Currently btrfs-progs will happily enumerate any device which has a
btrfs filesystem on it irrespective of its type. For the majority of
use cases that's fine and there haven't been any problems with that.
However, there was a recent report that in multipath scenario when
running "btrfs fi show" after a path flap (path going down and then
coming back up) instead of the multipath device being show the device
which represents the flapped path is shown. So a multipath filesystem
might look like:
Label: none uuid: d3c1261f-18be-4015-9fef-6b35759dfdba
Total devices 1 FS bytes used 192.00KiB
devid 1 size 10.00GiB used 536.00MiB path /dev/mapper/3600140501cc1f49e5364f0093869c763
/dev/mapper/xxx is actually backed by an arbitrary number of paths,
which in turn are presented to the system as ordinary SCSI devices i.e
/dev/sdX. If a path flaps and a user re-runs 'btrfs fi show' the output
would look like:
Label: none uuid: d3c1261f-18be-4015-9fef-6b35759dfdba
Total devices 1 FS bytes used 192.00KiB
devid 1 size 10.00GiB used 536.00MiB path /dev/sdd
This only occurs on unmounted filesystems as those are enumerated by
btrfs-progs, for mounted filesystem the kernel properly deals only with
the actual multipath device.
Turns out the output of this command is consumed by libraries and the
presence of a path device rather than the actual multipath causes
issues.
Fix this by checking for the presence of DM_MULTIPATH_DEVICE_PATH
udev attribute as multipath path devices are tagged with this attribute
by the multipath udev scripts.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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