nfsd4: add a separate (lockowner, inode) lookup

Address the possible performance regression mentioned in "nfsd4: hash
lockowners to simplify RELEASE_LOCKOWNER" by providing a separate
(lockowner, inode) hash.

Really, I doubt this matters much, but I think it's likely we'll change
these data structures here and I'd rather that the need for (owner,
inode) lookups be well-documented.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index a3cf384..89c2cd8 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -366,6 +366,7 @@
 
 struct nfs4_lockowner {
 	struct nfs4_stateowner	lo_owner; /* must be first element */
+	struct list_head	lo_owner_ino_hash; /* hash by owner,file */
 	struct list_head        lo_perstateid; /* for lockowners only */
 	struct list_head	lo_list; /* for temporary uses */
 };