diff options
Diffstat (limited to 'drivers/block/zram/zram_drv.h')
| -rw-r--r-- | drivers/block/zram/zram_drv.h | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h new file mode 100644 index 0000000..2a4f29c --- /dev/null +++ b/drivers/block/zram/zram_drv.h @@ -0,0 +1,118 @@ +/* + * Compressed RAM block device + * + * Copyright (C) 2008, 2009, 2010 Nitin Gupta + * 2012, 2013 Minchan Kim + * + * 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/zsmalloc.h> + +#include "zcomp.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 / 10 * 9; + +/* + * 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 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)) + + +/* + * The lower ZRAM_FLAG_SHIFT bits of table.value is for + * object size (excluding header), the higher bits is for + * zram_pageflags. + * + * zram is mainly used for memory efficiency so we want to keep memory + * footprint small so we can squeeze size and flags into a field. + * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header), + * the higher bits is for zram_pageflags. + */ +#define ZRAM_FLAG_SHIFT 24 + +/* Flags for zram pages (table[page_no].value) */ +enum zram_pageflags { + /* Page consists entirely of zeros */ + ZRAM_ZERO = ZRAM_FLAG_SHIFT + 1, + ZRAM_ACCESS, /* page in now accessed */ + + __NR_ZRAM_PAGEFLAGS, +}; + +/*-- Data structures */ + +/* Allocated for each disk page */ +struct zram_table_entry { + unsigned long handle; + unsigned long value; +}; + +struct zram_stats { + atomic64_t compr_data_size; /* compressed size of pages stored */ + atomic64_t num_reads; /* failed + successful */ + atomic64_t num_writes; /* --do-- */ + atomic64_t failed_reads; /* can happen when memory is too low */ + 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 */ + atomic64_t zero_pages; /* no. of zero filled pages */ + atomic64_t pages_stored; /* no. of pages currently stored */ +}; + +struct zram_meta { + struct zram_table_entry *table; + struct zs_pool *mem_pool; +}; + +struct zram { + struct zram_meta *meta; + struct request_queue *queue; + struct gendisk *disk; + struct zcomp *comp; + + /* 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 */ + int max_comp_streams; + struct zram_stats stats; + char compressor[10]; +}; +#endif |