ocfs2: Remove i_generation from inode lock names
OCFS2 puts inode meta data in the "lock value block" provided by the DLM.
Typically, i_generation is encoded in the lock name so that a deleted inode
on and a new one in the same block don't share the same lvb.
Unfortunately, that scheme means that the read in ocfs2_read_locked_inode()
is potentially thrown away as soon as the meta data lock is taken - we
cannot encode the lock name without first knowing i_generation, which
requires a disk read.
This patch encodes i_generation in the inode meta data lvb, and removes the
value from the inode meta data lock name. This way, the read can be covered
by a lock, and at the same time we can distinguish between an up to date and
a stale LVB.
This will help cold-cache stat(2) performance in particular.
Since this patch changes the protocol version, we take the opportunity to do
a minor re-organization of two of the LVB fields.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
diff --git a/fs/ocfs2/cluster/tcp_internal.h b/fs/ocfs2/cluster/tcp_internal.h
index da42b51..4b46aac 100644
--- a/fs/ocfs2/cluster/tcp_internal.h
+++ b/fs/ocfs2/cluster/tcp_internal.h
@@ -44,6 +44,9 @@
* locking semantics of the file system using the protocol. It should
* be somewhere else, I'm sure, but right now it isn't.
*
+ * New in version 4:
+ * - Remove i_generation from lock names for better stat performance.
+ *
* New in version 3:
* - Replace dentry votes with a cluster lock
*
@@ -51,7 +54,7 @@
* - full 64 bit i_size in the metadata lock lvbs
* - introduction of "rw" lock and pushing meta/data locking down
*/
-#define O2NET_PROTOCOL_VERSION 3ULL
+#define O2NET_PROTOCOL_VERSION 4ULL
struct o2net_handshake {
__be64 protocol_version;
__be64 connector_id;
