568 lines
22 KiB
ReStructuredText
568 lines
22 KiB
ReStructuredText
Changes (feature/version)
|
|
=========================
|
|
|
|
Major features or significant feature enhancements by kernel version. For more
|
|
information look below.
|
|
|
|
The version 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 :doc:`Status<Status>` page.
|
|
|
|
6.x
|
|
---
|
|
|
|
6.0 - send protocol v2
|
|
Send protocol update that adds new commands and extends existing
|
|
functionality to write large data chunks. Compressed (and encrypted)
|
|
extents can be optionally emitted and transferred as-is without the need
|
|
to re-compress (or re-encrypt) on the receiving side.
|
|
|
|
6.0 - sysfs exports commit stats
|
|
The file :file:`/sys/fs/btrfs/FSID/commit_stats` shows number of commits and
|
|
various time related statistics.
|
|
|
|
6.0 - sysfs exports chunk sizes
|
|
Chunk size value can be read from
|
|
:file:`/sys/fs/btrfs/FSID/allocation/PROFILE/chunk_size`.
|
|
|
|
6.0 - sysfs shows zoned mode among features
|
|
The zoned mode has been supported since 5.10 and adding functionality.
|
|
Now it's advertised among features.
|
|
|
|
6.0 - checksum implementation is logged at mount time
|
|
When a filesystem is mounted the implementation backing the checksums
|
|
is logged. The information is also accessible in
|
|
:file:`/sys/fs/btrfs/FSID/checksum`.
|
|
|
|
6.1 - sysfs support to temporarily skip exact qgroup accounting
|
|
Allow user override of qgroup accounting and make it temporarily out
|
|
of date e.g. in case when there are several subvolumes deleted and the
|
|
qgroup numbers need to be updated at some cost, an update after that
|
|
can amortize the costs.
|
|
|
|
6.1 - scrub also repairs superblock
|
|
An improvement to scrub in case the superblock is detected to be
|
|
corrupted, the repair happens immediately. Previously it was delayed
|
|
until the next transaction commit for performance reasons that would
|
|
store an updated and correct copy eventually.
|
|
|
|
6.1 - block group tree
|
|
An incompatible change that has to be enabled at mkfs time. Add a new
|
|
b-tree item that stores information about block groups in a compact way
|
|
that significantly improves mount time that's usually long due to
|
|
fragmentation and scattered b-tree items tracking the individual block
|
|
groups. Requires and also enables the free-space-tree and no-holes
|
|
features.
|
|
|
|
6.1 - discard stats available in sysfs
|
|
The directory :file:`/sys/fs/btrfs/FSID/discard` exports statistics and
|
|
tunables related to discard.
|
|
|
|
6.1 - additional qgroup stats in sysfs
|
|
The overall status of qgroups are exported in
|
|
:file:`/sys/sys/fs/btrfs/FSID/qgroups/`.
|
|
|
|
6.1 - check that super block is unchanged at thaw time
|
|
Do full check of super block once a filesystem is thawed. This namely
|
|
happens when system resumes from suspend or hibernation. Accidental
|
|
change by other operating systems will be detected.
|
|
|
|
6.2 - discard=async on by default
|
|
Devices that support trim/discard will enable the asynchronous discard
|
|
for the whole filesystem.
|
|
|
|
6.3 - discard=async settings tuned
|
|
The default IOPS limit has changed from 100 to 1000 and writing value 0
|
|
to :file:`/sys/fs/btrfs/FSID/discard/iops_limit` newly means to not do any
|
|
throttling.
|
|
|
|
6.3 - block group allocation class heuristics
|
|
Pack files by size (up to 128k, up to 8M, more) to avoid fragmentation
|
|
in block groups, assuming that file size and life time is correlated,
|
|
in particular this may help during balance. The stats about the number
|
|
of used classes per block group type is exported in
|
|
:file:`/sys/fs/btrfs/FSID/allocation/\*/size_classes`.
|
|
|
|
6.3 - in DEV_INFO ioctl export per-device FSID
|
|
A seeding device could have a different FSID, available in sysfs and now
|
|
available via DEV_INFO ioctl.
