diff options
| author | Tristan Ye <tristan.ye@oracle.com> | 2010-10-11 16:46:39 +0800 |
|---|---|---|
| committer | Joel Becker <joel.becker@oracle.com> | 2010-10-11 14:14:55 -0700 |
| commit | 7bdb0d18bfd381cc5491eb95973ec5604b356c7e (patch) | |
| tree | 1abe07df935a336eeac5c7705dc9b59341b47b0a /Documentation/filesystems | |
| parent | 75d9bbc73804285020aa4d99bd2a9600edea8945 (diff) | |
ocfs2: Add a mount option "coherency=*" to handle cluster coherency for O_DIRECT writes.
Currently, the default behavior of O_DIRECT writes was allowing
concurrent writing among nodes to the same file, with no cluster
coherency guaranteed (no EX lock held). This can leave stale data in
the cache for buffered reads on other nodes.
The new mount option introduce a chance to choose two different
behaviors for O_DIRECT writes:
* coherency=full, as the default value, will disallow
concurrent O_DIRECT writes by taking
EX locks.
* coherency=buffered, allow concurrent O_DIRECT writes
without EX lock among nodes, which
gains high performance at risk of
getting stale data on other nodes.
Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/ocfs2.txt | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/filesystems/ocfs2.txt b/Documentation/filesystems/ocfs2.txt index 1f7ae144f6d..5393e661169 100644 --- a/Documentation/filesystems/ocfs2.txt +++ b/Documentation/filesystems/ocfs2.txt @@ -87,3 +87,10 @@ dir_resv_level= (*) By default, directory reservations will scale with file reservations - users should rarely need to change this value. If allocation reservations are turned off, this option will have no effect. +coherency=full (*) Disallow concurrent O_DIRECT writes, cluster inode + lock will be taken to force other nodes drop cache, + therefore full cluster coherency is guaranteed even + for O_DIRECT writes. +coherency=buffered Allow concurrent O_DIRECT writes without EX lock among + nodes, which gains high performance at risk of getting + stale data on other nodes. |