From: Jan Kara <jack@suse.cz>
To: Tejun Heo <tj@kernel.org>
Cc: Jan Kara <jack@suse.cz>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Dmitry Vyukov <dvyukov@google.com>, Jens Axboe <axboe@kernel.dk>,
syzbot <syzbot+4a7438e774b21ddd8eca@syzkaller.appspotmail.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>,
linux-block@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] bdi: Fix another oops in wb_workfn()
Date: Mon, 18 Jun 2018 14:27:29 +0200 [thread overview]
Message-ID: <20180618122729.f5gh7nuaibuvf3e7@quack2.suse.cz> (raw)
In-Reply-To: <20180615120620.uyc7h6sudbpsecnm@quack2.suse.cz>
On Fri 15-06-18 14:06:20, Jan Kara wrote:
> On Wed 13-06-18 07:33:15, Tejun Heo wrote:
> > Hello, Jan.
> >
> > On Tue, Jun 12, 2018 at 05:57:54PM +0200, Jan Kara wrote:
> > > > Yeah, right, so the root cause is that we're walking the wb_list while
> > > > holding lock and expecting the object to stay there even after lock is
> > > > released. Hmm... we can use a mutex to synchronize the two
> > > > destruction paths. It's not like they're hot paths anyway.
> > >
> > > Hmm, do you mean like having a per-bdi or even a global mutex that would
> > > protect whole wb_shutdown()? Yes, that should work and we could get rid of
> > > WB_shutting_down bit as well with that. Just it seems a bit strange to
> >
> > Yeap.
> >
> > > introduce a mutex only to synchronize these two shutdown paths - usually
> > > locks protect data structures and in this case we have cgwb_lock for
> > > that so it looks like a duplication from a first look.
> >
> > Yeah, I feel a bit reluctant too but I think that's the right thing to
> > do here. This is an inherently weird case where there are two ways
> > that an object can go away with the immediate drain requirement from
> > one side. It's not a hot path and the dumber the synchronization the
> > better, right?
>
> Yeah, fair enough. Something like attached patch? It is indeed considerably
> simpler than fixing synchronization using WB_shutting_down. This one even
> got some testing using scsi_debug, I want to do more testing next week with
> more cgroup writeback included.
OK, the test has passed some beating with cgroup writeback running. I'll do
official posting shortly.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2018-06-18 12:27 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-26 9:15 general protection fault in wb_workfn (2) syzbot
2018-05-27 0:47 ` Tetsuo Handa
2018-05-27 2:21 ` [PATCH] bdi: Fix another oops in wb_workfn() Tetsuo Handa
2018-05-27 2:36 ` Tejun Heo
2018-05-28 13:35 ` general protection fault in wb_workfn (2) Jan Kara
2018-05-30 16:00 ` Tetsuo Handa
2018-05-31 11:42 ` Jan Kara
2018-05-31 13:19 ` Tetsuo Handa
2018-05-31 13:42 ` Jan Kara
2018-05-31 16:56 ` Jens Axboe
2018-06-05 13:45 ` Tetsuo Handa
2018-06-07 18:46 ` Dmitry Vyukov
2018-06-08 2:31 ` Tetsuo Handa
2018-06-08 14:45 ` Dmitry Vyukov
2018-06-08 15:16 ` Dmitry Vyukov
2018-06-08 16:53 ` Dmitry Vyukov
2018-06-08 17:14 ` Dmitry Vyukov
2018-06-09 5:30 ` Tetsuo Handa
2018-06-09 14:00 ` [PATCH] bdi: Fix another oops in wb_workfn() Tetsuo Handa
2018-06-11 9:12 ` Jan Kara
2018-06-11 16:01 ` Tejun Heo
2018-06-11 16:29 ` Jan Kara
2018-06-11 17:20 ` Tejun Heo
2018-06-12 15:57 ` Jan Kara
2018-06-13 10:43 ` Tetsuo Handa
2018-06-13 11:51 ` Tetsuo Handa
2018-06-13 14:06 ` Linus Torvalds
2018-06-13 14:46 ` Jan Kara
2018-06-13 14:55 ` Linus Torvalds
2018-06-13 16:20 ` Tetsuo Handa
2018-06-13 16:25 ` Linus Torvalds
2018-06-13 16:45 ` Jan Kara
2018-06-13 21:04 ` Tetsuo Handa
2018-06-14 10:11 ` Jan Kara
2018-06-13 14:33 ` Tejun Heo
2018-06-15 12:06 ` Jan Kara
2018-06-18 12:27 ` Jan Kara [this message]
2018-06-01 2:30 ` general protection fault in wb_workfn (2) Dave Chinner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180618122729.f5gh7nuaibuvf3e7@quack2.suse.cz \
--to=jack@suse.cz \
--cc=axboe@kernel.dk \
--cc=david@fromorbit.com \
--cc=dvyukov@google.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=syzbot+4a7438e774b21ddd8eca@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=tj@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).