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By feature

Major features or significant feature enhancements by kernel version. For more information look below.

WARNING: The "Version" row states at which version a feature has been merged into the mainline kernel. It does not tell anything about at which kernel version it is considered mature enough for production use. For an estimation on stability of features see Status page.

Feature Version Description Notes
scrub 3.0

Read all data and verify checksums, repair if possible.

auto raid repair 3.2

Automatic repair of broken data from a good copy

root backups 3.2

Save a few previous versions of the most imporant tree roots at commit time, used by -o recovery

integrity checker 3.3

Optional infrastructure to verify integrity of written metadata blocks

backref walking 3.3

Groundwork to allow tracking owner of blocks, used via inspect-internal

restriper 3.3

RAID profiles can be changed on-line, balance filters

big metadata blocks 3.4

Support for metadata blocks larger than page size

Default nodesize is 16k since btrfs-progs 3.12

error handling 3.4

Generic infrastructure for graceful error handling (EIO)

device statistics 3.5

Persistent statistics about device errors

fsync speedup 3.5

Noticeable improvements in fsync() implementation

qgroups 3.6

Subvolume-aware quotas

send/receive 3.6

Ability to transfer one filesystem via a data stream (full or incremental) and apply the changes on a remote filesystem.

extrefs 3.7

Hardlink count limit is lifted to 64k

Default since btrfs-progs 3.12

hole puching 3.7

Implement the FALLOC_FL_PUNCH_HOLE mode of fallocate

device replace 3.8

Efficient replacement of existing device (add/remove in one go)

raid 5/6 (incomplete) 3.9

Basic support for RAD5/6 profiles, no crash resiliency, replace and scrub support

snapshot-aware defrag 3.9

Defrag does not break links between shared extents (snapshots, reflinked files)

Disabled since 3.14 (and backported to some stable kernel versions) due to problems. Will be enabled in the future.

lightweight send 3.9

A mode of send that does not add the actual file data to the stream

on-line label set/get 3.9

Label editable on mounted filesystems

skinny metadata 3.10

Reduced metadata size (format change) of extents

Default since btrfs-progs 3.18

qgroup rescan 3.10

Sync qgroups with existing filesystem data

uuid tree 3.12

A map of subvolume/UUID that vastly speeds up send/receive

out-of-bound dedup 3.12

Support for deduplicating extents on a given set of files.

no-holes 3.14

No extent representation for file holes (format change), may reduce overall metadata consumption

feature bits in sysfs 3.14

/sys/fs/btrfs exports various bits about filesystem capabilities and feature support


Mode of open() to safely create a temporary file

search ioctl v2 3.16

The extended SEARCH_TREE ioctl able to get more than a 4k data

auto blockgroup reclaim 3.18

Automatically remove blockgroups (aka. chunks) that become completely empty.

raid56: scrub, replace 3.19

Scrub and device replace works on RAID56 filesystems.

store otime 4.0

Save creation time (otime) for all new files and directories. For future use, current tool cannot read it directly.

rootid ioctl accessible 4.2

The INO_LOOKUP will return root id (id of the containing subvolume), unrestricted and to all users if the treeid is 0.

dedupe possible on the same inode 4.2

The EXTENT_SAME ioctl will accept the same inode as source and destination (ranges must not overlap).

trim all free space 4.3

Trim will be performed also on the space that's not allocated by the chunks, not only free space within the allocated chunks.

balance filter updates 4.4

Enhanced syntax and new balance filters:

  • limit=min..max
  • usage=min..max
  • stripes=min..max

free space tree 4.5

Improved implementation of free space cache (aka v2), using b-trees.

Kernel 4.9 fixes endianity bugs on big-endian machines, x86* is ok

balance filter updates 4.5

Conversion to data/DUP profile possible through balance filters -- on single-device filesytem.

mkfs.btrfs allows creating DUP on single device in the non-mixed mode since 4.4

max_inline default 4.6

The default value of max_inline changed to 2048.

read features from control device 4.6

The existing ioctl GET_SUPPORTED_FEATURES can be now used on the control device (/dev/btrfs-control) and returns the supported features without any mounted filesystem.

delete device by id 4.7

Add new ioctl RM_DEV_V2, pass device to be deleted by its ID.

more renameat2 modes 4.7

Add support for RENAME_EXCHANGE and RENAME_WHITEOUT to renameat2 syscall. This also means that overlayfs is now supported on top of btrfs.

balance filter updates 4.7

Conversion to data/DUP profile possible through balance filters -- on multiple-device filesystems.

mkfs.btrfs allows creating DUP on multiple devices since 4.5.1

raid56: auto repair 4.12

Scrub will attempt auto-repair (similar to raid1/raid10)

statx 4.13

Support for the enhanced statx syscall; file creation timestamp

sysfs qgroups override 4.13

qgroups: new sysfs control file to allow temporary quota override with CAP_SYS_RESOURCE

deprecated mount option alloc_start 4.13

That was a debugging helper, not used and not supposed to be used nowadays.

ZSTD compression 4.14

New compression algorithm ZSTD, supposedly better ratio/speed performance.

improved degraded mount 4.14

Allow degraded mount based on the chunk constraints, not device number constraints. Eg. when one device is missing but the remaining one holds all single chunks.

deprecated user transaction ioctl 4.14

BTRFS_IOC_TRANS_START and BTRFS_IOC_TRANS_END, no known users, tricky to use; scheduled to be removed in 4.17

refine SSD optimizations 4.14

The mount option ssd does not make any assumptions about block layout or management by the device anymore, leaving only the speedups based on low seek cost active. This could avoid some corner cases leading to excessive fragmentation. The story so far.

overlayfs 4.15

Overlayfs can now use btrfs as the lower filesystem.

ref-verify 4.15

Debugging functionality to verify extent references. New mount option ref-verify, must be built with CONFIG_BTRFS_FS_REF_VERIFY.

zlib level 4.15

Allow to set the zlib compression level via mount option, eg. like compress=zlib:9. The levels match the default zlib compression levels. The default is 3.

v2 of LOGICAL_INO ioctl 4.15

An enhanced version of ioctl that can translate logical extent offset to inode numbers, "who owns this block". For certain usecases the V1 performs bad and this is addressed by V2. Read more.

compression heuristics 4.15

Apply a few heuristics to the data before they're compressed to decide if it's likely to gain any space savings. The methods: frequency sampling, repeated pattern detection, Shannon entropy calculation.

