xfs: add xfs_remount_ro() helper

Factor the remount read only code into a helper to simplify the
subsequent change from the super block method .remount_fs to the
mount-api fs_context_operations method .reconfigure.
Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_super.c

@@ -1246,6 +1246,47 @@ xfs_remount_rw(
 	return 0;
 }
 
+static int
+xfs_remount_ro(
+	struct xfs_mount	*mp)
+{
+	int error;
+
+	/*
+	 * Cancel background eofb scanning so it cannot race with the final
+	 * log force+buftarg wait and deadlock the remount.
+	 */
+	xfs_stop_block_reaping(mp);
+
+	/* Get rid of any leftover CoW reservations... */
+	error = xfs_icache_free_cowblocks(mp, NULL);
+	if (error) {
+		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+		return error;
+	}
+
+	/* Free the per-AG metadata reservation pool. */
+	error = xfs_fs_unreserve_ag_blocks(mp);
+	if (error) {
+		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+		return error;
+	}
+
+	/*
+	 * Before we sync the metadata, we need to free up the reserve block
+	 * pool so that the used block count in the superblock on disk is
+	 * correct at the end of the remount. Stash the current* reserve pool
+	 * size so that if we get remounted rw, we can return it to the same
+	 * size.
+	 */
+	xfs_save_resvblks(mp);
+
+	xfs_quiesce_attr(mp);
+	mp->m_flags |= XFS_MOUNT_RDONLY;
+
+	return 0;
+}
+
 STATIC int
 xfs_fs_remount(
 	struct super_block	*sb,
@@ -1316,37 +1357,9 @@ xfs_fs_remount(
 
 	/* rw -> ro */
 	if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (*flags & SB_RDONLY)) {
-		/*
-		 * Cancel background eofb scanning so it cannot race with the
-		 * final log force+buftarg wait and deadlock the remount.
-		 */
-		xfs_stop_block_reaping(mp);
-
-		/* Get rid of any leftover CoW reservations... */
-		error = xfs_icache_free_cowblocks(mp, NULL);
-		if (error) {
-			xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
-			return error;
-		}
-
-		/* Free the per-AG metadata reservation pool. */
-		error = xfs_fs_unreserve_ag_blocks(mp);
-		if (error) {
-			xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+		error = xfs_remount_ro(mp);
+		if (error)
 			return error;
-		}
-
-		/*
-		 * Before we sync the metadata, we need to free up the reserve
-		 * block pool so that the used block count in the superblock on
-		 * disk is correct at the end of the remount. Stash the current
-		 * reserve pool size so that if we get remounted rw, we can
-		 * return it to the same size.
-		 */
-		xfs_save_resvblks(mp);
-
-		xfs_quiesce_attr(mp);
-		mp->m_flags |= XFS_MOUNT_RDONLY;
 	}
 
 	return 0;