zram_drv.h

  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	bool wb_limit_enable;
131	u32 wb_batch_size;
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