ceph: try to send partial cap release on cap message on missing inode

If we have enough memory to allocate a new cap release message, do so, so
that we can send a partial release message immediately. This keeps us from
making the MDS wait when the cap release it needs is in a partially full
release message.

If we fail because of ENOMEM, oh well, they'll just have to wait a bit
longer.

Signed-off-by: Sage Weil <[e-mail]>

fs/ceph/caps.c

···
 		 * along for the mds (who clearly thinks we still have this
 		 * cap).
 		 */
+		ceph_add_cap_releases(mdsc, session, -1);
 		ceph_send_cap_releases(mdsc, session);
 		goto done;
 	}

fs/ceph/mds_client.c

···
  *
  * Called under s_mutex.
  */
-static int add_cap_releases(struct ceph_mds_client *mdsc,
-			    struct ceph_mds_session *session,
-			    int extra)
+int ceph_add_cap_releases(struct ceph_mds_client *mdsc,
+			  struct ceph_mds_session *session,
+			  int extra)
 {
 	struct ceph_msg *msg;
 	struct ceph_mds_cap_release *head;
···
 	}
 	mutex_unlock(&mdsc->mutex);
 
-	add_cap_releases(mdsc, req->r_session, -1);
+	ceph_add_cap_releases(mdsc, req->r_session, -1);
 	mutex_unlock(&session->s_mutex);
 
 	/* kick calling process */
···
 			send_renew_caps(mdsc, s);
 		else
 			ceph_con_keepalive(&s->s_con);
-		add_cap_releases(mdsc, s, -1);
+		ceph_add_cap_releases(mdsc, s, -1);
 		if (s->s_state == CEPH_MDS_SESSION_OPEN ||
 		    s->s_state == CEPH_MDS_SESSION_HUNG)
 			ceph_send_cap_releases(mdsc, s);

fs/ceph/mds_client.h

···
 	kref_put(&req->r_kref, ceph_mdsc_release_request);
 }
 
+extern int ceph_add_cap_releases(struct ceph_mds_client *mdsc,
+				 struct ceph_mds_session *session,
+				 int extra);
 extern void ceph_send_cap_releases(struct ceph_mds_client *mdsc,
 				   struct ceph_mds_session *session);