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[4.53.155.98]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0976ca5f9sm1331613a91.14.2026.09.23.16.57.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 16:57:04 -0700 (PDT) From: Tal Zussman Date: Wed, 23 Sep 2026 19:56:40 -0400 Subject: [PATCH v5 7/9] iomap: reject atomic writes in iomap_file_buffered_write() Precedence: bulk X-Mailing-List: linux-xfs@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: <20260923-blkdev-fixes-v5-7-89e60d66eb38@columbia.edu> References: <20260923-blkdev-fixes-v5-0-89e60d66eb38@columbia.edu> In-Reply-To: <20260923-blkdev-fixes-v5-0-89e60d66eb38@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-db0b7 X-Developer-Signature: v=1; a=ed25519-sha256; t=1790207813; l=1162; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=eekIRUkO6xctJzh0LDxpTW7f45r0xCkvZKYTjeZsvDw=; b=2YSDeglgyk07rr4XCceLzHJrMpahC9wn5HyPBCzFyGWpB4A7Jm0LwTpK53X+wg/uOg2P5jPVn EO951ZjrUh1C4yifGSMaj539bji3K60vVy92ozbmJFDFa2hZoDofx44 X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIzMDEwMCBTYWx0ZWRfX6JnkZgCvlAeI NMo63EBr11piQqGKqvo0xbmsLsX13laVRpGq3YK0lzIE20Uj0ZOgkbLdFKhahYNxjgPzu1OO+WO Ix4lNcl/um8bISasX13P5AnbYc19AJEEkQQ4UgLJ2J0DSneTAx2E X-Proofpoint-ORIG-GUID: n2XqOsNhvrDlomL2oFWVNl-isTcEiwqG X-Authority-Analysis: v=2.4 cv=cPp1IVeN c=1 sm=1 tr=0 ts=6ab46752 cx=c_pps a=0uOsjrqzRL749jD1oC5vDA==:117 a=6aZ3Ysb2zzbY2sELL/OBJw==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=x7bEGLp0ZPQA:10 a=A0y_DWxS2BwA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=G--0XuH5328wxK7v7Suf:22 a=ASVHLkjgWNnnwhGXR8EA:9 a=QEXdDO2ut3YA:10 a=mQ_c8vxmzFEMiUWkPHU9:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIzMDEwMCBTYWx0ZWRfX7bvpgG4z/yi8 ZzyELGde3rCGDBxfWoc+oA1xEg8G1WqPOxfiQc0G8Ac96l0/27IPAtYgmaJ+00co+lTQX9aG4yK YMIaDIvLZrEU+U3hgjsC/iwLZSdC1PJvMhFln6Vz2PsxILq56CZhrw1halTOOAM9vgTMv08vWwv HkgL5l0Mu/zzm8gFdvCUJBMK1numwOqNlMw8fh9P3N5M1OY2YmTUNRnJq6F5jJZHfTLPPfBJsTA pkriDODXzrAf2vF3aq6hHrRb370hb4Ky6IqSlvwSYUK7vm3y1yF9gNdCA+cnfF3W5Ck75rwuxKk vOrKdtmv1EqoEv0OidHFmFwqMBNhY84ZeYDom1QcnmvJgf0fky0WLStWtopHXxoieWvllHRjjkM APPOEfIPL1Jc8duJhFUVisba2Ph1qYSVsgRDrOcDbNRCuWh0I+EAkXZiYbzrtsUis4+gYiRTlpD su4gQvkx5WxsHVppHHQ== X-Proofpoint-GUID: n2XqOsNhvrDlomL2oFWVNl-isTcEiwqG X-Proofpoint-Virus-Version: vendor=nai engine=6900 definitions=11914 signatures=596817 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 impostorscore=10 priorityscore=1501 adultscore=0 phishscore=0 bulkscore=10 clxscore=1015 lowpriorityscore=10 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609230100 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 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