From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Stancek <jstancek@redhat.com>
Date: Mon, 29 Jun 2020 07:08:14 -0400 (EDT)
Subject: [LTP] [PATCH v4 1/2] tst_device: Add new api
 tst_find_backing_dev(path, dev)
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> > You said "But stat function has problem when filsystem uses virtual block
> > (such as btrfs,fuse, then major numer is 0)." - Why is that a problem
> > for comparison against /proc/self/mountinfo?
> > 
> Yes, you are right. I wrongly think btrfs filesystem affects the 10th
> columu value in /proc/self/mountinfo. In actually, it can show the
> correct backing block dev.

I haven't tested your pasted version, but that approach seems better,
since that should work for any path, not just the mount point.