Lines Matching +full:files +full:- +full:based
1 .. SPDX-License-Identifier: GPL-2.0
4 WHAT IS Flash-Friendly File System (F2FS)?
7 NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have
13 F2FS is a file system exploiting NAND flash memory-based storage devices, which
14 is based on Log-structured File System (LFS). The design has been focused on
18 Since a NAND flash memory-based storage device shows different characteristic
20 F2FS and its tools support various parameters not only for configuring on-disk
26 - git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git
30 - linux-f2fs-devel@lists.sourceforge.net
35 Log-structured File System (LFS)
36 --------------------------------
37 "A log-structured file system writes all modifications to disk sequentially in
38 a log-like structure, thereby speeding up both file writing and crash recovery.
40 files can be read back from the log efficiently. In order to maintain large free
44 implementation of a log-structured file system", ACM Trans. Computer Systems
48 ----------------------
57 [1] Bityutskiy, A. 2005. JFFS3 design issues. http://www.linux-mtd.infradead.org/
60 -----------------
61 Since LFS is based on out-of-place writes, it produces so many obsolete blocks
71 3. It checks the cross-reference between the data and its parent index structure.
82 ---------------
83 - Enlarge the random write area for better performance, but provide the high
85 - Align FS data structures to the operational units in FTL as best efforts
88 ----------------------
89 - Use a term, “node”, that represents inodes as well as various pointer blocks
90 - Introduce Node Address Table (NAT) containing the locations of all the “node”
94 -----------------
95 - Support a background cleaning process
96 - Support greedy and cost-benefit algorithms for victim selection policies
97 - Support multi-head logs for static/dynamic hot and cold data separation
98 - Introduce adaptive logging for efficient block allocation
113 disable_roll_forward Disable the roll-forward recovery routine
114 norecovery Disable the roll-forward recovery routine, mounted read-
115 only (i.e., -o ro,disable_roll_forward)
116 discard/nodiscard Enable/disable real-time discard in f2fs, if discard is
119 no_heap Disable heap-style segment allocation which finds free
130 is not aware of cold files such as media files.
136 files can be written into inode block.
154 extent_cache Enable an extent cache based on rb-tree, it can cache
158 noextent_cache Disable an extent cache based on rb-tree explicitly, see
212 layer. This supports "off", "user-based", and
213 "fs-based". In "off" mode (default), f2fs does not pass
214 down hints. In "user-based" mode, f2fs tries to pass
215 down hints given by users. And in "fs-based" mode, f2fs
226 based on "posix", but doesn't issue flush command for
227 non-atomic files likewise "nobarrier" mount option.
251 "lz4", "zstd" and "lzo-rle" algorithm.
256 compression on those corresponding files, e.g. if all files
260 For other files, we can still enable compression via ioctl.
262 can be set to enable compression for all files.
264 files using the blk-crypto framework rather than
265 filesystem-layer encryption. This allows the use of
266 inline encryption hardware. The on-disk format is
268 Documentation/block/inline-encryption.rst.
269 atgc Enable age-threshold garbage collection, it provides high
281 - major file system information managed by f2fs currently
282 - average SIT information about whole segments
283 - current memory footprint consumed by f2fs.
290 /sys/fs/f2fs based on its device name (i.e., /sys/fs/f2fs/sda).
291 The files in each per-device directory are shown in table below.
293 Files in /sys/fs/f2fs/<devname>
294 (see also Documentation/ABI/testing/sysfs-fs-f2fs)
312 # mkfs.f2fs -l label /dev/block_device
313 # mount -t f2fs /dev/block_device /mnt/f2fs
316 ---------
318 which builds a basic on-disk layout.
323 ``-l [label]`` Give a volume label, up to 512 unicode name.
324 ``-a [0 or 1]`` Split start location of each area for heap-based allocation.
327 ``-o [int]`` Set overprovision ratio in percent over volume size.
330 ``-s [int]`` Set the number of segments per section.
333 ``-z [int]`` Set the number of sections per zone.
336 ``-e [str]`` Set basic extension list. e.g. "mp3,gif,mov"
337 ``-t [0 or 1]`` Disable discard command or not.
345 ---------
346 The fsck.f2fs is a tool to check the consistency of an f2fs-formatted
347 partition, which examines whether the filesystem metadata and user-made data
348 are cross-referenced correctly or not.
353 -d debug level [default:0]
358 ---------
362 The dump.f2fs is used to debug on-disk data structures of the f2fs filesystem.
363 It shows on-disk inode information recognized by a given inode number, and is
364 able to dump all the SSA and SIT entries into predefined files, ./dump_ssa and
369 -d debug level [default:0]
370 -i inode no (hex)
371 -s [SIT dump segno from #1~#2 (decimal), for all 0~-1]
372 -a [SSA dump segno from #1~#2 (decimal), for all 0~-1]
376 # dump.f2fs -i [ino] /dev/sdx
377 # dump.f2fs -s 0~-1 /dev/sdx (SIT dump)
378 # dump.f2fs -a 0~-1 /dev/sdx (SSA dump)
383 ----------
384 The sload.f2fs gives a way to insert files and directories in the exisiting disk
385 image. This tool is useful when building f2fs images given compiled files.
