ceph: try to choose the auth MDS if possible for getattr

If any 'x' caps is issued we can just choose the auth MDS instead
of the random replica MDSes. Because only when the Locker is in
LOCK_EXEC state will the loner client could get the 'x' caps. And
if we send the getattr requests to any replica MDS it must auth pin
and tries to rdlock from the auth MDS, and then the auth MDS need
to do the Locker state transition to LOCK_SYNC. And after that the
lock state will change back.

This cost much when doing the Locker state transition and usually
will need to revoke caps from clients.

URL: https://tracker.ceph.com/issues/55240
Signed-off-by: Xiubo Li <[e-mail]>
Reviewed-by: Jeff Layton <[e-mail]>
Signed-off-by: Ilya Dryomov <[e-mail]>

fs/ceph/addr.c

···
 	struct iov_iter iter;
 	ssize_t err = 0;
 	size_t len;
+	int mode;
 
 	__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
 	__clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
···
 		goto out;
 
 	/* We need to fetch the inline data. */
-	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETATTR, USE_ANY_MDS);
+	mode = ceph_try_to_choose_auth_mds(inode, CEPH_STAT_CAP_INLINE_DATA);
+	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETATTR, mode);
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		goto out;

fs/ceph/inode.c

···
 	return err;
 }
 
+int ceph_try_to_choose_auth_mds(struct inode *inode, int mask)
+{
+	int issued = ceph_caps_issued(ceph_inode(inode));
+
+	/*
+	 * If any 'x' caps is issued we can just choose the auth MDS
+	 * instead of the random replica MDSes. Because only when the
+	 * Locker is in LOCK_EXEC state will the loner client could
+	 * get the 'x' caps. And if we send the getattr requests to
+	 * any replica MDS it must auth pin and tries to rdlock from
+	 * the auth MDS, and then the auth MDS need to do the Locker
+	 * state transition to LOCK_SYNC. And after that the lock state
+	 * will change back.
+	 *
+	 * This cost much when doing the Locker state transition and
+	 * usually will need to revoke caps from clients.
+	 */
+	if (((mask & CEPH_CAP_ANY_SHARED) && (issued & CEPH_CAP_ANY_EXCL))
+	    || (mask & CEPH_STAT_RSTAT))
+		return USE_AUTH_MDS;
+	else
+		return USE_ANY_MDS;
+}
+
 /*
  * Verify that we have a lease on the given mask.  If not,
  * do a getattr against an mds.
···
 	if (!force && ceph_caps_issued_mask_metric(ceph_inode(inode), mask, 1))
 			return 0;
 
-	mode = (mask & CEPH_STAT_RSTAT) ? USE_AUTH_MDS : USE_ANY_MDS;
+	mode = ceph_try_to_choose_auth_mds(inode, mask);
 	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETATTR, mode);
 	if (IS_ERR(req))
 		return PTR_ERR(req);

fs/ceph/super.h

···
 	ceph_queue_inode_work(inode, CEPH_I_WORK_FLUSH_SNAPS);
 }
 
+extern int ceph_try_to_choose_auth_mds(struct inode *inode, int mask);
 extern int __ceph_do_getattr(struct inode *inode, struct page *locked_page,
 			     int mask, bool force);
 static inline int ceph_do_getattr(struct inode *inode, int mask, bool force)