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/zsmalloc.h>
  20
  21 #include "zcomp.h"
  22
  23 /*-- Configurable parameters */
  24
  25 /*
  26  * Pages that compress to size greater than this are stored
  27  * uncompressed in memory.
  28  */
  29 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
  30
  31 /*
  32  * NOTE: max_zpage_size must be less than or equal to:
  33  *   ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
  34  * always return failure.
  35  */
  36
  37 /*-- End of configurable params */
  38
  39 #define SECTOR_SHIFT            9
  40 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  41 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  42 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
  43 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
  44 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK   \
  45         (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
  46
  47
  48 /*
  49  * The lower ZRAM_FLAG_SHIFT bits of table.value is for
  50  * object size (excluding header), the higher bits is for
  51  * zram_pageflags.
  52  *
  53  * zram is mainly used for memory efficiency so we want to keep memory
  54  * footprint small so we can squeeze size and flags into a field.
  55  * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
  56  * the higher bits is for zram_pageflags.
  57  */
  58 #define ZRAM_FLAG_SHIFT 24
  59
  60 /* Flags for zram pages (table[page_no].value) */
  61 enum zram_pageflags {
  62         /* Page consists entirely of zeros */
  63         ZRAM_ZERO = ZRAM_FLAG_SHIFT,
  64         ZRAM_ACCESS,    /* page is now accessed */
  65
  66         __NR_ZRAM_PAGEFLAGS,
  67 };
  68
  69 /*-- Data structures */
  70
  71 /* Allocated for each disk page */
  72 struct zram_table_entry {
  73         unsigned long handle;
  74         unsigned long value;
  75 };
  76
  77 struct zram_stats {
  78         atomic64_t compr_data_size;     /* compressed size of pages stored */
  79         atomic64_t num_reads;   /* failed + successful */
  80         atomic64_t num_writes;  /* --do-- */
  81         atomic64_t failed_reads;        /* can happen when memory is too low */
  82         atomic64_t failed_writes;       /* can happen when memory is too low */
  83         atomic64_t invalid_io;  /* non-page-aligned I/O requests */
  84         atomic64_t notify_free; /* no. of swap slot free notifications */
  85         atomic64_t zero_pages;          /* no. of zero filled pages */
  86         atomic64_t pages_stored;        /* no. of pages currently stored */
  87         atomic_long_t max_used_pages;   /* no. of maximum pages stored */
  88         atomic64_t writestall;          /* no. of write slow paths */
  89 };
  90
  91 struct zram_meta {
  92         struct zram_table_entry *table;
  93         struct zs_pool *mem_pool;
  94 };
  95
  96 struct zram {
  97         struct zram_meta *meta;
  98         struct zcomp *comp;
  99         struct gendisk *disk;
 100         /* Prevent concurrent execution of device init */
 101         struct rw_semaphore init_lock;
 102         /*
 103          * the number of pages zram can consume for storing compressed data
 104          */
 105         unsigned long limit_pages;
 106
 107         struct zram_stats stats;
 108         atomic_t refcount; /* refcount for zram_meta */
 109         /* wait all IO under all of cpu are done */
 110         wait_queue_head_t io_done;
 111         /*
 112          * This is the limit on amount of *uncompressed* worth of data
 113          * we can store in a disk.
 114          */
 115         u64 disksize;   /* bytes */
 116         char compressor[10];
 117         /*
 118          * zram is claimed so open request will be failed
 119          */
 120         bool claim; /* Protected by bdev->bd_mutex */
 121 };
 122 #endif