By version (btrfs-progs)

Tarballs: (announcement)

btrfs-progs v4.15 (Jan 2018)

  • mkfs --rootdir reworked, does not minimize the final image but can be still done using a new option --shrink
  • fix allocation of system chunk, don't allocate from the reserved area
  • other
    • new and updated tests
    • cleanups, refactoring
    • doc updates

btrfs-progs v4.15.1 (Feb 2018)

  • build
    • fix build on musl
    • support asciidoctor for doc generation
  • cleanups
    • sync some code with kernel
    • check: move code to own directory, split to more files
  • tests
    • more build tests in travis
    • tests now pass with asan and ubsan
    • testsuite can be exported and used separately

btrfs-progs v4.14 (Nov 2017)

  • build: libzstd now required by default
  • check: more lowmem mode repair enhancements
  • subvol set-default: also accept path
  • prop set: compression accepts no/none, same as ""
  • filesystem usage: enable for filesystem on top of a seed device
  • rescue: new command fix-device-size
  • other
    • new tests
    • cleanups and refactoring
    • doc updates

btrfs-progs v4.14.1 (Jan 2018)

  • dump-tree: print times of root items
  • check: fix several lowmem mode bugs
  • convert: fix rollback after balance
  • other
    • new and updated tests, enabled lowmem mode in CI
    • docs updates
    • fix travis CI build
    • build fixes
    • cleanups

btrfs-progs v4.13 (Sep 2017)

  • convert: reiserfs support
  • check: new option --force to allow check of a mounted filesystem (no repair)
  • mkfs: --rootdir will now copy special files
  • dump-tree: minor output changes
  • inspect rootid: accept file as arugment
  • dev usage: don't calculate slack space for missing devices
  • fi du: don't print error on EMPTY_SUBVOL (inode number 2)
  • build:
    • fixed support for sanitization features on gcc (tsan, asan, ubsan)
    • fix PIE build
  • other:
    • misc cleanups and stability fixes
    • travis CI enhancements
    • new tests, fuzzed images
    • testsuite cleanups

btrfs-progs v4.13.1 (Sep 2017)

  • image: speed up generating the sanitized names, do not generate unprintable chars
  • completion: add missing commands, better mount point detection
  • restore: add zstd support; libzstd detected automatically, will be requested by default in the future, or can be configured out
  • other:
    • misc fixes found by sparse
    • doc enhancements, ioctl manual page started
    • updated and new tests
    • build fixes

btrfs-progs v4.13.2 (Oct 2017)

  • subvol list:
    • don't list toplevel subvolume among deleted (broken since 4.8.3)
    • minor adjustments of uuid print format
  • subvol delete:
    • fix swapped behaviour of --commit-each and --commit-after
    • fix potentially lost sync if subvolumes are from different filesystems
  • check: add cache for metadata blocks, should improve performance
  • other:
    • new tests, testsuite updates
    • doc updates
    • cleanups

btrfs-progs v4.13.3 (Oct 2017)

  • check: fix --force, wrong check for a mounted block device
  • build: fix --with-convert parsing
  • subvol list: don't list TOPLEVEL
  • other: update tests

btrfs-progs v4.12 (Jul 2017)

  • subvol show: new options --rootid, --uuid to show subvol by the given spec
  • convert: progress report fixes, found by tsan
  • image: progress report fixes, found by tsan
  • fix infinite looping in find-root, or when looking for free extents
  • other:
    • code refactoring
    • docs updates
    • build: ThreadSanitizer support
    • tests: stricter checks for mounted filesystem

btrfs-progs v4.12.1 (Aug 2017)

  • build:
    • fix cross-compilation
    • use gnu90 explicitly
  • dump-tree: more relaxed checks so -b can print block on a damaged fs
  • convert: fix the 1MB range exclusion
  • check: more dir_item hash checks
  • other
    • added missing getopt spec for some options
    • doc fixes
    • cleanups
    • test updates

btrfs-progs v4.11 (May 2017)

  • receive: fix handling empty stream with -e (multi-stream)
  • send dump: fix printing long file names
  • stability fixes for: dump-super, print-tree, check
  • option parser updates: global options are parsed before the subcommand name (old xfstests will fail)
  • new and updated tests
  • documentation updates

btrfs-progs v4.11.1 (Jun 2017)

  • image: restoring from multiple devices
  • dev stats: make --check option work
  • check: fix false alert with extent hole on a NO_HOLE filesystem
  • check: lowmem mode, fix false alert in case of mixed inline and compressed extent
  • convert: work with large filesystems (many TB)
  • convert: fix overwriting of eb header flags
  • convert: do not clear NODATASUM flag in inodes when run with --no-datasum
  • docs updates
  • build: sync with Makefile
  • tests:
    • new tests
    • fix 008 and 009, shell quotation mistake

btrfs-progs 4.10 (Mar 2017)

  • send: dump output fixes: missing newlies
  • check: several fixes for the lowmem mode, improved error reporting
  • build
    • removed some library deps for binaries that not use them
    • ctags, cscope
    • split Makefile to the autotool generated part and the rest, not needed to after adding a file
  • shared code: sync easy parts with kernel sources
  • other
    • lots of cleanups
    • source file reorganization: convert, mkfs, utils
    • lots of spelling fixes in docs, other updates
    • more tests

btrfs-progs 4.10.1 (Mar 2017)

  • receive: handle subvolume in path clone
  • convert: rollback fixed (rewrite was needed to address previous design issues)
  • build: fix build of 3rd party tools, missing <linux/sizes.h>
  • dump-tree: print log trees
  • other: new and updated tests

btrfs-progs 4.10.2 (Mar 2017)

  • check: lowmem mode fix for false alert about lost backrefs
  • convert: minor bugfix
  • library: fix build, misisng symbols, added tests

btrfs-progs 4.9 (Dec 2016)

  • check: many lowmem mode updates
  • send: use splice syscall to copy buffer from kernel
  • receive: new option to dump the stream in textual form
  • convert:
    • move sources to own directory
    • prevent accounting of blocks beyond end of the device
    • make it work with 64k sectorsize
  • mkfs: move sources to own directory
  • defrag: warns if directory used without -r
  • dev stats:
    • new option to check stats for non-zero values
    • add long option for -z
  • library: version bump to 0.1.2, added subvol_uuid_search2
  • other:
    • cleanups
    • docs updates

btrfs-progs v4.9.1 (Jan 2017)

  • check:
    • use correct inode number for lost+found files
    • lowmem mode: fix false alert on dropped leaf
  • size reports: negative numbers might appear in size reports during device deletes (previously in EiB units)
  • mkfs: print device being trimmed
  • defrag: v1 ioctl support dropped
  • quota: print message before starting to wait for rescan
  • qgroup show: new option to sync before printing the stats
  • other:
    • corrupt-block enhancements
    • backtrace and co. cleanups
    • doc fixes

btrfs-progs 4.8 (Oct 2016)

  • error handling improvements all over the place
  • new fuzzed images, test updates
  • doc fixups
  • minor cleanups and improvements
  • kernel library helpers moved to own directory
  • qgroup: fix regression leading to incorrect status after check, introduced in 4.7

btrfs-progs v4.8.1 (Oct 2016)

  • build fixes: 32bit, "no backtrace"

btrfs-progs v4.8.2 (Oct 2016)

