int, 0644);
+MODULE_PARM_DESC(zfs_arc_min_prefetch_lifespan, "Min life of prefetch block");
+
+module_param(zfs_arc_num_sublists_per_state, int, 0644);
+MODULE_PARM_DESC(zfs_arc_num_sublists_per_state,
+ "Number of sublists used in each of the ARC state lists");
+
+module_param(l2arc_write_max, ulong, 0644);
+MODULE_PARM_DESC(l2arc_write_max, "Max write bytes per interval");
+
+module_param(l2arc_write_boost, ulong, 0644);
+MODULE_PARM_DESC(l2arc_write_boost, "Extra write bytes during device warmup");
+
+module_param(l2arc_headroom, ulong, 0644);
+MODULE_PARM_DESC(l2arc_headroom, "Number of max device writes to precache");
+
+module_param(l2arc_headroom_boost, ulong, 0644);
+MODULE_PARM_DESC(l2arc_headroom_boost, "Compressed l2arc_headroom multiplier");
+
+module_param(l2arc_feed_secs, ulong, 0644);
+MODULE_PARM_DESC(l2arc_feed_secs, "Seconds between L2ARC writing");
+
+module_param(l2arc_feed_min_ms, ulong, 0644);
+MODULE_PARM_DESC(l2arc_feed_min_ms, "Min feed interval in milliseconds");
+
+module_param(l2arc_noprefetch, int, 0644);
+MODULE_PARM_DESC(l2arc_noprefetch, "Skip caching prefetched buffers");
+
+module_param(l2arc_nocompress, int, 0644);
+MODULE_PARM_DESC(l2arc_nocompress, "Skip compressing L2ARC buffers");
+
+module_param(l2arc_feed_again, int, 0644);
+MODULE_PARM_DESC(l2arc_feed_again, "Turbo L2ARC warmup");
+
+module_param(l2arc_norw, int, 0644);
+MODULE_PARM_DESC(l2arc_norw, "No reads during writes");
+
+module_param(zfs_arc_lotsfree_percent, int, 0644);
+MODULE_PARM_DESC(zfs_arc_lotsfree_percent,
+ "System free memory I/O throttle in bytes");
+
+module_param(zfs_arc_sys_free, ulong, 0644);
+MODULE_PARM_DESC(zfs_arc_sys_free, "System free memory target size in bytes");
+
+#endif
projects / mirror_ubuntu-artful-kernel.git / blobdiff