From: Vladimir Panteleev <thecybershadow@gmail.com>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>, linux-btrfs@vger.kernel.org
Subject: Re: "kernel BUG" and segmentation fault with "device delete"
Date: Sat, 20 Jul 2019 10:59:23 +0000 [thread overview]
Message-ID: <811c2c41-e795-9562-0e8b-033b404bf43d@gmail.com> (raw)
In-Reply-To: <4a7c1c7b-bc1e-4aba-7a9d-581c0272aa86@gmx.com>
Hi,
I've done a few experiments and here are my findings.
First I probably should describe the filesystem: it is a snapshot
archive, containing a lot of snapshots for 4 subvolumes, totaling 2487
subvolumes/snapshots. There are also a few files (inside the snapshots)
that are probably very fragmented. This is probably what causes the bug.
Observations:
- If I delete all snapshots, the bug disappears (device delete succeeds).
- If I delete all but any single subvolume's snapshots, the bug disappears.
- If I delete one of two subvolumes' snapshots, the bug disappears, but
stays if I delete one of the other two subvolumes' snapshots.
It looks like two subvolumes' snapshots' data participates in causing
the bug.
In theory, I guess it would be possible to reduce the filesystem to the
minimal one causing the bug by iteratively deleting snapshots / files
and checking if the bug manifests, but it would be extremely
time-consuming, probably requiring weeks.
Anything else I can do to help diagnose / fix it? Or should I just order
more HDDs and clone the RAID10 the right way?
On 06/07/2019 05.51, Qu Wenruo wrote:
>
>
> On 2019/7/6 下午1:13, Vladimir Panteleev wrote:
> [...]
>>> I'm not sure if it's the degraded mount cause the problem, as the
>>> enospc_debug output looks like reserved/pinned/over-reserved space has
>>> taken up all space, while no new chunk get allocated.
>>
>> The problem happens after replace-ing the missing device (which succeeds
>> in full) and then attempting to remove it, i.e. without a degraded mount.
>>
>>> Would you please try to balance metadata to see if the ENOSPC still
>>> happens?
>>
>> The problem also manifests when attempting to rebalance the metadata.
>
> Have you tried to balance just one or two metadata block groups?
> E.g using -mdevid or -mvrange?
>
> And did the problem always happen at the same block group?
>
> Thanks,
> Qu
>>
>> Thanks!
>>
>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2019-07-20 10:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-05 4:39 "kernel BUG" and segmentation fault with "device delete" Vladimir Panteleev
2019-07-05 7:01 ` Vladimir Panteleev
2019-07-05 9:42 ` Andrei Borzenkov
2019-07-05 10:20 ` Vladimir Panteleev
2019-07-05 21:48 ` Chris Murphy
2019-07-05 22:04 ` Chris Murphy
2019-07-05 21:43 ` Chris Murphy
2019-07-06 0:05 ` Vladimir Panteleev
2019-07-06 2:38 ` Chris Murphy
2019-07-06 3:37 ` Vladimir Panteleev
2019-07-06 17:36 ` Chris Murphy
2019-07-06 5:01 ` Qu Wenruo
2019-07-06 5:13 ` Vladimir Panteleev
2019-07-06 5:51 ` Qu Wenruo
2019-07-06 15:09 ` Vladimir Panteleev
2019-07-20 10:59 ` Vladimir Panteleev [this message]
2019-08-08 20:40 ` Vladimir Panteleev
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