On 29/09/2021 14:59, Nikolay Borisov wrote:

On 29.09.21 г. 2:03, Anand Jain wrote:

quoted

On 28/09/2021 20:37, Nikolay Borisov wrote:

quoted

Currently btrfs-progs will happily enumerate any device which has a
btrfs filesystem on it. For the majority of use cases that's fine and
there haven't been any problems with that.

quoted

However, there was a recent
report

  Could you point to the report or if it is internal?

Internal

quoted

  Kernel message has the process of name for the device scan.
  We don't have to fix the btrfs-progs end if it is not doing it.

quoted

that in multipath scenario when running "btrfs fi show" after a
path flap

  It is better to use 'btrfs fi show -m' it provides kernel perspective.

[146822.972653] BTRFS warning: duplicate device /dev/sdd devid 1
generation 8 scanned by systemd-udevd (6254)

[146823.060984] BTRFS info (device dm-0): devid 1 device path
/dev/mapper/3600140501cc1f49e5364f0093869c763 changed to /dev/dm-0
scanned by systemd-udevd (6266)

   So /dev/sdd is a device-path of the multi-path
      /dev/mapper/3600140501cc1f49e5364f0093869c763 aka /dev/dm-0
   which, the kernel rejected to use, that's good.

[146823.075084] BTRFS info (device dm-0): devid 1 device path /dev/dm-0
changed to /dev/mapper/3600140501cc1f49e5364f0093869c763 scanned by
systemd-udevd (6266)

  systemd-udevd is scanning the same device too many times.

btrfs fi show -m is actually consistent with always showing the mapper
device.

  Do you mean either of /dev/mapper/3600140501cc1f49e5364f0093869c763
  or /dev/dm-0 but, never /dev/sdd? That's expected as per the above
  messages which is not a problem.

quoted

  What do you mean by path flap here? Do you mean a device-path in a
multi-path config disappeared forever or failed temporarily?

flap means going up and down. The gist is that btrfs fi show would show
the latest device being scanned, which in the case of multipath device
could be any of the paths.

  Do you mean 'btrfs fi show' shows a device of the multi-path however,
  'btrfs fi show -m' shows the correct multi-path device?

<snip>