diff options
Diffstat (limited to 'drivers/staging/zram/zram_drv.h')
| -rw-r--r-- | drivers/staging/zram/zram_drv.h | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h new file mode 100644 index 000000000000..945f9740442f --- /dev/null +++ b/drivers/staging/zram/zram_drv.h @@ -0,0 +1,164 @@ +/* + * 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 "zram_ioctl.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 unsigned 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) + +/* 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 { + /* basic stats */ + size_t compr_size; /* compressed size of pages stored - + * needed to enforce memlimit */ + /* more stats */ +#if defined(CONFIG_ZRAM_STATS) + 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 */ +#endif +}; + +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 mutex lock; /* protect compression buffers against + * concurrent writes */ + struct request_queue *queue; + struct gendisk *disk; + int init_done; + /* + * This is the limit on amount of *uncompressed* worth of data + * we can store in a disk. + */ + size_t disksize; /* bytes */ + + struct zram_stats stats; +}; + +/*-- */ + +/* Debugging and Stats */ +#if defined(CONFIG_ZRAM_STATS) +static void zram_stat_inc(u32 *v) +{ + *v = *v + 1; +} + +static void zram_stat_dec(u32 *v) +{ + *v = *v - 1; +} + +static void zram_stat64_inc(struct zram *zram, u64 *v) +{ + spin_lock(&zram->stat64_lock); + *v = *v + 1; + spin_unlock(&zram->stat64_lock); +} + +static u64 zram_stat64_read(struct zram *zram, u64 *v) +{ + u64 val; + + spin_lock(&zram->stat64_lock); + val = *v; + spin_unlock(&zram->stat64_lock); + + return val; +} +#else +#define zram_stat_inc(v) +#define zram_stat_dec(v) +#define zram_stat64_inc(r, v) +#define zram_stat64_read(r, v) +#endif /* CONFIG_ZRAM_STATS */ + +#endif |