Lines Matching +full:d +full:- +full:cache +full:- +full:sets
2 WHAT IS Flash-Friendly File System (F2FS)?
5 NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have
11 F2FS is a file system exploiting NAND flash memory-based storage devices, which
12 is based on Log-structured File System (LFS). The design has been focused on
16 Since a NAND flash memory-based storage device shows different characteristic
18 F2FS and its tools support various parameters not only for configuring on-disk
23 >> git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git
26 >> linux-f2fs-devel@lists.sourceforge.net
32 Log-structured File System (LFS)
33 --------------------------------
34 "A log-structured file system writes all modifications to disk sequentially in
35 a log-like structure, thereby speeding up both file writing and crash recovery.
41 implementation of a log-structured file system", ACM Trans. Computer Systems
45 ----------------------
54 [1] Bityutskiy, A. 2005. JFFS3 design issues. http://www.linux-mtd.infradead.org/
57 -----------------
58 Since LFS is based on out-of-place writes, it produces so many obsolete blocks
67 3. It checks the cross-reference between the data and its parent index structure.
79 ---------------
80 - Enlarge the random write area for better performance, but provide the high
82 - Align FS data structures to the operational units in FTL as best efforts
85 ----------------------
86 - Use a term, “node”, that represents inodes as well as various pointer blocks
87 - Introduce Node Address Table (NAT) containing the locations of all the “node”
91 -----------------
92 - Support a background cleaning process
93 - Support greedy and cost-benefit algorithms for victim selection policies
94 - Support multi-head logs for static/dynamic hot and cold data separation
95 - Introduce adaptive logging for efficient block allocation
109 disable_roll_forward Disable the roll-forward recovery routine
110 norecovery Disable the roll-forward recovery routine, mounted read-
111 only (i.e., -o ro,disable_roll_forward)
112 discard/nodiscard Enable/disable real-time discard in f2fs, if discard is
115 no_heap Disable heap-style segment allocation which finds free
150 extent_cache Enable an extent cache based on rb-tree, it can cache
153 increasing the cache hit ratio. Set by default.
154 noextent_cache Disable an extent cache based on rb-tree explicitly, see
160 reserve_root=%d Support configuring reserved space which is used for
163 resuid=%d The user ID which may use the reserved blocks.
164 resgid=%d The group ID which may use the reserved blocks.
165 fault_injection=%d Enable fault injection in all supported types with
167 fault_type=%d Support configuring fault injection type, should be
204 layer. This supports "off", "user-based", and
205 "fs-based". In "off" mode (default), f2fs does not pass
206 down hints. In "user-based" mode, f2fs tries to pass
207 down hints given by users. And in "fs-based" mode, f2fs
219 non-atomic files likewise "nobarrier" mount option.
247 - major file system information managed by f2fs currently
248 - average SIT information about whole segments
249 - current memory footprint consumed by f2fs.
258 The files in each per-device directory are shown in table below.
261 (see also Documentation/ABI/testing/sysfs-fs-f2fs)
322 ipu_policy This parameter controls the policy of in-place
329 in-place-updates. The number indicates percentage
334 in-place-updates when F2FS_IPU_FSYNC mode is set.
338 in-place-updates.
365 migration_granularity For large-sized sections, F2FS can stop GC given
441 # mkfs.f2fs -l label /dev/block_device
442 # mount -t f2fs /dev/block_device /mnt/f2fs
445 ---------
447 which builds a basic on-disk layout.
450 -l [label] : Give a volume label, up to 512 unicode name.
451 -a [0 or 1] : Split start location of each area for heap-based allocation.
453 -o [int] : Set overprovision ratio in percent over volume size.
455 -s [int] : Set the number of segments per section.
457 -z [int] : Set the number of sections per zone.
459 -e [str] : Set basic extension list. e.g. "mp3,gif,mov"
460 -t [0 or 1] : Disable discard command or not.
464 ---------
465 The fsck.f2fs is a tool to check the consistency of an f2fs-formatted
466 partition, which examines whether the filesystem metadata and user-made data
467 are cross-referenced correctly or not.
