tjh.dev
Linux kernel mirror (for testing)
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kernel
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linux
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/rwsem.h>
19#include <linux/zsmalloc.h>
20
21#include "zcomp.h"
22
23#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
24#define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
25#define ZRAM_LOGICAL_BLOCK_SHIFT 12
26#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
27#define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
28 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
29
30/*
31 * ZRAM is mainly used for memory efficiency so we want to keep memory
32 * footprint small and thus squeeze size and zram pageflags into a flags
33 * member. The lower ZRAM_FLAG_SHIFT bits is for object size (excluding
34 * header), which cannot be larger than PAGE_SIZE (requiring PAGE_SHIFT
35 * bits), the higher bits are for zram_pageflags.
36 *
37 * We use BUILD_BUG_ON() to make sure that zram pageflags don't overflow.
38 */
39#define ZRAM_FLAG_SHIFT (PAGE_SHIFT + 1)
40
41/* Only 2 bits are allowed for comp priority index */
42#define ZRAM_COMP_PRIORITY_MASK 0x3
43
44/* Flags for zram pages (table[page_no].flags) */
45enum zram_pageflags {
46 ZRAM_SAME = ZRAM_FLAG_SHIFT, /* Page consists the same element */
47 ZRAM_ENTRY_LOCK, /* entry access lock bit */
48 ZRAM_WB, /* page is stored on backing_device */
49 ZRAM_PP_SLOT, /* Selected for post-processing */
50 ZRAM_HUGE, /* Incompressible page */
51 ZRAM_IDLE, /* not accessed page since last idle marking */
52 ZRAM_INCOMPRESSIBLE, /* none of the algorithms could compress it */
53
54 ZRAM_COMP_PRIORITY_BIT1, /* First bit of comp priority index */
55 ZRAM_COMP_PRIORITY_BIT2, /* Second bit of comp priority index */
56
57 __NR_ZRAM_PAGEFLAGS,
58};
59
60/*
61 * Allocated for each disk page. We use bit-lock (ZRAM_ENTRY_LOCK bit
62 * of flags) to save memory. There can be plenty of entries and standard
63 * locking primitives (e.g. mutex) will significantly increase sizeof()
64 * of each entry and hence of the meta table.
65 */
66struct zram_table_entry {
67 unsigned long handle;
68 unsigned long flags;
69#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
70 ktime_t ac_time;
71#endif
72 struct lockdep_map dep_map;
73};
74
75struct zram_stats {
76 atomic64_t compr_data_size; /* compressed size of pages stored */
77 atomic64_t failed_reads; /* can happen when memory is too low */
78 atomic64_t failed_writes; /* can happen when memory is too low */
79 atomic64_t notify_free; /* no. of swap slot free notifications */
80 atomic64_t same_pages; /* no. of same element filled pages */
81 atomic64_t huge_pages; /* no. of huge pages */
82 atomic64_t huge_pages_since; /* no. of huge pages since zram set up */
83 atomic64_t pages_stored; /* no. of pages currently stored */
84 atomic_long_t max_used_pages; /* no. of maximum pages stored */
85 atomic64_t miss_free; /* no. of missed free */
86#ifdef CONFIG_ZRAM_WRITEBACK
87 atomic64_t bd_count; /* no. of pages in backing device */
88 atomic64_t bd_reads; /* no. of reads from backing device */
89 atomic64_t bd_writes; /* no. of writes from backing device */
90#endif
91};
92
93#ifdef CONFIG_ZRAM_MULTI_COMP
94#define ZRAM_PRIMARY_COMP 0U
95#define ZRAM_SECONDARY_COMP 1U
96#define ZRAM_MAX_COMPS 4U
97#else
98#define ZRAM_PRIMARY_COMP 0U
99#define ZRAM_SECONDARY_COMP 0U
100#define ZRAM_MAX_COMPS 1U
101#endif
102
103struct zram {
104 struct zram_table_entry *table;
105 struct zs_pool *mem_pool;
106 struct zcomp *comps[ZRAM_MAX_COMPS];
107 struct zcomp_params params[ZRAM_MAX_COMPS];
108 struct gendisk *disk;
109 /* Prevent concurrent execution of device init */
110 struct rw_semaphore init_lock;
111 /*
112 * the number of pages zram can consume for storing compressed data
113 */
114 unsigned long limit_pages;
115
116 struct zram_stats stats;
117 /*
118 * This is the limit on amount of *uncompressed* worth of data
119 * we can store in a disk.
120 */
121 u64 disksize; /* bytes */
122 const char *comp_algs[ZRAM_MAX_COMPS];
123 s8 num_active_comps;
124 /*
125 * zram is claimed so open request will be failed
126 */
127 bool claim; /* Protected by disk->open_mutex */
128#ifdef CONFIG_ZRAM_WRITEBACK
129 struct file *backing_dev;
130 spinlock_t wb_limit_lock;
131 bool wb_limit_enable;
132 u64 bd_wb_limit;
133 struct block_device *bdev;
134 unsigned long *bitmap;
135 unsigned long nr_pages;
136#endif
137#ifdef CONFIG_ZRAM_MEMORY_TRACKING
138 struct dentry *debugfs_dir;
139#endif
140 atomic_t pp_in_progress;
141};
142#endif