| f2fs.rst (e291c116f60f3c1ca98090f0f8e7c77e658562fb) | f2fs.rst (71644dff481180ba024ac4f5cb1f068756357adf) |
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| 1.. SPDX-License-Identifier: GPL-2.0 2 3========================================== 4WHAT IS Flash-Friendly File System (F2FS)? 5========================================== 6 7NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have 8been equipped on a variety systems ranging from mobile to server systems. Since --- 11 unchanged lines hidden (view full) --- 20F2FS and its tools support various parameters not only for configuring on-disk 21layout, but also for selecting allocation and cleaning algorithms. 22 23The following git tree provides the file system formatting tool (mkfs.f2fs), 24a consistency checking tool (fsck.f2fs), and a debugging tool (dump.f2fs). 25 26- git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git 27 | 1.. SPDX-License-Identifier: GPL-2.0 2 3========================================== 4WHAT IS Flash-Friendly File System (F2FS)? 5========================================== 6 7NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have 8been equipped on a variety systems ranging from mobile to server systems. Since --- 11 unchanged lines hidden (view full) --- 20F2FS and its tools support various parameters not only for configuring on-disk 21layout, but also for selecting allocation and cleaning algorithms. 22 23The following git tree provides the file system formatting tool (mkfs.f2fs), 24a consistency checking tool (fsck.f2fs), and a debugging tool (dump.f2fs). 25 26- git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git 27 |
| 28For reporting bugs and sending patches, please use the following mailing list: | 28For sending patches, please use the following mailing list: |
| 29 30- linux-f2fs-devel@lists.sourceforge.net 31 | 29 30- linux-f2fs-devel@lists.sourceforge.net 31 |
| 32For reporting bugs, please use the following f2fs bug tracker link: 33 34- https://bugzilla.kernel.org/enter_bug.cgi?product=File%20System&component=f2fs 35 |
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| 32Background and Design issues 33============================ 34 35Log-structured File System (LFS) 36-------------------------------- 37"A log-structured file system writes all modifications to disk sequentially in 38a log-like structure, thereby speeding up both file writing and crash recovery. 39The log is the only structure on disk; it contains indexing information so that --- 109 unchanged lines hidden (view full) --- 149 to eliminate redundant command issues. If the underlying 150 device handles the cache_flush command relatively slowly, 151 recommend to enable this option. 152nobarrier This option can be used if underlying storage guarantees 153 its cached data should be written to the novolatile area. 154 If this option is set, no cache_flush commands are issued 155 but f2fs still guarantees the write ordering of all the 156 data writes. | 36Background and Design issues 37============================ 38 39Log-structured File System (LFS) 40-------------------------------- 41"A log-structured file system writes all modifications to disk sequentially in 42a log-like structure, thereby speeding up both file writing and crash recovery. 43The log is the only structure on disk; it contains indexing information so that --- 109 unchanged lines hidden (view full) --- 153 to eliminate redundant command issues. If the underlying 154 device handles the cache_flush command relatively slowly, 155 recommend to enable this option. 156nobarrier This option can be used if underlying storage guarantees 157 its cached data should be written to the novolatile area. 158 If this option is set, no cache_flush commands are issued 159 but f2fs still guarantees the write ordering of all the 160 data writes. |
| 161barrier If this option is set, cache_flush commands are allowed to be 162 issued. |
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| 157fastboot This option is used when a system wants to reduce mount 158 time as much as possible, even though normal performance 159 can be sacrificed. 160extent_cache Enable an extent cache based on rb-tree, it can cache 161 as many as extent which map between contiguous logical 162 address and physical address per inode, resulting in 163 increasing the cache hit ratio. Set by default. 164noextent_cache Disable an extent cache based on rb-tree explicitly, see --- 29 unchanged lines hidden (view full) --- 194 FAULT_TRUNCATE 0x000000400 195 FAULT_READ_IO 0x000000800 196 FAULT_CHECKPOINT 0x000001000 197 FAULT_DISCARD 0x000002000 198 FAULT_WRITE_IO 0x000004000 199 FAULT_SLAB_ALLOC 0x000008000 200 FAULT_DQUOT_INIT 0x000010000 201 FAULT_LOCK_OP 0x000020000 | 163fastboot This option is used when a system wants to reduce mount 164 time as much as possible, even though normal performance 165 can be sacrificed. 166extent_cache Enable an extent cache based on rb-tree, it can cache 167 as many as extent which map between contiguous logical 168 address and physical address per inode, resulting in 169 increasing the cache hit ratio. Set by default. 170noextent_cache Disable an extent cache based on rb-tree explicitly, see --- 29 unchanged lines hidden (view full) --- 200 FAULT_TRUNCATE 0x000000400 201 FAULT_READ_IO 0x000000800 202 FAULT_CHECKPOINT 0x000001000 203 FAULT_DISCARD 0x000002000 204 FAULT_WRITE_IO 0x000004000 205 FAULT_SLAB_ALLOC 0x000008000 206 FAULT_DQUOT_INIT 0x000010000 207 FAULT_LOCK_OP 0x000020000 |
| 208 FAULT_BLKADDR 0x000040000 |
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| 202 =================== =========== 203mode=%s Control block allocation mode which supports "adaptive" 204 and "lfs". In "lfs" mode, there should be no random 205 writes towards main area. 206 "fragment:segment" and "fragment:block" are newly added here. 207 These are developer options for experiments to simulate filesystem 208 fragmentation/after-GC situation itself. The developers use these 209 modes to understand filesystem fragmentation/after-GC condition well, --- 125 unchanged lines hidden (view full) --- 335 default, it is helpful for large sized SMR or ZNS devices to 336 reduce memory cost by getting rid of fs metadata supports small 337 discard. 338memory=%s Control memory mode. This supports "normal" and "low" modes. 339 "low" mode is introduced to support low memory devices. 340 Because of the nature of low memory devices, in this mode, f2fs 341 will try to save memory sometimes by sacrificing performance. 342 "normal" mode is the default mode and same as before. | 209 =================== =========== 210mode=%s Control block allocation mode which supports "adaptive" 211 and "lfs". In "lfs" mode, there should be no random 212 writes towards main area. 213 "fragment:segment" and "fragment:block" are newly added here. 214 These are developer options for experiments to simulate filesystem 215 fragmentation/after-GC situation itself. The developers use these 216 modes to understand filesystem fragmentation/after-GC condition well, --- 125 unchanged lines hidden (view full) --- 342 default, it is helpful for large sized SMR or ZNS devices to 343 reduce memory cost by getting rid of fs metadata supports small 344 discard. 345memory=%s Control memory mode. This supports "normal" and "low" modes. 346 "low" mode is introduced to support low memory devices. 347 Because of the nature of low memory devices, in this mode, f2fs 348 will try to save memory sometimes by sacrificing performance. 349 "normal" mode is the default mode and same as before. |
| 350age_extent_cache Enable an age extent cache based on rb-tree. It records 351 data block update frequency of the extent per inode, in 352 order to provide better temperature hints for data block 353 allocation. |
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| 343======================== ============================================================ 344 345Debugfs Entries 346=============== 347 348/sys/kernel/debug/f2fs/ contains information about all the partitions mounted as 349f2fs. Each file shows the whole f2fs information. 350 --- 541 unchanged lines hidden --- | 354======================== ============================================================ 355 356Debugfs Entries 357=============== 358 359/sys/kernel/debug/f2fs/ contains information about all the partitions mounted as 360f2fs. Each file shows the whole f2fs information. 361 --- 541 unchanged lines hidden --- |