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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 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.
214 Deprecated Mount Options
215 ========================
217 =========================== ================
218 Name Removal Schedule
219 =========================== ================
220 =========================== ================
223 Removed Mount Options
224 =====================
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 =========================== =======
237 sysctls
238 =======
240 The following sysctls are available for the XFS filesystem:
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".
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.
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.
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.
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:
267 XFS_ERRLEVEL_OFF: 0
268 XFS_ERRLEVEL_LOW: 1
269 XFS_ERRLEVEL_HIGH: 5
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:
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
286 This option is intended for debugging only.
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).
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.
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.
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.
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.
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.
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.
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.
331 Deprecated Sysctls
332 ==================
334 None at present.
337 Removed Sysctls
338 ===============
340 ============================= =======
341 Name Removed
342 ============================= =======
343 fs.xfs.xfsbufd_centisec v4.0
344 fs.xfs.age_buffer_centisecs v4.0
345 ============================= =======
347 Error handling
348 ==============
350 XFS can act differently according to the type of error found during its
351 operation. The implementation introduces the following concepts to the error
352 handler:
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.
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.
365 -error handlers:
366 Defines the behavior for a specific error.
368 The filesystem behavior during an error can be set via ``sysfs`` files. Each
369 error handler works independently - the first condition met by an error handler
370 for a specific class will cause the error to be propagated rather than reset and
371 retried.
373 The action taken by the filesystem when the error is propagated is context
374 dependent - it may cause a shut down in the case of an unrecoverable error,
375 it may be reported back to userspace, or it may even be ignored because
376 there's nothing useful we can with the error or anyone we can report it to (e.g.
377 during unmount).
379 The configuration files are organized into the following hierarchy for each
380 mounted filesystem:
382 /sys/fs/xfs/<dev>/error/<class>/<error>/
384 Where:
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>): ..."
389 <class>
390 The subsystem the error configuration belongs to. As of 4.9, the defined
391 classes are:
393 - "metadata": applies metadata buffer write IO
395 <error>
396 The individual error handler configurations.
399 Each filesystem has "global" error configuration options defined in their top
400 level directory:
402 /sys/fs/xfs/<dev>/error/
404 fail_at_unmount (Min: 0 Default: 1 Max: 1)
405 Defines the filesystem error behavior at unmount time.
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.
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.
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.
425 Each filesystem has specific error class handlers that define the error
426 propagation behaviour for specific errors. There is also a "default" error
427 handler defined, which defines the behaviour for all errors that don't have
428 specific handlers defined. Where multiple retry constraints are configured for
429 a single error, the first retry configuration that expires will cause the error
430 to be propagated. The handler configurations are found in the directory:
432 /sys/fs/xfs/<dev>/error/<class>/<error>/
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.
440 Setting the value to "-1" will cause XFS to retry forever for this
441 specific error.
443 Setting the value to "0" will cause XFS to fail immediately when the
444 specific error is reported.
446 Setting the value to "N" (where 0 < N < Max) will make XFS retry the
447 operation "N" times before propagating the error.
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.
454 Setting the value to "-1" will allow XFS to retry forever for this
455 specific error.
457 Setting the value to "0" will cause XFS to fail immediately when the
458 specific error is reported.
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.
463 **Note:** The default behaviour for a specific error handler is dependent on both
464 the class and error context. For example, the default values for
465 "metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults
466 to "fail immediately" behaviour. This is done because ENODEV is a fatal,
467 unrecoverable error no matter how many times the metadata IO is retried.