nfsd: nfsd4_process_open2() must reference the delegation stateid

Ensure that nfsd4_process_open2() keeps a reference to the delegation
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

@@ -3325,6 +3325,8 @@ static struct nfs4_delegation *find_deleg_stateid(struct nfs4_client *cl, statei
 	ret = find_stateid_by_type(cl, s, NFS4_DELEG_STID);
 	if (!ret)
 		return NULL;
+	/* FIXME: move into find_stateid_by_type */
+	atomic_inc(&ret->sc_count);
 	return delegstateid(ret);
 }
 
@@ -3340,14 +3342,18 @@ nfs4_check_deleg(struct nfs4_client *cl, struct nfsd4_open *open,
 {
 	int flags;
 	__be32 status = nfserr_bad_stateid;
+	struct nfs4_delegation *deleg;
 
-	*dp = find_deleg_stateid(cl, &open->op_delegate_stateid);
-	if (*dp == NULL)
+	deleg = find_deleg_stateid(cl, &open->op_delegate_stateid);
+	if (deleg == NULL)
 		goto out;
 	flags = share_access_to_flags(open->op_share_access);
-	status = nfs4_check_delegmode(*dp, flags);
-	if (status)
-		*dp = NULL;
+	status = nfs4_check_delegmode(deleg, flags);
+	if (status) {
+		nfs4_put_stid(&deleg->dl_stid);
+		goto out;
+	}
+	*dp = deleg;
 out:
 	if (!nfsd4_is_deleg_cur(open))
 		return nfs_ok;
@@ -3828,6 +3834,8 @@ out:
 	if (!(open->op_openowner->oo_flags & NFS4_OO_CONFIRMED) &&
 	    !nfsd4_has_session(&resp->cstate))
 		open->op_rflags |= NFS4_OPEN_RESULT_CONFIRM;
+	if (dp)
+		nfs4_put_stid(&dp->dl_stid);
 
 	return status;
 }