1.. SPDX-License-Identifier: GPL-2.0 2 3====================== 4The SGI XFS Filesystem 5====================== 6 7XFS is a high performance journaling filesystem which originated 8on the SGI IRIX platform. It is completely multi-threaded, can 9support large files and large filesystems, extended attributes, 10variable block sizes, is extent based, and makes extensive use of 11Btrees (directories, extents, free space) to aid both performance 12and scalability. 13 14Refer to the documentation at https://xfs.wiki.kernel.org/ 15for further details. This implementation is on-disk compatible 16with the IRIX version of XFS. 17 18 19Mount Options 20============= 21 22When mounting an XFS filesystem, the following options are accepted. 23 24 allocsize=size 25 Sets the buffered I/O end-of-file preallocation size when 26 doing delayed allocation writeout (default size is 64KiB). 27 Valid values for this option are page size (typically 4KiB) 28 through to 1GiB, inclusive, in power-of-2 increments. 29 30 The default behaviour is for dynamic end-of-file 31 preallocation size, which uses a set of heuristics to 32 optimise the preallocation size based on the current 33 allocation patterns within the file and the access patterns 34 to the file. Specifying a fixed ``allocsize`` value turns off 35 the dynamic behaviour. 36 37 attr2 or noattr2 38 The options enable/disable an "opportunistic" improvement to 39 be made in the way inline extended attributes are stored 40 on-disk. When the new form is used for the first time when 41 ``attr2`` is selected (either when setting or removing extended 42 attributes) the on-disk superblock feature bit field will be 43 updated to reflect this format being in use. 44 45 The default behaviour is determined by the on-disk feature 46 bit indicating that ``attr2`` behaviour is active. If either 47 mount option is set, then that becomes the new default used 48 by the filesystem. 49 50 CRC enabled filesystems always use the ``attr2`` format, and so 51 will reject the ``noattr2`` mount option if it is set. 52 53 discard or nodiscard (default) 54 Enable/disable the issuing of commands to let the block 55 device reclaim space freed by the filesystem. This is 56 useful for SSD devices, thinly provisioned LUNs and virtual 57 machine images, but may have a performance impact. 58 59 Note: It is currently recommended that you use the ``fstrim`` 60 application to ``discard`` unused blocks rather than the ``discard`` 61 mount option because the performance impact of this option 62 is quite severe. 63 64 grpid/bsdgroups or nogrpid/sysvgroups (default) 65 These options define what group ID a newly created file 66 gets. When ``grpid`` is set, it takes the group ID of the 67 directory in which it is created; otherwise it takes the 68 ``fsgid`` of the current process, unless the directory has the 69 ``setgid`` bit set, in which case it takes the ``gid`` from the 70 parent directory, and also gets the ``setgid`` bit set if it is 71 a directory itself. 72 73 filestreams 74 Make the data allocator use the filestreams allocation mode 75 across the entire filesystem rather than just on directories 76 configured to use it. 77 78 ikeep or noikeep (default) 79 When ``ikeep`` is specified, XFS does not delete empty inode 80 clusters and keeps them around on disk. When ``noikeep`` is 81 specified, empty inode clusters are returned to the free 82 space pool. 83 84 inode32 or inode64 (default) 85 When ``inode32`` is specified, it indicates that XFS limits 86 inode creation to locations which will not result in inode 87 numbers with more than 32 bits of significance. 88 89 When ``inode64`` is specified, it indicates that XFS is allowed 90 to create inodes at any location in the filesystem, 91 including those which will result in inode numbers occupying 92 more than 32 bits of significance. 93 94 ``inode32`` is provided for backwards compatibility with older 95 systems and applications, since 64 bits inode numbers might 96 cause problems for some applications that cannot handle 97 large inode numbers. If applications are in use which do 98 not handle inode numbers bigger than 32 bits, the ``inode32`` 99 option should be specified. 100 101 largeio or nolargeio (default) 102 If ``nolargeio`` is specified, the optimal I/O reported in 103 ``st_blksize`` by **stat(2)** will be as small as possible to allow 104 user applications to avoid inefficient read/modify/write 105 I/O. This is typically the page size of the machine, as 106 this is the granularity of the page cache. 107 108 If ``largeio`` is specified, a filesystem that was created with a 109 ``swidth`` specified will return the ``swidth`` value (in bytes) 110 in ``st_blksize``. If the filesystem does not have a ``swidth`` 111 specified but does specify an ``allocsize`` then ``allocsize`` 112 (in bytes) will be returned instead. Otherwise the behaviour 113 is the same as if ``nolargeio`` was specified. 