[PATCH 3.16 114/217] vfs: show_vfsstat: do not ignore errors from show_devname method

[Ben Hutchings]

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Dmitry V. Levin" <ldv@xxxxxxxxxxxx>

commit 5f8d498d4364f544fee17125787a47553db02afa upstream.

Explicitly check show_devname method return code and bail out in case
of an error.  This fixes regression introduced by commit 9d4d65748a5c.

Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: add the 'out' label]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -191,6 +191,8 @@ static int show_vfsstat(struct seq_file
 	if (sb->s_op->show_devname) {
 		seq_puts(m, "device ");
 		err = sb->s_op->show_devname(m, mnt_path.dentry);
+		if (err)
+			goto out;
 	} else {
 		if (r->mnt_devname) {
 			seq_puts(m, "device ");
@@ -216,6 +218,7 @@ static int show_vfsstat(struct seq_file
 	}
 
 	seq_putc(m, '\n');
+out:
 	return err;
 }