  • convert: also convert file attributes
  • convert: fix wrong tree block alignment for unalianged block group
  • check: quota verify fixes, handle reloc tree
  • build: add stub for FIEMAP_EXTENT_SHARED, compiles on ancient kernels
  • build: add stub for BUILD_ASSERT when ioctl.h is included
  • dump-tree: don't crash on unrecognized tree id for -t
  • tests:
    • add more ioctl tests
    • convert: more symlink tests, attribute tests
    • quota verify for reloc tree
  • other cleanups

btrfs-progs v4.8.3 (Nov 2016)

  • check:
    • support for clearing space cache (v1)
    • size reduction of inode backref structure
  • send:
    • fix handling of multiple snapshots (-p and -c options)
    • transfer buffer increased (should reduce number of context switches)
    • reuse existing file for output (-f), eg. when root cannot create files (NFS)
  • dump-tree:
    • print missing items for various structures
    • new: dev stats, balance status item
    • sync key names with kernel (the persistent items)
  • subvol show: now able to print the toplevel subvolume -- the creation time might be wrong though
  • mkfs:
    • store the creation time of toplevel root inode
    • print UUID in the summary
  • build: travis CI for devel
  • other:
    • lots of cleanups and refactoring
    • switched to on-stack path structure
    • fixes from coverity, asan, ubsan
    • new tests
    • updates in testing infrastructure
    • fixed convert test 005

btrfs-progs v4.8.4 (Nov 2016)

  • check: support for clearing space cache v2 (free-space-tree)
  • send:
    • more sanity checks (with tests), cleanups
    • fix for fstests/btrfs/038 and btrfs/117 failures
  • build:
    • fix compilation of standalone ioctl.h, pull NULL definition
    • fix library link errors introduced in 4.8.3
  • tests:
    • add more fuzzed images from bugzilla
    • add bogus send stream checks
    • fixups and enhancements for CI environment builds
    • misc refinements and updates of testing framework
  • other:
    • move sources for btrfs-image to own directory
    • deprecated and not build by default: btrfs-calc-size, btrfs-show-super
    • docs updates

btrfs-progs v4.8.5 (Nov 2016)

  • receive: fix detection of end of stream (error reported even for valid streams)
  • other:
    • added test for the receive bug
    • fix linking of library-test

btrfs-progs 4.7 (Jul 2016)

do not use, see 4.7.2

  • convert: fix creating discontig extents
  • check: speed up traversing heavily reflinked extents within a file
  • check: verify qgroups of higher levels
  • check: repair can now fix wrong qgroup numbers
  • balance: new option to run in the background
  • defrag: default extent target size changed to 32MiB
  • du: silently skip non-btrfs dirs/files
  • documentation updates: btrfs(5), btrfs(8), balance, subvolume, scrub, filesystem, convert
  • bugfixes:
    • unaligned access (reported for sparc64) in raid56 parity calculations
    • use /bin/bash
    • other stability fixes and cleanups
  • more tests

btrfs-progs 4.7.1 (Aug 2016)

do not use, see 4.7.2

  • check:
    • new optional mode: optimized for low memory usage (memory/io tradeoff)
    • --mode=lowmem, not default, still considered experimental
    • does not work with --repair yet
  • convert: regression fix, ext2_subvol/image rw permissions
  • mkfs/convert:
    • two-staged creation, partially created filesystem will not be recognized
    • improved error handling (fewer BUG_ONs)
  • convert: preparation for more filesystems to convert from
  • documentation updates: quota, qgroup
  • other
    • message updates
    • more tests
    • more build options, enhanced debugging

btrfs-progs 4.7.2 (Sep 2016)

  • check:
    • urgent fix: false report of backref mismatches; do not --repair, last unaffected version 4.6.1 (code reverted to that state)
  • fuzzing and fixes
    • added more sanity checks for various structures
    • testing images added
  • build: udev compatibility: do not install .rules on version < 190
  • other:
    • dump-super: do not crash on garbage value in csum_type
    • minor improvements in messages and help strings
  • documentation:
    • filesystem features

btrfs-progs 4.7.3 (Sep 2016)

  • fixed free space tree compat status
  • check: low-mem mode: handle partially dropped snapshots
  • dump-super: consolidate options for superblock copy
  • tree-stats: check mount status
  • subvol delete: handle verbosity option
  • defrag: print correct error string
  • mkfs: fix reading rotational status
  • other:
    • UBSAN build option
    • documentation updates
    • enhanced tests: convert, fuzzed images, more tools to run on fuzzed images

btrfs-progs 4.6 (Jun 2016)

  • convert - major rewrite:
    • fix a long-standing bug that led to mixing data blocks into metadata block groups
    • the workaround was to do full balance after conversion, which was recommended practice anyway
    • explicitly set the lowest supported version of e2fstools to 1.41
  • provide and install udev rules file that addresses problems with device mapper devices, renames after removal
  • send: new option: quiet
  • dev usage: report slack space (device size minus filesystem area on the dev)
  • image: support DUP
  • build: short options to enable debugging builds
  • other:
    • code cleanups
    • build fixes
    • more tests and other enhancements

btrfs-progs 4.5 (Mar 2016)

  • new/moved commands
    • btrfs-show-super -> btrfs inspect-internal dump-super
    • btrfs-debug-tree -> btrfs inspect-internal dump-tree
  • new commands
    • btrfs fi du - calculate disk usage, including shared extents
  • enhancements
    • device delete - delete by id (needs kernel support, not merged to 4.6)
    • check - new option to specify chunk root
    • debug-tree/dump-tree - option -t understands human readable name of the tree (along numerical ids)
    • btrfs-debugfs - can dump block group information
  • bugfixes
    • all commands should accept the option separator "--"
    • several fixes in device scan
    • restore works on filesystems with sectorsize > 4k
    • debug-tree/dump-tree - print compression type as string
    • subvol sync: fix crash, memory corruption
    • argument parsing fixes: subvol get-default, qgroup create/destroy/assign, inspect subvolid-resolve
    • check for block device or regular file in several commands
  • other
    • documentation updates
    • manual pages for the moved tools now point to btrfs-filesystem
    • testsuite updates

btrfs-progs 4.5.1 (Mar 2016)

  • mkfs: allow DUP on multi-device filesystems
  • bugfixes: build fixes, assorted other fixes

btrfs-progs 4.5.2 (May 2016)

  • new/moved command: btrfs-calc-stats -> btrfs inspect tree-stats
  • check: fix false alert for metadata blocks crossing stripe boundary
  • check: catch when qgroup numbers mismatch
  • check: detect running quota rescan and report mismatches
  • balance start: add safety delay before doing a full balance
  • fi sync: is now silent
  • fi show: don't miss filesystems with partially matching uuids
  • dev ready: accept only one argument for device
  • dev stats: print "devid:N" for a missing device instead of "(null)"
  • other:
    • lowest supported version of e2fsprogs is 1.41
    • minor cleanups, test updates

btrfs-progs 4.5.3 (Mar 2016)

  • ioctl: fix unaligned access in buffer from TREE_SEARCH; might cause SIGBUS on architectures that do not support unaligned access and do not performa any fixups
  • improved validation checks of superblock and chunk-related structures
  • subvolume sync: fix handling of -s option
  • balance: adjust timing of safety delay countdown with --full-balance
  • rescue super-recover: fix reversed condition check
  • check: fix bytes_used accounting
  • documentation updates: mount options, scrub, send, receive, select-super, check, mkfs
  • testing: new fuzzed images, for superblock and chunks

btrfs-progs 4.4 (Jan 2016)

User visible changes:

  • mkfs.btrfs --data dup

People asked about duplicating data on a single device for a long time. There are no technical obstacles preventing that, so it got enabled with a warning about potential dangers when the device will not do the duplicated copies. See mkfs.btrfs section DUP PROFILES ON A SINGLE DEVICE.

