drivers/staging/zram/zram_drv.h

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #ifndef _ZRAM_DRV_H_
  16 #define _ZRAM_DRV_H_
  17
  18 #include <linux/spinlock.h>
  19 #include <linux/mutex.h>
  20
  21 #include "../zsmalloc/zsmalloc.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 /* Default zram disk size: 25% of total RAM */
  32 static const unsigned default_disksize_perc_ram = 25;
  33
  34 /*
  35  * Pages that compress to size greater than this are stored
  36  * uncompressed in memory.
  37  */
  38 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
  39
  40 /*
  41  * NOTE: max_zpage_size must be less than or equal to:
  42  *   ZS_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
  43  * otherwise, xv_malloc() would always return failure.
  44  */
  45
  46 /*-- End of configurable params */
  47
  48 #define SECTOR_SHIFT            9
  49 #define SECTOR_SIZE             (1 << SECTOR_SHIFT)
  50 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  51 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  52 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
  53 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
  54 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK   \
  55         (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
  56
  57 /* Flags for zram pages (table[page_no].flags) */
  58 enum zram_pageflags {
  59         /* Page consists entirely of zeros */
  60         ZRAM_ZERO,
  61
  62         __NR_ZRAM_PAGEFLAGS,
  63 };
  64
  65 /*-- Data structures */
  66
  67 /* Allocated for each disk page */
  68 struct table {
  69         unsigned long handle;
  70         u16 size;       /* object size (excluding header) */
  71         u8 count;       /* object ref count (not yet used) */
  72         u8 flags;
  73 } __aligned(4);
  74
  75 struct zram_stats {
  76         u64 compr_size;         /* compressed size of pages stored */
  77         u64 num_reads;          /* failed + successful */
  78         u64 num_writes;         /* --do-- */
  79         u64 failed_reads;       /* should NEVER! happen */
  80         u64 failed_writes;      /* can happen when memory is too low */
  81         u64 invalid_io;         /* non-page-aligned I/O requests */
  82         u64 notify_free;        /* no. of swap slot free notifications */
  83         u32 pages_zero;         /* no. of zero filled pages */
  84         u32 pages_stored;       /* no. of pages currently stored */
  85         u32 good_compress;      /* % of pages with compression ratio<=50% */
  86         u32 bad_compress;       /* % of pages with compression ratio>=75% */
  87 };
  88
  89 struct zram {
  90         struct zs_pool *mem_pool;
  91         void *compress_workmem;
  92         void *compress_buffer;
  93         struct table *table;
  94         spinlock_t stat64_lock; /* protect 64-bit stats */
  95         struct rw_semaphore lock; /* protect compression buffers and table
  96                                    * against concurrent read and writes */
  97         struct request_queue *queue;
  98         struct gendisk *disk;
  99         int init_done;
 100         /* Prevent concurrent execution of device init, reset and R/W request */
 101         struct rw_semaphore init_lock;
 102         /*
 103          * This is the limit on amount of *uncompressed* worth of data
 104          * we can store in a disk.
 105          */
 106         u64 disksize;   /* bytes */
 107
 108         struct zram_stats stats;
 109 };
 110
 111 extern struct zram *zram_devices;
 112 unsigned int zram_get_num_devices(void);
 113 #ifdef CONFIG_SYSFS
 114 extern struct attribute_group zram_disk_attr_group;
 115 #endif
 116
 117 extern int zram_init_device(struct zram *zram);
 118 extern void __zram_reset_device(struct zram *zram);
 119
 120 #endif