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[49.180.184.88]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-746d5c642f7sm45212b3a.3.2025.05.27.16.52.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 May 2025 16:52:03 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.98.2) (envelope-from ) id 1uK45Q-00000008zYO-2o3v; Wed, 28 May 2025 09:52:00 +1000 Date: Wed, 28 May 2025 09:52:00 +1000 From: Dave Chinner To: Jens Axboe Cc: Christian Brauner , "Darrick J. Wong" , "linux-xfs@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" Subject: Re: [PATCH v2] iomap: don't lose folio dropbehind state for overwrites Message-ID: References: <5153f6e8-274d-4546-bf55-30a5018e0d03@kernel.dk> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5153f6e8-274d-4546-bf55-30a5018e0d03@kernel.dk> On Tue, May 27, 2025 at 05:01:31PM -0600, Jens Axboe wrote: > DONTCACHE I/O must have the completion punted to a workqueue, just like > what is done for unwritten extents, as the completion needs task context > to perform the invalidation of the folio(s). However, if writeback is > started off filemap_fdatawrite_range() off generic_sync() and it's an > overwrite, then the DONTCACHE marking gets lost as iomap_add_to_ioend() > don't look at the folio being added and no further state is passed down > to help it know that this is a dropbehind/DONTCACHE write. > > Check if the folio being added is marked as dropbehind, and set > IOMAP_IOEND_DONTCACHE if that is the case. Then XFS can factor this into > the decision making of completion context in xfs_submit_ioend(). > Additionally include this ioend flag in the NOMERGE flags, to avoid > mixing it with unrelated IO. > > Since this is the 3rd flag that will cause XFS to punt the completion to > a workqueue, add a helper so that each one of them can get appropriately > commented. > > This fixes extra page cache being instantiated when the write performed > is an overwrite, rather than newly instantiated blocks. > > Fixes: b2cd5ae693a3 ("iomap: make buffered writes work with RWF_DONTCACHE") > Signed-off-by: Jens Axboe LGTM. Reviewed-by: Dave Chinner -- Dave Chinner david@fromorbit.com