commit 3e500a8f116b0515d1507fe0ab4bf617664a6cdc

Author: Eric Sandeen <sandeen@redhat.com>

Date:   Fri Jul 4 23:07:36 2014 -0400

    e2fsprogs: add mount options to ext4.5

    This is a straight cut and paste from the util-linux

    mount manpage to ext4.5 (with commented-out lines

    removed).

    It's pretty much impossible for util-linux to keep up

    with every filesystem out there, and Karel has more than

    once expressed a wish that mount options move into fs-specific

    manpages.

    So, here we go.

    Signed-off-by: Eric Sandeen <sandeen@redhat.com>

    Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/ext4.5.in b/misc/ext4.5.in

index 134c19f..9112b3d 100644

--- a/misc/ext4.5.in

+++ b/misc/ext4.5.in

@@ -251,10 +251,368 @@ and it also speeds up the time required for

 .BR mke2fs (8)

 to create the file system.

 .RE

+.SH MOUNT OPTIONS

+This section describes mount options which are specific to ext2, ext3,

+and ext4.  Other generic mount options may be used as well; see

+.BR mount (8)

+for details.

+.SH "Mount options for ext2"

+The `ext2' filesystem is the standard Linux filesystem.

+Since Linux 2.5.46, for most mount options the default

+is determined by the filesystem superblock. Set them with

+.BR tune2fs (8).

+.TP

+.BR acl | noacl

+Support POSIX Access Control Lists (or not).

+.TP

+.BR bsddf | minixdf

+Set the behavior for the

+.I statfs

+system call. The

+.B minixdf

+behavior is to return in the

+.I f_blocks

+field the total number of blocks of the filesystem, while the

+.B bsddf

+behavior (which is the default) is to subtract the overhead blocks

+used by the ext2 filesystem and not available for file storage. Thus

+.sp 1

+% mount /k \-o minixdf; df /k; umount /k

+.TS

+tab(#);

+l2 l2 r2 l2 l2 l

+l c r c c l.

+Filesystem#1024-blocks#Used#Available#Capacity#Mounted on

+/dev/sda6#2630655#86954#2412169#3%#/k

+.TE

+.sp 1

+% mount /k \-o bsddf; df /k; umount /k

+.TS

+tab(#);

+l2 l2 r2 l2 l2 l

+l c r c c l.

+Filesystem#1024-blocks#Used#Available#Capacity#Mounted on

+/dev/sda6#2543714#13#2412169#0%#/k

+.TE

+.sp 1

+(Note that this example shows that one can add command line options

+to the options given in

+.IR /etc/fstab .)

+.TP

+.BR check=none " or " nocheck

+No checking is done at mount time. This is the default. This is fast.

+It is wise to invoke

+.BR e2fsck (8)

+every now and then, e.g.\& at boot time. The non-default behavior is unsupported

+(check=normal and check=strict options have been removed). Note that these mount options

+don't have to be supported if ext4 kernel driver is used for ext2 and ext3 filesystems.

+.TP

+.B debug

+Print debugging info upon each (re)mount.

+.TP

+.BR errors= { continue | remount-ro | panic }

+Define the behavior when an error is encountered.

+(Either ignore errors and just mark the filesystem erroneous and continue,

+or remount the filesystem read-only, or panic and halt the system.)

+The default is set in the filesystem superblock, and can be

+changed using

+.BR tune2fs (8).

+.TP

+.BR grpid | bsdgroups " and " nogrpid | sysvgroups

+These options define what group id a newly created file gets.

+When

+.B 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

+.BR grpquota | noquota | quota | usrquota

+The usrquota (same as quota) mount option enables user quota support on the

+filesystem. grpquota enables group quotas support. You need the quota utilities

+to actually enable and manage the quota system.

+.TP

+.B nouid32

+Disables 32-bit UIDs and GIDs.  This is for interoperability with older

+kernels which only store and expect 16-bit values.

