Re: Unexpected raid1 behaviour

[Anand Jain <anand.jain@oracle.com>]

>>> what was intended that it should be able to detect a previous
>>> member block-device becoming available again as a different
>>> device inode, which currently is very dangerous in some vital
>>> situations.

  Peter, What's the dangerous part here ?

>>   If device disappears, the patch [4] will completely take out the
>>   device from btrfs, and continues to RW in degraded mode.
>>   When it reappears then [5] will bring it back to the RW list.
> 
> but [5] relies on someone from userspace (presumably udev) actually
> invoking BTRFS_IOC_SCAN_DEV/IOSC_DEVICES_READY, no ?

  Nikoly, Yes. Most of the destro udev already does that. udev calls
  btrfs dev scan when SB is overwritten from userland or when a device
  with primary SB as btrfs (re)appears.

> Because
> device_list_add is only ever called from btrfs_scan_one_device, which in
> turn is called by either of the aforementioned IOCTLS or during mount
> (which is not at play here).

  Hm. as above.

Thanks Anand