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/*
* Compressed RAM block device
*
* Copyright (C) 2008, 2009, 2010 Nitin Gupta
*
* This code is released using a dual license strategy: BSD/GPL
* You can choose the licence that better fits your requirements.
*
* Released under the terms of 3-clause BSD License
* Released under the terms of GNU General Public License Version 2.0
*
* Project home: http://compcache.googlecode.com
*/
#ifndef _ZRAM_DRV_H_
#define _ZRAM_DRV_H_
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include "xvmalloc.h"
/*
* Some arbitrary value. This is just to catch
* invalid value for num_devices module parameter.
*/
static const unsigned max_num_devices = 32;
/*
* Stored at beginning of each compressed object.
*
* It stores back-reference to table entry which points to this
* object. This is required to support memory defragmentation.
*/
struct zobj_header {
#if 0
u32 table_idx;
#endif
};
/*-- Configurable parameters */
/* Default zram disk size: 25% of total RAM */
static const unsigned default_disksize_perc_ram = 25;
/*
* Pages that compress to size greater than this are stored
* uncompressed in memory.
*/
static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
/*
* NOTE: max_zpage_size must be less than or equal to:
* XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
* otherwise, xv_malloc() would always return failure.
*/
/*-- End of configurable params */
#define SECTOR_SHIFT 9
#define SECTOR_SIZE (1 << SECTOR_SHIFT)
#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
#define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
#define ZRAM_LOGICAL_BLOCK_SHIFT 12
#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
#define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
/* Flags for zram pages (table[page_no].flags) */
enum zram_pageflags {
/* Page is stored uncompressed */
ZRAM_UNCOMPRESSED,
/* Page consists entirely of zeros */
ZRAM_ZERO,
__NR_ZRAM_PAGEFLAGS,
};
/*-- Data structures */
/* Allocated for each disk page */
struct table {
struct page *page;
u16 offset;
u8 count; /* object ref count (not yet used) */
u8 flags;
} __attribute__((aligned(4)));
struct zram_stats {
u64 compr_size; /* compressed size of pages stored */
u64 num_reads; /* failed + successful */
u64 num_writes; /* --do-- */
u64 failed_reads; /* should NEVER! happen */
u64 failed_writes; /* can happen when memory is too low */
u64 invalid_io; /* non-page-aligned I/O requests */
u64 notify_free; /* no. of swap slot free notifications */
u32 pages_zero; /* no. of zero filled pages */
u32 pages_stored; /* no. of pages currently stored */
u32 good_compress; /* % of pages with compression ratio<=50% */
u32 pages_expand; /* % of incompressible pages */
};
struct zram {
struct xv_pool *mem_pool;
void *compress_workmem;
void *compress_buffer;
struct table *table;
spinlock_t stat64_lock; /* protect 64-bit stats */
struct rw_semaphore lock; /* protect compression buffers and table
* against concurrent read and writes */
struct request_queue *queue;
struct gendisk *disk;
int init_done;
/* Prevent concurrent execution of device init, reset and R/W request */
struct rw_semaphore init_lock;
/*
* This is the limit on amount of *uncompressed* worth of data
* we can store in a disk.
*/
u64 disksize; /* bytes */
struct zram_stats stats;
};
extern struct zram *zram_devices;
extern unsigned int zram_num_devices;
#ifdef CONFIG_SYSFS
extern struct attribute_group zram_disk_attr_group;
#endif
extern int zram_init_device(struct zram *zram);
extern void __zram_reset_device(struct zram *zram);
#endif
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