Re: btrfs receive deadlock and questions

From: Eli V <eliventer@gmail.com>
To: fdmanana@gmail.com
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: btrfs receive deadlock and questions
Date: Tue, 22 Jan 2019 11:03:42 -0500	[thread overview]
Message-ID: <CAJtFHUR8G927m1bx3UEgps9-dxPbZh+j4JTvzAn-yqcKRMLfTg@mail.gmail.com> (raw)
In-Reply-To: <CAL3q7H4HsGMLS5mjTLSugQ-YoF-M24Fy6eCEAF9=04g_=A=jFA@mail.gmail.com>

On Tue, Jan 22, 2019 at 10:42 AM Filipe Manana <fdmanana@gmail.com> wrote:
>
> On Tue, Jan 22, 2019 at 3:26 PM Eli V <eliventer@gmail.com> wrote:
> >
> > I seem to have it a deadlock trying out btrfs send & receive. Now I
> > haven't used btrfs send & receive much, so don't have much experience
> > with them. Anyways, bug report and stack traces:
> > https://bugzilla.kernel.org/show_bug.cgi?id=202383
>
> This is the same you reported at:
> https://bugzilla.kernel.org/show_bug.cgi?id=199753
>
> It just happens through a different path, unrelated to send/receive.
> You are running a 4.19.16 kernel, which doesn't have the fix [1]:
>
> $ git tag --contains 5ce555578e0919237fa4bda92b4670e2dd176f85
> v4.20
> v4.20-rc1
> v4.20-rc2
> v4.20-rc3
> v4.20-rc4
> v4.20-rc5
> v4.20-rc6
> v4.20-rc7
> v4.20.1
> v4.20.2
> v4.20.3
> v5.0-rc1
> v5.0-rc2
> v5.0-rc3
>
> All the deadlock problems you reported are fixed by [1] and [2].
> The second, related to the free space tree, is very recent and only on 5.0-rcs:
>
> $ git tag --contains a6d8654d885d7d79a3fb82da64eaa489ca332a82
> v5.0-rc2
> v5.0-rc3
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5ce555578e0919237fa4bda92b4670e2dd176f85
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a6d8654d885d7d79a3fb82da64eaa489ca332a82
>
>

Sounds good, thanks for the links. I thought the stack traces looked
different, thus the 2 different reports. I guess no further info is
needed from the hung tasks and I can start killing it and figuring out
how to resume the process.

> >
> > Seems like the receive is hung as well as several kworkers. It's about
> > 1.2TB into a 9TB or so transfer onto a brand new pretty empty fs. This
> > is just a btrfs send snapshot, not an incremental. That was supposed
> > to come next. If this was an rsync based backup I'd just kill the
> > rsync process and restart it, not sure if there's a way to restart a
> > btrfs send receive, or if I'd have to delete the partially created
> > snapshot on the destination and restart the send. I guess I could just
> > use rsync to finish the copy of the initial snapshot as well before
> > using send | receive for the incrementals. Thoughts and options would
> > be appreciated, thanks.
> >
> > -Eli
>
>
>
> --
> Filipe David Manana,
>
> “Whether you think you can, or you think you can't — you're right.”