mount: update xfs docs

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 173 insertions, 171 deletions

diff --git a/sys-utils/mount.8 b/sys-utils/mount.8
index a9c68fd11..28e0b2a55 100644
--- a/sys-utils/mount.8
+++ b/sys-utils/mount.8
@@ -2596,198 +2596,200 @@ None.
 
 .SH "Mount options for xfs"
 .TP
-.BI allocsize= size
+.BR allocsize=size
 Sets the buffered I/O end-of-file preallocation size when
 doing delayed allocation writeout (default size is 64KiB).
 Valid values for this option are page size (typically 4KiB)
 through to 1GiB, inclusive, in power-of-2 increments.
+.sp
+The default behaviour is for dynamic end-of-file
+preallocation size, which uses a set of heuristics to
+optimise the preallocation size based on the current
+allocation patterns within the file and the access patterns
+to the file. Specifying a fixed allocsize value turns off
+the dynamic behaviour.
 .TP
 .BR attr2 | noattr2
-The options enable/disable (default is enabled) an "opportunistic"
-improvement to be made in the way inline extended attributes are
-stored on-disk.
-When the new form is used for the first time (by setting or
-removing extended attributes) the on-disk superblock feature
-bit field will be updated to reflect this format being in use.
-.TP
-.B barrier
-Enables the use of block layer write barriers for writes into
-the journal and unwritten extent conversion.  This allows for
-drive level write caching to be enabled, for devices that
-support write barriers.
-.TP
-.B dmapi
-Enable the DMAPI (Data Management API) event callouts.
-Use with the
-.B mtpt
-option.
+The options enable/disable an "opportunistic" improvement to
+be made in the way inline extended attributes are stored
+on-disk.  When the new form is used for the first time when
+attr2 is selected (either when setting or removing extended
+attributes) the on-disk superblock feature bit field will be
+updated to reflect this format being in use.
+.sp
+The default behaviour is determined by the on-disk feature
+bit indicating that attr2 behaviour is active. If either
+mount option it set, then that becomes the new default used
+by the filesystem.
+.sp
+CRC enabled filesystems always use the attr2 format, and so
+will reject the noattr2 mount option if it is set.
+.TP
+.BR barrier | nobarrier
+Enables/disables the use of block layer write barriers for
+writes into the journal and for data integrity operations.
+This allows for drive level write caching to be enabled, for
+devices that support write barriers.
+.TP
+.BR discard | nodiscard
+Enable/disable the issuing of commands to let the block
+device reclaim space freed by the filesystem.  This is
+useful for SSD devices, thinly provisioned LUNs and virtual
+machine images, but may have a performance impact.
+.sp
+Note: It is currently recommended that you use the fstrim
+application to discard unused blocks rather than the discard
+mount option because the performance impact of this option
+is quite severe.
+.TP
+.BR grpid | bsdgroups | nogrpid | sysvgroups
+These options define what group ID a newly created file
+gets.  When grpid is set, it takes the group ID of the
+directory in which it is created; otherwise it takes the
+fsgid of the current process, unless the directory has the
+setgid bit set, in which case it takes the gid from the
+parent directory, and also gets the setgid bit set if it is
+a directory itself.
+.TP
+.BR filestreams
+Make the data allocator use the filestreams allocation mode
+across the entire filesystem rather than just on directories
+configured to use it.
+.TP
+.BP ikeep | noikeep
+When ikeep is specified, XFS does not delete empty inode
+clusters and keeps them around on disk.  When noikeep is
+specified, empty inode clusters are returned to the free
+space pool.
+.TP
+.BR inode32 | inode64
+When inode32 is specified, it indicates that XFS limits
+inode creation to locations which will not result in inode
+numbers with more than 32 bits of significance.
+.sp
+When inode64 is specified, it indicates that XFS is allowed
+to create inodes at any location in the filesystem,
+including those which will result in inode numbers occupying
+more than 32 bits of significance. 
+.sp
+inode32 is provided for backwards compatibility with older
+systems and applications, since 64 bits inode numbers might
+cause problems for some applications that cannot handle
+large inode numbers.  If applications are in use which do
+not handle inode numbers bigger than 32 bits, the inode32
+option should be specified.
+.TP
+.BR  largeio | nolargeio
+If "nolargeio" is specified, the optimal I/O reported in
+st_blksize by stat(2) will be as small as possible to allow
+user applications to avoid inefficient read/modify/write
+I/O.  This is typically the page size of the machine, as
+this is the granularity of the page cache.
