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/spinlock.h>
19 #include <linux/zsmalloc.h>
23 /*-- Configurable parameters */
26 * Pages that compress to size greater than this are stored
27 * uncompressed in memory.
29 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
32 * NOTE: max_zpage_size must be less than or equal to:
33 * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
34 * always return failure.
37 /*-- End of configurable params */
39 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
40 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
41 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
42 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
43 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
44 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
48 * The lower ZRAM_FLAG_SHIFT bits of table.value is for
49 * object size (excluding header), the higher bits is for
52 * zram is mainly used for memory efficiency so we want to keep memory
53 * footprint small so we can squeeze size and flags into a field.
54 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
55 * the higher bits is for zram_pageflags.
57 #define ZRAM_FLAG_SHIFT 24
59 /* Flags for zram pages (table[page_no].value) */
61 /* Page consists entirely of zeros */
62 ZRAM_ZERO = ZRAM_FLAG_SHIFT,
63 ZRAM_ACCESS, /* page is now accessed */
68 /*-- Data structures */
70 /* Allocated for each disk page */
71 struct zram_table_entry {
77 atomic64_t compr_data_size; /* compressed size of pages stored */
78 atomic64_t num_reads; /* failed + successful */
79 atomic64_t num_writes; /* --do-- */
80 atomic64_t failed_reads; /* can happen when memory is too low */
81 atomic64_t failed_writes; /* can happen when memory is too low */
82 atomic64_t invalid_io; /* non-page-aligned I/O requests */
83 atomic64_t notify_free; /* no. of swap slot free notifications */
84 atomic64_t zero_pages; /* no. of zero filled pages */
85 atomic64_t pages_stored; /* no. of pages currently stored */
86 atomic_long_t max_used_pages; /* no. of maximum pages stored */
90 struct zram_table_entry *table;
91 struct zs_pool *mem_pool;
95 struct zram_meta *meta;
98 /* Prevent concurrent execution of device init */
99 struct rw_semaphore init_lock;
101 * the number of pages zram can consume for storing compressed data
103 unsigned long limit_pages;
104 int max_comp_streams;
106 struct zram_stats stats;
107 atomic_t refcount; /* refcount for zram_meta */
108 /* wait all IO under all of cpu are done */
109 wait_queue_head_t io_done;
111 * This is the limit on amount of *uncompressed* worth of data
112 * we can store in a disk.
114 u64 disksize; /* bytes */
117 * zram is claimed so open request will be failed
119 bool claim; /* Protected by bdev->bd_mutex */