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path: root/fs/btrfs/compression.h
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2012-03-22btrfs: return void in functions without error conditionsJeff Mahoney
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
2011-05-02btrfs: rename variables clashing with global function namesDavid Sterba
reported by gcc -Wshadow: page_index, page_offset, new_inode, dev_name Signed-off-by: David Sterba <dsterba@suse.cz>
2010-12-22btrfs: Extract duplicate decompress codeLi Zefan
Add a common function to copy decompressed data from working buffer to bio pages. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2010-12-22btrfs: Add lzo compression supportLi Zefan
Lzo is a much faster compression algorithm than gzib, so would allow more users to enable transparent compression, and some users can choose from compression ratio and speed for different applications Usage: # mount -t btrfs -o compress[=<zlib,lzo>] dev /mnt or # mount -t btrfs -o compress-force[=<zlib,lzo>] dev /mnt "-o compress" without argument is still allowed for compatability. Compatibility: If we mount a filesystem with lzo compression, it will not be able be mounted in old kernels. One reason is, otherwise btrfs will directly dump compressed data, which sits in inline extent, to user. Performance: The test copied a linux source tarball (~400M) from an ext4 partition to the btrfs partition, and then extracted it. (time in second) lzo zlib nocompress copy: 10.6 21.7 14.9 extract: 70.1 94.4 66.6 (data size in MB) lzo zlib nocompress copy: 185.87 108.69 394.49 extract: 193.80 132.36 381.21 Changelog: v1 -> v2: - Select LZO_COMPRESS and LZO_DECOMPRESS in btrfs Kconfig. - Add incompability flag. - Fix error handling in compress code. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2010-12-22btrfs: Allow to add new compression algorithmLi Zefan
Make the code aware of compression type, instead of always assuming zlib compression. Also make the zlib workspace function as common code for all compression types. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2008-10-29Btrfs: Add zlib compression supportChris Mason
This is a large change for adding compression on reading and writing, both for inline and regular extents. It does some fairly large surgery to the writeback paths. Compression is off by default and enabled by mount -o compress. Even when the -o compress mount option is not used, it is possible to read compressed extents off the disk. If compression for a given set of pages fails to make them smaller, the file is flagged to avoid future compression attempts later. * While finding delalloc extents, the pages are locked before being sent down to the delalloc handler. This allows the delalloc handler to do complex things such as cleaning the pages, marking them writeback and starting IO on their behalf. * Inline extents are inserted at delalloc time now. This allows us to compress the data before inserting the inline extent, and it allows us to insert an inline extent that spans multiple pages. * All of the in-memory extent representations (extent_map.c, ordered-data.c etc) are changed to record both an in-memory size and an on disk size, as well as a flag for compression. From a disk format point of view, the extent pointers in the file are changed to record the on disk size of a given extent and some encoding flags. Space in the disk format is allocated for compression encoding, as well as encryption and a generic 'other' field. Neither the encryption or the 'other' field are currently used. In order to limit the amount of data read for a single random read in the file, the size of a compressed extent is limited to 128k. This is a software only limit, the disk format supports u64 sized compressed extents. In order to limit the ram consumed while processing extents, the uncompressed size of a compressed extent is limited to 256k. This is a software only limit and will be subject to tuning later. Checksumming is still done on compressed extents, and it is done on the uncompressed version of the data. This way additional encodings can be layered on without having to figure out which encoding to checksum. Compression happens at delalloc time, which is basically singled threaded because it is usually done by a single pdflush thread. This makes it tricky to spread the compression load across all the cpus on the box. We'll have to look at parallel pdflush walks of dirty inodes at a later time. Decompression is hooked into readpages and it does spread across CPUs nicely. Signed-off-by: Chris Mason <chris.mason@oracle.com>