+.sp
+If "largeio" specified, a filesystem that was created with a
+"swidth" specified will return the "swidth" value (in bytes)
+in st_blksize. If the filesystem does not have a "swidth"
+specified but does specify an "allocsize" then "allocsize"
+(in bytes) will be returned instead. Otherwise the behaviour
+is the same as if "nolargeio" was specified.
+.TP
+.BR logbufs=value
+Set the number of in-memory log buffers.  Valid numbers
+range from 2-8 inclusive.
+.sp
+The default value is 8 buffers.
+.sp
+If the memory cost of 8 log buffers is too high on small
+systems, then it may be reduced at some cost to performance
+on metadata intensive workloads. The logbsize option below
+controls the size of each buffer and so is also relevent to
+this case.
+.TP
+.BR logbsize=value
+Set the size of each in-memory log buffer.  The size may be
+specified in bytes, or in kilobytes with a "k" suffix.
+Valid sizes for version 1 and version 2 logs are 16384 (16k)
+and 32768 (32k).  Valid sizes for version 2 logs also
+include 65536 (64k), 131072 (128k) and 262144 (256k). The
+logbsize must be an integer multiple of the log
+stripe unit configured at mkfs time.
+.sp
+The default value for for version 1 logs is 32768, while the
+default value for version 2 logs is MAX(32768, log_sunit).
 .TP
-.BR grpid | bsdgroups " and " nogrpid | sysvgroups
-These options define what group ID a newly created file gets.
-When grpid is set, it takes the group ID of the directory in
-which it is created; otherwise (the default) it takes the fsgid
-of the current process, unless the directory has the setgid bit
-set, in which case it takes the gid from the parent directory,
-and also gets the setgid bit set if it is a directory itself.
-.TP
-.BI ihashsize= value
-Sets the number of hash buckets available for hashing the
-in-memory inodes of the specified mount point.  If a value
-of zero is used, the value selected by the default algorithm
-will be displayed in
-.IR /proc/mounts .
-.TP
-.BR ikeep | noikeep
-When inode clusters are emptied of inodes, keep them around
-on the disk (ikeep) - this is the traditional XFS behaviour
-and is still the default for now.  Using the noikeep option,
-inode clusters are returned to the free space pool.
-.TP
-.B inode64
-Indicates that XFS is allowed to create inodes at any location
-in the filesystem, including those which will result in inode
-numbers occupying more than 32 bits of significance.  This is
-provided for backwards compatibility, but causes problems for
-backup applications that cannot handle large inode numbers.
-.TP
-.BR largeio | nolargeio
-If
-.B nolargeio
-is specified, the optimal I/O reported in
-st_blksize by
-.BR stat (2)
-will be as small as possible to allow user
-applications to avoid inefficient read/modify/write I/O.
-If
-.B largeio
-is specified, a filesystem that has a
-.B swidth
-specified
-will return the
-.B swidth
-value (in bytes) in st_blksize. If the
-filesystem does not have a
-.B swidth
-specified but does specify
-an
-.B allocsize
-then
-.B allocsize
-(in bytes) will be returned
-instead.
-If neither of these two options are specified, then filesystem
-will behave as if
-.B nolargeio
-was specified.
-.TP
-.BI logbufs= value
-Set the number of in-memory log buffers.  Valid numbers range
-from 2-8 inclusive.
-The default value is 8 buffers for any recent kernel.
-.TP
-.BI logbsize= value
-Set the size of each in-memory log buffer.
-Size may be specified in bytes, or in kilobytes with a "k" suffix.
-Valid sizes for version 1 and version 2 logs are 16384 (16k) and
-32768 (32k).  Valid sizes for version 2 logs also include
-65536 (64k), 131072 (128k) and 262144 (256k).
-The default value for any recent kernel is 32768.
-.TP
-\fBlogdev=\fP\fIdevice\fP and \fBrtdev=\fP\fIdevice\fP
+.BR logdev=device and rtdev=device
 Use an external log (metadata journal) and/or real-time device.
-An XFS filesystem has up to three parts: a data section, a log section,
-and a real-time section.
-The real-time section is optional, and the log section can be separate
-from the data section or contained within it.
-Refer to
-.BR xfs (5).
-.TP
-.BI  mtpt= mountpoint
-Use with the
-.B dmapi
-option. The value specified here will be
-included in the DMAPI mount event, and should be the path of
-the actual mountpoint that is used.
-.TP
-.B noalign
-Data allocations will not be aligned at stripe unit boundaries.
-.TP
-.B noatime
-Access timestamps are not updated when a file is read.
-.TP
-.B norecovery
+An XFS filesystem has up to three parts: a data section, a log
+section, and a real-time section.  The real-time section is
+optional, and the log section can be separate from the data
+section or contained within it.