  • support balance filters added/enhanced in linux 4.4
    • usage=min..max -- enhanced to take range
    • stripes=min..max -- new, filter by stripes for raid0/10/5/6
    • limit=min..max -- enhanced to take range

Noe: due to backward compatibility, the range maximum for 'usage' is not inclusive as for the others, to keep the same behaviour as usage=N .

  • manual pages enhanced (btrfs, mkfs, mount, filesystem, balance)
  • error messages updates, rewordings -- some fstests may break due to that
  • added support for free-space-tree implementation of space cache -- this requires kernel 4.5 and is not recommended for non-developers yet
  • btrfs filesystem usage works with mixed blockgroups


  • installation to /usr/local -- this has unintentionally changed during conversion to autotools in 3.19
  • check: fix a false alert where extent record has wrong metadata flag
  • improved stability on fuzzed/crafted images when reading sys array in superblock
  • build: the 'ar' tool is properly deteced during cross-compilation
  • debug-tree: option -t understands ids for tree root and chnuk tree
  • preparatory work for btrfs-convert rewrite
  • sparse, gcc warning fixes
  • more memory allocation failure handling
  • cleanups
  • more tests


  • chunk recovery: fix floating point exception
  • chunk recovery: endianity bugfix during rebuild
  • mkfs with 64K pages and nodesize reported superblock checksum mismatch
  • check: properly reset nlink of multi-linked file

btrfs-progs 4.4.1 (Feb 2016)

  • find-root: don't skip the first chunk
  • free-space-tree compat bits fix
  • build: target symlinks
  • documentation updates
  • test updates

btrfs-progs 4.3 (Nov 2015)

  • mkfs
    • mixed mode is not forced for filesystems smaller than 1GiB
    • mixed mode broken with mismatching sectorsize and nodesize, fixed
    • print version info earlier
    • print devices sorted by id
    • do not truncate target image with --rootsize
  • fi usage:
    • don't print global block reserve
    • print device id
    • minor output tuning
    • other cleanups
  • calc-size:
    • div-by-zero fix on an empty filesystem
    • fix crash
  • bugfixes:
    • more superblock sanity checks
    • consistently round size of all devices down to sectorsize
    • misc leak fixes
    • convert: don't try to rollback with a half-deleted ext2_saved subvolume
  • other:
    • check: add progress indicator
    • scrub: enahced error message
    • show-super: read superblock from a given offset
    • add README
    • docs: update manual page for mkfs.btrfs, btrfstune, balance, convert and inspect-internal
    • build: optional build with more warnings (W=...)
    • build: better support for static checkers
    • build: html output of documentation
    • pretty-print: last_snapshot for root_item
    • pretty-print: stripe dev uuid
    • error reporting wrappers, introduced and example use
    • refactor open_file_or_dir
    • other docs and help updates
  • testing:
    • test for nodes crossing stripes
    • test for broken 'subvolume sync'
    • basic tests for mkfs, raid option combinations
    • basic tests for fuzzed images (check)
    • command intrumentation (eg valgrind)
    • print commands if requested
    • add README for tests

btrfs-progs 4.3.1 (Nov 2015)

  • fixes
    • device delete: recognize 'missing' again
    • mkfs: long names are not trimmed when doing ssd check
    • support partitioned loop devices
  • other
    • replace several mallocs with on-stack variables
    • more memory allocation failure handling
    • add tests for bugs fixed
    • cmd-device: switch to new message printing helpers
    • minor code cleanups

btrfs-progs 4.2 (Sep 2015)

  • enhancements:
    • mkfs: do not create extra single chunks on multiple devices
    • resize: try to guess the minimal size, 'inspect min-dev-size'
    • qgroup assign: add option to schedule rescan
    • chunk-recover: be more verbose about the scanning process
  • fixes:
    • check:
      • find stripes crossing stripe boundary -- created by convert
      • print correct range for file hole when there are no extents and learn how to fix it
    • replace: more sanity checks
    • convert: concurrency fixes related to reporting progress
    • find-root: option -a will not skip the current root anymore
    • subvol list: fix occasional crash
    • do not create stripes crossing stripe boundary
  • build:
    • fixes for musl libc
    • preliminary support for android (not working yet, more code changes needed)
  • other:
    • lots of cleanups
    • tests: lots of updates, new tests, framework improvements
    • documentation updates
    • debugging: print-tree shows stripe length

btrfs-progs 4.2.1 (Sep 2015)

  • fix an off-by-one error in cross-stripe boundary check
    • if nodesize was 64k, any metadata block was reported as crossing, this leads to mkfs failure for example due to "no free blocks found"
    • for other nodesizes, if the end of the metadata block was 64k aligned, it was incorrectly reported by fsck
  • convert: don't write uninitialized data to image
  • image:
    • don't loop with option -t0
    • don't create threads if compression is not requested
  • other: minor cleanups

btrfs-progs 4.2.2 (Oct 2015)

  • fi label: use fallback if the label ioctl is not available
  • convert: check nodesize constraints against commandline features (-O)
  • scrub: report status 'running' until all devices are finished
  • device scanning might crash in some scenarios
  • fi usage: print summary for non-root users

btrfs-progs 4.2.3 (Oct 2015)

  • subvol sync: make it actually work again: it's been broken since 4.1.2, due to a reversed condition it returned immediatelly instead of waiting
  • scanning: do not scan already discovered filesystems (minor optimization)
  • convert: better error message in case the filesystem is not finalized
  • restore: off-by-one symlink path check fix

btrfs-progs 4.1 (Jun 2015)

