nfsd4: check for uninitialized slot

This fixes an oops when a buggy client tries to use an initial seqid of
0 on a new slot, which we may misinterpret as a replay.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/state.h

@@ -134,6 +134,7 @@ struct nfsd4_slot {
 	u16	sl_opcnt;
 #define NFSD4_SLOT_INUSE	(1 << 0)
 #define NFSD4_SLOT_CACHETHIS	(1 << 1)
+#define NFSD4_SLOT_INITIALIZED	(1 << 2)
 	u8	sl_flags;
 	char	sl_data[];
 };