From 06705bff9114531a997a7d0c2520bea0f2927410 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sat, 28 Mar 2009 10:59:57 -0400 Subject: ext4: Regularize mount options Add support for using the mount options "barrier" and "nobarrier", and "auto_da_alloc" and "noauto_da_alloc", which is more consistent than "barrier=<0|1>" or "auto_da_alloc=<0|1>". Most other ext3/ext4 mount options use the foo/nofoo naming convention. We allow the old forms of these mount options for backwards compatibility. Signed-off-by: "Theodore Ts'o" --- Documentation/filesystems/ext4.txt | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) (limited to 'Documentation/filesystems') diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 5c484aec2ba..97882df0486 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -183,8 +183,8 @@ commit=nrsec (*) Ext4 can be told to sync all its data and metadata performance. barrier=<0|1(*)> This enables/disables the use of write barriers in - the jbd code. barrier=0 disables, barrier=1 enables. - This also requires an IO stack which can support +barrier(*) the jbd code. barrier=0 disables, barrier=1 enables. +nobarrier This also requires an IO stack which can support barriers, and if jbd gets an error on a barrier write, it will disable again with a warning. Write barriers enforce proper on-disk ordering @@ -192,6 +192,9 @@ barrier=<0|1(*)> This enables/disables the use of write barriers in safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. + The mount options "barrier" and "nobarrier" can + also be used to enable or disable barriers, for + consistency with other ext4 mount options. inode_readahead=n This tuning parameter controls the maximum number of inode table blocks that ext4's inode @@ -313,6 +316,24 @@ journal_ioprio=prio The I/O priority (from 0 to 7, where 0 is the a slightly higher priority than the default I/O priority. +auto_da_alloc(*) Many broken applications don't use fsync() when +noauto_da_alloc 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 + commited. 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. + Data Mode ========= There are 3 different data modes: -- cgit v1.2.3