From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>,
linux-fsdevel@vger.kernel.org,
Chris Mason <chris.mason@oracle.com>
Subject: Re: [PATCH] block: fix DISCARD_BARRIER requests
Date: Thu, 17 Jun 2010 18:54:53 +0200 [thread overview]
Message-ID: <20100617165453.GA15824@lst.de> (raw)
In-Reply-To: <4C19D86A.5030709@kernel.dk>
On Thu, Jun 17, 2010 at 10:10:18AM +0200, Jens Axboe wrote:
> Thanks, applied. There was a recent problem report on btrfs using
> discard, could possibly explain it if Chris assumed it was a full
> barrier.
We actually have a much bigger issue with the DISCARD_BARRIER type.
If the discard request needs to get split into multiple smaller ones
we don't keep the queue drained atomically around them, so requests
could sneak inbetween them. Depending on how the realtime discard
is implemented that could cause issues. In my XFS prototype for it
I only deleted the extents from the tracking betree after the discard
request has returned, but other filesystems rely on full barrier
semantics of DISCARD_BARRIER this could cause real problems.
next prev parent reply other threads:[~2010-06-17 16:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-17 7:54 [PATCH] block: fix DISCARD_BARRIER requests Christoph Hellwig
2010-06-17 8:10 ` Jens Axboe
2010-06-17 11:49 ` Matthew Wilcox
2010-06-17 12:06 ` Jens Axboe
2010-06-17 16:54 ` Christoph Hellwig [this message]
2010-06-17 19:22 ` Chris Mason
2010-06-18 13:29 ` Kyungmin Park
2010-06-19 2:22 ` Kyungmin Park
2010-06-18 15:29 ` Jamie Lokier
2010-06-18 20:30 ` Chris Mason
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