nfsd: nfsd4_locku() must reference the lock stateid

Ensure that nfsd4_locku() keeps a reference to the lock stateid
until it is done working with it. Necessary step toward client_mutex
removal.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -5147,10 +5147,12 @@ nfsd4_locku(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 					&stp, nn);
 	if (status)
 		goto out;
+	/* FIXME: move into nfs4_preprocess_seqid_op */
+	atomic_inc(&stp->st_stid.sc_count);
 	filp = find_any_file(stp->st_stid.sc_file);
 	if (!filp) {
 		status = nfserr_lock_range;
-		goto out;
+		goto put_stateid;
 	}
 	file_lock = locks_alloc_lock();
 	if (!file_lock) {
@@ -5180,6 +5182,8 @@ nfsd4_locku(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	memcpy(&locku->lu_stateid, &stp->st_stid.sc_stateid, sizeof(stateid_t));
 fput:
 	fput(filp);
+put_stateid:
+	nfs4_put_stid(&stp->st_stid);
 out:
 	nfsd4_bump_seqid(cstate, status);
 	if (!cstate->replay_owner)