| blob | 86de8a1ad91c2313f20e493dc775e1fcd90289c6 |
1 .. SPDX-License-Identifier: GPL-2.0
3 ======================
4 The SGI XFS Filesystem
5 ======================
7 XFS is a high performance journaling filesystem which originated
8 on the SGI IRIX platform. It is completely multi-threaded, can
9 support large files and large filesystems, extended attributes,
10 variable block sizes, is extent based, and makes extensive use of
11 Btrees (directories, extents, free space) to aid both performance
12 and scalability.
14 Refer to the documentation at https://xfs.wiki.kernel.org/
15 for further details. This implementation is on-disk compatible
16 with the IRIX version of XFS.
19 Mount Options
20 =============
22 When mounting an XFS filesystem, the following options are accepted.
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.
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.
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.
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.
50 CRC enabled filesystems always use the ``attr2`` format, and so
51 will reject the ``noattr2`` mount option if it is set.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
115 logbufs=value
116 Set the number of in-memory log buffers. Valid numbers
117 range from 2-8 inclusive.
119 The default value is 8 buffers.
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.
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.
136 The default value for version 1 logs is 32768, while the
137 default value for version 2 logs is MAX(32768, log_sunit).
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.
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)**.
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.
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.
166 noquota
167 Forcibly turns off all quota accounting and enforcement
168 within the filesystem.
170 uquota/usrquota/uqnoenforce/quota
171 User disk quota accounting enabled, and limits (optionally)
172 enforced. Refer to **xfs_quota(8)** for further details.
174 gquota/grpquota/gqnoenforce
175 Group disk quota accounting enabled and limits (optionally)
176 enforced. Refer to **xfs_quota(8)** for further details.
178 pquota/prjquota/pqnoenforce
179 Project disk quota accounting enabled and limits (optionally)
180 enforced. Refer to **xfs_quota(8)** for further details.
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.
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.
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.
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.
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.
213 Deprecation of V4 Format
214 ========================
216 The V4 filesystem format lacks certain features that are supported by
217 the V5 format, such as metadata checksumming, strengthened metadata
218 verification, and the ability to store timestamps past the year 2038.
219 Because of this, the V4 format is deprecated. All users should upgrade
220 by backing up their files, reformatting, and restoring from the backup.
222 Administrators and users can detect a V4 filesystem by running xfs_info
223 against a filesystem mountpoint and checking for a string containing
224 "crc=". If no such string is found, please upgrade xfsprogs to the
225 latest version and try again.
227 The deprecation will take place in two parts. Support for mounting V4
228 filesystems can now be disabled at kernel build time via Kconfig option.
229 The option will default to yes until September 2025, at which time it
230 will be changed to default to no. In September 2030, support will be
231 removed from the codebase entirely.
233 Note: Distributors may choose to withdraw V4 format support earlier than
234 the dates listed above.
236 Deprecated Mount Options
237 ========================
239 =========================== ================
240 Name Removal Schedule
241 =========================== ================
242 Mounting with V4 filesystem September 2030
243 ikeep/noikeep September 2025
244 attr2/noattr2 September 2025
245 =========================== ================
248 Removed Mount Options
249 =====================
251 =========================== =======
252 Name Removed
253 =========================== =======
254 delaylog/nodelaylog v4.0
255 ihashsize v4.0
256 irixsgid v4.0
257 osyncisdsync/osyncisosync v4.0
258 barrier v4.19
259 nobarrier v4.19
260 =========================== =======
262 sysctls
263 =======
265 The following sysctls are available for the XFS filesystem:
267 fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1)
268 Setting this to "1" clears accumulated XFS statistics
269 in /proc/fs/xfs/stat. It then immediately resets to "0".
271 fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000)
272 The interval at which the filesystem flushes metadata
273 out to disk and runs internal cache cleanup routines.
275 fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000)
276 The interval at which the filesystem ages filestreams cache
277 references and returns timed-out AGs back to the free stream
278 pool.
280 fs.xfs.speculative_prealloc_lifetime
281 (Units: seconds Min: 1 Default: 300 Max: 86400)
282 The interval at which the background scanning for inodes
283 with unused speculative preallocation runs. The scan
284 removes unused preallocation from clean inodes and releases
285 the unused space back to the free pool.
287 fs.xfs.error_level (Min: 0 Default: 3 Max: 11)
288 A volume knob for error reporting when internal errors occur.
289 This will generate detailed messages & backtraces for filesystem
290 shutdowns, for example. Current threshold values are:
292 XFS_ERRLEVEL_OFF: 0
293 XFS_ERRLEVEL_LOW: 1
294 XFS_ERRLEVEL_HIGH: 5
296 fs.xfs.panic_mask (Min: 0 Default: 0 Max: 256)
297 Causes certain error conditions to call BUG(). Value is a bitmask;
298 OR together the tags which represent errors which should cause panics:
300 XFS_NO_PTAG 0
301 XFS_PTAG_IFLUSH 0x00000001
302 XFS_PTAG_LOGRES 0x00000002
303 XFS_PTAG_AILDELETE 0x00000004
304 XFS_PTAG_ERROR_REPORT 0x00000008
305 XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010
306 XFS_PTAG_SHUTDOWN_IOERROR 0x00000020
307 XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040
308 XFS_PTAG_FSBLOCK_ZERO 0x00000080
309 XFS_PTAG_VERIFIER_ERROR 0x00000100
311 This option is intended for debugging only.
313 fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1)
314 Controls whether symlinks are created with mode 0777 (default)
315 or whether their mode is affected by the umask (irix mode).
317 fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1)
318 Controls files created in SGID directories.
319 If the group ID of the new file does not match the effective group
320 ID or one of the supplementary group IDs of the parent dir, the
321 ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
322 is set.
324 fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1)
325 Setting this to "1" will cause the "sync" flag set
326 by the **xfs_io(8)** chattr command on a directory to be
327 inherited by files in that directory.
329 fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1)
330 Setting this to "1" will cause the "nodump" flag set
331 by the **xfs_io(8)** chattr command on a directory to be
332 inherited by files in that directory.
334 fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1)
335 Setting this to "1" will cause the "noatime" flag set
336 by the **xfs_io(8)** chattr command on a directory to be
337 inherited by files in that directory.
339 fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1)
340 Setting this to "1" will cause the "nosymlinks" flag set
341 by the **xfs_io(8)** chattr command on a directory to be
342 inherited by files in that directory.
344 fs.xfs.inherit_nodefrag (Min: 0 Default: 1 Max: 1)
345 Setting this to "1" will cause the "nodefrag" flag set
346 by the **xfs_io(8)** chattr command on a directory to be
347 inherited by files in that directory.
349 fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256)
350 In "inode32" allocation mode, this option determines how many
351 files the allocator attempts to allocate in the same allocation
352 group before moving to the next allocation group. The intent
353 is to control the rate at which the allocator moves between
354 allocation groups when allocating extents for new files.
356 Deprecated Sysctls
357 ==================
359 =========================== ================
360 Name Removal Schedule
361 =========================== ================
362 fs.xfs.irix_sgid_inherit September 2025
363 fs.xfs.irix_symlink_mode September 2025
364 =========================== ================
367 Removed Sysctls
368 ===============
370 ============================= =======
371 Name Removed
372 ============================= =======
373 fs.xfs.xfsbufd_centisec v4.0
374 fs.xfs.age_buffer_centisecs v4.0
375 ============================= =======
377 Error handling
378 ==============
380 XFS can act differently according to the type of error found during its
381 operation. The implementation introduces the following concepts to the error
382 handler:
384 -failure speed:
385 Defines how fast XFS should propagate an error upwards when a specific
386 error is found during the filesystem operation. It can propagate
387 immediately, after a defined number of retries, after a set time period,
388 or simply retry forever.
390 -error classes:
391 Specifies the subsystem the error configuration will apply to, such as
392 metadata IO or memory allocation. Different subsystems will have
393 different error handlers for which behaviour can be configured.
395 -error handlers:
396 Defines the behavior for a specific error.
398 The filesystem behavior during an error can be set via ``sysfs`` files. Each
399 error handler works independently - the first condition met by an error handler
400 for a specific class will cause the error to be propagated rather than reset and
401 retried.
403 The action taken by the filesystem when the error is propagated is context
404 dependent - it may cause a shut down in the case of an unrecoverable error,
405 it may be reported back to userspace, or it may even be ignored because
406 there's nothing useful we can with the error or anyone we can report it to (e.g.
407 during unmount).
409 The configuration files are organized into the following hierarchy for each
410 mounted filesystem:
412 /sys/fs/xfs/<dev>/error/<class>/<error>/
414 Where:
415 <dev>
416 The short device name of the mounted filesystem. This is the same device
417 name that shows up in XFS kernel error messages as "XFS(<dev>): ..."
419 <class>
420 The subsystem the error configuration belongs to. As of 4.9, the defined
421 classes are:
423 - "metadata": applies metadata buffer write IO
425 <error>
426 The individual error handler configurations.
429 Each filesystem has "global" error configuration options defined in their top
430 level directory:
432 /sys/fs/xfs/<dev>/error/
434 fail_at_unmount (Min: 0 Default: 1 Max: 1)
435 Defines the filesystem error behavior at unmount time.
437 If set to a value of 1, XFS will override all other error configurations
438 during unmount and replace them with "immediate fail" characteristics.
439 i.e. no retries, no retry timeout. This will always allow unmount to
440 succeed when there are persistent errors present.
442 If set to 0, the configured retry behaviour will continue until all
443 retries and/or timeouts have been exhausted. This will delay unmount
444 completion when there are persistent errors, and it may prevent the
445 filesystem from ever unmounting fully in the case of "retry forever"
446 handler configurations.
448 Note: there is no guarantee that fail_at_unmount can be set while an
449 unmount is in progress. It is possible that the ``sysfs`` entries are
450 removed by the unmounting filesystem before a "retry forever" error
451 handler configuration causes unmount to hang, and hence the filesystem
452 must be configured appropriately before unmount begins to prevent
453 unmount hangs.
455 Each filesystem has specific error class handlers that define the error
456 propagation behaviour for specific errors. There is also a "default" error
457 handler defined, which defines the behaviour for all errors that don't have
458 specific handlers defined. Where multiple retry constraints are configured for
459 a single error, the first retry configuration that expires will cause the error
460 to be propagated. The handler configurations are found in the directory:
462 /sys/fs/xfs/<dev>/error/<class>/<error>/
464 max_retries (Min: -1 Default: Varies Max: INTMAX)
465 Defines the allowed number of retries of a specific error before
466 the filesystem will propagate the error. The retry count for a given
467 error context (e.g. a specific metadata buffer) is reset every time
468 there is a successful completion of the operation.
470 Setting the value to "-1" will cause XFS to retry forever for this
471 specific error.
473 Setting the value to "0" will cause XFS to fail immediately when the
474 specific error is reported.
476 Setting the value to "N" (where 0 < N < Max) will make XFS retry the
477 operation "N" times before propagating the error.
479 retry_timeout_seconds (Min: -1 Default: Varies Max: 1 day)
480 Define the amount of time (in seconds) that the filesystem is
481 allowed to retry its operations when the specific error is
482 found.
484 Setting the value to "-1" will allow XFS to retry forever for this
485 specific error.
487 Setting the value to "0" will cause XFS to fail immediately when the
488 specific error is reported.
490 Setting the value to "N" (where 0 < N < Max) will allow XFS to retry the
491 operation for up to "N" seconds before propagating the error.
493 **Note:** The default behaviour for a specific error handler is dependent on both
494 the class and error context. For example, the default values for
495 "metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults
496 to "fail immediately" behaviour. This is done because ENODEV is a fatal,
497 unrecoverable error no matter how many times the metadata IO is retried.