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Diffstat (limited to 'Documentation/filesystems/f2fs.rst')
| -rw-r--r-- | Documentation/filesystems/f2fs.rst | 251 |
1 files changed, 192 insertions, 59 deletions
diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index 220f3e0d3f55..cb90d1ae82d0 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -1,8 +1,11 @@ .. SPDX-License-Identifier: GPL-2.0 -========================================== -WHAT IS Flash-Friendly File System (F2FS)? -========================================== +================================= +Flash-Friendly File System (F2FS) +================================= + +Overview +======== NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have been equipped on a variety systems ranging from mobile to server systems. Since @@ -126,9 +129,7 @@ norecovery Disable the roll-forward recovery routine, mounted read- discard/nodiscard Enable/disable real-time discard in f2fs, if discard is enabled, f2fs will issue discard/TRIM commands when a segment is cleaned. -no_heap Disable heap-style segment allocation which finds free - segments for data from the beginning of main area, while - for node from the end of main area. +heap/no_heap Deprecated. nouser_xattr Disable Extended User Attributes. Note: xattr is enabled by default if CONFIG_F2FS_FS_XATTR is selected. noacl Disable POSIX Access Control List. Note: acl is enabled @@ -158,7 +159,7 @@ nobarrier This option can be used if underlying storage guarantees If this option is set, no cache_flush commands are issued but f2fs still guarantees the write ordering of all the data writes. -barrier If this option is set, cache_flush commands are allowed to be +barrier If this option is set, cache_flush commands are allowed to be issued. fastboot This option is used when a system wants to reduce mount time as much as possible, even though normal performance @@ -175,38 +176,48 @@ data_flush Enable data flushing before checkpoint in order to persist data of regular and symlink. reserve_root=%d Support configuring reserved space which is used for allocation from a privileged user with specified uid or - gid, unit: 4KB, the default limit is 0.2% of user blocks. -resuid=%d The user ID which may use the reserved blocks. -resgid=%d The group ID which may use the reserved blocks. + gid, unit: 4KB, the default limit is 12.5% of user blocks. +reserve_node=%d Support configuring reserved nodes which are used for + allocation from a privileged user with specified uid or + gid, the default limit is 12.5% of all nodes. +resuid=%d The user ID which may use the reserved blocks and nodes. +resgid=%d The group ID which may use the reserved blocks and nodes. fault_injection=%d Enable fault injection in all supported types with specified injection rate. fault_type=%d Support configuring fault injection type, should be enabled with fault_injection option, fault type value is shown below, it supports single or combined type. - =================== =========== - Type_Name Type_Value - =================== =========== - FAULT_KMALLOC 0x000000001 - FAULT_KVMALLOC 0x000000002 - FAULT_PAGE_ALLOC 0x000000004 - FAULT_PAGE_GET 0x000000008 - FAULT_ALLOC_BIO 0x000000010 (obsolete) - FAULT_ALLOC_NID 0x000000020 - FAULT_ORPHAN 0x000000040 - FAULT_BLOCK 0x000000080 - FAULT_DIR_DEPTH 0x000000100 - FAULT_EVICT_INODE 0x000000200 - FAULT_TRUNCATE 0x000000400 - FAULT_READ_IO 0x000000800 - FAULT_CHECKPOINT 0x000001000 - FAULT_DISCARD 0x000002000 - FAULT_WRITE_IO 0x000004000 - FAULT_SLAB_ALLOC 0x000008000 - FAULT_DQUOT_INIT 0x000010000 - FAULT_LOCK_OP 0x000020000 - FAULT_BLKADDR 0x000040000 - =================== =========== + .. code-block:: none + + =========================== ========== + Type_Name Type_Value + =========================== ========== + FAULT_KMALLOC 0x00000001 + FAULT_KVMALLOC 0x00000002 + FAULT_PAGE_ALLOC 0x00000004 + FAULT_PAGE_GET 0x00000008 + FAULT_ALLOC_BIO 0x00000010 (obsolete) + FAULT_ALLOC_NID 0x00000020 + FAULT_ORPHAN 0x00000040 + FAULT_BLOCK 0x00000080 + FAULT_DIR_DEPTH 0x00000100 + FAULT_EVICT_INODE 0x00000200 + FAULT_TRUNCATE 0x00000400 + FAULT_READ_IO 0x00000800 + FAULT_CHECKPOINT 0x00001000 + FAULT_DISCARD 0x00002000 + FAULT_WRITE_IO 0x00004000 + FAULT_SLAB_ALLOC 0x00008000 + FAULT_DQUOT_INIT 0x00010000 + FAULT_LOCK_OP 0x00020000 + FAULT_BLKADDR_VALIDITY 0x00040000 + FAULT_BLKADDR_CONSISTENCE 0x00080000 + FAULT_NO_SEGMENT 0x00100000 + FAULT_INCONSISTENT_FOOTER 0x00200000 + FAULT_TIMEOUT 0x00400000 (1000ms) + FAULT_VMALLOC 0x00800000 + =========================== ========== mode=%s Control block allocation mode which supports "adaptive" and "lfs". In "lfs" mode, there should be no random writes towards main area. @@ -215,7 +226,7 @@ mode=%s Control block allocation mode which supports "adaptive" fragmentation/after-GC situation itself. The developers use these modes to understand filesystem fragmentation/after-GC condition well, and eventually get some insights to handle them better. - In "fragment:segment", f2fs allocates a new segment in ramdom + In "fragment:segment", f2fs allocates a new segment in random position. With this, we can simulate the after-GC condition. In "fragment:block", we can scatter block allocation with "max_fragment_chunk" and "max_fragment_hole" sysfs nodes. @@ -228,8 +239,6 @@ mode=%s Control block allocation mode which supports "adaptive" option for more randomness. Please, use these options for your experiments and we strongly recommend to re-format the filesystem after using these options. -io_bits=%u Set the bit size of write IO requests. It should be set - with "mode=lfs". usrquota Enable plain user disk quota accounting. grpquota Enable plain group disk quota accounting. prjquota Enable plain project quota accounting. @@ -237,9 +246,9 @@ usrjquota=<file> Appoint specified file and type during mount, so that quota grpjquota=<file> information can be properly updated during recovery flow, prjjquota=<file> <quota file>: must be in root directory; jqfmt=<quota type> <quota type>: [vfsold,vfsv0,vfsv1]. -offusrjquota Turn off user journalled quota. -offgrpjquota Turn off group journalled quota. -offprjjquota Turn off project journalled quota. +usrjquota= Turn off user journalled quota. +grpjquota= Turn off group journalled quota. +prjjquota= Turn off project journalled quota. quota Enable plain user disk quota accounting. noquota Disable all plain disk quota option. alloc_mode=%s Adjust block allocation policy, which supports "reuse" @@ -260,11 +269,11 @@ test_dummy_encryption=%s The argument may be either "v1" or "v2", in order to select the corresponding fscrypt policy version. checkpoint=%s[:%u[%]] Set to "disable" to turn off checkpointing. Set to "enable" - to reenable checkpointing. Is enabled by default. While + to re-enable checkpointing. Is enabled by default. While disabled, any unmounting or unexpected shutdowns will cause the filesystem contents to appear as they did when the filesystem was mounted with that option. - While mounting with checkpoint=disabled, the filesystem must + While mounting with checkpoint=disable, the filesystem must run garbage collection to ensure that all available space can be used. If this takes too much time, the mount may return EAGAIN. You may optionally add a value to indicate how much @@ -289,10 +298,15 @@ nocheckpoint_merge Disable checkpoint merge feature. compress_algorithm=%s Control compress algorithm, currently f2fs supports "lzo", "lz4", "zstd" and "lzo-rle" algorithm. compress_algorithm=%s:%d Control compress algorithm and its compress level, now, only - "lz4" and "zstd" support compress level config. - algorithm level range - lz4 3 - 16 - zstd 1 - 22 + "lz4" and "zstd" support compress level config:: + + ========= =========== + algorithm level range + ========= =========== + lz4 3 - 16 + zstd 1 - 22 + ========= =========== + compress_log_size=%u Support configuring compress cluster size. The size will be 4KB * (1 << %u). The default and minimum sizes are 16KB. compress_extension=%s Support adding specified extension, so that f2fs can enable @@ -351,6 +365,48 @@ age_extent_cache Enable an age extent cache based on rb-tree. It records data block update frequency of the extent per inode, in order to provide better temperature hints for data block allocation. +errors=%s Specify f2fs behavior on critical errors. This supports modes: + "panic", "continue" and "remount-ro", respectively, trigger + panic immediately, continue without doing anything, and remount + the partition in read-only mode. By default it uses "continue" + mode. + + .. code-block:: none + + ====================== =============== =============== ======== + mode continue remount-ro panic + ====================== =============== =============== ======== + access ops normal normal N/A + syscall errors -EIO -EROFS N/A + mount option rw ro N/A + pending dir write keep keep N/A + pending non-dir write drop keep N/A + pending node write drop keep N/A + pending meta write keep keep N/A + ====================== =============== =============== ======== +nat_bits Enable nat_bits feature to enhance full/empty nat blocks access, + by default it's disabled. +lookup_mode=%s Control the directory lookup behavior for casefolded + directories. This option has no effect on directories + that do not have the casefold feature enabled. + + .. code-block:: none + + ================== ======================================== + Value Description + ================== ======================================== + perf (Default) Enforces a hash-only lookup. + The linear search fallback is always + disabled, ignoring the on-disk flag. + compat Enables the linear search fallback for + compatibility with directory entries + created by older kernel that used a + different case-folding algorithm. + This mode ignores the on-disk flag. + auto F2FS determines the mode based on the + on-disk `SB_ENC_NO_COMPAT_FALLBACK_FL` + flag. + ================== ======================================== ======================== ============================================================ Debugfs Entries @@ -464,7 +520,7 @@ Note: please refer to the manpage of dump.f2fs(8) to get full option list. sload.f2fs ---------- -The sload.f2fs gives a way to insert files and directories in the exisiting disk +The sload.f2fs gives a way to insert files and directories in the existing disk image. This tool is useful when building f2fs images given compiled files. Note: please refer to the manpage of sload.f2fs(8) to get full option list. @@ -760,6 +816,37 @@ In order to identify whether the data in the victim segment are valid or not, F2FS manages a bitmap. Each bit represents the validity of a block, and the bitmap is composed of a bit stream covering whole blocks in main area. +Write-hint Policy +----------------- + +F2FS sets the whint all the time with the below policy. + +===================== ======================== =================== +User F2FS Block +===================== ======================== =================== +N/A META WRITE_LIFE_NONE|REQ_META +N/A HOT_NODE WRITE_LIFE_NONE +N/A WARM_NODE WRITE_LIFE_MEDIUM +N/A COLD_NODE WRITE_LIFE_LONG +ioctl(COLD) COLD_DATA WRITE_LIFE_EXTREME +extension list " " + +-- buffered io +------------------------------------------------------------------ +N/A COLD_DATA WRITE_LIFE_EXTREME +N/A HOT_DATA WRITE_LIFE_SHORT +N/A WARM_DATA WRITE_LIFE_NOT_SET + +-- direct io +------------------------------------------------------------------ +WRITE_LIFE_EXTREME COLD_DATA WRITE_LIFE_EXTREME +WRITE_LIFE_SHORT HOT_DATA WRITE_LIFE_SHORT +WRITE_LIFE_NOT_SET WARM_DATA WRITE_LIFE_NOT_SET +WRITE_LIFE_NONE " WRITE_LIFE_NONE +WRITE_LIFE_MEDIUM " WRITE_LIFE_MEDIUM +WRITE_LIFE_LONG " WRITE_LIFE_LONG +===================== ======================== =================== + Fallocate(2) Policy ------------------- @@ -776,7 +863,7 @@ Allocating disk space as a method of optimally implementing that function. However, once F2FS receives ioctl(fd, F2FS_IOC_SET_PIN_FILE) in prior to -fallocate(fd, DEFAULT_MODE), it allocates on-disk block addressess having +fallocate(fd, DEFAULT_MODE), it allocates on-disk block addresses having zero or random data, which is useful to the below scenario where: 1. create(fd) @@ -867,24 +954,26 @@ compression enabled files (refer to "Compression implementation" section for how enable compression on a regular inode). 1) compress_mode=fs -This is the default option. f2fs does automatic compression in the writeback of the -compression enabled files. + + This is the default option. f2fs does automatic compression in the writeback of the + compression enabled files. 2) compress_mode=user -This disables the automatic compression and gives the user discretion of choosing the -target file and the timing. The user can do manual compression/decompression on the -compression enabled files using F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE -ioctls like the below. -To decompress a file, + This disables the automatic compression and gives the user discretion of choosing the + target file and the timing. The user can do manual compression/decompression on the + compression enabled files using F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE + ioctls like the below. -fd = open(filename, O_WRONLY, 0); -ret = ioctl(fd, F2FS_IOC_DECOMPRESS_FILE); +To decompress a file:: -To compress a file, + fd = open(filename, O_WRONLY, 0); + ret = ioctl(fd, F2FS_IOC_DECOMPRESS_FILE); -fd = open(filename, O_WRONLY, 0); -ret = ioctl(fd, F2FS_IOC_COMPRESS_FILE); +To compress a file:: + + fd = open(filename, O_WRONLY, 0); + ret = ioctl(fd, F2FS_IOC_COMPRESS_FILE); NVMe Zoned Namespace devices ---------------------------- @@ -900,3 +989,47 @@ NVMe Zoned Namespace devices can start before the zone-capacity and span across zone-capacity boundary. Such spanning segments are also considered as usable segments. All blocks past the zone-capacity are considered unusable in these segments. + +Device aliasing feature +----------------------- + +f2fs can utilize a special file called a "device aliasing file." This file allows +the entire storage device to be mapped with a single, large extent, not using +the usual f2fs node structures. This mapped area is pinned and primarily intended +for holding the space. + +Essentially, this mechanism allows a portion of the f2fs area to be temporarily +reserved and used by another filesystem or for different purposes. Once that +external usage is complete, the device aliasing file can be deleted, releasing +the reserved space back to F2FS for its own use. + +.. code-block:: + + # ls /dev/vd* + /dev/vdb (32GB) /dev/vdc (32GB) + # mkfs.ext4 /dev/vdc + # mkfs.f2fs -c /dev/vdc@vdc.file /dev/vdb + # mount /dev/vdb /mnt/f2fs + # ls -l /mnt/f2fs + vdc.file + # df -h + /dev/vdb 64G 33G 32G 52% /mnt/f2fs + + # mount -o loop /dev/vdc /mnt/ext4 + # df -h + /dev/vdb 64G 33G 32G 52% /mnt/f2fs + /dev/loop7 32G 24K 30G 1% /mnt/ext4 + # umount /mnt/ext4 + + # f2fs_io getflags /mnt/f2fs/vdc.file + get a flag on /mnt/f2fs/vdc.file ret=0, flags=nocow(pinned),immutable + # f2fs_io setflags noimmutable /mnt/f2fs/vdc.file + get a flag on noimmutable ret=0, flags=800010 + set a flag on /mnt/f2fs/vdc.file ret=0, flags=noimmutable + # rm /mnt/f2fs/vdc.file + # df -h + /dev/vdb 64G 753M 64G 2% /mnt/f2fs + +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. |