xfs: wire up the show_stats super operation

The show_stats option allows a file system to dump plain text statistic
on a per-mount basis into /proc/*/mountstats.  Wire up a no-op version
which will grow useful information for zoned file systems later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

Author: Christoph Hellwig

fs/xfs/xfs_super.c

@@ -1258,6 +1258,14 @@ xfs_fs_shutdown(
 	xfs_force_shutdown(XFS_M(sb), SHUTDOWN_DEVICE_REMOVED);
 }
 
+static int
+xfs_fs_show_stats(
+	struct seq_file		*m,
+	struct dentry		*root)
+{
+	return 0;
+}
+
 static const struct super_operations xfs_super_operations = {
 	.alloc_inode		= xfs_fs_alloc_inode,
 	.destroy_inode		= xfs_fs_destroy_inode,
@@ -1272,6 +1280,7 @@ static const struct super_operations xfs_super_operations = {
 	.nr_cached_objects	= xfs_fs_nr_cached_objects,
 	.free_cached_objects	= xfs_fs_free_cached_objects,
 	.shutdown		= xfs_fs_shutdown,
+	.show_stats		= xfs_fs_show_stats,
 };
 
 static int