|
|
|
|
6.3 - send utimes cache, reduced stream size
|
|
Utimes for directories are emitted into the send stream only when
|
|
finalizing the directory, the cache also gains significant speedups (up
|
|
to 10x).
|
|
|
|
6.7 - raid-stripe-tree
|
|
New tree for logical mapping, allows some RAID modes for zoned mode.
|
|
|
|
6.7 - simplified quota accounting
|
|
A simplified mode of qgroups accounting
|
|
|
|
6.7 - temporary fsid
|
|
Mount of cloned devices is now possible, the filesystem will get a new
|
|
randomly generated UUID on mount
|
|
|
|
6.8 - new mount API
|
|
Use new mount API (https://lwn.net/Articles/753473/)
|
|
|
|
5.x
|
|
---
|
|
|
|
5.0 - swapfile
|
|
With some limitations where COW design does not work well with the swap
|
|
implementation (nodatacow file, no compression, cannot be snapshotted,
|
|
not possible on multiple devices, ...), as this is the most restricted
|
|
but working setup, we'll try to improve that in the future
|
|
|
|
5.0 - metadata uuid
|
|
An optional incompat feature to assign a new filesystem UUID without
|
|
overwriting all metadata blocks, stored only in superblock, unlike what
|
|
:command:`btrfstune -u`
|
|
|
|
5.1 - FORGET_DEV ioctl
|
|
Unregister devices previously added by the scan ioctl, same effect as
|
|
if the kernel module is reloaded.
|
|
|
|
5.1 - ZSTD level
|
|
Allow to set the ZSTD compression level via mount option, e.g. like
|
|
*compress=zstd:9*. The levels match the default ZSTD compression
|
|
levels. The default is 3, maximum is 15.
|
|
|
|
5.2 - pre-write checks
|
|
Verify metadata blocks before submitting them to the devices. This can
|
|
catch consistency problems or bitflips.
|
|
|
|
5.5 - more checksums
|
|
New checksum algorithms: xxhash (64b), SHA256 (256b), BLAKE2b (256b).
|
|
|
|
5.5 - RAID1C34
|
|
RAID1 with 3- and 4- copies (over all devices).
|
|
|
|
5.6 - async discard
|
|
Mode of discard (*mount -o discard=async*) that merges freed extents to
|
|
larger chunks and submits them for discard in a less intrusive way
|
|
|
|
5.6 - device info in sysfs
|
|
More information about device state can be found in per-filesystem sysfs directory.
|
|
|
|
5.7 - reflink/clone works on inline files
|
|
Inline files can be reflinked to the tail extent of other files
|
|
|
|
5.7 - faster balance cancel
|
|
More cancellation points in balance that will shorten the time to stop
|
|
processing once :command:`btrfs balance cancel` is called.
|
|
|
|
5.7 - *removed flag BTRFS_SUBVOL_CREATE_ASYNC*
|
|
Remove support of flag BTRFS_SUBVOL_CREATE_ASYNC from subvolume creation ioctl.
|
|
|
|
5.7 - v2 of snapshot deletion ioctl
|
|
New ioctl BTRFS_IOC_SNAP_DESTROY_V2, deletion by subvolume id is now possible.
|
|
|
|
5.9 - mount option *rescue*
|
|
Unified mount option for actions that may help to access a damaged
|
|
filesystem. Now supports: nologreplay, usebackuproot
|
|
|
|
5.9 - qgroups in sysfs
|
|
The information about qgroup status and relations is exported in :file:`/sys/fs/UUID/qgroups`
|
|
|
|
5.9 - FS_INFO ioctl
|
|
Export more information: checksum type, checksum size, generation, metadata_uuid
|
|
|
|
5.10 - exclusive ops in sysfs
|
|
Export which filesystem exclusive operation is running (balance,
|
|
resize, device add/delete/replace, ...)
|
|
|
|
5.11 - remove *inode_cache*
|
|
Remove inode number caching feature (mount -o inode_cache)
|
|
|
|
5.11 - more rescue= modes
|
|
Additional modes for mount option *rescue=*: ignorebadroots/ibadroots,
|
|
ignoredatacsums/idatacsums. All are exported in
|
|
:file:`/sys/fs/btrfs/features/supported_rescue_options`.
