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 #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))
33 * ZRAM is mainly used for memory efficiency so we want to keep memory
34 * footprint small and thus squeeze size and zram pageflags into a flags
35 * member. The lower ZRAM_FLAG_SHIFT bits is for object size (excluding
36 * header), which cannot be larger than PAGE_SIZE (requiring PAGE_SHIFT
37 * bits), the higher bits are for zram_pageflags.
39 * We use BUILD_BUG_ON() to make sure that zram pageflags don't overflow.
41 #define ZRAM_FLAG_SHIFT (PAGE_SHIFT + 1)
43 /* Only 2 bits are allowed for comp priority index */
44 #define ZRAM_COMP_PRIORITY_MASK 0x3
46 /* Flags for zram pages (table[page_no].flags) */
48 /* zram slot is locked */
49 ZRAM_LOCK = ZRAM_FLAG_SHIFT,
50 ZRAM_SAME, /* Page consists the same element */
51 ZRAM_WB, /* page is stored on backing_device */
52 ZRAM_UNDER_WB, /* page is under writeback */
53 ZRAM_HUGE, /* Incompressible page */
54 ZRAM_IDLE, /* not accessed page since last idle marking */
55 ZRAM_INCOMPRESSIBLE, /* none of the algorithms could compress it */
57 ZRAM_COMP_PRIORITY_BIT1, /* First bit of comp priority index */
58 ZRAM_COMP_PRIORITY_BIT2, /* Second bit of comp priority index */
63 /*-- Data structures */
65 /* Allocated for each disk page */
66 struct zram_table_entry {
69 unsigned long element;
72 #ifdef CONFIG_PREEMPT_RT
75 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
81 atomic64_t compr_data_size; /* compressed size of pages stored */
82 atomic64_t failed_reads; /* can happen when memory is too low */
83 atomic64_t failed_writes; /* can happen when memory is too low */
84 atomic64_t notify_free; /* no. of swap slot free notifications */
85 atomic64_t same_pages; /* no. of same element filled pages */
86 atomic64_t huge_pages; /* no. of huge pages */
87 atomic64_t huge_pages_since; /* no. of huge pages since zram set up */
88 atomic64_t pages_stored; /* no. of pages currently stored */
89 atomic_long_t max_used_pages; /* no. of maximum pages stored */
90 atomic64_t writestall; /* no. of write slow paths */
91 atomic64_t miss_free; /* no. of missed free */
92 #ifdef CONFIG_ZRAM_WRITEBACK
93 atomic64_t bd_count; /* no. of pages in backing device */
94 atomic64_t bd_reads; /* no. of reads from backing device */
95 atomic64_t bd_writes; /* no. of writes from backing device */
99 #ifdef CONFIG_ZRAM_MULTI_COMP
100 #define ZRAM_PRIMARY_COMP 0U
101 #define ZRAM_SECONDARY_COMP 1U
102 #define ZRAM_MAX_COMPS 4U
104 #define ZRAM_PRIMARY_COMP 0U
105 #define ZRAM_SECONDARY_COMP 0U
106 #define ZRAM_MAX_COMPS 1U
110 struct zram_table_entry *table;
111 struct zs_pool *mem_pool;
112 struct zcomp *comps[ZRAM_MAX_COMPS];
113 struct gendisk *disk;
114 /* Prevent concurrent execution of device init */
115 struct rw_semaphore init_lock;
117 * the number of pages zram can consume for storing compressed data
119 unsigned long limit_pages;
121 struct zram_stats stats;
123 * This is the limit on amount of *uncompressed* worth of data
124 * we can store in a disk.
126 u64 disksize; /* bytes */
127 const char *comp_algs[ZRAM_MAX_COMPS];
130 * zram is claimed so open request will be failed
132 bool claim; /* Protected by disk->open_mutex */
133 #ifdef CONFIG_ZRAM_WRITEBACK
134 struct file *backing_dev;
135 spinlock_t wb_limit_lock;
136 bool wb_limit_enable;
138 struct block_device *bdev;
139 unsigned long *bitmap;
140 unsigned long nr_pages;
142 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
143 struct dentry *debugfs_dir;