2 * Compressed RAM block device
4 * Copyright (C) 2008, 2009, 2010 Nitin Gupta
5 * 2012, 2013 Minchan Kim
7 * This code is released using a dual license strategy: BSD/GPL
8 * You can choose the licence that better fits your requirements.
10 * Released under the terms of 3-clause BSD License
11 * Released under the terms of GNU General Public License Version 2.0
18 #include <linux/rwsem.h>
19 #include <linux/zsmalloc.h>
20 #include <linux/crypto.h>
24 /*-- Configurable parameters */
27 * Pages that compress to size greater than this are stored
28 * uncompressed in memory.
30 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
33 * NOTE: max_zpage_size must be less than or equal to:
34 * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
35 * always return failure.
38 /*-- End of configurable params */
40 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
41 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
42 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
43 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
44 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
45 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
49 * The lower ZRAM_FLAG_SHIFT bits of table.value is for
50 * object size (excluding header), the higher bits is for
53 * zram is mainly used for memory efficiency so we want to keep memory
54 * footprint small so we can squeeze size and flags into a field.
55 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
56 * the higher bits is for zram_pageflags.
58 #define ZRAM_FLAG_SHIFT 24
60 /* Flags for zram pages (table[page_no].value) */
62 /* Page consists the same element */
63 ZRAM_SAME = ZRAM_FLAG_SHIFT,
64 ZRAM_ACCESS, /* page is now accessed */
65 ZRAM_WB, /* page is stored on backing_device */
70 /*-- Data structures */
72 /* Allocated for each disk page */
73 struct zram_table_entry {
76 unsigned long element;
82 atomic64_t compr_data_size; /* compressed size of pages stored */
83 atomic64_t num_reads; /* failed + successful */
84 atomic64_t num_writes; /* --do-- */
85 atomic64_t failed_reads; /* can happen when memory is too low */
86 atomic64_t failed_writes; /* can happen when memory is too low */
87 atomic64_t invalid_io; /* non-page-aligned I/O requests */
88 atomic64_t notify_free; /* no. of swap slot free notifications */
89 atomic64_t same_pages; /* no. of same element filled pages */
90 atomic64_t pages_stored; /* no. of pages currently stored */
91 atomic_long_t max_used_pages; /* no. of maximum pages stored */
92 atomic64_t writestall; /* no. of write slow paths */
96 struct zram_table_entry *table;
97 struct zs_pool *mem_pool;
100 /* Prevent concurrent execution of device init */
101 struct rw_semaphore init_lock;
103 * the number of pages zram can consume for storing compressed data
105 unsigned long limit_pages;
107 struct zram_stats stats;
109 * This is the limit on amount of *uncompressed* worth of data
110 * we can store in a disk.
112 u64 disksize; /* bytes */
113 char compressor[CRYPTO_MAX_ALG_NAME];
115 * zram is claimed so open request will be failed
117 bool claim; /* Protected by bdev->bd_mutex */
118 #ifdef CONFIG_ZRAM_WRITEBACK
119 struct file *backing_dev;
120 struct block_device *bdev;
121 unsigned int old_block_size;
122 unsigned long *bitmap;
123 unsigned long nr_pages;
124 spinlock_t bitmap_lock;