xref: /openbmc/linux/drivers/block/zram/zram_drv.h (revision b34e08d5)
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/spinlock.h>
19 #include <linux/zsmalloc.h>
20 
21 #include "zcomp.h"
22 
23 /*
24  * Some arbitrary value. This is just to catch
25  * invalid value for num_devices module parameter.
26  */
27 static const unsigned max_num_devices = 32;
28 
29 /*-- Configurable parameters */
30 
31 /*
32  * Pages that compress to size greater than this are stored
33  * uncompressed in memory.
34  */
35 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
36 
37 /*
38  * NOTE: max_zpage_size must be less than or equal to:
39  *   ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
40  * always return failure.
41  */
42 
43 /*-- End of configurable params */
44 
45 #define SECTOR_SHIFT		9
46 #define SECTOR_SIZE		(1 << SECTOR_SHIFT)
47 #define SECTORS_PER_PAGE_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
48 #define SECTORS_PER_PAGE	(1 << SECTORS_PER_PAGE_SHIFT)
49 #define ZRAM_LOGICAL_BLOCK_SHIFT 12
50 #define ZRAM_LOGICAL_BLOCK_SIZE	(1 << ZRAM_LOGICAL_BLOCK_SHIFT)
51 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK	\
52 	(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
53 
54 /* Flags for zram pages (table[page_no].flags) */
55 enum zram_pageflags {
56 	/* Page consists entirely of zeros */
57 	ZRAM_ZERO,
58 
59 	__NR_ZRAM_PAGEFLAGS,
60 };
61 
62 /*-- Data structures */
63 
64 /* Allocated for each disk page */
65 struct table {
66 	unsigned long handle;
67 	u16 size;	/* object size (excluding header) */
68 	u8 flags;
69 } __aligned(4);
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;	/* should NEVER! happen */
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 zero_pages;		/* no. of zero filled pages */
80 	atomic64_t pages_stored;	/* no. of pages currently stored */
81 };
82 
83 struct zram_meta {
84 	rwlock_t tb_lock;	/* protect table */
85 	struct table *table;
86 	struct zs_pool *mem_pool;
87 };
88 
89 struct zram {
90 	struct zram_meta *meta;
91 	struct request_queue *queue;
92 	struct gendisk *disk;
93 	struct zcomp *comp;
94 
95 	/* Prevent concurrent execution of device init, reset and R/W request */
96 	struct rw_semaphore init_lock;
97 	/*
98 	 * This is the limit on amount of *uncompressed* worth of data
99 	 * we can store in a disk.
100 	 */
101 	u64 disksize;	/* bytes */
102 	int max_comp_streams;
103 	struct zram_stats stats;
104 	char compressor[10];
105 };
106 #endif
107