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