zfs/include/sys/zfs_rlock.h

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 #ifndef _SYS_FS_ZFS_RLOCK_H
  27 #define _SYS_FS_ZFS_RLOCK_H
  28
  29 #ifdef  __cplusplus
  30 extern "C" {
  31 #endif
  32
  33 #ifdef _KERNEL
  34
  35 #include <sys/list.h>
  36 #include <sys/avl.h>
  37 #include <sys/condvar.h>
  38
  39 typedef enum {
  40         RL_READER,
  41         RL_WRITER,
  42         RL_APPEND
  43 } rl_type_t;
  44
  45 typedef struct zfs_rlock {
  46         kmutex_t zr_mutex;      /* protects changes to zr_avl */
  47         avl_tree_t zr_avl;      /* avl tree of range locks */
  48         uint64_t *zr_size;      /* points to znode->z_size */
  49         uint_t *zr_blksz;       /* points to znode->z_blksz */
  50         uint64_t *zr_max_blksz; /* points to zsb->z_max_blksz */
  51 } zfs_rlock_t;
  52
  53 typedef struct rl {
  54         zfs_rlock_t *r_zrl;
  55         avl_node_t r_node;      /* avl node link */
  56         uint64_t r_off;         /* file range offset */
  57         uint64_t r_len;         /* file range length */
  58         uint_t r_cnt;           /* range reference count in tree */
  59         rl_type_t r_type;       /* range type */
  60         kcondvar_t r_wr_cv;     /* cv for waiting writers */
  61         kcondvar_t r_rd_cv;     /* cv for waiting readers */
  62         uint8_t r_proxy;        /* acting for original range */
  63         uint8_t r_write_wanted; /* writer wants to lock this range */
  64         uint8_t r_read_wanted;  /* reader wants to lock this range */
  65         list_node_t rl_node;    /* used for deferred release */
  66 } rl_t;
  67
  68 /*
  69  * Lock a range (offset, length) as either shared (RL_READER)
  70  * or exclusive (RL_WRITER or RL_APPEND).  RL_APPEND is a special type that
  71  * is converted to RL_WRITER that specified to lock from the start of the
  72  * end of file.  Returns the range lock structure.
  73  */
  74 rl_t *zfs_range_lock(zfs_rlock_t *zrl, uint64_t off, uint64_t len,
  75     rl_type_t type);
  76
  77 /* Unlock range and destroy range lock structure. */
  78 void zfs_range_unlock(rl_t *rl);
  79
  80 /*
  81  * Reduce range locked as RW_WRITER from whole file to specified range.
  82  * Asserts the whole file was previously locked.
  83  */
  84 void zfs_range_reduce(rl_t *rl, uint64_t off, uint64_t len);
  85
  86 /*
  87  * AVL comparison function used to order range locks
  88  * Locks are ordered on the start offset of the range.
  89  */
  90 int zfs_range_compare(const void *arg1, const void *arg2);
  91
  92 static inline void
  93 zfs_rlock_init(zfs_rlock_t *zrl)
  94 {
  95         mutex_init(&zrl->zr_mutex, NULL, MUTEX_DEFAULT, NULL);
  96         avl_create(&zrl->zr_avl, zfs_range_compare,
  97             sizeof (rl_t), offsetof(rl_t, r_node));
  98         zrl->zr_size = NULL;
  99         zrl->zr_blksz = NULL;
 100         zrl->zr_max_blksz = NULL;
 101 }
 102
 103 static inline void
 104 zfs_rlock_destroy(zfs_rlock_t *zrl)
 105 {
 106         avl_destroy(&zrl->zr_avl);
 107         mutex_destroy(&zrl->zr_mutex);
 108 }
 109 #endif /* _KERNEL */
 110
 111 #ifdef  __cplusplus
 112 }
 113 #endif
 114
 115 #endif  /* _SYS_FS_ZFS_RLOCK_H */