Hi Neil,

----- Original Message -----

From: "Andrei Warkentin" <redacted>
To: "NeilBrown" <redacted>
Cc: linux-raid@vger.kernel.org, "Andrei Warkentin" <redacted>
Sent: Tuesday, October 18, 2011 1:07:24 PM
Subject: Re: [PATCH] MD: Allow restarting an interrupted incremental recovery.

quoted

Also I realised that clearing saved_raid_disk when an array is not
degraded
is no longer enough.  We also need to clear it when the device
becomes
In_sync.
Consider a 3-drive RAID1 with two drives missing.  You add back one
of them
and when it is recovered it needs saved_raid_disk cleared so that
the
superblock gets written out.

So below is what I applied.

Wouldn't all drives being In_sync imply the array is not degraded -
i.e. can the
check for a degraded array be omitted then, at all? I.e. if after the
resync the
In_sync bit is set - drop saved_raid_role.

Come to think of it - checking for !mddev->degraded might not be a good idea at all. After all, you
could imagine a situation where in a RAID1 array with A and B, A is recovered from B and then B goes away before
the SBs are flushed due to resync finishing - you would still want A's SB to be flushed, even if array is degraded.

Otherwise you'll end up with another incremental rebuilding A, and lost/inconsistent data after array became degraded (since it was going to A, but we never wrote out its SB, since array is degraded).

What do you think?

A