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#define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  25#define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  26#define ZRAM_LOGICAL_BLOCK_SHIFT 12
  27#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
  28#define ZRAM_SECTOR_PER_LOGICAL_BLOCK   \
  29        (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
  30
  31
  32/*
  33 * The lower ZRAM_FLAG_SHIFT bits of table.value is for
  34 * object size (excluding header), the higher bits is for
  35 * zram_pageflags.
  36 *
  37 * zram is mainly used for memory efficiency so we want to keep memory
  38 * footprint small so we can squeeze size and flags into a field.
  39 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
  40 * the higher bits is for zram_pageflags.
  41 */
  42#define ZRAM_FLAG_SHIFT 24
  43
  44/* Flags for zram pages (table[page_no].value) */
  45enum zram_pageflags {
  46        /* zram slot is locked */
  47        ZRAM_LOCK = ZRAM_FLAG_SHIFT,
  48        ZRAM_SAME,      /* Page consists the same element */
  49        ZRAM_WB,        /* page is stored on backing_device */
  50        ZRAM_HUGE,      /* Incompressible page */
  51
  52        __NR_ZRAM_PAGEFLAGS,
  53};
  54
  55/*-- Data structures */
  56
  57/* Allocated for each disk page */
  58struct zram_table_entry {
  59        union {
  60                unsigned long handle;
  61                unsigned long element;
  62        };
  63        unsigned long value;
  64#ifdef CONFIG_ZRAM_MEMORY_TRACKING
  65        ktime_t ac_time;
  66#endif
  67};
  68
  69struct zram_stats {
  70        atomic64_t compr_data_size;     /* compressed size of pages stored */
  71        atomic64_t num_reads;   /* failed + successful */
  72        atomic64_t num_writes;  /* --do-- */
  73        atomic64_t failed_reads;        /* can happen when memory is too low */
  74        atomic64_t failed_writes;       /* can happen when memory is too low */
  75        atomic64_t invalid_io;  /* non-page-aligned I/O requests */
  76        atomic64_t notify_free; /* no. of swap slot free notifications */
  77        atomic64_t same_pages;          /* no. of same element filled pages */
  78        atomic64_t huge_pages;          /* no. of huge pages */
  79        atomic64_t pages_stored;        /* no. of pages currently stored */
  80        atomic_long_t max_used_pages;   /* no. of maximum pages stored */
  81        atomic64_t writestall;          /* no. of write slow paths */
  82};
  83
  84struct zram {
  85        struct zram_table_entry *table;
  86        struct zs_pool *mem_pool;
  87        struct zcomp *comp;
  88        struct gendisk *disk;
  89        /* Prevent concurrent execution of device init */
  90        struct rw_semaphore init_lock;
  91        /*
  92         * the number of pages zram can consume for storing compressed data
  93         */
  94        unsigned long limit_pages;
  95
  96        struct zram_stats stats;
  97        /*
  98         * This is the limit on amount of *uncompressed* worth of data
  99         * we can store in a disk.
 100         */
 101        u64 disksize;   /* bytes */
 102        char compressor[CRYPTO_MAX_ALG_NAME];
 103        /*
 104         * zram is claimed so open request will be failed
 105         */
 106        bool claim; /* Protected by bdev->bd_mutex */
 107#ifdef CONFIG_ZRAM_WRITEBACK
 108        struct file *backing_dev;
 109        struct block_device *bdev;
 110        unsigned int old_block_size;
 111        unsigned long *bitmap;
 112        unsigned long nr_pages;
 113        spinlock_t bitmap_lock;
 114#endif
 115#ifdef CONFIG_ZRAM_MEMORY_TRACKING
 116        struct dentry *debugfs_dir;
 117#endif
 118};
 119#endif
 120