From: Oleg Nesterov <oleg@redhat.com>
To: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>,
Nikolay Borisov <kernel@kyup.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths
Date: Tue, 27 Sep 2016 19:29:01 +0200 [thread overview]
Message-ID: <20160927172901.GA11879@redhat.com> (raw)
In-Reply-To: <20160927065135.GA1139@quack2.suse.cz>
On 09/27, Jan Kara wrote:
>
> On Mon 26-09-16 18:55:25, Oleg Nesterov wrote:
> >
> > Heh ;) if only I knew how to test this... I ran the following script
> > under qemu
> >
> > mkfs.xfs -f /dev/vda
> > mkfs.xfs -f /dev/vdb
> >
> > mkdir -p TEST SCRATCH
> >
> > TEST_DEV=/dev/vda TEST_DIR=TEST SCRATCH_DEV=/dev/vdb SCRATCH_MNT=SCRATCH \
> > ./check `grep -il freeze tests/*/???`
>
> You can run either:
>
> ./check -g freeze
passed all 6 tests.
> to check just the freezing tests or
>
> ./check
>
> to run all sensible tests which is what I'd do (but it will take couple of
> hours to pass). If that passes, chances are good there are no easy false
> positives.
It seems that generic/001 just hangs on my laptop. With or without this change.
Or perhaps I didn't wait enough... Or perhaps something is wrong with my very
limited testing environment. I'll reserve a testing machine tomorrow.
> > And yes, I'm afraid this change can uncover some false positives later.
> > But at the same time potentially it can find the real problems.
>
> Well, sure it's not an end of world if there is some false positive - we
> can just revert the change - but lockdep false positives are always
> annoying because they take time to analyze and until they are fixed, you
> are unable to see other probles found by lockdep...
Yes, yes, agreed.
> > It would be nice to remove another hack in __sb_start_write under
> > ifdef(CONFIG_LOCKDEP), but iirc XFS actually takes the same rw_sem twice
> > for reading, so we can't do this.
>
> Yes, and I don't really consider this a hack.
Ah, sorry, I didn't try to blame XFS/fs. I meant, this "force_trylock" hack
doesn't look nice. Perhaps we can use rwsem_acquire_nest() instead.
> Reviewed-by: Jan Kara <jack@suse.cz>
Thanks!
Oleg.
next prev parent reply other threads:[~2016-09-27 17:29 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 16:07 [PATCH 0/2] (Was: BUG_ON in rcu_sync_func triggered) Oleg Nesterov
2016-09-26 16:07 ` [PATCH 1/2] fs/super.c: fix race between freeze_super() and thaw_super() Oleg Nesterov
2016-09-26 16:11 ` Jan Kara
2016-09-26 16:08 ` [PATCH 2/2] fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths Oleg Nesterov
2016-09-26 16:18 ` Jan Kara
2016-09-26 16:55 ` [PATCH V2 " Oleg Nesterov
2016-09-27 6:51 ` Jan Kara
2016-09-27 7:14 ` Dave Chinner
2016-09-27 17:29 ` Oleg Nesterov [this message]
2016-09-30 17:14 ` Oleg Nesterov
2016-10-02 21:42 ` Dave Chinner
2016-10-03 16:44 ` Oleg Nesterov
2016-10-04 11:43 ` Oleg Nesterov
2016-10-04 11:48 ` Michal Hocko
2016-10-06 13:44 ` Johannes Weiner
2016-10-07 16:52 ` Oleg Nesterov
2016-10-04 16:58 ` Oleg Nesterov
2016-10-04 20:03 ` Dave Chinner
2016-10-05 16:33 ` Oleg Nesterov
2016-10-04 19:44 ` Dave Chinner
2016-10-05 16:44 ` Oleg Nesterov
2016-10-06 7:27 ` Jan Kara
2016-10-06 17:17 ` Oleg Nesterov
2016-10-06 21:59 ` Dave Chinner
2016-10-07 17:15 ` Oleg Nesterov
2016-10-07 22:52 ` Dave Chinner
2016-10-09 16:14 ` Oleg Nesterov
2016-10-10 1:02 ` Dave Chinner
2016-10-13 16:58 ` Oleg Nesterov
2016-10-13 17:10 ` [PATCH 0/2] (Was: BUG_ON in rcu_sync_func triggered) Oleg Nesterov
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