nfsd: fix bug on nfs4 stateid deallocation

NFS4_OO_PURGE_CLOSE is not handled properly. To avoid memory leak, nfs4
stateid which is pointed by oo_last_closed_stid is freed in nfsd4_close(),
but NFS4_OO_PURGE_CLOSE isn't cleared meanwhile. So the stateid released in
THIS close procedure may be freed immediately in the coming encoding function.
Sorry that Signed-off-by was forgotten in last version.
Signed-off-by: NYanchuan Nian <ycnian@gmail.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -3823,6 +3823,7 @@ nfsd4_close(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	nfsd4_close_open_stateid(stp);
 	release_last_closed_stateid(oo);
+	oo->oo_flags &= ~NFS4_OO_PURGE_CLOSE;
 	oo->oo_last_closed_stid = stp;
 
 	if (list_empty(&oo->oo_owner.so_stateids)) {