LXR linux/drivers/block/zram/zram

   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 */
  30static 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) */
  62enum 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 */
  73struct zram_table_entry {
  74        union {
  75                unsigned long handle;
  76                unsigned long element;
  77        };
  78        unsigned long value;
  79};
  80
  81struct 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
  95struct 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
 120