+.TP

+.BR oldalloc " or " orlov

+Use old allocator or Orlov allocator for new inodes. Orlov is default.

+.TP

+\fBresgid=\fP\,\fIn\fP and \fBresuid=\fP\,\fIn\fP

+The ext2 filesystem reserves a certain percentage of the available

+space (by default 5%, see

+.BR mke2fs (8)

+and

+.BR tune2fs (8)).

+These options determine who can use the reserved blocks.

+(Roughly: whoever has the specified uid, or belongs to the specified group.)

+.TP

+.BI sb= n

+Instead of block 1, use block

+.I n

+as superblock. This could be useful when the filesystem has been damaged.

+(Earlier, copies of the superblock would be made every 8192 blocks: in

+block 1, 8193, 16385, \&...\& (and one got thousands of copies on

+a big filesystem). Since version 1.08,

+.B mke2fs

+has a \-s (sparse superblock) option to reduce the number of backup

+superblocks, and since version 1.15 this is the default. Note

+that this may mean that ext2 filesystems created by a recent

+.B mke2fs

+cannot be mounted r/w under Linux 2.0.*.)

+The block number here uses 1\ k units. Thus, if you want to use logical

+block 32768 on a filesystem with 4\ k blocks, use "sb=131072".

+.TP

+.BR user_xattr | nouser_xattr

+Support "user." extended attributes (or not).

+

+

+.SH "Mount options for ext3"

+The ext3 filesystem is a version of the ext2 filesystem which has been

+enhanced with journaling.  It supports the same options as ext2 as

+well as the following additions:

+.TP

+.B journal=update

+Update the ext3 filesystem's journal to the current format.

+.TP

+.B journal=inum

+When a journal already exists, this option is ignored. Otherwise, it

+specifies the number of the inode which will represent the ext3 filesystem's

+journal file; ext3 will create a new journal, overwriting the old contents

+of the file whose inode number is

+.IR inum .

+.TP

+.BR journal_dev=devnum / journal_path=path

+When the external journal device's major/minor numbers

+have changed, these options allow the user to specify

+the new journal location.  The journal device is

+identified either through its new major/minor numbers encoded

+in devnum, or via a path to the device.

+.TP

+.BR norecovery / noload

+Don't load the journal on mounting.  Note that

+if the filesystem was not unmounted cleanly,

+skipping the journal replay will lead to the

+filesystem containing inconsistencies that can

+lead to any number of problems.

+.TP

+.BR data= { journal | ordered | writeback }

+Specifies the journaling mode for file data.  Metadata is always journaled.

+To use modes other than

+.B ordered

+on the root filesystem, pass the mode to the kernel as boot parameter, e.g.\&

+.IR rootflags=data=journal .

+.RS

+.TP

+.B journal

+All data is committed into the journal prior to being written into the

+main filesystem.

+.TP

+.B ordered

+This is the default mode.  All data is forced directly out to the main file

+system prior to its metadata being committed to the journal.

+.TP

+.B writeback

+Data ordering is not preserved \(en data may be written into the main

+filesystem after its metadata has been committed to the journal.

+This is rumoured to be the highest-throughput option.  It guarantees

+internal filesystem integrity, however it can allow old data to appear

+in files after a crash and journal recovery.

+.RE

+.TP

+.B data_err=ignore

+Just print an error message if an error occurs in a file data buffer in

+ordered mode.

+.TP

+.B data_err=abort

+Abort the journal if an error occurs in a file data buffer in ordered mode.

+.TP

+.BR barrier=0 " / " barrier=1 "

+This disables / enables the use of write barriers in the jbd code.  barrier=0

+disables, barrier=1 enables (default). This also requires an IO stack which can

+support barriers, and if jbd gets an error on a barrier write, it will disable

+barriers again with a warning.  Write barriers enforce proper on-disk ordering

+of journal commits, making volatile disk write caches safe to use, at some

+performance penalty.  If your disks are battery-backed in one way or another,

+disabling barriers may safely improve performance.

