From: Christoph Hellwig <hch@lst.de>
To: Brian Foster <bfoster@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, xfs@oss.sgi.com
Subject: Re: [PATCH 3/3] xfs: optimize bio handling in the buffer writeback path
Date: Fri, 11 Mar 2016 16:06:06 +0100 [thread overview]
Message-ID: <20160311150606.GA3016@lst.de> (raw)
In-Reply-To: <20160304133854.GB3758@bfoster.bfoster>
On Fri, Mar 04, 2016 at 08:38:55AM -0500, Brian Foster wrote:
> One thing I'm a bit suspicious about still is whether the error
> propagation is racy. For example, consider we've created two chained
> bios A and B, such that A is the parent and thus bio(io_remaining) for
> each is A(2) and B(1). Suppose bio A happens to complete first with an
> error. A->bi_error is set and bio_endio(A) is called, which IIUC
> basically just does A(2)->A(1). If bio B completes successfully,
> B->bi_error presumably remains set to 0 and bio_endio(B) is called. The
> latter checks that B->bi_end_io == bio_chain_endio, propagates
> B->bi_error to A->bi_error unconditionally and then walks up to the
> parent bio to drop its reference and finally call A->bi_end_io().
>
> Doesn't this mean that we can potentially lose errors in the chain? I
> could easily still be missing something here...
Yes, it looks like bio_chain_endio and bio_endio should be fixed
to only set parent->bi_error if it's not already set. I'll send a
patch.
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next prev parent reply other threads:[~2016-03-11 15:06 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 8:20 futher writeback updates Christoph Hellwig
2016-02-24 8:20 ` [PATCH 1/3] xfs: build bios directly in xfs_add_to_ioend Christoph Hellwig
2016-03-03 15:17 ` Brian Foster
2016-02-24 8:20 ` [PATCH 2/3] xfs: don't release bios on completion immediately Christoph Hellwig
2016-03-03 15:17 ` Brian Foster
2016-03-11 14:47 ` Christoph Hellwig
2016-03-11 17:52 ` Brian Foster
2016-02-24 8:20 ` [PATCH 3/3] xfs: optimize bio handling in the buffer writeback path Christoph Hellwig
2016-03-03 15:17 ` Brian Foster
2016-03-04 13:38 ` Brian Foster
2016-03-11 15:06 ` Christoph Hellwig [this message]
2016-03-11 14:55 ` Christoph Hellwig
2016-03-01 13:01 ` futher writeback updates Christoph Hellwig
2016-03-01 21:42 ` Dave Chinner
-- strict thread matches above, loose matches on Subject: below --
2016-03-16 11:44 further writeback updates V2 Christoph Hellwig
2016-03-16 11:44 ` [PATCH 3/3] xfs: optimize bio handling in the buffer writeback path Christoph Hellwig
2016-03-17 13:05 ` Brian Foster
2016-05-31 15:35 ` Eric Sandeen
2016-05-31 16:31 ` Christoph Hellwig
2016-05-31 16:44 ` Eric Sandeen
2016-05-31 17:35 ` Eric Sandeen
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