|
|
|
|
5.12 - zoned mode
|
|
Support for zoned devices with special allocation/write mode to
|
|
fixed-size zones. See :doc:`Zoned<Zoned-mode>`.
|
|
|
|
5.13 - supported_sectorsizes in sysfs
|
|
List supported sector sizes in sysfs file :file:`/sys/fs/btrfs/features/supported_sectorsizes`.
|
|
|
|
5.14 - sysfs scrub bw limit
|
|
Tunable bandwidth limit
|
|
:file:`/sys/fs/btrfs/FSID/devinfo/DEVID/scrub_speed_max` for scrub (and
|
|
device replace) for a given device.
|
|
|
|
5.14 - sysfs device stats
|
|
The device stats can be also found in :file:`/sys/fs/btrfs/FSID/devinfo/DEVID/error_stats`.
|
|
|
|
5.14 - cancellable resize, device delete
|
|
The filesystem resize and device delete operations can be cancelled by
|
|
specifying *cancel* as the device name.
|
|
|
|
5.14 - property value reset
|
|
Change how empty value is interpreted. New behaviour will delete the
|
|
value and reset it to default. This affects *btrfs.compression* where
|
|
value *no* sets NOCOMPRESS bit while empty value resets all compression
|
|
settings (either compression or NOCOMPRESS bit).
|
|
|
|
5.15 - fsverity
|
|
The fs-verity is a support layer that filesystems can hook into to
|
|
support transparent integrity and authenticity protection of read-only
|
|
files. https://www.kernel.org/doc/html/latest/filesystems/fsverity.html
|
|
|
|
5.15 - idmapped mount
|
|
Support mount with UID/GID mapped according to another namespace.
|
|
https://lwn.net/Articles/837566/
|
|
|
|
5.16 - ZNS in zoned
|
|
Zoned namespaces. https://zonedstorage.io/docs/introduction/zns ,
|
|
https://lwn.net/Articles/865988/
|
|
|
|
5.17 - send and relocation
|
|
Send and relocation (balance, device remove, shrink, block group
|
|
reclaim) can now work in parallel.
|
|
|
|
5.17 - device add vs balance
|
|
It is possible to add a device with paused balance.
|
|
|
|
.. note::
|
|
Since kernel 5.17.7 and btrfs-progs 5.17.1
|
|
|
|
5.17 - *no warning with flushoncommit*
|
|
Mounting with *-o flushoncommit* does not trigger the (harmless)
|
|
warning at each transaction commit.
|
|
|
|
.. note::
|
|
Also backported to 5.15.27 and 5.16.13
|
|
|
|
5.18 - zoned and DUP metadata
|
|
DUP metadata works with zoned mode.
|
|
|
|
5.18 - encoded data ioctl
|
|
New ioctls to read and write pre-encoded data (i.e. no transformation
|
|
and directly written as extents), now works for compressed data.
|
|
|
|
5.18 - *removed balance ioctl v1*
|
|
The support for ioctl BTRFS_IOC_BALANCE has been removed, superseded by
|
|
BTRFS_IOC_BALANCE_V2 long time ago.
|
|
|
|
5.18 - *cross-mount reflink works*
|
|
The VFS limitation to reflink files on separate subvolume mounts of the
|
|
same filesystem has been removed.
|
|
|
|
5.18 - syslog error messages with filesystem state
|
|
Messages are printed with a one letter tag ("state: X") that denotes in
|
|
which state the filesystem was at this point:
|
|
|
|
* A - transaction aborted (permanent)
|
|
* E - filesystem error (permanent)
|
|
* M - remount in progress (transient)
|
|
* R - device replace in progress (transient)
|
|
* C - checksum checks disabled by mount option (rescue=ignoredatacsums)
|
|
* L - log tree replay did not complete due to some error
|
|
|
|
5.18 - tree-checker verifies transaction id pre-write
|
|
Metadata buffer to be written gets an extra check if the stored
|
|
transaction number matches the current state of the filesystem.
|
|
|
|
5.19 - subpage support pages > 4KiB
|
|
Metadata node size is supported regardless of the CPU page size
|
|
(minimum size is 4KiB), data sector size is supported <= page size.