+.TP

+.BI commit= nrsec

+Sync all data and metadata every

+.I nrsec

+seconds. The default value is 5 seconds. Zero means default.

+.TP

+.B user_xattr

+Enable Extended User Attributes. See the

+.BR attr (5)

+manual page.

+.TP

+.B acl

+Enable POSIX Access Control Lists. See the

+.BR acl (5)

+manual page.

+.TP

+.BR usrjquota=aquota.user | grpjquota=aquota.group | jqfmt=vfsv0

+Apart from the old quota system (as in ext2, jqfmt=vfsold aka version 1 quota)

+ext3 also supports journaled quotas (version 2 quota). jqfmt=vfsv0

+enables journaled quotas. For journaled quotas the mount options

+usrjquota=aquota.user and grpjquota=aquota.group are required to tell the

+quota system which quota database files to use. Journaled quotas have the

+advantage that even after a crash no quota check is required.

+

+.SH "Mount options for ext4"

+The ext4 filesystem is an advanced level of the ext3 filesystem which

+incorporates scalability and reliability enhancements for supporting large

+filesystem.

+

+The options

+.B journal_dev, norecovery, noload, data, commit, orlov, oldalloc, [no]user_xattr

+.B [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid

+.B sysvgroups, resgid, resuid, sb, quota, noquota, grpquota, usrquota

+.B usrjquota, grpjquota and jqfmt

+are backwardly compatible with ext3 or ext2.

+.TP

+.B journal_checksum

+Enable checksumming of the journal transactions.  This will allow the recovery

+code in e2fsck and the kernel to detect corruption in the kernel.  It is a

+compatible change and will be ignored by older kernels.

+.TP

+.B journal_async_commit

+Commit block can be written to disk without waiting for descriptor blocks. If

+enabled older kernels cannot mount the device.

+This will enable 'journal_checksum' internally.

+.TP

+.BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier

+These mount options have the same effect as in ext3.  The mount options

+"barrier" and "nobarrier" are added for consistency with other ext4 mount

+options.

+

+The ext4 filesystem enables write barriers by default.

+.TP

+.BI inode_readahead_blks= n

+This tuning parameter controls the maximum number of inode table blocks that

+ext4's inode table readahead algorithm will pre-read into the buffer cache.

+The value must be a power of 2. The default value is 32 blocks.

+.TP

+.BI stripe= n

+Number of filesystem blocks that mballoc will try to use for allocation size

+and alignment. For RAID5/6 systems this should be the number of data disks *

+RAID chunk size in filesystem blocks.

+.TP

+.B delalloc

+Deferring block allocation until write-out time.

+.TP

+.B nodelalloc

+Disable delayed allocation. Blocks are allocated when data is copied from user

+to page cache.

+.TP

+.BI max_batch_time= usec

+Maximum amount of time ext4 should wait for additional filesystem operations to

+be batch together with a synchronous write operation. Since a synchronous

+write operation is going to force a commit and then a wait for the I/O

+complete, it doesn't cost much, and can be a huge throughput win, we wait for a

+small amount of time to see if any other transactions can piggyback on the

+synchronous write. The algorithm used is designed to automatically tune for

+the speed of the disk, by measuring the amount of time (on average) that it

+takes to finish committing a transaction. Call this time the "commit time".

+If the time that the transaction has been running is less than the commit time,

+ext4 will try sleeping for the commit time to see if other operations will join

+the transaction. The commit time is capped by the max_batch_time, which

+defaults to 15000\ \[mc]s (15\ ms). This optimization can be turned off entirely by

+setting max_batch_time to 0.

+.TP

+.BI min_batch_time= usec

+This parameter sets the commit time (as described above) to be at least

+min_batch_time. It defaults to zero microseconds. Increasing this parameter

+may improve the throughput of multi-threaded, synchronous workloads on very

+fast disks, at the cost of increasing latency.