  • bugfixes
    • fsck.btrfs: no bash-isms
    • bugzilla 97171: invalid memory access (with tests)
    • receive:
      • cloning works with --chroot
      • capabilities not lost
    • mkfs: do not try to register bare file images
    • option --help accepted by the standalone utilities
  • enhancements
    • corrupt block: ability to remove csums
    • mkfs:
      • warn if metadata redundancy is lower than for data
      • options to make the output quiet (only errors)
      • mixed case names of raid profiles accepted
      • rework the output:
        • more comprehensive, 'key: value' format
    • subvol:
      • show:
        • print received uuid
        • update the output
        • new options to specify size units
      • sync: grab all deleted ids and print them as they're removed, previous implementation only checked if there are any to be deleted - change in command semantics
    • scrub: print timestamps in days HMS format
    • receive:
      • can specify mount point, do not rely on /proc
      • can work inside subvolumes
    • send: new option to send stream without data (NO_FILE_DATA)
    • convert: specify incompat features on the new fs
    • qgroup:
      • show: distinguish no limits and 0 limit value
      • limit: ability to clear the limit
    • help for 'btrfs' is shorter, 1st level command overview
    • debug tree: print key names according to their C name
  • new
    • rescure zero-log
    • btrfsune:
      • rewrite uuid on a filesystem image
      • new option to turn on NO_HOLES incompat feature
  • deprecated
    • standalone btrfs-zero-log
  • other
    • testing framework updates
      • uuid rewrite test
      • btrfstune feature setting test
      • zero-log tests
      • more testing image formats
    • manual page updates
    • ioctl.h synced with current kernel uapi version
    • convert: preparatory works for more filesystems (reiserfs pending)
    • use static buffers for path handling where possible
    • add new helpers for send uilts that check memory allocations, switch all users, deprecate old helpers
    • Makefile: fix build dependency generation
    • map-logical: make it work again

btrfs-progs 4.1.1 (Jul 2015)

Do not use this version

  • bugfixes
    • defrag: threshold overflow fix
    • fsck:
      • check if items fit into the leaf space
      • fix wrong nbytes
    • mkfs:
      • create only desired block groups for single device
      • preparatory work for fix on multiple devices
  • enhancements
    • new alias for 'device delete': 'device remove'
  • other
    • fix compilation on old gcc (4.3)
    • documentation updates
    • debug-tree: print nbytes
    • test: image for corrupted nbytes
    • corupt-block: let it kill nbytes

btrfs-progs 4.1.2 (Jul 2015)

  • urgent bugfix: mkfs creates invalid filesystem, must be recreated

btrfs-progs 4.0 (Apr 2015)

  • resize:
    • don't accept file as an argument (it's confusing)
    • print better error message in case of an error
  • restore: optionally restore metadata (time, mode, uid/gid)
  • receive: optionally enforce chroot
  • new rescue subcommand 'zero-log', same as btrfs-zero-log, but now also part of the main utility
  • check:
    • free space checks match kernel, fixes incorrect reports
  • convert: fix setting of checksum bit if --no-datasum is used
  • fsck.btrfs: don't print messages
  • fix quota rescan on PPC64 (mangled ioctl number)
  • test updates
  • documentation: files renamed to .asciidoc, misc fixups

btrfs-progs 4.0.1 (May 2015)

  • restore:
    • can restore symlinks, new option --symlinks
    • long option variants added
  • convert: dropped dependency on acl.h header and libacl is not required for build
  • fix for 'check' crash
  • device remove error message fix
  • preparatory works for fsid change

btrfs-progs 3.19 (Mar 2015)

  • build converted to autotools
  • btrfs-image
    • restore can now run in parallel threads
    • fixed restore of multiple image from multiple devices onto a single dev
    • introduced metadump v2
  • check: make --init-csum-tree and --init-extent-tree work together
  • find-new: option to search through all metadata even if a root was already found
  • convert: show progress by default, can be turned off
  • corrupt-block: option to work on a specific root
  • bash completion script for all subcommands

btrfs-progs 3.19.1 (Mar 2015)

  • convert:
    • new option to specify metadata block size
    • --no-progress actually works
  • restore: properly handle the page boundary corner case
  • build fixes:
    • missing macro from public header, BTRFS_BUILD_VERSION
    • wrong handling of --enable-convert
  • fi usage: reports correct space for degraded mounts
  • other:
    • mkfs: help string updates
    • completion: added 'usage' subcommands
    • cleanups in qgroup code, preparatory work

btrfs-progs 3.18 (Dec 2014)

  • mkfs - skinny metadata feature is now on by default, first introduced in kernel 3.10
  • filesystem usage - give an overview of fs usage in a way that's more comprehensible than existing 'fi df'
  • device usage - more detailed information about per-device allocations
  • check
    • option to set a different tree root byte number
    • ability to link lost files to lost+found, caused by a recent kernel bug
    • repair of severely corrupted fs (use with care)
  • convert - option to show progress
  • subvol create - print the commit mode inline, print the global mode only if --verbose
  • other updates: musl-libc support, coverity bugfixes, new test images, documentation

btrfs-progs 3.18.1 (Jan 2015)

  • minor fixes
  • documentation updates

btrfs-progs 3.18.2 (Jan 2015)

  • qgroup show: print human readable sizes, options to say otherwise
  • check: new option to explicitly say no to writes
  • mkfs: message about trimming is not printed to stderr
  • fi show: fixed return value
  • tests: new infrastructure
  • btrfstune: force flag can be used together with seeding option
  • backtrace support is back
  • getopt cleanups
  • doc and help updates

btrfs-progs 3.17 (Oct 2014)

  • check: --init-csum-tree actually does something useful, rebuilds the whole csum tree
  • /dev scanning for btrfs devices is gone
  • /proc/partitions scanning is gone, blkid is used exclusively
  • new subcommand subvolume sync
  • filesystem df: new options to set unit format
  • convert: allow to copy label from the origin, or specify a new one

btrfs-progs 3.17.1 (Nov 2014)

  • fi df: argument handling
  • fix linking with libbtrfs
  • replace: better error reporting
  • fi show: fixed stall if run concurrently with balance
  • check: fixed argument parsing for --subvol-extents
  • fi df: SI prefixes corrected

btrfs-progs 3.17.2 (Nov 2014)

  • check improvements
    • add ability to replace missing dir item/dir indexes
    • fix missing inode items
    • create missing root dirid
  • corrupt block: enhancements for testing fsck
  • zero-log: able to reset a fs with bogus log tree pointer (bug 72151)

btrfs-progs 3.17.3 (Dec 2014)

  • convert: fix conversion of sparse ext* filesystems
  • show: resolve to the correct path
  • fsck: more verbose error for root dir problems

btrfs-progs 3.16 (Aug 2014)

  • mkfs: new option to specify UUID, drop experimental notice
  • check: new option to verify quotas, reduced memory requirements, new option to print extent sharing
  • restore: check length before decompression, more error handling, option to loop during restoring
  • balance: new filter 'limit'
  • recover: allow to read all sb copies
  • btrfstune: new option to force dangerous changes
  • receive: new option to limit number of errors
  • show-super: skip unrecognized sb, add option to force
  • debug-tree: print tree by id
  • documentation updates

btrfs-progs 3.16.1 (Sep 2014)

  • print GlobalReserve in fi df output
  • new option -R in subvol list
  • library version defines
  • static build is fixed
  • build without documentation is possible

btrfs-progs 3.16.2 (Oct 2014)

  • a few fixes in fsck and image tools

btrfs-progs 3.14 (Apr 2014)

  • fsck: fixes and enhancements to --init-extent-tree mode
  • fsck: chunk-recover updates
  • scrub: add force option -f
  • send: check if subvolumes are read-only
  • subvol delete: add options to affect commit behaviour
  • btrfs: add property command group
  • restore: add dry-run option
  • restore: fix restoring of compressed files
  • mkfs: support for no-holes feature
  • mkfs: option -r deals with hardlinks and relative paths
  • mkfs: discard phase is interruptible
  • documentation updates

btrfs-progs 3.14.1 (Apr 2014)

  • properties: fix handling of option -t
  • restore: fix reading of compressed extents
  • minor code and doc updates

btrfs-progs 3.14.2 (May 2014)

  • documentation is now written in asciidoc and there are manpages for each subcommand
  • misc bugfixes

btrfs-progs 3.12 (Nov 2013)

By version (linux kernel)

v4.15 (Jan 2018)

  • new features
    • extend mount options to specify zlib compression level, -o compress=zlib:9
    • v2 of ioctl "extent to inode mapping"
    • populate compression heuristics logic
    • enable indexing for btrfs as lower filesystem in overlayfs
    • speedup page cache readahead during send on large files
  • internal changes
    • more sanity checks of b-tree items when reading them from disk
    • more EINVAL/EUCLEAN fixups, missing BLK_STS_* conversion, other errno or error handling fixes
    • remove some homegrown IO-related logic, that's been obsoleted by core block layer changes (batching, plug/unplug, own counters)
    • add ref-verify, optional debugging feature to verify extent reference accounting
    • simplify code handling outstanding extents, make it more clear where and how the accounting is done
    • make delalloc reservations per-inode, simplify the code and make the logic more straightforward
    • extensive cleanup of delayed refs code
  • fix send ioctl on 32bit with 64bit kernel

v4.14 (Nov 2017)

  • added zstd compression
  • fine-grained check for degraded mount (verify raid constraints on chunk level, not device level)
  • userspace transaction ioctl has been deprecated, scheduled for removal in 4.17
  • foundation code for compression heuristics
  • mount option 'ssd' does not force block allocation alignments
  • fixes
    • potential raid repair and compression crash
    • prevent to set invalid default subvolid
    • resume qgroup rescan on rw remount
    • better reporting of detected checksum mismatches for DIO
    • compression for defrag vs per-file behaves as expected, respecting the requested value
    • possible deadlock with readdir and pagefault
    • emission of invalid clone operations in send
  • cleanups and refactoring

v4.13 (Sep 2017)

  • deprecated: mount option alloc_start
  • qgroups: new sysctl to allow temporary quota override with CAP_SYS_RESOURCE
  • statx syscall support
  • nowait AIO support
  • lots of cleanups around bio processing and error handling
  • memory allocation constraint cleanups and improvements
  • more sanity checks (for dir_item)
  • compression will be skipped if there's no improvement (at least one block)
  • fix invalid extent maps due to hole punching
  • fix: sgid not cleared when changing acls
  • some enospc corner case fixes
  • send fixes
  • other cleanups

v4.12 (Jul 2017)

  • new tracepoints: file item
  • fix qgoup accounting when inode_cache is in use
  • fix incorrect number report in stat::t_blocks under certain conditions
  • raid56 fixes:
    • enable auto-repair during read (ie. similar to what raid1 and raid10 do)
    • fix potential crash with concurrent scrub and dev-replace
    • fix potential crash when cancelling dev-replace
    • fix false reports during scrub when it's possible to do repair
    • fix wrong mirror report during repair
  • many cleanups

v4.11 (May 2017)

  • mostly a cleanup release
  • improved csum mismatch messages
  • move some qgroup work out of transaction commit
  • let unlink temporarily exceed quotas
  • fix truncate and lockless DIO writes
  • incremental send fixes
  • fix remount using ssd and nossd combinations

v4.10 (Feb 2017)

  • balance: human readable block group descripion in the log
  • balance: fix storing of stripes_min, stripes_max filters to the on-disk item
  • qgroup: fix accounting bug during concurrent balance run
  • better worker thread resource limit checks
  • fix ENOSPC during hole punching
  • fix ENOSPC when reflinking a heavily fragmented file
  • fix crash when certain tracepoints are enabled
  • fix compat ioctl calls on non-compat systems
  • improved delayed ref iteration performance
  • many cleanups

v4.9 (Dec 2016)

  • improved performance of extent sharing detection in FIEMAP
  • fixes:
    • device delete hang at the end of the operation
    • free space tree bitmap endianity fixed on big-endian machines
    • parallel incremental send and balance issue fixed
    • cloning ioctl can be interrupted by a fatal signal
  • other stability fixes or cleanups

v4.8 (Oct 2016)

  • space reservations and handling uses ticketed system, this should improve latency and fairness in case when there are several threads blocked on flushing
  • fixes of bugs triggered by fuzzed images
  • global ratelmit of all printed messages
  • several send, qgroup fixes
  • cleanups

v4.7 (Jul 2016)

  • allow balancing to dup with multi-device
  • device deletion by id (additionally to by path)
  • renameat2: add support for RENAME_EXCHANGE and RENAME_WHITEOUT
  • enhanced selftests
  • more preparatory work for "blocksize < page size"
  • more validation checks of superblock (discovered by fuzzing)
  • advertise which crc32c implementation is being used at module load
  • fixed space report by df with mixed block groups
  • log replay fixes
  • device replace fixes

v4.6 (May 2016)

  • mount options:
    • usebackuproot - replace 'recovery' (works but is deprecated)
    • logreplay, nologreplay - disable log replay at mount time, does no writes to the device
    • norecovery - synthetic option to disable recovery at mount time and disable writes (now does: nologreplay)
  • default inline limit is now 2048 (instead of page size, usually 4096)
  • /dev/btrfs-control now understands the GET_SUPPORTE_FEATURES ioctl
  • get rid of harmless message "could not find root %llu"
  • preparatory work for subpage-blocksize patchset
  • fix bug when using overlayfs
  • fixes in readahead, log replay, fsync, and more

v4.5 (Mar 2016)

  • free space cache v2: an incompat feature to track the free space cache as a b-tree
  • balance:
    • '-dconvert=dup' supported
    • continue but warn if metadata have lower redundancy than data
  • fixes:
    • trim does not overwrite bootloader area (introduced in 4.3, fixed in 4.4.x stable kernels)
  • assorted bugfixes, improvements or cleanups

v4.4 (Jan 2016)

  • send fixes: cloning, sending with parent
  • improved handling of framgented space using bitmaps
  • new mount option for debugging: fragment=data|metadata|all
  • updated balance filters: limit, stripes, usage
  • more bugfixes and cleanups

v4.3 (Nov 2015)

  • fix raid56 rebuild with missing device
  • discard ioctl will return the number of bytes
  • more bugfixes and cleanups

v4.2 (Aug 2015)