114 115 logbufs=value 116 Set the number of in-memory log buffers. Valid numbers 117 range from 2-8 inclusive. 118 119 The default value is 8 buffers. 120 121 If the memory cost of 8 log buffers is too high on small 122 systems, then it may be reduced at some cost to performance 123 on metadata intensive workloads. The ``logbsize`` option below 124 controls the size of each buffer and so is also relevant to 125 this case. 126 127 logbsize=value 128 Set the size of each in-memory log buffer. The size may be 129 specified in bytes, or in kilobytes with a "k" suffix. 130 Valid sizes for version 1 and version 2 logs are 16384 (16k) 131 and 32768 (32k). Valid sizes for version 2 logs also 132 include 65536 (64k), 131072 (128k) and 262144 (256k). The 133 logbsize must be an integer multiple of the log 134 stripe unit configured at **mkfs(8)** time. 135 136 The default value for for version 1 logs is 32768, while the 137 default value for version 2 logs is MAX(32768, log_sunit). 138 139 logdev=device and rtdev=device 140 Use an external log (metadata journal) and/or real-time device. 141 An XFS filesystem has up to three parts: a data section, a log 142 section, and a real-time section. The real-time section is 143 optional, and the log section can be separate from the data 144 section or contained within it. 145 146 noalign 147 Data allocations will not be aligned at stripe unit 148 boundaries. This is only relevant to filesystems created 149 with non-zero data alignment parameters (``sunit``, ``swidth``) by 150 **mkfs(8)**. 151 152 norecovery 153 The filesystem will be mounted without running log recovery. 154 If the filesystem was not cleanly unmounted, it is likely to 155 be inconsistent when mounted in ``norecovery`` mode. 156 Some files or directories may not be accessible because of this. 157 Filesystems mounted ``norecovery`` must be mounted read-only or 158 the mount will fail. 159 160 nouuid 161 Don't check for double mounted file systems using the file 162 system ``uuid``. This is useful to mount LVM snapshot volumes, 163 and often used in combination with ``norecovery`` for mounting 164 read-only snapshots. 165 166 noquota 167 Forcibly turns off all quota accounting and enforcement 168 within the filesystem. 169 170 uquota/usrquota/uqnoenforce/quota 171 User disk quota accounting enabled, and limits (optionally) 172 enforced. Refer to **xfs_quota(8)** for further details. 173 174 gquota/grpquota/gqnoenforce 175 Group disk quota accounting enabled and limits (optionally) 176 enforced. Refer to **xfs_quota(8)** for further details. 177 178 pquota/prjquota/pqnoenforce 179 Project disk quota accounting enabled and limits (optionally) 180 enforced. Refer to **xfs_quota(8)** for further details. 181 182 sunit=value and swidth=value 183 Used to specify the stripe unit and width for a RAID device 184 or a stripe volume. "value" must be specified in 512-byte 185 block units. These options are only relevant to filesystems 186 that were created with non-zero data alignment parameters. 187 188 The ``sunit`` and ``swidth`` parameters specified must be compatible 189 with the existing filesystem alignment characteristics. In 190 general, that means the only valid changes to ``sunit`` are 191 increasing it by a power-of-2 multiple. Valid ``swidth`` values 192 are any integer multiple of a valid ``sunit`` value. 193 194 Typically the only time these mount options are necessary if 195 after an underlying RAID device has had it's geometry 196 modified, such as adding a new disk to a RAID5 lun and 197 reshaping it. 198 199 swalloc 200 Data allocations will be rounded up to stripe width boundaries 201 when the current end of file is being extended and the file 202 size is larger than the stripe width size. 203 204 wsync 205 When specified, all filesystem namespace operations are 206 executed synchronously. This ensures that when the namespace 207 operation (create, unlink, etc) completes, the change to the 208 namespace is on stable storage. This is useful in HA setups 209 where failover must not result in clients seeing 210 inconsistent namespace presentation during or after a 211 failover event. 212 213 214Deprecated Mount Options 215======================== 216 217=========================== ================ 218 Name Removal Schedule 219=========================== ================ 220=========================== ================ 221 222 223Removed Mount Options 224===================== 225 226=========================== ======= 227 Name Removed 228=========================== ======= 229 delaylog/nodelaylog v4.0 230 ihashsize v4.0 231 irixsgid v4.0 232 osyncisdsync/osyncisosync v4.0 233 barrier v4.19 234 nobarrier v4.19 235=========================== ======= 236 237sysctls 238======= 239 240The following sysctls are available for the XFS filesystem: 241 242 fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1) 243 Setting this to "1" clears accumulated XFS statistics 244 in /proc/fs/xfs/stat. It then immediately resets to "0". 