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 #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) */
  45 enum 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 */
  58 struct 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
  69 struct 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
  84 struct 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