|
|
Additionally subpage also supports RAID56.
|
|
|
|
5.19 - per-type background threshold for reclaim
|
|
Add sysfs tunable for background reclaim threshold for all block group
|
|
types (data, metadata, system).
|
|
|
|
5.19 - automatically repair device number mismatch
|
|
Device information is stored in two places, the number in the super
|
|
block and items in the device tree. When this is goes out of sync, e.g.
|
|
by device removal short before unmount, the next mount could fail.
|
|
The b-tree is an authoritative information an can be used to override
|
|
the stale value in the superblock.
|
|
|
|
5.19 - defrag can convert inline files to regular ones
|
|
The logic has been changed so that inline files are considered for
|
|
defragmentation even if the mount option max_inline would prevent that.
|
|
No defragmentation might happen but the inlined files are not skipped.
|
|
|
|
5.19 - explicit minimum zone size is 4MiB
|
|
Set the minimum limit of zone on zoned devices to 4MiB. Real devices
|
|
zones are much larger, this is for emulated devices.
|
|
|
|
5.19 - sysfs tunable for automatic block group reclaim
|
|
Add possibility to set a threshold to automatically reclaim block groups
|
|
also in non-zoned mode. By default completely empty block groups are
|
|
reclaimed automatically but the threshold can be tuned in
|
|
:file:`/sys/fs/btrfs/FSID/allocation/PROFILE/bg_reclaim_threshold`.
|
|
|
|
5.19 - tree-checker verifies metadata block ownership
|
|
Additional check done by tree-checker to verify relationship between a
|
|
tree block and it's tree root owner.
|
|
|
|
4.x
|
|
---
|
|
|
|
4.0 - store otime
|
|
Save creation time (otime) for all new files and directories. For
|
|
future use, current tool cannot read it directly.
|
|
|
|
4.2 - rootid ioctl accessible
|
|
The INO_LOOKUP will return root id (id of the containing subvolume),
|
|
unrestricted and to all users if the *treeid* is 0.
|
|
|
|
4.2 - dedupe possible on the same inode
|
|
The EXTENT_SAME ioctl will accept the same inode as source and
|
|
destination (ranges must not overlap).
|
|
|
|
4.3 - trim all free space
|
|
Trim will be performed also on the space that's not allocated by the
|
|
chunks, not only free space within the allocated chunks.
|
|
|
|
4.4 - balance filter updates
|
|
Enhanced syntax and new balance filters:
|
|
|
|
* limit=min..max
|
|
* usage=min..max
|
|
* stripes=min..max
|
|
|
|
4.5 - free space tree
|
|
Improved implementation of free space cache (aka v2), using b-trees.
|
|
|
|
.. note::
|
|
Default since btrfs-progs 5.15, Kernel 4.9 fixes endianity bugs on
|
|
big-endian machines, x86* is ok
|
|
|
|
4.5 - balance filter updates
|
|
Conversion to data/DUP profile possible through balance filters -- on single-device filesystem.
|
|
|
|
.. note::
|
|
mkfs.btrfs allows creating DUP on single device in the non-mixed mode since 4.4
|
|
|
|
4.6 - max_inline default
|
|
The default value of max_inline changed to 2048.
|
|
|
|
4.6 - read features from control device
|
|
The existing ioctl GET_SUPPORTED_FEATURES can be now used on the
|
|
control device (:file:`/dev/btrfs-control`) and returns the supported features
|
|
without any mounted filesystem.
|
|
|
|
4.7 - delete device by id
|
|
Add new ioctl RM_DEV_V2, pass device to be deleted by its ID.
|
|
|
|
4.7 - more renameat2 modes
|
|
Add support for RENAME_EXCHANGE and RENAME_WHITEOUT to *renameat2*
|
|
syscall. This also means that *overlayfs* is now supported on top of
|
|
btrfs.
|
|
|
|
4.7 - balance filter updates
|
|
Conversion to data/DUP profile possible through balance filters -- on multiple-device filesystems.
