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[128.59.178.194]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5359b77d0eesm22234701cf.19.2026.10.09.09.50.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Oct 2026 09:50:26 -0700 (PDT) From: Tal Zussman Date: Fri, 09 Oct 2026 12:50:15 -0400 Subject: [PATCH v6 7/9] iomap: reject atomic writes in iomap_file_buffered_write() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261009-blkdev-fixes-v6-7-307939c387df@columbia.edu> References: <20261009-blkdev-fixes-v6-0-307939c387df@columbia.edu> In-Reply-To: <20261009-blkdev-fixes-v6-0-307939c387df@columbia.edu> To: Jens Axboe , Christoph Hellwig , Johannes Thumshirn , Luis Chamberlain , Hannes Reinecke , "Matthew Wilcox (Oracle)" , John Garry , Christian Brauner , "Darrick J. Wong" , Keith Busch , "Martin K. Petersen" Cc: Shin'ichiro Kawasaki , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Tal Zussman X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1791564615; l=1258; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=dQNMb5/wuPELUla+30Ybhb/m9cvIEvZQydg6aWFrln0=; b=WZGuKbqgstXPQfB88htkX6didpQHdTq8xJ1ra6e3bXkVqmC3AAsryMkhYBbhxHoVysg1omLol 13qicZ+RfMGDf2fzWd785at2EVFZXPrUx3L88zIp/oAJyI6/Yv8cEDa X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Authority-Analysis: v=2.4 cv=eaGo7LEH c=1 sm=1 tr=0 ts=6ac91b55 cx=c_pps a=mPf7EqFMSY9/WdsSgAYMbA==:117 a=u0MKzLA9JmpizDwXU9Rxjg==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=x7bEGLp0ZPQA:10 a=A0y_DWxS2BwA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=BpGzv1V74M3SfeTrGa8v:22 a=VwQbUJbxAAAA:8 a=ASVHLkjgWNnnwhGXR8EA:9 a=QEXdDO2ut3YA:10 a=dawVfQjAaf238kedN5IG:22 X-Proofpoint-ORIG-GUID: Ij6Z8nExhQc4cJXHw6dZcm7YPTk1-5fP X-Proofpoint-GUID: Ij6Z8nExhQc4cJXHw6dZcm7YPTk1-5fP X-Proofpoint-Spam-Info: AW1haW4tMjYxMDA5MDA2NyBTYWx0ZWRfX5+O12CTFxphY 9UtvJIg6R/9zoZs5TJXsjsWqFKY/UzCtnvUQnHbLBu5dsUmHih7NWhdIf6UfombJp1VxGjlNcOc D535kJ2FJYt96Sk0c+OZ7SYjKPD0b37byobxHxmJLTF0sWRisfJv X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDA5MDA2NyBTYWx0ZWRfX9v6yI+vaMiec 1PxFJAX7SSnT1Vg2qnVm8EhTQLmrmVrAAAtfszx9RM1NILg1rWtSWmZ3XBogVHqn1R20CPHcxPE 5diuRXmqog/nn7D7rZGdydvXTznzNYLKsYqZOxtUU5JQUN+3qb3rIS2ByWOO8M/cSwYdcI3EMqO 6m0KRQYWGbZAZZI3jwPeHMtod0nOCbuJ64CTDqEZ+GiavZ3McdblJWKlPk4CfXNhsFPlvPGMAtX fmFTAsSL3eTGeFnZwxY2+HSHB1n7JOLrBwBWXWVs4cSvZvGIcU/tuGW8gU+JD9bIylxmibK16C2 zh82W+YbHRz6F2fIb2wvHkcvN0yu4tSaRVlc5VMoOZ4EXcebvaJhKNavw95WEMwSDjJXZL0SdHz tP4Erl2SeV2pH/nvXyH9O9WaNu6gViUWin5kj2b6OcQX6iAKgk1UfPSZI4UCQLcc96YP3DqN0Az YTTwBScr600uhb9b1Xw== X-Proofpoint-Virus-Version: vendor=nai engine=6900 definitions=11930 signatures=596817 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 priorityscore=1501 impostorscore=10 lowpriorityscore=10 malwarescore=0 phishscore=0 bulkscore=10 adultscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610020000 definitions=main-2610090067 Buffered atomic writes are not currently supported. The page cache writes folios back independently, so it cannot guarantee that a range is written atomically. iomap_file_buffered_write() does not check for IOCB_ATOMIC, so a direct write that falls back to it would complete an atomic write without atomicity. While no such case currently exists, fail IOCB_ATOMIC writes with -EOPNOTSUPP, so that a future fallback cannot complete an atomic write non-atomically. Suggested-by: John Garry Reviewed-by: John Garry Reviewed-by: Hannes Reinecke Signed-off-by: Tal Zussman --- fs/iomap/buffered-io.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 0a5ebfda90f1..e6654cfe1cbf 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -1304,6 +1304,10 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i, }; ssize_t ret; + /* Buffered atomic writes are not supported */ + if (iocb->ki_flags & IOCB_ATOMIC) + return -EOPNOTSUPP; + if (iocb->ki_flags & IOCB_NOWAIT) iter.flags |= IOMAP_NOWAIT; if (iocb->ki_flags & IOCB_DONTCACHE) -- 2.39.5