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[4.53.155.98]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0976ca5f9sm1331613a91.14.2026.09.23.16.56.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 16:56:55 -0700 (PDT) From: Tal Zussman Date: Wed, 23 Sep 2026 19:56:34 -0400 Subject: [PATCH v5 1/9] block: use iomap_dirty_folio for block devices Precedence: bulk X-Mailing-List: linux-block@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-v5-1-89e60d66eb38@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, Sashiko , Tal Zussman X-Mailer: b4 0.17-dev-db0b7 X-Developer-Signature: v=1; a=ed25519-sha256; t=1790207813; l=2128; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=i12hnJ0eqOMt0VRMSQ5nUYBLPvQvZ5w4YLNVMjTdOTI=; b=R1EL1ScX2aVYbpHYS0yrNGfXhtAVJe9OIq3govPDMYOK98H2vXi5VkQ/PuISAl9x0AynVtyKf yFgkE1ENpDOAsxbyiP9gCJJi+T6K0FFxraeu19m6jAssaHCY+Vpo7jV X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIzMDEwMCBTYWx0ZWRfXx3OtWtkhMqBj Cr3YjyGiP6FSBVYnV4bUOU80D2uXcGbkjMxOznCoiaqN+c+v6Szsk53+YszQZxHXl+bh/6bpQsn M78hOSZKr3RGObPMjiCqdsLrtI9TOhFTZRqtDFKaFHnFGrrL/jEJpF54ujRaMYkg8ToceROY4yq WcPgUnWtNHkU5iqTiBLj4SF4QvfKImGX3lmzuxDJDb3L0r54lple3njeNwdnAtyzszCscCLAKe4 gi558cRif4Y/7P27z0crXUJIIFTRfbgfonOWExZTFzdkIy7h8gFnCLOjzY+HgF0QLmO0XBFXYd/ LmG7MavQfTVF8g3wnnhSNcWmyIxruY+VXuZHT/9xI82eDsuP1EoEND6tXfKIA8oLLJNZRb3XmPN PldDjS4JBpaXYEhy3/xuLHBJvYE/ZE45X409MGyTppqWKL3VIu2rNsi4Fw8+KH0wywUs4R1MJ9u 8RiQR/kgnuBpR37de3w== X-Proofpoint-GUID: rMRt9_V2pdY4KYOVv4_9IaC3DZKabTKw X-Proofpoint-ORIG-GUID: rMRt9_V2pdY4KYOVv4_9IaC3DZKabTKw X-Authority-Analysis: v=2.4 cv=LtYHWXdc c=1 sm=1 tr=0 ts=6ab46749 cx=c_pps a=vVfyC5vLCtgYJKYeQD43oA==: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=SsB-OO3BMngHh3ZO9fOt:22 a=NEAV23lmAAAA:8 a=c92rfblmAAAA:8 a=VwQbUJbxAAAA:8 a=lHyHCDWJ2e6pF_oXpYUA:9 a=QEXdDO2ut3YA:10 a=rl5im9kqc5Lf4LNbBjHf:22 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIzMDEwMCBTYWx0ZWRfX4EYhxeV65Ygo /0k+7CLkIuPug/k+AYg+IzgJ4KZLF32MpOlUKJ1mTZmajPOtUiPjRYWCacd+loqJPaq2DLag6hx 7RSzgh4LgvmRG1gJaptxoJOnV/njfcOQ/UV3h9n76rdEmkAmhxmx X-Proofpoint-Virus-Version: vendor=nai engine=6900 definitions=11914 signatures=596817 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 suspectscore=0 spamscore=0 lowpriorityscore=10 clxscore=1015 malwarescore=0 bulkscore=10 adultscore=0 impostorscore=10 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609230100 With CONFIG_BUFFER_HEAD=n, block devices are written back through iomap, but def_blk_aops uses filemap_dirty_folio, which only sets PG_dirty. It does not set the per-block dirty bits in the folio's iomap_folio_state, so iomap_writeback_folio() finds no dirty range, submits no I/O and clears PG_dirty, resulting in data loss. Other iomap users set .dirty_folio to iomap_dirty_folio, which marks the folio's blocks dirty before calling filemap_dirty_folio(). This is only observable with block size < folio size. With a single block there is no iomap_folio_state to get out of sync and iomap_writeback_folio() marks the whole folio dirty itself. For a page-aligned device, this may require using the BLKBSZSET ioctl to set the block size, which requires CAP_SYS_ADMIN. A device whose size is not page aligned already gets a sub-page block size from set_init_blocksize(), so no ioctl and no privilege is needed. To reproduce, on a device with a sub-page block size, write a known pattern with O_DIRECT, mmap the same range, store to it, msync() and fsync(), then read it back with O_DIRECT. A reproducer is available at [1]. [1] https://gist.github.com/tzussman/18ab05cba4b3fdc79cce0a69d1fd05b4 Fixes: 925c86a19bac ("fs: add CONFIG_BUFFER_HEAD") Reported-by: Sashiko Link: https://sashiko.dev/#/patchset/20260730-blk-dontcache-v7-0-3e8e6850068d%40columbia.edu?part=5 Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Signed-off-by: Tal Zussman --- block/fops.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/fops.c b/block/fops.c index c915ec0126d7..8d74d0e57f43 100644 --- a/block/fops.c +++ b/block/fops.c @@ -565,7 +565,7 @@ static int blkdev_writepages(struct address_space *mapping, } const struct address_space_operations def_blk_aops = { - .dirty_folio = filemap_dirty_folio, + .dirty_folio = iomap_dirty_folio, .release_folio = iomap_release_folio, .invalidate_folio = iomap_invalidate_folio, .read_folio = blkdev_read_folio, -- 2.39.5