From: Jan Kara <jack@suse.cz>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>,
linux-ext4@vger.kernel.org, Eryu Guan <eguan@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/4] ext4: Fix deadlock during page writeback
Date: Mon, 4 Jul 2016 17:47:09 +0200 [thread overview]
Message-ID: <20160704154709.GA12022@quack2.suse.cz> (raw)
In-Reply-To: <20160704152043.GA15193@thunk.org>
On Mon 04-07-16 11:20:43, Ted Tso wrote:
> On Mon, Jul 04, 2016 at 04:00:12PM +0200, Jan Kara wrote:
> > OK, but we do all the block mappings, page locking etc. while the handle is
> > started so it is not exactly a really short lived handle. The patch adds
> > there a submission of a bio (we have the IO plugged so it will just add the
> > bio to the list of submitted bios), unlock locked pages, drop refcount to
> > ioend (unless IO is already completed, only refcount update is done, if IO
> > is completed we defer any real work to workqueue anyway). So although we
> > add some work which is done while the handle is still running, it is not
> > that much.
>
> Good point that the block device is plugged. Ultimately I suspect the
> way to fix the scalability problem will be move to dioread nolock as
> the default, and use separate transaction to map the blocks using the
> uninitialized flags, and then do a separate transaction to convert
> them afterwards.
This is what already happens currently - we only reserve a handle for
conversion during writeback but that reservation fluently moves between
running transactions until a point where the reserved handle is started -
then the handle is pinned to the currently running transaction - and this
happens only in the completion handler after IO is completed.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2016-07-04 15:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 10:42 [PATCH 0/4] ext4: Fix deadlock during page writeback Jan Kara
2016-06-16 10:42 ` [PATCH 1/4] " Jan Kara
2016-06-30 15:05 ` Theodore Ts'o
2016-07-01 9:09 ` Jan Kara
2016-07-01 16:53 ` Theodore Ts'o
2016-07-01 17:40 ` Jan Kara
2016-07-01 21:26 ` Theodore Ts'o
2016-07-04 14:00 ` Jan Kara
2016-07-04 15:20 ` Theodore Ts'o
2016-07-04 15:47 ` Jan Kara [this message]
2016-07-05 2:43 ` Theodore Ts'o
2016-07-06 7:04 ` Jan Kara
2016-07-04 14:14 ` Theodore Ts'o
2016-07-04 15:51 ` Jan Kara
2016-07-05 3:38 ` Theodore Ts'o
2016-07-06 7:51 ` Jan Kara
2016-07-06 12:35 ` Theodore Ts'o
2016-07-06 12:52 ` Jan Kara
2016-07-06 14:27 ` Theodore Ts'o
2016-07-06 14:41 ` Jan Kara
2016-06-16 10:42 ` [PATCH 2/4] jbd2: Move lockdep instrumentation for jbd2 handles Jan Kara
2016-06-30 15:34 ` Theodore Ts'o
2016-06-16 10:42 ` [PATCH 3/4] jbd2: Move lockdep tracking to journal_s Jan Kara
2016-06-16 11:42 ` kbuild test robot
2016-06-30 15:40 ` Theodore Ts'o
2016-06-16 10:42 ` [PATCH 4/4] jbd2: Track more dependencies on transaction commit Jan Kara
2016-06-30 15:45 ` Theodore Ts'o
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