From: Mike Snitzer <snitzer@redhat.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, dm-devel@redhat.com,
Damien Le Moal <damien.lemoal@opensource.wdc.com>
Subject: Re: [PATCH 5/8] dm: always setup ->orig_bio in alloc_io
Date: Tue, 12 Apr 2022 16:52:40 -0400 [thread overview]
Message-ID: <YlXmmB6IO7usz2c1@redhat.com> (raw)
In-Reply-To: <20220412085616.1409626-6-ming.lei@redhat.com>
On Tue, Apr 12 2022 at 4:56P -0400,
Ming Lei <ming.lei@redhat.com> wrote:
> The current DM codes setup ->orig_bio after __map_bio() returns,
> and not only cause kernel panic for dm zone, but also a bit ugly
> and tricky, especially the waiting until ->orig_bio is set in
> dm_submit_bio_remap().
>
> The reason is that one new bio is cloned from original FS bio to
> represent the mapped part, which just serves io accounting.
>
> Now we have switched to bdev based io accounting interface, and we
> can retrieve sectors/bio_op from both the real original bio and the
> added fields of .sector_offset & .sectors easily, so the new cloned
> bio isn't necessary any more.
>
> Not only fixes dm-zone's kernel panic, but also cleans up dm io
> accounting & split a bit.
You're conflating quite a few things here. DM zone really has no
business accessing io->orig_bio (dm-zone.c can just as easily inspect
the tio->clone, because it hasn't been remapped yet it reflects the
io->origin_bio, so there is no need to look at io->orig_bio) -- but
yes I clearly broke things during the 5.18 merge and it needs fixing
ASAP.
But I'm (ab)using io->orig_bio assignment to indicate to completion
that it may proceed. See these dm-5.19 commits to see it imposed even
further:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.19&id=311a8e6650601a79079000466db77386c5ec2abb
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.19&id=56219ebb5f5c84785aa821f755d545eae41bdb1a
And then leveraged here:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.19&id=4aa7a368370c2a172d5a0b8927c6332c4b6a3514
Could be all these dm-5.19 changes suck.. but I do know dm-zone.c is
too tightly coupled to DM core. So I'll focus on that first, fix
5.18, and then circle back to "what's next?".
Mike
next prev parent reply other threads:[~2022-04-12 21:24 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-12 8:56 [PATCH 0/8] dm: io accounting & polling improvement Ming Lei
2022-04-12 8:56 ` [PATCH 1/8] block: replace disk based account with bdev's Ming Lei
2022-04-16 5:57 ` Christoph Hellwig
2022-04-12 8:56 ` [PATCH 2/8] dm: don't pass bio to __dm_start_io_acct and dm_end_io_acct Ming Lei
2022-04-12 8:56 ` [PATCH 3/8] dm: pass 'dm_io' instance to dm_io_acct directly Ming Lei
2022-04-12 20:28 ` Mike Snitzer
2022-04-13 1:43 ` Ming Lei
2022-04-12 8:56 ` [PATCH 4/8] dm: switch to bdev based io accounting interface Ming Lei
2022-04-12 8:56 ` [PATCH 5/8] dm: always setup ->orig_bio in alloc_io Ming Lei
2022-04-12 20:52 ` Mike Snitzer [this message]
2022-04-12 22:38 ` Damien Le Moal
2022-04-12 23:00 ` Mike Snitzer
2022-04-12 23:31 ` Damien Le Moal
2022-04-13 0:00 ` Damien Le Moal
2022-04-13 1:56 ` Ming Lei
2022-04-13 6:12 ` Mike Snitzer
2022-04-13 12:26 ` Ming Lei
2022-04-13 17:58 ` Mike Snitzer
2022-04-14 0:36 ` Ming Lei
2022-04-14 2:25 ` Mike Snitzer
2022-04-14 3:57 ` Ming Lei
2022-04-14 17:45 ` Mike Snitzer
2022-04-15 0:14 ` Ming Lei
2022-04-15 21:06 ` Mike Snitzer
2022-04-17 2:22 ` Ming Lei
2022-04-12 8:56 ` [PATCH 6/8] dm: don't grab target io reference in dm_zone_map_bio Ming Lei
2022-04-12 8:56 ` [PATCH 7/8] dm: improve target io referencing Ming Lei
2022-04-12 8:56 ` [PATCH 8/8] dm: put all polled io into one single list Ming Lei
2022-04-12 17:15 ` [PATCH 0/8] dm: io accounting & polling improvement Mike Snitzer
2022-04-16 5:58 ` Christoph Hellwig
2022-04-17 1:23 ` Mike Snitzer
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