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authorTristan Ye <tristan.ye@oracle.com>2010-10-11 16:46:39 +0800
committerJoel Becker <joel.becker@oracle.com>2010-10-11 14:14:55 -0700
commit7bdb0d18bfd381cc5491eb95973ec5604b356c7e (patch)
tree1abe07df935a336eeac5c7705dc9b59341b47b0a /Documentation/filesystems/ocfs2.txt
parent75d9bbc73804285020aa4d99bd2a9600edea8945 (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/ocfs2.txt')
-rw-r--r--Documentation/filesystems/ocfs2.txt7
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.