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Diffstat (limited to 'Documentation/filesystems/f2fs.rst')
| -rw-r--r-- | Documentation/filesystems/f2fs.rst | 62 |
1 files changed, 55 insertions, 7 deletions
diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index 7e4031631286..771216f45207 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -137,6 +137,15 @@ noacl Disable POSIX Access Control List. Note: acl is enabled active_logs=%u Support configuring the number of active logs. In the current design, f2fs supports only 2, 4, and 6 logs. Default number is 6. + When the underlying block device exposes write + streams, the default active_logs=6 configuration + maps hot, warm, and cold DATA writes to streams 1, + 2, and 3, respectively. If only one or two write + streams are available, f2fs falls back to mapping + all DATA writes to stream 1 or mapping hot/warm + to stream 1 and cold to stream 2. If no write + streams are exposed, f2fs leaves the stream + unset. disable_ext_identify Disable the extension list configured by mkfs, so f2fs is not aware of cold files such as media files. inline_xattr Enable the inline xattrs feature. @@ -342,12 +351,10 @@ compress_mode=%s Control file compression mode. This supports "fs" and "user" compress_cache Support to use address space of a filesystem managed inode to cache compressed block, in order to improve cache hit ratio of random read. -inlinecrypt When possible, encrypt/decrypt the contents of encrypted - files using the blk-crypto framework rather than - filesystem-layer encryption. This allows the use of - inline encryption hardware. The on-disk format is - unaffected. For more details, see - Documentation/block/inline-encryption.rst. +inlinecrypt When possible, encrypt/decrypt the contents of + encrypted files using inline encryption hardware rather + than the CPU. For more details, see + Documentation/filesystems/fscrypt.rst. atgc Enable age-threshold garbage collection, it provides high effectiveness and efficiency on background GC. discard_unit=%s Control discard unit, the argument can be "block", "segment" @@ -408,7 +415,13 @@ lookup_mode=%s Control the directory lookup behavior for casefolded auto F2FS determines the mode based on the on-disk `SB_ENC_NO_COMPAT_FALLBACK_FL` flag. - ================== ======================================== +resizable_tail_secno=%u Control the number of sections at the tail of the + filesystem reserved for online resizing. Pinned files + will only be allocated within sections 0 to + (MAIN_SECS - resizable_tail_secno) - 1. If set to 0 + (default), there is no tail restriction unless running + on a zoned block device where conventional zones are + used. ======================== ============================================================ Debugfs Entries @@ -1036,6 +1049,41 @@ So, the key idea is, user can do any file operations on /dev/vdc, and reclaim the space after the use, while the space is counted as /data. That doesn't require modifying partition size and filesystem format. +Dynamic Device Aliasing Management +---------------------------------- + +In addition to static device aliasing by deleting the aliasing file, F2FS +supports dynamic management of device aliasing. This mechanism allows the system +to dynamically transition partition ownership between F2FS userdata and external +entities (e.g., zRAM, raw partition) based on system requirements without +deleting the master aliasing file or requiring unmount/remount. + +The master aliasing file is created during the initial format of the file system +and remains as a persistent control entity (ioctl gateway) in the root directory. + +- Partition Reservation (In-service to Aliased) + When a specific partition needs to be dedicated to external services (e.g., zRAM), + a user can reserve the device alias range via ioctl. The kernel resets GC victim + information for the target range, marks segments as in-use to prevent new + allocations, and triggers forced GC to migrate existing valid data out of the + range. Finally, it reserves these blocks in the SIT to effectively exclude the + device from the usable capacity. + +- Partition Release (Aliased to In-service) + When external usage concludes, the space is reclaimed not by deleting the file, + but through the release ioctl. The kernel truncates blocks associated with + the file, releasing them back to general filesystem allocation. + +.. code-block:: + + # f2fs_io dev_alias release /mnt/f2fs/vdc.file + # df -h + /dev/vdb 64G 753M 64G 2% /mnt/f2fs + + # f2fs_io dev_alias reserve /mnt/f2fs/vdc.file + # df -h + /dev/vdb 64G 33G 32G 52% /mnt/f2fs + Per-file Read-Only Large Folio Support -------------------------------------- |