  • enhancements
    • transaction abort now reports the caller, not the helper function
    • INO_LOOKUP ioctl: unprivileged if used to just get the rootid (aka. subvolume id)
    • unified subvol= and subvolid= mounting, show the mounted subvol in mount options; also, /proc/self/mountinfo now always correctly shows the mounted subvolume
    • reworked internal qgroup logic
    • send: use received_uuid of parent during send
    • sysfs: preparatory works for exporting more stats about devices
    • deduplication on the same inode works
    • deduplication does not change mtime/ctime
  • fixes:
    • in send: cloning, renames, orphans,
    • few more ENOSPC fixes in case of block group creation/removal
    • fix hang during inode eviction due to concurrent readahead
    • EXTENT_SAME ioctl: handle unaligned length
    • more fixes around automatic block group removal
    • deadlock with EXTENT_SAME and readahead
    • for feature NO_HOLES: fsync, truncate

v4.1 (Jun 2015)

  • fixes
    • regression in chunk removal, conversion to raid1 possible again
    • log tree corruption fix with -o discard mount
    • bare xattr namespace attribute is not accepted
    • orphan cleanup is started for implicitly mounted default subvolume
    • send fixes
    • cloning within same file
    • EXTENT_SAME ioctl infinite loop fix
    • avoid more ENOSPC in delayed-iput context
    • a few ENOMEM fixes
    • automatic empty block group removal fixups
  • speedups
    • large file deletion: run delayed refs more often
    • large file deletion: don't build up too much work from crc
    • transaction commit latency improved
    • block group cache writeout
  • qgroup:
    • limits are shared upon snapshot
    • allow to remove qgroup which has parent but no child
    • fix status of qgroup consistency after rescan
    • fix quota status bits after dsiabling
    • mark qgroups inconsistent after assign/delete actions
  • code cleanups

v4.0 (Apr 2015)

  • file creation time is stored (no easy interface to read it yet)
  • fsync and log replay fixes
  • lots of cleanups and other fixes

v3.19 (Feb 2015)

  • raid56 supports scrub and device replace

v3.18 (Dec 2014)

v3.17 (Oct 2014)

  • fix for the infamous deadlock [1]
  • fixed longstanding bug in qgroups accounting after snapshot deletion [2]
  • updated (less inaccurate) df numbers [3]
  • speedup for rename and truncate, less strict flushes [4]
  • updated and fixes to the seeding feature

v3.16 (Aug 2014)

  • O_TMPFILE support [5]
  • reworked qgroup accounting, to fix negative numbers after subvol deletion
  • SEARCH_TREE ioctl v2, extended for retrieving more data [6]
  • new balance filter limit for more finegrained balancing [7]
  • ioctl FS_INFO and it's sysfs counterpart export information about nodesize, sectorsize and clone_alignment
  • snapshots are protected during send

v3.15 (Jun 2014)

  • pile of send fixes (stability, speed)
  • worker threads now use kernel workqueues

v3.14 (Mar 2014)

  • optional incompat disk format improvement aiming at speedup, removing file hole representation, named no-holes
  • ioctl to query/change feature bits (e.g. switching on extended refs on-line now possible)
  • export filesystem info through sysfs: features, allocation profiles
  • added pairing mount options (for remount)
  • heap of small performance optimizations
  • snapshot-aware defrag was disabled due to problems

v3.13 (Jan 2014)

  • fiemap exports information about shared extents
  • bugfix and stability foucsed release

v3.12 (Nov 2013)

  • Major performance improvement for send/receive with large numbers of subvolumes
  • Support for batch deduplication (userspace tools required)
  • new mount option commit to set the commit interval
  • Lots of stability and bugfix patches

v3.11 (Sep 2013)

  • extent cloning within one file
  • ioctl to wait for quota rescan completion
  • device deletion returns error code to userspace (not in syslog anymore)
  • usual load of small fixes and improvements

v3.10 (Jun 2013)

  • reduced size of metadata by so-called skinny extents [8]
  • enhanced syslog message format [9]
  • the mount option subvolrootid is deprecated
  • lots of stability improvements, removed many BUG_ONs
  • qgroups are automatically created when quotas are enabled [10]
  • qgroups are able to rescan current filesystem and sync the quota state with the existing subvolumes
  • enhanced send/recv format for multiplexing more data into one stream [11]
  • various unsorted code cleanups, minor performance updates

v3.9 (Apr 2013)

  • preliminary Raid 5/6 support (details in the announcement)
  • snapshot-aware defrag
  • a mode of send to avoid transferring file data
  • direct IO speedup (numbers)
  • new ioctls to set/get filesystem label
  • defrag is cancellable

v3.8 (Feb 2013)

  • ability to replace devices at runtime in an effective way (description)
  • speed improvements (cumulative effect of many small improvements)
  • a few more bugfixes

v3.7 (Dec 2012)

  • fsync speedups
  • removed limitation of number of hardlinks in a single directory
  • file hole punching (LWN article)
  • per-file NOCOW
  • fixes to send/receive

v3.6 (Sep 2012)

  • subvolume-aware quotas (qgroups)
  • support for send/receive between snapshot changes (LWN article)
  • atime is not updated on read-only snapshots (LWN article)
  • allowed cross-subvolume file clone (aka. reflink)
  • remount with no compression possible
  • new ioctl to read device readiness status
  • speed improvement for concurrent multithreaded reads

v3.5 (Jun 2012)

  • collect device statistics (read/write failures, checksum errors, corrupted blocks)
  • integrity checker (3.3+) supports bigblocks (3.4+)
  • more friendly NFS support (native i_version)
  • thread_pool mount option tunable via remount
  • fsync speed improvements
  • several fixes related to read-only mounts
  • scrub thread priority lowered to idle
  • preparatory works for 3.6 features (tree_mod_log)

v3.4 (May 2012)

  • Allow metadata blocks larger than the page size (4K). This allows metadata blocks up to 64KB in size. In practice 16K and 32K seem to work best. For workloads with lots of metadata, this cuts down the size of the extent allocation tree dramatically and fragments much less. (Chris Mason)
  • Improved error handling (IO errors). This gives Btrfs the ability to abort transactions and go read-only on errors other than internal logic errors and ENOMEM more gracefully instead of crashing. (Jeff Mahoney)
  • Reworked the way in which metadata interacts with the page cache. page->private now points to the btrfs extent_buffer object, which makes everything faster. The code was changed so it now writes a whole extent buffer at a time instead of allowing individual pages to go down. It is now more aggressive about dropping pages for metadata blocks that were freed due to COW. Overall, metadata caching is much faster now. (Josef Bacik)

v3.3 (Mar 2012)

  • restriper - infrastructure to change btrfs raid profiles on the fly via balance
  • optional integrity checker infrastructure (details)
  • fixed a few corner cases where TRIM did not process some blocks
  • cluster allocator improvements (less fragmentation, some speedups)

v3.2 (Jan 2012)

  • Log of past roots to aid recovery (option recovery)
  • Subvolumes mountable by full path
  • Added nospace_cache option
  • Lots of space accounting fixes
  • Improved scrub performance thanks to new read-ahead infrastructure
  • Scrub prints paths of corrupted files
  • ioctl for resolving logical->inode and inode->path
  • Integrated raid-repair (if possible)
  • Data corruption fix for parallel snapshot creation
  • Write barriers for multiple devices were fixed to be more resistant in case of power failure

v3.1 (Oct 2011)