245 246 fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000) 247 The interval at which the filesystem flushes metadata 248 out to disk and runs internal cache cleanup routines. 249 250 fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000) 251 The interval at which the filesystem ages filestreams cache 252 references and returns timed-out AGs back to the free stream 253 pool. 254 255 fs.xfs.speculative_prealloc_lifetime 256 (Units: seconds Min: 1 Default: 300 Max: 86400) 257 The interval at which the background scanning for inodes 258 with unused speculative preallocation runs. The scan 259 removes unused preallocation from clean inodes and releases 260 the unused space back to the free pool. 261 262 fs.xfs.error_level (Min: 0 Default: 3 Max: 11) 263 A volume knob for error reporting when internal errors occur. 264 This will generate detailed messages & backtraces for filesystem 265 shutdowns, for example. Current threshold values are: 266 267 XFS_ERRLEVEL_OFF: 0 268 XFS_ERRLEVEL_LOW: 1 269 XFS_ERRLEVEL_HIGH: 5 270 271 fs.xfs.panic_mask (Min: 0 Default: 0 Max: 256) 272 Causes certain error conditions to call BUG(). Value is a bitmask; 273 OR together the tags which represent errors which should cause panics: 274 275 XFS_NO_PTAG 0 276 XFS_PTAG_IFLUSH 0x00000001 277 XFS_PTAG_LOGRES 0x00000002 278 XFS_PTAG_AILDELETE 0x00000004 279 XFS_PTAG_ERROR_REPORT 0x00000008 280 XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010 281 XFS_PTAG_SHUTDOWN_IOERROR 0x00000020 282 XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040 283 XFS_PTAG_FSBLOCK_ZERO 0x00000080 284 XFS_PTAG_VERIFIER_ERROR 0x00000100 285 286 This option is intended for debugging only. 287 288 fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1) 289 Controls whether symlinks are created with mode 0777 (default) 290 or whether their mode is affected by the umask (irix mode). 291 292 fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1) 293 Controls files created in SGID directories. 294 If the group ID of the new file does not match the effective group 295 ID or one of the supplementary group IDs of the parent dir, the 296 ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl 297 is set. 298 299 fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1) 300 Setting this to "1" will cause the "sync" flag set 301 by the **xfs_io(8)** chattr command on a directory to be 302 inherited by files in that directory. 303 304 fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1) 305 Setting this to "1" will cause the "nodump" flag set 306 by the **xfs_io(8)** chattr command on a directory to be 307 inherited by files in that directory. 308 309 fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1) 310 Setting this to "1" will cause the "noatime" flag set 311 by the **xfs_io(8)** chattr command on a directory to be 312 inherited by files in that directory. 313 314 fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1) 315 Setting this to "1" will cause the "nosymlinks" flag set 316 by the **xfs_io(8)** chattr command on a directory to be 317 inherited by files in that directory. 318 319 fs.xfs.inherit_nodefrag (Min: 0 Default: 1 Max: 1) 320 Setting this to "1" will cause the "nodefrag" flag set 321 by the **xfs_io(8)** chattr command on a directory to be 322 inherited by files in that directory. 323 324 fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256) 325 In "inode32" allocation mode, this option determines how many 326 files the allocator attempts to allocate in the same allocation 327 group before moving to the next allocation group. The intent 328 is to control the rate at which the allocator moves between 329 allocation groups when allocating extents for new files. 330 331Deprecated Sysctls 332================== 333 334None at present. 335 336 337Removed Sysctls 338=============== 339 340============================= ======= 341 Name Removed 342============================= ======= 343 fs.xfs.xfsbufd_centisec v4.0 344 fs.xfs.age_buffer_centisecs v4.0 345============================= ======= 346 347Error handling 348============== 349 350XFS can act differently according to the type of error found during its 351operation. The implementation introduces the following concepts to the error 352handler: 353 354 -failure speed: 355 Defines how fast XFS should propagate an error upwards when a specific 356 error is found during the filesystem operation. It can propagate 357 immediately, after a defined number of retries, after a set time period, 358 or simply retry forever. 