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[128.59.178.194]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5359b77d0eesm22234701cf.19.2026.10.09.09.50.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Oct 2026 09:50:18 -0700 (PDT) From: Tal Zussman Date: Fri, 09 Oct 2026 12:50:09 -0400 Subject: [PATCH v6 1/9] block: use iomap_dirty_folio for block devices 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-v6-1-307939c387df@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, Sashiko , Tal Zussman X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1791564615; l=2128; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=QWCjvSArrnPRtD+0j04CDKUtmIxaPixLlth1E/uEyZQ=; b=qMLmvZeuSixOMS38x6EmKAp4mC0Z6ytGiXLIW869jZX/sxWmXGZmFtbD16FIcyMxeAhASjd36 cYbRlGpBwoXDkw8TKIZpbqkBpJXceSkdRkCWwmS9nmmdt9xDp92Ohvj X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Proofpoint-Spam-Info: AW1haW4tMjYxMDA5MDA2NyBTYWx0ZWRfXzp7KwSedjdsk ieP2hlyR9gO/RsbSNmiII0SUpPTt/emopPyTT+aBdD62l01S2cI+0erxm+Vl9C3ru7uAXMxOe8u H1/RSXgcgxb8EHU7MaOCDpebRtsI0i2DtlEfoDdYmVYGRn7SMlT6 X-Proofpoint-ORIG-GUID: bhifgWBqFsuTJngHPppjDr1FDj2HheFy X-Proofpoint-GUID: bhifgWBqFsuTJngHPppjDr1FDj2HheFy X-Authority-Analysis: v=2.4 cv=JaUpPkKV c=1 sm=1 tr=0 ts=6ac91b4c 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=svvvyxlR1OQQkelhaPoB:22 a=NEAV23lmAAAA:8 a=c92rfblmAAAA:8 a=VwQbUJbxAAAA:8 a=lHyHCDWJ2e6pF_oXpYUA:9 a=QEXdDO2ut3YA:10 a=dawVfQjAaf238kedN5IG:22 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDA5MDA2NyBTYWx0ZWRfXwjxhVQFOHTbM 0WrilhUq6DUUyYfYrWtr5DlhQ2O34LvG8vaDKFUfKGCgLkakX2u5KbpeSN5IOlrE1kgiV3mob/G 7Nee4LJVQiDfGJaDDwJmbn58zdnLqf5SdJbn+3/CPWdXYRrjqjdhexSCZpCDnCP/ldJzB9/S8j3 pyv2YCvVg1fzgQLffncMVU17w5/2tnm17XAWbjZrsYJmAM6mBw8TF0IrHNtRpQJiNfKHCYc/KSz oIZ+hCadOgj9dHUF06bkJ2fhR4N8FxFo8p1v5EqZDu3/PEmR278TamuzMKRWCAE4iDJJa9Q4RQ/ jNUMqRa+2fUI5gOrkkuho3h9M+jKsoYZSB/Tu93qJ81Abv5A4xRdJOyKdlIzh+z5sxE7ZLyCsqJ VkU0MhE0yI/SKEr2Qf0nlipeyboENp9rvBIIMTQgHCcLXjbfM2DV9eNpxuwzTEHVpFnm4zog0oB N4mNjthLve/nB0T8sRA== X-Proofpoint-Virus-Version: vendor=nai engine=6900 definitions=11930 signatures=596817 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=10 suspectscore=0 bulkscore=10 spamscore=0 clxscore=1015 phishscore=0 lowpriorityscore=10 priorityscore=1501 malwarescore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610020000 definitions=main-2610090067 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 b917bc0f6b44..5a559fcfadf9 100644 --- a/block/fops.c +++ b/block/fops.c @@ -575,7 +575,7 @@ 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