Lines Matching +full:i +full:- +full:cache +full:- +full:block +full:- +full:size
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 ----------------------
47 pointer block is updated due to the changed location. Then the indirect pointer
48 block is also updated due to the direct pointer block update. In this manner,
49 the upper index structures such as inode, inode map, and checkpoint block are
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
102 collection, triggered in background when I/O subsystem is
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
129 inline_xattr_size=%u Support configuring inline xattr size, it depends on
132 files can be written into inode block.
134 directory entries can be written into inode block. The
135 space of inode block which is used to store inline
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
186 mode=%s Control block allocation mode which supports "adaptive"
189 io_bits=%u Set the bit size of write IO requests. It should be set
203 whint_mode=%s Control which write hints are passed down to block
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
209 alloc_mode=%s Adjust block allocation policy, which supports "reuse"
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.
257 /sys/fs/f2fs based on its device name (i.e., /sys/fs/f2fs/sda).
258 The files in each per-device directory are shown in table below.
261 (see also Documentation/ABI/testing/sysfs-fs-f2fs)
296 volume size, f2fs tries to conduct checkpoint to
300 main_blkaddr This value gives the first block address of
310 command size. It will issue discard commands iif
311 the size is larger than given granularity. Its
312 unit size is 4KB, and 4 (=16KB) is set by default.
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.
347 SSR block allocation. If this is large, SSR mode
363 which covers 8GB block address range.
365 migration_granularity For large-sized sections, F2FS can stop GC given
440 4. Format the block device, and then mount as f2fs
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 --------------
502 to 2MB in size. A section is composed of consecutive segments, and a zone
504 segment size identically, but users can easily modify the sizes by mkfs.
509 align with the zone size <-|
510 |-> align with the segment size
528 - Superblock (SB)
533 - Checkpoint (CP)
537 - Segment Information Table (SIT)
538 : It contains segment information such as valid block count and bitmap for the
541 - Node Address Table (NAT)
542 : It is composed of a block address table for all the node blocks stored in
545 - Segment Summary Area (SSA)
549 - Main Area
552 In order to avoid misalignment between file system and flash-based storage, F2FS
553 aligns the start block address of CP with the segment size. Also, it aligns the
554 start block address of Main area with the zone size by reserving some segments
561 ------------------------------
572 +--------+----------+---------+
574 +--------+----------+---------+
578 +-------+-------+--------+--------+--------+--------+
580 +-------+-------+--------+--------+--------+--------+
583 `----------------------------------------'
586 ---------------
590 indirect node. F2FS assigns 4KB to an inode block which contains 923 data block
592 indirect node pointer as described below. One direct node block contains 1018
593 data blocks, and one indirect node block contains also 1018 node blocks. Thus,
594 one inode block (i.e., a file) covers:
598 Inode block (4KB)
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
625 A dentry block consists of 214 dentry slots and file names. Therein a bitmap is
626 used to represent whether each dentry is valid or not. A dentry block occupies
629 Dentry Block(4 K) = bitmap (27 bytes) + reserved (3 bytes) +
633 +--------------------------------+
634 |dentry block 1 | dentry block 2 |
635 +--------------------------------+
638 . [Dentry Block Structure: 4KB] .
639 +--------+----------+----------+------------+
641 +--------+----------+----------+------------+
642 [Dentry Block: 4KB] . .
645 +------+------+-----+------+
647 +------+------+-----+------+
650 F2FS implements multi-level hash tables for directory structure. Each level has
654 ----------------------
656 B : block
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
707 File size = 7 File size = 7
709 Default Block Allocation
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
733 segment in a unit of section. F2FS expects that the section size would be the
734 same as the unit size of garbage collection in FTL. Furthermore, with respect
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
751 log block thrashing problem in the greedy algorithm. F2FS adopts the greedy
752 algorithm for on-demand cleaner, while background cleaner adopts cost-benefit
756 F2FS manages a bitmap. Each bit represents the validity of a block, and the
759 Write-hint Policy
760 -----------------
764 2) whint_mode=user-based. F2FS tries to pass down hints given by
767 User F2FS Block
768 ---- ---- -----
776 -- buffered io
784 -- direct io
792 3) whint_mode=fs-based. F2FS passes down hints with its policy.
794 User F2FS Block
795 ---- ---- -----
803 -- buffered io
811 -- direct io
820 -------------------
825 The default operation (i.e., mode is zero) of fallocate() allocates
827 file size (as reported by stat(2)) will be changed if offset+len is
828 greater than the file size. Any subregion within the range specified
835 fallocate(fd, DEFAULT_MODE), it allocates on-disk blocks addressess having
839 3. fallocate(fd, 0, 0, size)