From: Christoph Hellwig <hch@infradead.org>
To: "Daniel Glöckner" <dg@emlix.com>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-block@vger.kernel.org, dm-devel@redhat.com,
Mikulas Patocka <mpatocka@redhat.com>,
Mike Snitzer <snitzer@redhat.com>
Subject: Re: [dm-devel] [PATCH] dm integrity: reinitialize __bi_remaining when reusing bio
Date: Tue, 25 Feb 2020 14:02:54 -0800 [thread overview]
Message-ID: <20200225220254.GA13356@infradead.org> (raw)
In-Reply-To: <a932a297-266e-4dee-f030-40ecbc9899ca@emlix.com>
On Tue, Feb 25, 2020 at 08:54:07PM +0100, Daniel Glöckner wrote:
> bio_reset will reset too many fields. As you can see in the context of
> the diff, dm-integrity expects f.ex. the values modified by bio_advance
> to stay intact and the transfer should of course use the same disk and
> operation.
>
> How about doing the atomic_set in bio_remaining_done (in block/bio.c)
> where the BIO_CHAIN flag is cleared once __bi_remaining hits zero?
> Or is requeuing a bio without bio_reset really a no-go? In that case a
> one-liner won't do...
That tends to add a overhead to the fast path for a rather exotic
case. I'm having a bit of a hard time understanding the dm-integrity
code due to it's annoyingly obsfucated code, but it seems like it
tries to submit a bio again after it came out of a ->end_io handler.
That might have some other problems, but if we only want to paper
over the remaining count a isngle call to bio_inc_remaining might be all
you need.
next prev parent reply other threads:[~2020-02-25 22:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 17:07 [PATCH] dm integrity: reinitialize __bi_remaining when reusing bio Daniel Glöckner
2020-02-25 17:07 ` Daniel Glöckner
2020-02-25 19:12 ` [dm-devel] " Christoph Hellwig
2020-02-25 19:54 ` Daniel Glöckner
2020-02-25 22:02 ` Christoph Hellwig [this message]
2020-02-26 1:22 ` Mike Snitzer
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