+.TP

+.BI journal_ioprio= prio

+The I/O priority (from 0 to 7, where 0 is the highest priority) which should be

+used for I/O operations submitted by kjournald2 during a commit operation.

+This defaults to 3, which is a slightly higher priority than the default I/O

+priority.

+.TP

+.B abort

+Simulate the effects of calling ext4_abort() for

+debugging purposes.  This is normally used while

+remounting a filesystem which is already mounted.

+.TP

+.BR auto_da_alloc | noauto_da_alloc

+Many broken applications don't use fsync() when

+replacing existing files via patterns such as

+

+fd = open("foo.new")/write(fd,...)/close(fd)/ rename("foo.new", "foo")

+

+or worse yet

+

+fd = open("foo", O_TRUNC)/write(fd,...)/close(fd).

+

+If auto_da_alloc is enabled, ext4 will detect the replace-via-rename and

+replace-via-truncate patterns and force that any delayed allocation blocks are

+allocated such that at the next journal commit, in the default data=ordered

+mode, the data blocks of the new file are forced to disk before the rename()

+operation is committed.  This provides roughly the same level of guarantees as

+ext3, and avoids the "zero-length" problem that can happen when a system

+crashes before the delayed allocation blocks are forced to disk.

+.TP

+.B noinit_itable

+Do not initialize any uninitialized inode table blocks in the background. This

+feature may be used by installation CD's so that the install process can

+complete as quickly as possible; the inode table initialization process would

+then be deferred until the next time the filesystem is mounted.

+.TP

+.B init_itable=n

+The lazy itable init code will wait n times the number of milliseconds it took

+to zero out the previous block group's inode table. This minimizes the impact on

+system performance while the filesystem's inode table is being initialized.

+.TP

+.BR discard / nodiscard

+Controls whether ext4 should issue discard/TRIM commands to the underlying

+block device when blocks are freed.  This is useful for SSD devices and

+sparse/thinly-provisioned LUNs, but it is off by default until sufficient

+testing has been done.

+.TP

+.B nouid32

+Disables 32-bit UIDs and GIDs.  This is for

+interoperability  with  older kernels which only

+store and expect 16-bit values.

+.TP

+.BR block_validity / noblock_validity

+This options allows to enables/disables the in-kernel facility for tracking

+filesystem metadata blocks within internal data structures. This allows multi-\c

+block allocator and other routines to quickly locate extents which might

+overlap with filesystem metadata blocks. This option is intended for debugging

+purposes and since it negatively affects the performance, it is off by default.

+.TP

+.BR dioread_lock / dioread_nolock

+Controls whether or not ext4 should use the DIO read locking. If the

+dioread_nolock option is specified ext4 will allocate uninitialized extent

+before buffer write and convert the extent to initialized after IO completes.

+This approach allows ext4 code to avoid using inode mutex, which improves

+scalability on high speed storages. However this does not work with data

+journaling and dioread_nolock option will be ignored with kernel warning.

+Note that dioread_nolock code path is only used for extent-based files.

+Because of the restrictions this options comprises it is off by default

+(e.g.\& dioread_lock).

+.TP

+.B max_dir_size_kb=n

+This limits the size of the directories so that any attempt to expand them

+beyond the specified limit in kilobytes will cause an ENOSPC error. This is

+useful in memory-constrained environments, where a very large directory can

+cause severe performance problems or even provoke the Out Of Memory killer. (For

+example, if there is only 512\ MB memory available, a 176\ MB directory may

+seriously cramp the system's style.)

+.TP

+.B i_version

+Enable 64-bit inode version support. This option is off by default.

+

 .SH SEE ALSO

 .BR mke2fs (8),

 .BR mke2fs.conf (5),

 .BR e2fsck (8),

 .BR dumpe2fs (8),

 .BR tune2fs (8),

-.BR debugfs (8)

+.BR debugfs (8),

+.BR mount (8)