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/spinlock.h>
  19 #include <linux/zsmalloc.h>
  20
  21 #include "zcomp.h"
  22
  23 /*
  24  * Some arbitrary value. This is just to catch
  25  * invalid value for num_devices module parameter.
  26  */
  27 static const unsigned max_num_devices = 32;
  28
  29 /*-- Configurable parameters */
  30
  31 /*
  32  * Pages that compress to size greater than this are stored
  33  * uncompressed in memory.
  34  */
  35 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
  36
  37 /*
  38  * NOTE: max_zpage_size must be less than or equal to:
  39  *   ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
  40  * always return failure.
  41  */
  42
  43 /*-- End of configurable params */
  44
  45 #define SECTOR_SHIFT            9
  46 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  47 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  48 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
  49 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
  50 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK   \
  51         (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
  52
  53
  54 /*
  55  * The lower ZRAM_FLAG_SHIFT bits of table.value is for
  56  * object size (excluding header), the higher bits is for
  57  * zram_pageflags.
  58  *
  59  * zram is mainly used for memory efficiency so we want to keep memory
  60  * footprint small so we can squeeze size and flags into a field.
  61  * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
  62  * the higher bits is for zram_pageflags.
  63  */
  64 #define ZRAM_FLAG_SHIFT 24
  65
  66 /* Flags for zram pages (table[page_no].value) */
  67 enum zram_pageflags {
  68         /* Page consists entirely of zeros */
  69         ZRAM_ZERO = ZRAM_FLAG_SHIFT + 1,
  70         ZRAM_ACCESS,    /* page in now accessed */
  71
  72         __NR_ZRAM_PAGEFLAGS,
  73 };
  74
  75 /*-- Data structures */
  76
  77 /* Allocated for each disk page */
  78 struct zram_table_entry {
  79         unsigned long handle;
  80         unsigned long value;
  81 };
  82
  83 struct zram_stats {
  84         atomic64_t compr_data_size;     /* compressed size of pages stored */
  85         atomic64_t num_reads;   /* failed + successful */
  86         atomic64_t num_writes;  /* --do-- */
  87         atomic64_t failed_reads;        /* should NEVER! happen */
  88         atomic64_t failed_writes;       /* can happen when memory is too low */
  89         atomic64_t invalid_io;  /* non-page-aligned I/O requests */
  90         atomic64_t notify_free; /* no. of swap slot free notifications */
  91         atomic64_t zero_pages;          /* no. of zero filled pages */
  92         atomic64_t pages_stored;        /* no. of pages currently stored */
  93 };
  94
  95 struct zram_meta {
  96         struct zram_table_entry *table;
  97         struct zs_pool *mem_pool;
  98 };
  99
 100 struct zram {
 101         struct zram_meta *meta;
 102         struct request_queue *queue;
 103         struct gendisk *disk;
 104         struct zcomp *comp;
 105
 106         /* Prevent concurrent execution of device init, reset and R/W request */
 107         struct rw_semaphore init_lock;
 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         int max_comp_streams;
 114         struct zram_stats stats;
 115         char compressor[10];
 116 };
 117 #endif