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/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 */
  29static 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) */
  61enum 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 */
  72struct zram_table_entry {
  73        unsigned long handle;
  74        unsigned long value;
  75};
  76
  77struct 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};
  89
  90struct zram_meta {
  91        struct zram_table_entry *table;
  92        struct zs_pool *mem_pool;
  93};
  94
  95struct zram {
  96        struct zram_meta *meta;
  97        struct zcomp *comp;
  98        struct gendisk *disk;
  99        /* Prevent concurrent execution of device init */
 100        struct rw_semaphore init_lock;
 101        /*
 102         * the number of pages zram can consume for storing compressed data
 103         */
 104        unsigned long limit_pages;
 105        int max_comp_streams;
 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
 123