diff options
Diffstat (limited to 'fs/btrfs/compression.h')
| -rw-r--r-- | fs/btrfs/compression.h | 30 |
1 files changed, 20 insertions, 10 deletions
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h index 09879579fbc8..39ec43ab8df1 100644 --- a/fs/btrfs/compression.h +++ b/fs/btrfs/compression.h @@ -19,20 +19,32 @@ #ifndef __BTRFS_COMPRESSION_ #define __BTRFS_COMPRESSION_ +/* + * We want to make sure that amount of RAM required to uncompress an extent is + * reasonable, so we limit the total size in ram of a compressed extent to + * 128k. This is a crucial number because it also controls how easily we can + * spread reads across cpus for decompression. + * + * We also want to make sure the amount of IO required to do a random read is + * reasonably small, so we limit the size of a compressed extent to 128k. + */ + +/* Maximum length of compressed data stored on disk */ +#define BTRFS_MAX_COMPRESSED (SZ_128K) +/* Maximum size of data before compression */ +#define BTRFS_MAX_UNCOMPRESSED (SZ_128K) + void btrfs_init_compress(void); void btrfs_exit_compress(void); int btrfs_compress_pages(int type, struct address_space *mapping, - u64 start, unsigned long len, - struct page **pages, - unsigned long nr_dest_pages, + u64 start, struct page **pages, unsigned long *out_pages, unsigned long *total_in, - unsigned long *total_out, - unsigned long max_out); + unsigned long *total_out); int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen); -int btrfs_decompress_buf2page(char *buf, unsigned long buf_start, +int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, unsigned long total_out, u64 disk_start, struct bio *bio); @@ -59,13 +71,11 @@ struct btrfs_compress_op { int (*compress_pages)(struct list_head *workspace, struct address_space *mapping, - u64 start, unsigned long len, + u64 start, struct page **pages, - unsigned long nr_dest_pages, unsigned long *out_pages, unsigned long *total_in, - unsigned long *total_out, - unsigned long max_out); + unsigned long *total_out); int (*decompress_bio)(struct list_head *workspace, struct page **pages_in, |