471 -d debug level [default:0]
474 ---------
478 The dump.f2fs is used to debug on-disk data structures of the f2fs filesystem.
479 It shows on-disk inode information recognized by a given inode number, and is
484 -d debug level [default:0]
485 -i inode no (hex)
486 -s [SIT dump segno from #1~#2 (decimal), for all 0~-1]
487 -a [SSA dump segno from #1~#2 (decimal), for all 0~-1]
490 # dump.f2fs -i [ino] /dev/sdx
491 # dump.f2fs -s 0~-1 /dev/sdx (SIT dump)
492 # dump.f2fs -a 0~-1 /dev/sdx (SSA dump)
498 On-disk Layout
499 --------------
509 align with the zone size <-|
510 |-> align with the segment size
528 - Superblock (SB)
533 - Checkpoint (CP)
534 : It contains file system information, bitmaps for valid NAT/SIT sets, orphan
537 - Segment Information Table (SIT)
541 - Node Address Table (NAT)
545 - Segment Summary Area (SSA)
549 - Main Area
552 In order to avoid misalignment between file system and flash-based storage, F2FS
561 ------------------------------
572 +--------+----------+---------+
574 +--------+----------+---------+
578 +-------+-------+--------+--------+--------+--------+
580 +-------+-------+--------+--------+--------+--------+
583 `----------------------------------------'
586 ---------------
599 |- data (923)
600 |- direct node (2)
601 | `- data (1018)
602 |- indirect node (2)
603 | `- direct node (1018)
604 | `- data (1018)
605 `- double indirect node (1)
606 `- indirect node (1018)
607 `- direct node (1018)
608 `- data (1018)
616 -------------------
620 - hash hash value of the file name
621 - ino inode number
622 - len the length of file name
623 - type file type such as directory, symlink, etc
633 +--------------------------------+
635 +--------------------------------+
639 +--------+----------+----------+------------+
641 +--------+----------+----------+------------+
645 +------+------+-----+------+
647 +------+------+-----+------+
650 F2FS implements multi-level hash tables for directory structure. Each level has
654 ----------------------
658 ----------------------
662 level #1 | A(2B) - A(2B)
664 level #2 | A(2B) - A(2B) - A(2B) - A(2B)
666 level #N/2 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B)
668 level #N | A(4B) - A(4B) - A(4B) - A(4B) - A(4B) - ... - A(4B)
672 ,- 2, if n < MAX_DIR_HASH_DEPTH / 2,
674 `- 4, Otherwise
676 ,- 2^(n + dir_level),
679 `- 2^((MAX_DIR_HASH_DEPTH / 2) - 1),
697 --------------> Dir <--------------
701 child - child [hole] - child
703 child - child - child [hole] - [hole] - child
710 ------------------------
715 - Hot node contains direct node blocks of directories.
716 - Warm node contains direct node blocks except hot node blocks.
717 - Cold node contains indirect node blocks
718 - Hot data contains dentry blocks
719 - Warm data contains data blocks except hot and cold data blocks
720 - Cold data contains multimedia data or migrated data blocks
722 LFS has two schemes for free space management: threaded log and copy-and-compac-
723 tion. The copy-and-compaction scheme which is known as cleaning, is well-suited
728 scheme where the copy-and-compaction scheme is adopted by default, but the
732 In order to align F2FS with underlying flash-based storage, F2FS allocates a
740 ----------------
742 F2FS does cleaning both on demand and in the background. On-demand cleaning is
747 F2FS supports two victim selection policies: greedy and cost-benefit algorithms.
749 of valid blocks. In the cost-benefit algorithm, F2FS selects a victim segment
752 algorithm for on-demand cleaner, while background cleaner adopts cost-benefit
759 Write-hint Policy
760 -----------------
764 2) whint_mode=user-based. F2FS tries to pass down hints given by
768 ---- ---- -----
776 -- buffered io
784 -- direct io
792 3) whint_mode=fs-based. F2FS passes down hints with its policy.
795 ---- ---- -----
803 -- buffered io
811 -- direct io
820 -------------------
835 fallocate(fd, DEFAULT_MODE), it allocates on-disk blocks addressess having