NFSv4: Validate the stateid before applying it to state recovery

If the stateid is the zero or invalid stateid, then it is pointless
to attempt to use it for recovery. In that case, try to fall back
to using the open state stateid, or just doing a general recovery
of all state on a given inode.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -428,6 +428,22 @@ static int nfs4_delay(long *timeout, bool interruptible)
 	return nfs4_delay_killable(timeout);
 }
 
+static const nfs4_stateid *
+nfs4_recoverable_stateid(const nfs4_stateid *stateid)
+{
+	if (!stateid)
+		return NULL;
+	switch (stateid->type) {
+	case NFS4_OPEN_STATEID_TYPE:
+	case NFS4_LOCK_STATEID_TYPE:
+	case NFS4_DELEGATION_STATEID_TYPE:
+		return stateid;
+	default:
+		break;
+	}
+	return NULL;
+}
+
 /* This is the error handling routine for processes that are allowed
  * to sleep.
  */
@@ -436,7 +452,7 @@ static int nfs4_do_handle_exception(struct nfs_server *server,
 {
 	struct nfs_client *clp = server->nfs_client;
 	struct nfs4_state *state = exception->state;
-	const nfs4_stateid *stateid = exception->stateid;
+	const nfs4_stateid *stateid;
 	struct inode *inode = exception->inode;
 	int ret = errorcode;
 
@@ -444,8 +460,9 @@ static int nfs4_do_handle_exception(struct nfs_server *server,
 	exception->recovering = 0;
 	exception->retry = 0;
 
+	stateid = nfs4_recoverable_stateid(exception->stateid);
 	if (stateid == NULL && state != NULL)
-		stateid = &state->stateid;
+		stateid = nfs4_recoverable_stateid(&state->stateid);
 
 	switch(errorcode) {
 		case 0: