From: Mike Snitzer <snitzer@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Eric Sandeen <sandeen@sandeen.net>,
linux-xfs <linux-xfs@vger.kernel.org>,
dm-devel@redhat.com
Subject: Re: error propagation problem on xfs over dm stripe
Date: Wed, 1 Feb 2017 09:33:51 -0500 [thread overview]
Message-ID: <20170201143351.GA18848@redhat.com> (raw)
In-Reply-To: <20170201074249.GA22669@infradead.org>
On Wed, Feb 01 2017 at 2:42am -0500,
Christoph Hellwig <hch@infradead.org> wrote:
> On Tue, Jan 31, 2017 at 09:12:07PM -0600, Eric Sandeen wrote:
> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index 3086da5..3555ba8 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -808,7 +808,9 @@ static void dec_pending(struct dm_io *io, int error)
> > } else {
> > /* done with normal IO or empty flush */
> > trace_block_bio_complete(md->queue, bio, io_error);
> > - bio->bi_error = io_error;
> > + /* don't overwrite or clear existing errors */
> > + if (!bio->bi_error)
> > + bio->bi_error = io_error;
> > bio_endio(bio);
> > }
> > }
> >
> > but Mike was a little uneasy, not knowing for sure how we got here to
> > overwrite this bio's error (hopefully I'm representing his concerns
> > fairly and correctly).
Well that is just it, I'm not seeing how io_error (io->error) can ever
transition from non-zero to zero. And bio->bi_error shouldn't be set
without having first set io->error. But just cause I cannot see it
doesn't change the fact that it is clearly happening to you.
It does concern me that this kind of fundamental error propagation
change is needed. Speaks to a regression. Would be nice to bisect
this.. Eric? ;)
> FYI, what we do both in the XFS buffer cache and the new direct I/O
> code is to use a
>
> cmpxchg(&dio->error, 0, ret);
>
> in a similar situation, which should work here, too.
What is the benefit? Faster than the conditional?
WARNING: multiple messages have this Message-ID (diff)
From: Mike Snitzer <snitzer@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-xfs <linux-xfs@vger.kernel.org>,
dm-devel@redhat.com, Eric Sandeen <sandeen@sandeen.net>
Subject: Re: error propagation problem on xfs over dm stripe
Date: Wed, 1 Feb 2017 09:33:51 -0500 [thread overview]
Message-ID: <20170201143351.GA18848@redhat.com> (raw)
In-Reply-To: <20170201074249.GA22669@infradead.org>
On Wed, Feb 01 2017 at 2:42am -0500,
Christoph Hellwig <hch@infradead.org> wrote:
> On Tue, Jan 31, 2017 at 09:12:07PM -0600, Eric Sandeen wrote:
> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index 3086da5..3555ba8 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -808,7 +808,9 @@ static void dec_pending(struct dm_io *io, int error)
> > } else {
> > /* done with normal IO or empty flush */
> > trace_block_bio_complete(md->queue, bio, io_error);
> > - bio->bi_error = io_error;
> > + /* don't overwrite or clear existing errors */
> > + if (!bio->bi_error)
> > + bio->bi_error = io_error;
> > bio_endio(bio);
> > }
> > }
> >
> > but Mike was a little uneasy, not knowing for sure how we got here to
> > overwrite this bio's error (hopefully I'm representing his concerns
> > fairly and correctly).
Well that is just it, I'm not seeing how io_error (io->error) can ever
transition from non-zero to zero. And bio->bi_error shouldn't be set
without having first set io->error. But just cause I cannot see it
doesn't change the fact that it is clearly happening to you.
It does concern me that this kind of fundamental error propagation
change is needed. Speaks to a regression. Would be nice to bisect
this.. Eric? ;)
> FYI, what we do both in the XFS buffer cache and the new direct I/O
> code is to use a
>
> cmpxchg(&dio->error, 0, ret);
>
> in a similar situation, which should work here, too.
What is the benefit? Faster than the conditional?
next prev parent reply other threads:[~2017-02-01 14:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-01 3:12 error propagation problem on xfs over dm stripe Eric Sandeen
2017-02-01 7:42 ` [dm-devel] " Christoph Hellwig
2017-02-01 7:42 ` Christoph Hellwig
2017-02-01 14:33 ` Mike Snitzer [this message]
2017-02-01 14:33 ` Mike Snitzer
2017-02-01 14:49 ` Christoph Hellwig
2017-02-01 14:49 ` Christoph Hellwig
2017-02-01 10:28 ` [dm-devel] " Junichi Nomura
2017-02-01 10:28 ` Junichi Nomura
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