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