xref: /openbmc/linux/drivers/block/zram/zram_drv.h (revision f5ad1c74)
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 #include <linux/crypto.h>
21 
22 #include "zcomp.h"
23 
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))
30 
31 
32 /*
33  * The lower ZRAM_FLAG_SHIFT bits of table.flags is for
34  * object size (excluding header), the higher bits is for
35  * zram_pageflags.
36  *
37  * zram is mainly used for memory efficiency so we want to keep memory
38  * footprint small so we can squeeze size and flags into a field.
39  * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
40  * the higher bits is for zram_pageflags.
41  */
42 #define ZRAM_FLAG_SHIFT 24
43 
44 /* Flags for zram pages (table[page_no].flags) */
45 enum zram_pageflags {
46 	/* zram slot is locked */
47 	ZRAM_LOCK = ZRAM_FLAG_SHIFT,
48 	ZRAM_SAME,	/* Page consists the same element */
49 	ZRAM_WB,	/* page is stored on backing_device */
50 	ZRAM_UNDER_WB,	/* page is under writeback */
51 	ZRAM_HUGE,	/* Incompressible page */
52 	ZRAM_IDLE,	/* not accessed page since last idle marking */
53 
54 	__NR_ZRAM_PAGEFLAGS,
55 };
56 
57 /*-- Data structures */
58 
59 /* Allocated for each disk page */
60 struct zram_table_entry {
61 	union {
62 		unsigned long handle;
63 		unsigned long element;
64 	};
65 	unsigned long flags;
66 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
67 	ktime_t ac_time;
68 #endif
69 };
70 
71 struct zram_stats {
72 	atomic64_t compr_data_size;	/* compressed size of pages stored */
73 	atomic64_t num_reads;	/* failed + successful */
74 	atomic64_t num_writes;	/* --do-- */
75 	atomic64_t failed_reads;	/* can happen when memory is too low */
76 	atomic64_t failed_writes;	/* can happen when memory is too low */
77 	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
78 	atomic64_t notify_free;	/* no. of swap slot free notifications */
79 	atomic64_t same_pages;		/* no. of same element filled pages */
80 	atomic64_t huge_pages;		/* no. of huge pages */
81 	atomic64_t huge_pages_since;	/* no. of huge pages since zram set up */
82 	atomic64_t pages_stored;	/* no. of pages currently stored */
83 	atomic_long_t max_used_pages;	/* no. of maximum pages stored */
84 	atomic64_t writestall;		/* no. of write slow paths */
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 struct zram {
94 	struct zram_table_entry *table;
95 	struct zs_pool *mem_pool;
96 	struct zcomp *comp;
97 	struct gendisk *disk;
98 	/* Prevent concurrent execution of device init */
99 	struct rw_semaphore init_lock;
100 	/*
101 	 * the number of pages zram can consume for storing compressed data
102 	 */
103 	unsigned long limit_pages;
104 
105 	struct zram_stats stats;
106 	/*
107 	 * This is the limit on amount of *uncompressed* worth of data
108 	 * we can store in a disk.
109 	 */
110 	u64 disksize;	/* bytes */
111 	char compressor[CRYPTO_MAX_ALG_NAME];
112 	/*
113 	 * zram is claimed so open request will be failed
114 	 */
115 	bool claim; /* Protected by bdev->bd_mutex */
116 	struct file *backing_dev;
117 #ifdef CONFIG_ZRAM_WRITEBACK
118 	spinlock_t wb_limit_lock;
119 	bool wb_limit_enable;
120 	u64 bd_wb_limit;
121 	struct block_device *bdev;
122 	unsigned int old_block_size;
123 	unsigned long *bitmap;
124 	unsigned long nr_pages;
125 #endif
126 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
127 	struct dentry *debugfs_dir;
128 #endif
129 };
130 #endif
131