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 */
27static 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 */
35static 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 SECTORS_PER_PAGE_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
47#define SECTORS_PER_PAGE	(1 << SECTORS_PER_PAGE_SHIFT)
48#define ZRAM_LOGICAL_BLOCK_SHIFT 12
49#define ZRAM_LOGICAL_BLOCK_SIZE	(1 << ZRAM_LOGICAL_BLOCK_SHIFT)
50#define ZRAM_SECTOR_PER_LOGICAL_BLOCK	\
51	(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
52
53
54/*
55 * The lower ZRAM_FLAG_SHIFT bits of table.value is for
56 * object size (excluding header), the higher bits is for
57 * zram_pageflags.
58 *
59 * zram is mainly used for memory efficiency so we want to keep memory
60 * footprint small so we can squeeze size and flags into a field.
61 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header),
62 * the higher bits is for zram_pageflags.
63 */
64#define ZRAM_FLAG_SHIFT 24
65
66/* Flags for zram pages (table[page_no].value) */
67enum zram_pageflags {
68	/* Page consists entirely of zeros */
69	ZRAM_ZERO = ZRAM_FLAG_SHIFT,
70	ZRAM_ACCESS,	/* page is now accessed */
71
72	__NR_ZRAM_PAGEFLAGS,
73};
74
75/*-- Data structures */
76
77/* Allocated for each disk page */
78struct zram_table_entry {
79	unsigned long handle;
80	unsigned long value;
81};
82
83struct zram_stats {
84	atomic64_t compr_data_size;	/* compressed size of pages stored */
85	atomic64_t num_reads;	/* failed + successful */
86	atomic64_t num_writes;	/* --do-- */
87	atomic64_t num_migrated;	/* no. of migrated object */
88	atomic64_t failed_reads;	/* can happen when memory is too low */
89	atomic64_t failed_writes;	/* can happen when memory is too low */
90	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
91	atomic64_t notify_free;	/* no. of swap slot free notifications */
92	atomic64_t zero_pages;		/* no. of zero filled pages */
93	atomic64_t pages_stored;	/* no. of pages currently stored */
94	atomic_long_t max_used_pages;	/* no. of maximum pages stored */
95};
96
97struct zram_meta {
98	struct zram_table_entry *table;
99	struct zs_pool *mem_pool;
100};
101
102struct zram {
103	struct zram_meta *meta;
104	struct zcomp *comp;
105	struct gendisk *disk;
106	/* Prevent concurrent execution of device init */
107	struct rw_semaphore init_lock;
108	/*
109	 * the number of pages zram can consume for storing compressed data
110	 */
111	unsigned long limit_pages;
112	int max_comp_streams;
113
114	struct zram_stats stats;
115	atomic_t refcount; /* refcount for zram_meta */
116	/* wait all IO under all of cpu are done */
117	wait_queue_head_t io_done;
118	/*
119	 * This is the limit on amount of *uncompressed* worth of data
120	 * we can store in a disk.
121	 */
122	u64 disksize;	/* bytes */
123	char compressor[10];
124};
125#endif
126