|
|
|
|
.. note::
|
|
mkfs.btrfs allows creating DUP on multiple devices since 4.5.1
|
|
|
|
4.12 - RAID56: auto repair
|
|
Scrub will attempt auto-repair (similar to raid1/raid10)
|
|
|
|
4.13 - statx
|
|
Support for the enhanced statx syscall; file creation timestamp
|
|
|
|
4.13 - sysfs qgroups override
|
|
qgroups: new sysfs control file to allow temporary quota override with CAP_SYS_RESOURCE
|
|
|
|
4.13 - *deprecated mount option alloc_start*
|
|
That was a debugging helper, not used and not supposed to be used nowadays.
|
|
|
|
4.14 - ZSTD compression
|
|
New compression algorithm ZSTD, supposedly better ratio/speed performance.
|
|
|
|
4.14 - improved degraded mount
|
|
Allow degraded mount based on the chunk constraints, not device number
|
|
constraints. E.g. when one device is missing but the remaining one holds
|
|
all *single* chunks.
|
|
|
|
4.14 - *deprecated user transaction ioctl*
|
|
BTRFS_IOC_TRANS_START and BTRFS_IOC_TRANS_END, no known users, tricky
|
|
to use; scheduled to be removed in 4.17
|
|
|
|
4.14 - refine SSD optimizations
|
|
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.
|
|
https://git.kernel.org/linus/583b723151794e2ff1691f1510b4e43710293875
|
|
The story so far.
|
|
|
|
4.15 - overlayfs
|
|
Overlayfs can now use btrfs as the lower filesystem.
|
|
|
|
4.15 - *ref-verify*
|
|
Debugging functionality to verify extent references. New mount option
|
|
*ref-verify*, must be built with CONFIG_BTRFS_FS_REF_VERIFY.
|
|
|
|
4.15 - ZLIB level
|
|
Allow to set the ZLIB compression level via mount option, e.g. like
|
|
*compress=zlib:9*. The levels match the default ZLIB compression
|
|
levels. The default is 3.
|
|
|
|
4.15 - v2 of LOGICAL_INO ioctl
|
|
An enhanced version of ioctl that can translate logical extent offset
|
|
to inode numbers, "who owns this block". For certain use cases the V1
|
|
performs bad and this is addressed by V2.
|
|
See for more https://git.kernel.org/linus/d24a67b2d997c860a42516076f3315c2ad2d2884 .
|
|
|
|
4.15 - compression heuristics
|
|
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.
|
|
|
|
4.16 - fallocate: zero range
|
|
Mode of the *fallocate* syscall to zero file range.
|
|
|
|
4.17 - *removed user transaction ioctl*
|
|
Deprecated in 4.14, see above.
|
|
|
|
4.17 - *rmdir* on subvolumes
|
|
Allow *rmdir* to delete an empty subvolume.
|
|
|
|
4.18 - XFLAGS ioctl
|
|
Add support for ioctl FS_IOC_FSSETXATTR/FS_IOC_FSGETXATTR, successor of
|
|
FS_IOC_SETFLAGS/FS_IOC_GETFLAGS ioctl. Currently supports: APPEND,
|
|
IMMUTABLE, NOATIME, NODUMP, SYNC. Note that the naming is very
|
|
confusing, though it's named *xattr*, it does not mean the extended
|
|
attributes. It should be referenced as extended inode flags or
|
|
*xflags*.
|
|
|
|
4.18 - EXTENT_SAME ioctl / 16MiB chunks
|
|
The range for out-of-band deduplication implemented by the EXTENT_SAME
|
|
ioctl will split the range into 16MiB chunks. Up to now this was the
|
|
overall limit and effectively only the first 16MiB was deduplicated.
|
|
|
|
4.18 - GET_SUBVOL_INFO ioctl
|
|
New ioctl to read subvolume information (id, directory name,
|
|
generation, flags, UUIDs, time). This does not require root
|
|
permissions, only the regular access to to the subvolume.
|
|
|
|
4.18 - GET_SUBVOL_ROOTREF ioctl
|
|
New ioctl to enumerate subvolume references of a given subvolume. This
|
|
does not require root permissions, only the regular access to to the
|
|
subvolume.
|
|
|
|
4.18 - INO_LOOKUP_USER ioctl
|
|
New ioctl to lookup path by inode number. This does not require root
|
|
permissions, only the regular access to to the subvolume, unlike the
|
|
INO_LOOKUP ioctl.
