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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 <linux/zsmalloc.h>
/*
* Some arbitrary value. This is just to catch
* invalid value for num_devices module parameter.
*/
static const unsigned max_num_devices = 32;
/*-- Configurable parameters */
/*
* 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:
* ZS_MAX_ALLOC_SIZE. Otherwise, zs_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 consists entirely of zeros */
ZRAM_ZERO,
__NR_ZRAM_PAGEFLAGS,
};
/*-- Data structures */
/* Allocated for each disk page */
struct table {
unsigned long handle;
u16 size; /* object size (excluding header) */
u8 count; /* object ref count (not yet used) */
u8 flags;
} __aligned(4);
/*
* All 64bit fields should only be manipulated by 64bit atomic accessors.
* All modifications to 32bit counter should be protected by zram->lock.
*/
struct zram_stats {
atomic64_t compr_size; /* compressed size of pages stored */
atomic64_t num_reads; /* failed + successful */
atomic64_t num_writes; /* --do-- */
atomic64_t failed_reads; /* should NEVER! happen */
atomic64_t failed_writes; /* can happen when memory is too low */
atomic64_t invalid_io; /* non-page-aligned I/O requests */
atomic64_t 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 bad_compress; /* % of pages with compression ratio>=75% */
};
struct zram_meta {
void *compress_workmem;
void *compress_buffer;
struct table *table;
struct zs_pool *mem_pool;
};
struct zram_slot_free {
unsigned long index;
struct zram_slot_free *next;
};
struct zram {
struct zram_meta *meta;
struct rw_semaphore lock; /* protect compression buffers, table,
* 32bit stat counters against concurrent
* notifications, reads and writes */
struct work_struct free_work; /* handle pending free request */
struct zram_slot_free *slot_free_rq; /* list head of free request */
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 */
spinlock_t slot_free_lock;
struct zram_stats stats;
};
#endif
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