Re: btrfs fi defrag interfering (maybe) with Ceph OSD operation

[Lionel Bouton <lionel-subscription@bouton.name>]

Le 29/09/2015 16:49, Lionel Bouton a écrit :
> Le 27/09/2015 17:34, Lionel Bouton a écrit :
>> [...]
>> It's not clear to me that "btrfs fi defrag <file>" can't interfere with
>> another process trying to use the file. I assume basic reading and
>> writing is OK but there might be restrictions on unlinking/locking/using
>> other ioctls... Are there any I should be aware of and should look for
>> in Ceph OSDs? This is on a 3.8.19 kernel (with Gentoo patches which
>> don't touch BTRFS sources) with btrfs-progs 4.0.1. We have 5 servers on
>> our storage network : 2 are running a 4.0.5 kernel and 3 are running
>> 3.8.19. The 3.8.19 servers are waiting for an opportunity to reboot on
>> 4.0.5 (or better if we have the time to test a more recent kernel before
>> rebooting : 4.1.8 and 4.2.1 are our candidates for testing right now).
> Apparently this isn't the problem : we just had another similar Ceph OSD
> crash without any concurrent defragmentation going on.

However the Ceph developpers confirmed that BTRFS returned an EIO while
reading data from disk. Is there a known bug  in kernel 3.18.9 (sorry
for the initial typo) that could lead to that? I couldn't find any on
the wiki.
The last crash was on a filesystem mounted with these options:

rw,noatime,nodiratime,compress=lzo,space_cache,recovery,autodefrag

Some of the extents have been recompressed to zlib (though at the time
of the crash there was no such activity as I disabled it 2 days before
to simplify diagnostics).

Best regards,

Lionel Bouton