drivers/block/zram/zram_drv.h

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *               2012, 2013 Minchan Kim
   6  *
   7  * This code is released using a dual license strategy: BSD/GPL
   8  * You can choose the licence that better fits your requirements.
   9  *
  10  * Released under the terms of 3-clause BSD License
  11  * Released under the terms of GNU General Public License Version 2.0
  12  *
  13  */
  14
  15 #ifndef _ZRAM_DRV_H_
  16 #define _ZRAM_DRV_H_
  17
  18 #include <linux/spinlock.h>
  19 #include <linux/mutex.h>
  20 #include <linux/zsmalloc.h>
  21
  22 /*
  23  * Some arbitrary value. This is just to catch
  24  * invalid value for num_devices module parameter.
  25  */
  26 static const unsigned max_num_devices = 32;
  27
  28 /*-- Configurable parameters */
  29
  30 /*
  31  * Pages that compress to size greater than this are stored
  32  * uncompressed in memory.
  33  */
  34 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
  35
  36 /*
  37  * NOTE: max_zpage_size must be less than or equal to:
  38  *   ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
  39  * always return failure.
  40  */
  41
  42 /*-- End of configurable params */
  43
  44 #define SECTOR_SHIFT            9
  45 #define SECTOR_SIZE             (1 << SECTOR_SHIFT)
  46 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  47 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  48 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
  49 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
  50 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK   \
  51         (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
  52
  53 /* Flags for zram pages (table[page_no].flags) */
  54 enum zram_pageflags {
  55         /* Page consists entirely of zeros */
  56         ZRAM_ZERO,
  57
  58         __NR_ZRAM_PAGEFLAGS,
  59 };
  60
  61 /*-- Data structures */
  62
  63 /* Allocated for each disk page */
  64 struct table {
  65         unsigned long handle;
  66         u16 size;       /* object size (excluding header) */
  67         u8 count;       /* object ref count (not yet used) */
  68         u8 flags;
  69 } __aligned(4);
  70
  71 struct zram_stats {
  72         atomic64_t compr_size;  /* compressed size of pages stored */
  73         atomic64_t num_reads;   /* failed + successful */
  74         atomic64_t num_writes;  /* --do-- */
  75         atomic64_t failed_reads;        /* should NEVER! happen */
  76         atomic64_t failed_writes;       /* can happen when memory is too low */
  77         atomic64_t invalid_io;  /* non-page-aligned I/O requests */
  78         atomic64_t notify_free; /* no. of swap slot free notifications */
  79         atomic_t pages_zero;            /* no. of zero filled pages */
  80         atomic_t pages_stored;  /* no. of pages currently stored */
  81         atomic_t good_compress; /* % of pages with compression ratio<=50% */
  82         atomic_t bad_compress;  /* % of pages with compression ratio>=75% */
  83 };
  84
  85 struct zram_meta {
  86         rwlock_t tb_lock;       /* protect table */
  87         void *compress_workmem;
  88         void *compress_buffer;
  89         struct table *table;
  90         struct zs_pool *mem_pool;
  91         struct mutex buffer_lock; /* protect compress buffers */
  92 };
  93
  94 struct zram {
  95         struct zram_meta *meta;
  96         struct request_queue *queue;
  97         struct gendisk *disk;
  98         int init_done;
  99         /* Prevent concurrent execution of device init, reset and R/W request */
 100         struct rw_semaphore init_lock;
 101         /*
 102          * This is the limit on amount of *uncompressed* worth of data
 103          * we can store in a disk.
 104          */
 105         u64 disksize;   /* bytes */
 106
 107         struct zram_stats stats;
 108 };
 109 #endif