  • Stability fixes (lots of them, really), notably fixing early ENOSPC, improved handling of a few error paths and corner cases, fix for the crash during log replay.

v3.0 (Jul 2011)

  • Filesystem scrub
  • Auto-defragmentation (autodefrag mount option)
  • Improved block allocator
  • Sped up file creation/deletion by delayed operation

v2.6.39 (May 2011)

Per-file compression and NOCOW control. Support for bulk TRIM on SSDs.

v2.6.38 (March 2011)

Added LZO compression method, FIEMAP bugfixes with delalloc, subvol flags get/set ioctl, allow compression during defrag.

v2.6.37 (January 2011)

On-disk free space cache, asynchronous snapshots, unprivileged subvolume deletion, extent buffer switches from a rbtree with spinlocks to a radix tree with RCU. (Explanations of these features are described in this article [registration needed]).

v2.6.35 (August 2010)

Direct I/O support and -ENOSPC handling of volume management operations, completing the -ENOSPC support.

v2.6.34 (May 2010)

Support for changing the default subvolume, a new userspace tool (btrfs), an ioctl that lists all subvolumes, an ioctl to allow improved df math, and other improvements.

v2.6.33 (February 2010)

Some minor -ENOSPC improvements.

v2.6.32 (December 2009)


Btrfs has not had serious -ENOSPC ("no space") handling, the COW oriented design makes handling such situations more difficult than filesystems that just rewrite the blocks. In this release Josef Bacik (Red Hat) has added the necessary infrastructure to fix that problem. Note: The filesystem may run out of space and still show some free space. That space comes from a data/metadata chunk that can't get filled because there's not space left to create its metadata/data counterpart chunk. This is unrelated to the -ENOSPC handling and will be fixed in the future. Code: (commit)

Proper snapshot and subvolume deletion

In the last btrfs-progs version you have options that allow to delete snapshots and subvolumes without having to use rm. This is much faster because it does the deletion via btree walking. It's also now possible to rename snapshots and subvols. Work done by Yan Zheng (Oracle). Code: (commit 1), 2)

Performance improvements

Streaming writes on very fast hardware were previously CPU bound at around 400MB/s. Chris Mason (Oracle) has improved the code so that now it can push over 1GB/s while using the same CPU as XFS (factoring out checksums). There are also improvements for writing large portions of extents, and other workloads. Multidevice setups are also much faster due to the per-BDI writeback changes. The performance of fsync() was greatly improved, which fixed a severe slowdown while using yum in Fedora 11.

Support for "discard" operation on SSD devices

"Discard" support is a way to telling SSD devices which blocks are free so that the underlying firmware knows that it's safe to do some optimizations (commit), (commit)

v0.19 (June 2009)

v0.19 is a forward rolling format change, which means that it can read the v0.18 disk format but older kernels and older btrfs-progs code will not be able to read filesystems created with v0.19. The new code changes the way that extent back references are recorded, making them significantly more efficient. In general, v0.19 is a dramatic speed improvement over v0.18 in almost every workload.

The v0.19 utilities are meant for use with kernels 2.6.31-rc1 and higher. Git trees are available with the new format code for 2.6.30 kernels, please see the download section for details.

If you do not wish to roll forward to the new disk format, use the v0.18 utilities.

v0.18 (January 2009)

v0.18 has the same disk format as 0.17, but a bug was found in the ioctl interface shared between 32 bit and 64 bit programs. This was fixed by changing the ioctl interface. Anyone using 2.6.29-rc2 will need to update to v0.18 of the btrfs progs.

There is no need to reformat though, the disk format is still compatible.

v0.17 (January 2009)

Btrfs is now in 2.6.29-rc1!

v0.17 has a new disk format since v0.16. Future releases will try to maintain backwards compatibility with this new format.


Transparent zlib compression of file data is enabled by mount -o compress.

Improved block allocation routines (Josef Bacik)

Many performance problems in the allocator are addressed in this release

Improved block sharing while moving extents (Yan Zheng)

The btrfs-vol commands to add, remove and balance space across devices triggers a COW of metadata and data blocks. This release is much better at maintaining shared blocks between snapshots when that COW happens.

Seed Device support

It is now possible to create a filesystem to seed other Btrfs filesystems. The original filesystem and devices are included as a readonly starting point to the new FS. All modifications go onto different devices and the COW machinery makes sure the original is unchanged.

Many bug fixes and performance improvements

v0.16 (August 2008)

v0.16 does change the disk format from v0.15, and it includes a long list of performance and stability updates.

Fine grained Btree locking

Locking is now done in a top down fashion while searching the btree, and higher level locks are freed when they are no longer required. Extent allocations still have a coarse grained lock, but that will be improved in the next release.

Improved data=ordered

Ordered data mode loosely means any system that prevents garbage or stale data blocks after a crash. It was previously implemented the same way ext3 does it, which is to force pending data writes down before a transaction commits.

The data=ordered code was changed to only modify metadata in the btree after data extents are fully written on disk. This allows a transaction commit to proceed without waiting for all the data writes on the FS to finish.

A single fsync or synchronous write no longer forces all the dirty data on the FS to disk, as it does in ext3 and reiserfsv3.

Although it is not implemented yet, the new data=ordered code would allow atomic writes of almost any size to a single file to be exported to userland.

ACL support (Josef Bacik)

ACLs are implemented and enabled by default.

Lost file prevention (Josef Bacik)

The VFS and posix APIs force filesystems allow files to be unlinked from a directory before they are deleted from the FS. If the system crashes between the unlink and the deletion, the file is still consuming space on disk, but not listed in any directory.

Btrfs now tracks these files and makes sure they are reclaimed if the system crashes before they are fully deleted.

New directory index format (Josef Bacik)

Btrfs indexes directories in two ways. The first index allows fast name lookups, and the second is optimized to return inodes in something close to disk order for readdir. The second index is an important part of good performance for full filesystem backups.

A per-directory sequence number is now used for the second index, removing some worst case conditions around files that are hard linked into the same directory many times.

Faster unmount times (Yan Zheng)

Btrfs waits for old transactions to be completely removed from the FS before unmount finishes. A new reference count cache was added to make this much less IO intensive, improving FS performance in all workloads.

Improved streaming reads and writes

The new data=ordered code makes streaming writes much faster. Streaming reads are improved by tuning the thread pools used to process data checksums after the read is done. On machines with sufficient CPU power to keep up with the disks, data checksumming is able to run as fast as nodatasum mounts.

v0.15 (May 29, 2008)

  • Metadata back references
  • Online growing and shrinking
  • Conversion program from Ext3
  • data=ordered support
  • COW-free data writes.
  • focus on stability fixes for the multiple device code

v0.14 (April 30, 2008)

  • Support for multiple devices
  • raid0, raid1 and raid10, single spindle metadata duplication

v0.13 and older

  • Copy on write FS
  • Checksumming
  • Transactions
  • Snapshotting
  • Subvolumes
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