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.flags 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].flags) */
  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_UNDER_WB,  /* page is under writeback */
  51        ZRAM_HUGE,      /* Incompressible page */
  52        ZRAM_IDLE,      /* not accessed page since last idle marking */
  53
  54        __NR_ZRAM_PAGEFLAGS,
  55};
  56
  57/*-- Data structures */
  58
  59/* Allocated for each disk page */
  60struct zram_table_entry {
  61        union {
  62                unsigned long handle;
  63                unsigned long element;
  64        };
  65        unsigned long flags;
  66#ifdef CONFIG_ZRAM_MEMORY_TRACKING
  67        ktime_t ac_time;
  68#endif
  69};
  70
  71struct zram_stats {
  72        atomic64_t compr_data_size;     /* compressed size of pages stored */
  73        atomic64_t num_reads;   /* failed + successful */
  74        atomic64_t num_writes;  /* --do-- */
  75        atomic64_t failed_reads;        /* can happen when memory is too low */
  76        atomic64_t failed_writes;       /* can happen when memory is too low */
  77        atomic64_t invalid_io;  /* non-page-aligned I/O requests */
  78        atomic64_t notify_free; /* no. of swap slot free notifications */
  79        atomic64_t same_pages;          /* no. of same element filled pages */
  80        atomic64_t huge_pages;          /* no. of huge pages */
  81        atomic64_t huge_pages_since;    /* no. of huge pages since zram set up */
  82        atomic64_t pages_stored;        /* no. of pages currently stored */
  83        atomic_long_t max_used_pages;   /* no. of maximum pages stored */
  84        atomic64_t writestall;          /* no. of write slow paths */
  85        atomic64_t miss_free;           /* no. of missed free */
  86#ifdef  CONFIG_ZRAM_WRITEBACK
  87        atomic64_t bd_count;            /* no. of pages in backing device */
  88        atomic64_t bd_reads;            /* no. of reads from backing device */
  89        atomic64_t bd_writes;           /* no. of writes from backing device */
  90#endif
  91};
  92
  93struct zram {
  94        struct zram_table_entry *table;
  95        struct zs_pool *mem_pool;
  96        struct zcomp *comp;
  97        struct gendisk *disk;
  98        /* Prevent concurrent execution of device init */
  99        struct rw_semaphore init_lock;
 100        /*
 101         * the number of pages zram can consume for storing compressed data
 102         */
 103        unsigned long limit_pages;
 104
 105        struct zram_stats stats;
 106        /*
 107         * This is the limit on amount of *uncompressed* worth of data
 108         * we can store in a disk.
 109         */
 110        u64 disksize;   /* bytes */
 111        char compressor[CRYPTO_MAX_ALG_NAME];
 112        /*
 113         * zram is claimed so open request will be failed
 114         */
 115        bool claim; /* Protected by disk->open_mutex */
 116#ifdef CONFIG_ZRAM_WRITEBACK
 117        struct file *backing_dev;
 118        spinlock_t wb_limit_lock;
 119        bool wb_limit_enable;
 120        u64 bd_wb_limit;
 121        struct block_device *bdev;
 122        unsigned long *bitmap;
 123        unsigned long nr_pages;
 124#endif
 125#ifdef CONFIG_ZRAM_MEMORY_TRACKING
 126        struct dentry *debugfs_dir;
 127#endif
 128};
 129#endif
 130