backfill_unfound state reset to clean after osd restart

Hi, I would like to bring some attention to a problem we have been observing with nautilus, and which I reported here [1]. If a pg is in backfill_unfound state ("unfound" objects were detected during backfill), and one of the osds from the active set is restarted the state changes to clean, losing the information about unfound objects. And when I tired to reproduce the issue on the master with the same scenario, the status did not change, but I was observing the primary osd crash after a non-primary restart. I looked through the commit log and did not find a commit explicitely saying (or giving a hint) this problem was adressing in the master and I see there was large refactoring in the related code since nautilus. So probably the issue was "solved" during refactoring? We would love to see the problem fixed in the nautilus, and I would like to backport the "fix", but right now I don't have a clear understanding if there really was a fix in the master and what to do with that crash that may be related to the "fix". I might try to find the commit that changed the behaviour by bisecting, but this looks like a long way, so I want to ask here first if anybody has a hint. [1] https://tracker.ceph.com/issues/50351 Thanks, -- Mykola Golub