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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
38============= 38=============
39 39
40When mounting a btrfs filesystem, the following option are accepted. 40When mounting a btrfs filesystem, the following option are accepted.
41Unless otherwise specified, all options default to off. 41Options with (*) are default options and will not show in the mount options.
42 42
43 alloc_start=<bytes> 43 alloc_start=<bytes>
44 Debugging option to force all block allocations above a certain 44 Debugging option to force all block allocations above a certain
@@ -46,10 +46,12 @@ Unless otherwise specified, all options default to off.
46 bytes, optionally with a K, M, or G suffix, case insensitive. 46 bytes, optionally with a K, M, or G suffix, case insensitive.
47 Default is 1MB. 47 Default is 1MB.
48 48
49 noautodefrag(*)
49 autodefrag 50 autodefrag
50 Detect small random writes into files and queue them up for the 51 Disable/enable auto defragmentation.
51 defrag process. Works best for small files; Not well suited for 52 Auto defragmentation detects small random writes into files and queue
52 large database workloads. 53 them up for the defrag process. Works best for small files;
54 Not well suited for large database workloads.
53 55
54 check_int 56 check_int
55 check_int_data 57 check_int_data
@@ -96,21 +98,26 @@ Unless otherwise specified, all options default to off.
96 can be avoided. Especially useful when trying to mount a multi-device 98 can be avoided. Especially useful when trying to mount a multi-device
97 setup as root. May be specified multiple times for multiple devices. 99 setup as root. May be specified multiple times for multiple devices.
98 100
101 nodiscard(*)
99 discard 102 discard
100 Issue frequent commands to let the block device reclaim space freed by 103 Disable/enable discard mount option.
101 the filesystem. This is useful for SSD devices, thinly provisioned 104 Discard issues frequent commands to let the block device reclaim space
105 freed by the filesystem.
106 This is useful for SSD devices, thinly provisioned
102 LUNs and virtual machine images, but may have a significant 107 LUNs and virtual machine images, but may have a significant
103 performance impact. (The fstrim command is also available to 108 performance impact. (The fstrim command is also available to
104 initiate batch trims from userspace). 109 initiate batch trims from userspace).
105 110
111 noenospc_debug(*)
106 enospc_debug 112 enospc_debug
107 Debugging option to be more verbose in some ENOSPC conditions. 113 Disable/enable debugging option to be more verbose in some ENOSPC conditions.
108 114
109 fatal_errors=<action> 115 fatal_errors=<action>
110 Action to take when encountering a fatal error: 116 Action to take when encountering a fatal error:
111 "bug" - BUG() on a fatal error. This is the default. 117 "bug" - BUG() on a fatal error. This is the default.
112 "panic" - panic() on a fatal error. 118 "panic" - panic() on a fatal error.
113 119
120 noflushoncommit(*)
114 flushoncommit 121 flushoncommit
115 The 'flushoncommit' mount option forces any data dirtied by a write in a 122 The 'flushoncommit' mount option forces any data dirtied by a write in a
116 prior transaction to commit as part of the current commit. This makes 123 prior transaction to commit as part of the current commit. This makes
@@ -134,26 +141,32 @@ Unless otherwise specified, all options default to off.
134 Specify that 1 metadata chunk should be allocated after every <value> 141 Specify that 1 metadata chunk should be allocated after every <value>
135 data chunks. Off by default. 142 data chunks. Off by default.
136 143
144 acl(*)
137 noacl 145 noacl
138 Disable support for Posix Access Control Lists (ACLs). See the 146 Enable/disable support for Posix Access Control Lists (ACLs). See the
139 acl(5) manual page for more information about ACLs. 147 acl(5) manual page for more information about ACLs.
140 148
149 barrier(*)
141 nobarrier 150 nobarrier
142 Disables the use of block layer write barriers. Write barriers ensure 151 Enable/disable the use of block layer write barriers. Write barriers
143 that certain IOs make it through the device cache and are on persistent 152 ensure that certain IOs make it through the device cache and are on
144 storage. If used on a device with a volatile (non-battery-backed) 153 persistent storage. If disabled on a device with a volatile
145 write-back cache, this option will lead to filesystem corruption on a 154 (non-battery-backed) write-back cache, nobarrier option will lead to
146 system crash or power loss. 155 filesystem corruption on a system crash or power loss.
147 156
157 datacow(*)
148 nodatacow 158 nodatacow
149 Disable data copy-on-write for newly created files. Implies nodatasum, 159 Enable/disable data copy-on-write for newly created files.
150 and disables all compression. 160 Nodatacow implies nodatasum, and disables all compression.
151 161
162 datasum(*)
152 nodatasum 163 nodatasum
153 Disable data checksumming for newly created files. 164 Enable/disable data checksumming for newly created files.
165 Datasum implies datacow.
154 166
167 treelog(*)
155 notreelog 168 notreelog
156 Disable the tree logging used for fsync and O_SYNC writes. 169 Enable/disable the tree logging used for fsync and O_SYNC writes.
157 170
158 recovery 171 recovery
159 Enable autorecovery attempts if a bad tree root is found at mount time. 172 Enable autorecovery attempts if a bad tree root is found at mount time.