390 -----------
391 The resize.f2fs lets a user resize the f2fs-formatted disk image, while preserving
392 all the files and directories stored in the image.
397 -----------
405 -------
407 f2fs-specific ones, which is very useful for QA tests.
414 On-disk Layout
415 --------------
425 align with the zone size <-|
426 |-> align with the segment size
444 - Superblock (SB)
449 - Checkpoint (CP)
453 - Segment Information Table (SIT)
457 - Node Address Table (NAT)
461 - Segment Summary Area (SSA)
465 - Main Area
468 In order to avoid misalignment between file system and flash-based storage, F2FS
477 ------------------------------
488 +--------+----------+---------+
490 +--------+----------+---------+
494 +-------+-------+--------+--------+--------+--------+
496 +-------+-------+--------+--------+--------+--------+
499 `----------------------------------------'
502 ---------------
515 |- data (923)
516 |- direct node (2)
517 | `- data (1018)
518 |- indirect node (2)
519 | `- direct node (1018)
520 | `- data (1018)
521 `- double indirect node (1)
522 `- indirect node (1018)
523 `- direct node (1018)
524 `- data (1018)
532 -------------------
536 - hash hash value of the file name
537 - ino inode number
538 - len the length of file name
539 - type file type such as directory, symlink, etc
551 +--------------------------------+
553 +--------------------------------+
557 +--------+----------+----------+------------+
559 +--------+----------+----------+------------+
563 +------+------+-----+------+
565 +------+------+-----+------+
568 F2FS implements multi-level hash tables for directory structure. Each level has
574 ----------------------
578 ----------------------
582 level #1 | A(2B) - A(2B)
584 level #2 | A(2B) - A(2B) - A(2B) - A(2B)
586 level #N/2 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B)
588 level #N | A(4B) - A(4B) - A(4B) - A(4B) - A(4B) - ... - A(4B)
592 ,- 2, if n < MAX_DIR_HASH_DEPTH / 2,
594 `- 4, Otherwise
596 ,- 2^(n + dir_level),
599 `- 2^((MAX_DIR_HASH_DEPTH / 2) - 1),
607 one bucket determined by the following equation, which shows O(log(# of files))
618 --------------> Dir <--------------
622 child - child [hole] - child
624 child - child - child [hole] - [hole] - child
631 ------------------------
636 - Hot node contains direct node blocks of directories.
637 - Warm node contains direct node blocks except hot node blocks.
638 - Cold node contains indirect node blocks
639 - Hot data contains dentry blocks
640 - Warm data contains data blocks except hot and cold data blocks
641 - Cold data contains multimedia data or migrated data blocks
643 LFS has two schemes for free space management: threaded log and copy-and-compac-
644 tion. The copy-and-compaction scheme which is known as cleaning, is well-suited
649 scheme where the copy-and-compaction scheme is adopted by default, but the
653 In order to align F2FS with underlying flash-based storage, F2FS allocates a
661 ----------------
663 F2FS does cleaning both on demand and in the background. On-demand cleaning is
668 F2FS supports two victim selection policies: greedy and cost-benefit algorithms.
670 of valid blocks. In the cost-benefit algorithm, F2FS selects a victim segment
673 algorithm for on-demand cleaner, while background cleaner adopts cost-benefit
680 Write-hint Policy
681 -----------------
685 2) whint_mode=user-based. F2FS tries to pass down hints given by
698 -- buffered io
706 -- direct io
715 3) whint_mode=fs-based. F2FS passes down hints with its policy.
727 -- buffered io
735 -- direct io
745 -------------------
760 fallocate(fd, DEFAULT_MODE), it allocates on-disk block addressess having
771 --------------------------
773 - New term named cluster is defined as basic unit of compression, file can
778 - In cluster metadata layout, one special block address is used to indicate
780 metadata maps cluster to [1, 4 << n - 1] physical blocks, in where f2fs
783 - In order to eliminate write amplification during overwrite, F2FS only
784 support compression on write-once file, data can be compressed only when
788 - To enable compression on regular inode, there are three ways:
792 * mount w/ -o compress_extension=ext; touch file.ext
797 +-----------------------------------------------+
799 +-----------------------------------------------+
803 +----------+---------+---------+---------+ +---------+---------+---------+---------+
805 +----------+---------+---------+---------+ +---------+---------+---------+---------+
809 +-------------+-------------+----------+----------------------------+
811 +-------------+-------------+----------+----------------------------+
814 ----------------------------
816 - ZNS defines a per-zone capacity which can be equal or less than the
817 zone-size. Zone-capacity is the number of usable blocks in the zone.
818 F2FS checks if zone-capacity is less than zone-size, if it is, then any
819 segment which starts after the zone-capacity is marked as not-free in
823 zone-capacity is not aligned to default segment size(2MB), then a segment
824 can start before the zone-capacity and span across zone-capacity boundary.
826 past the zone-capacity are considered unusable in these segments.