|
|
|
|
4.19 - defrag ro/rw
|
|
Allow to run defrag on files that are normally accessible for
|
|
read-write, but are currently opened in read-only mode.
|
|
|
|
3.x
|
|
---
|
|
|
|
3.0 - scrub
|
|
Read all data and verify checksums, repair if possible.
|
|
|
|
3.2 - auto raid repair
|
|
Automatic repair of broken data from a good copy
|
|
|
|
3.2 - root backups
|
|
Save a few previous versions of the most important tree roots at commit time, used by *-o recovery*
|
|
|
|
3.3 - integrity checker
|
|
Optional infrastructure to verify integrity of written metadata blocks
|
|
|
|
3.3 - backref walking
|
|
Groundwork to allow tracking owner of blocks, used via *inspect-internal*
|
|
|
|
3.3 - restriper
|
|
RAID profiles can be changed on-line, balance filters
|
|
|
|
3.4 - big metadata blocks
|
|
Support for metadata blocks larger than page size
|
|
|
|
.. note::
|
|
Default nodesize is 16KiB since btrfs-progs 3.12
|
|
|
|
3.4 - error handling
|
|
Generic infrastructure for graceful error handling (EIO)
|
|
|
|
3.5 - device statistics
|
|
Persistent statistics about device errors
|
|
|
|
3.5 - fsync speedup
|
|
Noticeable improvements in fsync() implementation
|
|
|
|
3.6 - qgroups
|
|
Subvolume-aware quotas
|
|
|
|
3.6 - send/receive
|
|
Ability to transfer one filesystem via a data stream (full or
|
|
incremental) and apply the changes on a remote filesystem.
|
|
|
|
3.7 - extrefs
|
|
Hardlink count limit is lifted to 65536.
|
|
|
|
.. note::
|
|
Default since btrfs-progs 3.12
|
|
|
|
3.7 - hole punching
|
|
Implement the FALLOC_FL_PUNCH_HOLE mode of *fallocate*.
|
|
|
|
3.8 - device replace
|
|
Efficient replacement of existing device (add/remove in one go).
|
|
|
|
3.9 - raid 5/6 *(incomplete)*
|
|
Basic support for RAID5/6 profiles, no crash resiliency, replace and
|
|
scrub support.
|
|
|
|
3.9 - snapshot-aware defrag
|
|
Defrag does not break links between shared extents (snapshots,
|
|
reflinked files).
|
|
|
|
.. note::
|
|
Disabled since 3.14 (and backported to some stable kernel versions)
|
|
due to problems. Has been completely removed in 5.6.
|
|
|
|
3.9 - lightweight send
|
|
A mode of *send* that does not add the actual file data to the stream.
|
|
|
|
3.9 - on-line label set/get
|
|
Label editable on mounted filesystems.
|
|
|
|
3.10 - skinny metadata
|
|
Reduced metadata size (format change) of extents.
|
|
|
|
.. note::
|
|
Default since btrfs-progs 3.18
|
|
|
|
3.10 - qgroup rescan
|
|
Sync qgroups with existing filesystem data.
|
|
|
|
3.12 - UUID tree
|
|
A map of subvolume/UUID that vastly speeds up send/receive.
|
|
|
|
3.12 - out-of-bound deduplication
|
|
Support for deduplicating extents on a given set of files.
|
|
|
|
3.14 - no-holes
|
|
No extent representation for file holes (format change), may reduce
|
|
overall metadata consumption
|
|
|
|
3.14 - feature bits in sysfs
|
|
:file:`/sys/fs/btrfs` exports various bits about filesystem
|
|
capabilities and feature support
|
|
|
|
3.16 - O_TMPFILE
|
|
Mode of open() to safely create a temporary file
|
|
|
|
3.16 - search ioctl v2
|
|
The extended SEARCH_TREE ioctl able to get more than a 4k data
|
|
|
|
3.18 - auto block group reclaim
|
|
Automatically remove block groups (aka. chunks) that become completely empty.
|
|
|
|
3.19 - RAID56: scrub, replace
|
|
Scrub and device replace works on RAID56 filesystems.
|