release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/staging/zram/zram_drv.h

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #ifndef _ZRAM_DRV_H_
  16 #define _ZRAM_DRV_H_
  17
  18 #include <linux/spinlock.h>
  19 #include <linux/mutex.h>
  20
  21 #include "zram_ioctl.h"
  22 #include "xvmalloc.h"
  23
  24 /*
  25  * Some arbitrary value. This is just to catch
  26  * invalid value for num_devices module parameter.
  27  */
  28 static const unsigned max_num_devices = 32;
  29
  30 /*
  31  * Stored at beginning of each compressed object.
  32  *
  33  * It stores back-reference to table entry which points to this
  34  * object. This is required to support memory defragmentation.
  35  */
  36 struct zobj_header {
  37 };
  38
  39 /*-- Configurable parameters */
  40
  41 /* Default zram disk size: 25% of total RAM */
  42 static const unsigned default_disksize_perc_ram = 25;
  43
  44 /*
  45  * Pages that compress to size greater than this are stored
  46  * uncompressed in memory.
  47  */
  48 static const unsigned max_zpage_size = PAGE_SIZE / 4 * 3;
  49
  50 /*
  51  * NOTE: max_zpage_size must be less than or equal to:
  52  *   XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
  53  * otherwise, xv_malloc() would always return failure.
  54  */
  55
  56 /*-- End of configurable params */
  57
  58 #define SECTOR_SHIFT            9
  59 #define SECTOR_SIZE             (1 << SECTOR_SHIFT)
  60 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  61 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  62
  63 /* Flags for zram pages (table[page_no].flags) */
  64 enum zram_pageflags {
  65         /* Page is stored uncompressed */
  66         ZRAM_UNCOMPRESSED,
  67
  68         /* Page consists entirely of zeros */
  69         ZRAM_ZERO,
  70
  71         __NR_ZRAM_PAGEFLAGS,
  72 };
  73
  74 /*-- Data structures */
  75
  76 /* Allocated for each disk page */
  77 struct table {
  78         struct page *page;
  79         u16 offset;
  80         u8 count;       /* object ref count (not yet used) */
  81         u8 flags;
  82 } __attribute__((aligned(4)));
  83
  84 struct zram_stats {
  85         /* basic stats */
  86         size_t compr_size;      /* compressed size of pages stored -
  87                                  * needed to enforce memlimit */
  88         /* more stats */
  89 #if defined(CONFIG_ZRAM_STATS)
  90         u64 num_reads;          /* failed + successful */
  91         u64 num_writes;         /* --do-- */
  92         u64 failed_reads;       /* should NEVER! happen */
  93         u64 failed_writes;      /* can happen when memory is too low */
  94         u64 invalid_io;         /* non-page-aligned I/O requests */
  95         u64 notify_free;        /* no. of swap slot free notifications */
  96         u32 pages_zero;         /* no. of zero filled pages */
  97         u32 pages_stored;       /* no. of pages currently stored */
  98         u32 good_compress;      /* % of pages with compression ratio<=50% */
  99         u32 pages_expand;       /* % of incompressible pages */
 100 #endif
 101 };
 102
 103 struct zram {
 104         struct xv_pool *mem_pool;
 105         void *compress_workmem;
 106         void *compress_buffer;
 107         struct table *table;
 108         spinlock_t stat64_lock; /* protect 64-bit stats */
 109         struct mutex lock;      /* protect compression buffers against
 110                                  * concurrent writes */
 111         struct request_queue *queue;
 112         struct gendisk *disk;
 113         int init_done;
 114         /*
 115          * This is the limit on amount of *uncompressed* worth of data
 116          * we can store in a disk.
 117          */
 118         size_t disksize;        /* bytes */
 119
 120         struct zram_stats stats;
 121 };
 122
 123 /*-- */
 124
 125 /* Debugging and Stats */
 126 #if defined(CONFIG_ZRAM_STATS)
 127 static void zram_stat_inc(u32 *v)
 128 {
 129         *v = *v + 1;
 130 }
 131
 132 static void zram_stat_dec(u32 *v)
 133 {
 134         *v = *v - 1;
 135 }
 136
 137 static void zram_stat64_inc(struct zram *zram, u64 *v)
 138 {
 139         spin_lock(&zram->stat64_lock);
 140         *v = *v + 1;
 141         spin_unlock(&zram->stat64_lock);
 142 }
 143
 144 static u64 zram_stat64_read(struct zram *zram, u64 *v)
 145 {
 146         u64 val;
 147
 148         spin_lock(&zram->stat64_lock);
 149         val = *v;
 150         spin_unlock(&zram->stat64_lock);
 151
 152         return val;
 153 }
 154 #else
 155 #define zram_stat_inc(v)
 156 #define zram_stat_dec(v)
 157 #define zram_stat64_inc(r, v)
 158 #define zram_stat64_read(r, v)
 159 #endif /* CONFIG_ZRAM_STATS */
 160
 161 #endif