+.TP
+.BR noalign
+Data allocations will not be aligned at stripe unit
+boundaries. This is only relevant to filesystems created
+with non-zero data alignment parameters (sunit, swidth) by
+mkfs.
+.TP
+.BR norecovery
 The filesystem will be mounted without running log recovery.
 If the filesystem was not cleanly unmounted, it is likely to
-be inconsistent when mounted in
-.B norecovery
-mode.
+be inconsistent when mounted in "norecovery" mode.
 Some files or directories may not be accessible because of this.
-Filesystems mounted
-.B norecovery
-must be mounted read-only or the mount will fail.
-.TP
-.B nouuid
-Don't check for double mounted filesystems using the filesystem uuid.
-This is useful to mount LVM snapshot volumes.
-.TP
-.B osyncisosync
-Make O_SYNC writes implement true O_SYNC.  WITHOUT this option,
-Linux XFS behaves as if an
-.B osyncisdsync
-option is used,
-which will make writes to files opened with the O_SYNC flag set
-behave as if the O_DSYNC flag had been used instead.
-This can result in better performance without compromising
-data safety.
-However if this option is not in effect, timestamp updates from
-O_SYNC writes can be lost if the system crashes.
-If timestamp updates are critical, use the
-.B osyncisosync
-option.
+Filesystems mounted "norecovery" must be mounted read-only or
+the mount will fail.
+.TP
+.BR nouuid
+Don't check for double mounted file systems using the file
+system uuid.  This is useful to mount LVM snapshot volumes,
+and often used in combination with "norecovery" for mounting
+read-only snapshots.
+.TP
+.BR noquota
+Forcibly turns off all quota accounting and enforcement
+within the filesystem.
 .TP
-.BR uquota | usrquota | uqnoenforce | quota
+.BR uquota/usrquota/uqnoenforce/quota
 User disk quota accounting enabled, and limits (optionally)
-enforced.  Refer to
-.BR xfs_quota (8)
-for further details.
+enforced.  Refer to xfs_quota(8) for further details.
 .TP
-.BR gquota | grpquota | gqnoenforce
+.BR gquota/grpquota/gqnoenforce
 Group disk quota accounting enabled and limits (optionally)
-enforced. Refer to
-.BR xfs_quota (8)
-for further details.
+enforced.  Refer to xfs_quota(8) for further details.
 .TP
-.BR pquota | prjquota | pqnoenforce
+.BR pquota/prjquota/pqnoenforce
 Project disk quota accounting enabled and limits (optionally)
-enforced. Refer to
-.BR xfs_quota (8)
-for further details.
+enforced.  Refer to xfs_quota(8) for further details.
 .TP
-\fBsunit=\fP\fIvalue\fP and \fBswidth=\fP\fIvalue\fP
-Used to specify the stripe unit and width for a RAID device or a stripe
-volume.
-.I value
-must be specified in 512-byte block units.
-If this option is not specified and the filesystem was made on a stripe
-volume or the stripe width or unit were specified for the RAID device at
-mkfs time, then the mount system call will restore the value from the
-superblock.
-For filesystems that are made directly on RAID devices, these options can be
-used to override the information in the superblock if the underlying disk
-layout changes after the filesystem has been created.
-The
-.B swidth
-option is required if the
-.B sunit
-option has been specified,
-and must be a multiple of the
-.B sunit
-value.
-.TP
-.B swalloc
+.BR sunit=value " and " swidth=value
+Used to specify the stripe unit and width for a RAID device
+or a stripe volume.  "value" must be specified in 512-byte
+block units. These options are only relevant to filesystems
+that were created with non-zero data alignment parameters.
+.sp
+The sunit and swidth parameters specified must be compatible
+with the existing filesystem alignment characteristics.  In
+general, that means the only valid changes to sunit are
+increasing it by a power-of-2 multiple. Valid swidth values
+are any integer multiple of a valid sunit value.
+.sp
+Typically the only time these mount options are necessary if
+after an underlying RAID device has had it's geometry
+modified, such as adding a new disk to a RAID5 lun and
+reshaping it.
+.TP
+.BR swalloc
 Data allocations will be rounded up to stripe width boundaries
 when the current end of file is being extended and the file
 size is larger than the stripe width size.
+.TP
+.BR wsync
+When specified, all filesystem namespace operations are
+executed synchronously. This ensures that when the namespace
+operation (create, unlink, etc) completes, the change to the
+namespace is on stable storage. This is useful in HA setups
+where failover must not result in clients seeing
+inconsistent namespace presentation during or after a
+failover event.
 
 .SH "Mount options for xiafs"
 None. Although nothing is wrong with xiafs, it is not used much,