From: Roman Mamedov <rm@romanrm.net>
To: nexus@smoula.net
Cc: linux-btrfs@vger.kernel.org
Subject: Re: ENOSPC while creating snapshot
Date: Sat, 5 Mar 2016 03:49:10 +0500 [thread overview]
Message-ID: <20160305034910.576d2230@natsu> (raw)
In-Reply-To: <c2e396477401f3441bdc364456b399f4@smoula.net>
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On Fri, 04 Mar 2016 22:10:57 +0100
nexus@smoula.net wrote:
> Hello,
>
> I'm encountering weird enospc problem while writing to filesystem and
> creating snapshot at a same time:
>
> Steps to reproduce:
>
> start writing data to filesystem:
>
> # LC_ALL=C dd if=/dev/zero of=/foobar
> dd: writing to '/foobar': No space left on device
> 3003803+0 records in
> 3003802+0 records out
> 1537946624 bytes (1.5 GB, 1.4 GiB) copied, 10.8072 s, 142 MB/s
>
> in other terminal create read-only (or r/w - results are the same)
> # btrfs sub snap -r / /.snap1
> Create a readonly snapshot of '/' in '//.snap1'
>
> while creating this snapshot, ENOSPC is produced.
>
> Interesting is that I can reproduce this on some filesystems but not on
> others while all of available information are the same. There IS free
> space in data, metadata and global reserve.
>
> I've tried balancing and defragmenting with no success. I've tried
> debugging by using enospc_debug but nothing is written to dmesg or any
> system log
>
> Does anybody have a clue what may be the cause?
>
> # uname -a
> Linux interceptor 4.4.3-1-ARCH #1 SMP PREEMPT Fri Feb 26 15:09:29 CET
> 2016 x86_64 GNU/Linux
As you use the nodatacow mount option, this seems to be another case of
http://www.spinics.net/lists/linux-btrfs/msg51276.html
http://www.spinics.net/lists/linux-btrfs/msg51819.html
and is fixed by
https://patchwork.kernel.org/patch/7967161/
Unfortunately the bug is known since the start of the 4.4 series and the patch
is out for 2 months, but it didn't get included into even 4.4.4 released
recently. You have to apply it by yourself and recompile the kernel.
--
With respect,
Roman
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next prev parent reply other threads:[~2016-03-04 22:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-04 21:10 ENOSPC while creating snapshot nexus
2016-03-04 22:37 ` Chris Murphy
[not found] ` <CAJ88j0axsFA3HFc6Cr5o-dtYxLau_iDS2Mx2uVzKvF5HCe9F5Q@mail.gmail.com>
2016-03-05 2:46 ` Chris Murphy
2016-03-05 5:34 ` Duncan
2016-03-05 10:24 ` Martin Mlynář
2016-03-04 22:49 ` Roman Mamedov [this message]
2016-03-05 2:09 ` Duncan
2016-03-05 10:46 ` Filipe Manana
2016-03-05 12:29 ` Martin Mlynář
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