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-rw-r--r--Documentation/filesystems/btrfs.txt47
1 files changed, 30 insertions, 17 deletions
diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
index 5dd282dda55c..d11cc2f8077b 100644
--- a/Documentation/filesystems/btrfs.txt
+++ b/Documentation/filesystems/btrfs.txt
@@ -38,7 +38,7 @@ Mount Options
=============
When mounting a btrfs filesystem, the following option are accepted.
-Unless otherwise specified, all options default to off.
+Options with (*) are default options and will not show in the mount options.
alloc_start=<bytes>
Debugging option to force all block allocations above a certain
@@ -46,10 +46,12 @@ Unless otherwise specified, all options default to off.
bytes, optionally with a K, M, or G suffix, case insensitive.
Default is 1MB.
+ noautodefrag(*)
autodefrag
- Detect small random writes into files and queue them up for the
- defrag process. Works best for small files; Not well suited for
- large database workloads.
+ Disable/enable auto defragmentation.
+ Auto defragmentation detects small random writes into files and queue
+ them up for the defrag process. Works best for small files;
+ Not well suited for large database workloads.
check_int
check_int_data
@@ -96,21 +98,26 @@ Unless otherwise specified, all options default to off.
can be avoided. Especially useful when trying to mount a multi-device
setup as root. May be specified multiple times for multiple devices.
+ nodiscard(*)
discard
- Issue frequent commands to let the block device reclaim space freed by
- the filesystem. This is useful for SSD devices, thinly provisioned
+ Disable/enable discard mount option.
+ Discard issues frequent 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 significant
performance impact. (The fstrim command is also available to
initiate batch trims from userspace).
+ noenospc_debug(*)
enospc_debug
- Debugging option to be more verbose in some ENOSPC conditions.
+ Disable/enable debugging option to be more verbose in some ENOSPC conditions.
fatal_errors=<action>
Action to take when encountering a fatal error:
"bug" - BUG() on a fatal error. This is the default.
"panic" - panic() on a fatal error.
+ noflushoncommit(*)
flushoncommit
The 'flushoncommit' mount option forces any data dirtied by a write in a
prior transaction to commit as part of the current commit. This makes
@@ -134,26 +141,32 @@ Unless otherwise specified, all options default to off.
Specify that 1 metadata chunk should be allocated after every <value>
data chunks. Off by default.
+ acl(*)
noacl
- Disable support for Posix Access Control Lists (ACLs). See the
+ Enable/disable support for Posix Access Control Lists (ACLs). See the
acl(5) manual page for more information about ACLs.
+ barrier(*)
nobarrier
- Disables the use of block layer write barriers. Write barriers ensure
- that certain IOs make it through the device cache and are on persistent
- storage. If used on a device with a volatile (non-battery-backed)
- write-back cache, this option will lead to filesystem corruption on a
- system crash or power loss.
+ Enable/disable the use of block layer write barriers. Write barriers
+ ensure that certain IOs make it through the device cache and are on
+ persistent storage. If disabled on a device with a volatile
+ (non-battery-backed) write-back cache, nobarrier option will lead to
+ filesystem corruption on a system crash or power loss.
+ datacow(*)
nodatacow
- Disable data copy-on-write for newly created files. Implies nodatasum,
- and disables all compression.
+ Enable/disable data copy-on-write for newly created files.
+ Nodatacow implies nodatasum, and disables all compression.
+ datasum(*)
nodatasum
- Disable data checksumming for newly created files.
+ Enable/disable data checksumming for newly created files.
+ Datasum implies datacow.
+ treelog(*)
notreelog
- Disable the tree logging used for fsync and O_SYNC writes.
+ Enable/disable the tree logging used for fsync and O_SYNC writes.
recovery
Enable autorecovery attempts if a bad tree root is found at mount time.