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Diffstat (limited to 'drivers/block/zram/zram_drv.h')
| -rw-r--r-- | drivers/block/zram/zram_drv.h | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h new file mode 100644 index 000000000000..d8f6596513c3 --- /dev/null +++ b/drivers/block/zram/zram_drv.h @@ -0,0 +1,124 @@ +/* + * 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 |