359 360 -error classes: 361 Specifies the subsystem the error configuration will apply to, such as 362 metadata IO or memory allocation. Different subsystems will have 363 different error handlers for which behaviour can be configured. 364 365 -error handlers: 366 Defines the behavior for a specific error. 367 368The filesystem behavior during an error can be set via ``sysfs`` files. Each 369error handler works independently - the first condition met by an error handler 370for a specific class will cause the error to be propagated rather than reset and 371retried. 372 373The action taken by the filesystem when the error is propagated is context 374dependent - it may cause a shut down in the case of an unrecoverable error, 375it may be reported back to userspace, or it may even be ignored because 376there's nothing useful we can with the error or anyone we can report it to (e.g. 377during unmount). 378 379The configuration files are organized into the following hierarchy for each 380mounted filesystem: 381 382 /sys/fs/xfs/<dev>/error/<class>/<error>/ 383 384Where: 385 <dev> 386 The short device name of the mounted filesystem. This is the same device 387 name that shows up in XFS kernel error messages as "XFS(<dev>): ..." 388 389 <class> 390 The subsystem the error configuration belongs to. As of 4.9, the defined 391 classes are: 392 393 - "metadata": applies metadata buffer write IO 394 395 <error> 396 The individual error handler configurations. 397 398 399Each filesystem has "global" error configuration options defined in their top 400level directory: 401 402 /sys/fs/xfs/<dev>/error/ 403 404 fail_at_unmount (Min: 0 Default: 1 Max: 1) 405 Defines the filesystem error behavior at unmount time. 406 407 If set to a value of 1, XFS will override all other error configurations 408 during unmount and replace them with "immediate fail" characteristics. 409 i.e. no retries, no retry timeout. This will always allow unmount to 410 succeed when there are persistent errors present. 411 412 If set to 0, the configured retry behaviour will continue until all 413 retries and/or timeouts have been exhausted. This will delay unmount 414 completion when there are persistent errors, and it may prevent the 415 filesystem from ever unmounting fully in the case of "retry forever" 416 handler configurations. 417 418 Note: there is no guarantee that fail_at_unmount can be set while an 419 unmount is in progress. It is possible that the ``sysfs`` entries are 420 removed by the unmounting filesystem before a "retry forever" error 421 handler configuration causes unmount to hang, and hence the filesystem 422 must be configured appropriately before unmount begins to prevent 423 unmount hangs. 424 425Each filesystem has specific error class handlers that define the error 426propagation behaviour for specific errors. There is also a "default" error 427handler defined, which defines the behaviour for all errors that don't have 428specific handlers defined. Where multiple retry constraints are configured for 429a single error, the first retry configuration that expires will cause the error 430to be propagated. The handler configurations are found in the directory: 431 432 /sys/fs/xfs/<dev>/error/<class>/<error>/ 433 434 max_retries (Min: -1 Default: Varies Max: INTMAX) 435 Defines the allowed number of retries of a specific error before 436 the filesystem will propagate the error. The retry count for a given 437 error context (e.g. a specific metadata buffer) is reset every time 438 there is a successful completion of the operation. 439 440 Setting the value to "-1" will cause XFS to retry forever for this 441 specific error. 442 443 Setting the value to "0" will cause XFS to fail immediately when the 444 specific error is reported. 445 446 Setting the value to "N" (where 0 < N < Max) will make XFS retry the 447 operation "N" times before propagating the error. 448 449 retry_timeout_seconds (Min: -1 Default: Varies Max: 1 day) 450 Define the amount of time (in seconds) that the filesystem is 451 allowed to retry its operations when the specific error is 452 found. 453 454 Setting the value to "-1" will allow XFS to retry forever for this 455 specific error. 456 457 Setting the value to "0" will cause XFS to fail immediately when the 458 specific error is reported. 459 460 Setting the value to "N" (where 0 < N < Max) will allow XFS to retry the 461 operation for up to "N" seconds before propagating the error. 462 463**Note:** The default behaviour for a specific error handler is dependent on both 464the class and error context. For example, the default values for 465"metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults 466to "fail immediately" behaviour. This is done because ENODEV is a fatal, 467unrecoverable error no matter how many times the metadata IO is retried. 468