From: Brian Foster <bfoster@redhat.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH] xfs: fix shared extent data corruption due to missing cow reservation
Date: Thu, 15 Nov 2018 10:58:12 -0500 [thread overview]
Message-ID: <20181115155812.GA27656@bfoster> (raw)
In-Reply-To: <63420b28-0415-061e-37cd-efe6f6a19f4b@sandeen.net>
On Thu, Nov 15, 2018 at 09:51:58AM -0600, Eric Sandeen wrote:
> On 11/13/18 11:08 AM, Brian Foster wrote:
>
> > For example, a buffered write occurs across the file offset (in FSB
> > units) range of [29, 57]. A shared extent exists at blocks [29, 35]
> > and COW reservation already exists at blocks [32, 34]. After
> > accommodating a COW extent size hint of 32 blocks and the existing
> > reservation at offset 32, xfs_reflink_reserve_cow() allocates 32
> > blocks of reservation at offset 0 and returns with COW reservation
> > across the range of [0, 34]. The associated data fork extent is
> > still [29, 35], however, which isn't fully covered by the COW
> > reservation.
> >
> > This leads to a buffered write at file offset 35 over a shared
> > extent without associated COW reservation. Writeback eventually
> > kicks in, performs an overwrite of the underlying shared block and
> > causes the associated data corruption.
>
> Can you write this in the form of an xfstests reproducer please? :)
>
I'll add it to the todo list.
Brian
> -Eric
next prev parent reply other threads:[~2018-11-16 2:06 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-13 17:08 [PATCH] xfs: fix shared extent data corruption due to missing cow reservation Brian Foster
2018-11-15 5:50 ` Darrick J. Wong
2018-11-15 9:49 ` Christoph Hellwig
2018-11-15 12:33 ` Brian Foster
2018-11-16 4:35 ` Dave Chinner
2018-11-16 13:32 ` Brian Foster
2018-11-16 21:19 ` Dave Chinner
2018-11-17 13:33 ` Brian Foster
2018-11-15 9:50 ` Christoph Hellwig
2018-11-15 15:51 ` Eric Sandeen
2018-11-15 15:58 ` Brian Foster [this message]
2018-11-15 15:59 ` Eric Sandeen
2018-11-15 16:10 ` Brian Foster
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