ceph: don't request excl caps when mount is readonly

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/caps.c

@@ -1862,6 +1862,9 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,
 			 * revoking the shared cap on every create/unlink
 			 * operation.
 			 */
+			if (IS_RDONLY(inode))
+				want = CEPH_CAP_ANY_SHARED;
+			else
 				want = CEPH_CAP_ANY_SHARED | CEPH_CAP_FILE_EXCL;
 			retain |= want;
 		} else {