From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 12 Oct 2018 11:16:16 +1100 From: Dave Chinner To: "Darrick J. Wong" Cc: sandeen@redhat.com, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, ocfs2-devel@oss.oracle.com Subject: Re: [PATCH 05/25] vfs: avoid problematic remapping requests into partial EOF block Message-ID: <20181012001615.GR6311@dastard> References: <153923113649.5546.9840926895953408273.stgit@magnolia> <153923117420.5546.13317703807467393934.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <153923117420.5546.13317703807467393934.stgit@magnolia> Sender: owner-linux-mm@kvack.org List-ID: On Wed, Oct 10, 2018 at 09:12:54PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong > > A deduplication data corruption is exposed by fstests generic/505 on > XFS. It is caused by extending the block match range to include the > partial EOF block, but then allowing unknown data beyond EOF to be > considered a "match" to data in the destination file because the > comparison is only made to the end of the source file. This corrupts the > destination file when the source extent is shared with it. > > The VFS remapping prep functions only support whole block dedupe, but > we still need to appear to support whole file dedupe correctly. Hence > if the dedupe request includes the last block of the souce file, don't > include it in the actual dedupe operation. If the rest of the range > dedupes successfully, then reject the entire request. A subsequent > patch will enable us to shorten dedupe requests correctly. Ok, so this patch rejects whole file dedupe requests, and then a later patch adds support back in for it? Doesn't that leave a bisect landmine behind? Why separate the functionality like this? Cheers, Dave. -- Dave Chinner david@fromorbit.com