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[160.39.33.242]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-899c716caebsm46535886d6.15.2026.02.27.08.41.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Feb 2026 08:41:27 -0800 (PST) From: Tal Zussman Date: Fri, 27 Feb 2026 11:41:08 -0500 Subject: [PATCH RFC v3 2/2] block: enable RWF_DONTCACHE 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: <20260227-blk-dontcache-v3-2-cd309ccd5868@columbia.edu> References: <20260227-blk-dontcache-v3-0-cd309ccd5868@columbia.edu> In-Reply-To: <20260227-blk-dontcache-v3-0-cd309ccd5868@columbia.edu> To: "Matthew Wilcox (Oracle)" , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Jens Axboe , Alexander Viro , Christian Brauner , Jan Kara Cc: Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Tal Zussman X-Mailer: b4 0.14.3-dev-d7477 X-Developer-Signature: v=1; a=ed25519-sha256; t=1772210483; l=4224; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=8jgmldQQbiZzzlvIZlNR4V+9tVlk4w4gZb+9NNCt4y8=; b=vm0JkGcE+Uz0XFcsWwyvUOREbVMTCc75ksaV58G85KW5Z1ue6w4/8TqYICgOvWLed9AR0ZKdg MXRWrkfiaqjDOu1E1bJGDUJ5l8zmf/6G8O+4wBj6LctSBz2MF/pSI8J X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Proofpoint-GUID: aP-22-0ymSdj6beMMvriRll7wme-4hQF X-Proofpoint-ORIG-GUID: aP-22-0ymSdj6beMMvriRll7wme-4hQF X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjI3MDE0OCBTYWx0ZWRfX7R/7WQ8/QPzn bNpKmBtkNs6uAd4plhsBSKV/OmyrTZR50/LKHUIY51FQ0GRwl8DcHNdKKD0ErEhQ6pO6mQDzdG8 HIzO7zXFfVCxDDBVFdv84A3ePmkmYpi7x+cGiHidy1AiHcocaTOoSh/FHsxhIArZGdlNZ4QGCRG imlwxdu0U3d/Js7xD+x5QeBDKjMyi+qF5CsCukHJrSnM6L/L48shPpN7AModb5D3jSWJdFGCtVb c3tF5optklwLhCWBpQIkcxp4Szwd0xdj2me1VdJmUo1ocTSeECtqpPxi/mPFz5XN1zVJ/K8SWW7 toNzM1uIfR8FzfOgHeTUNiJA55NN4/FXMEXisv0KjuGJ/mM4CHtdsp7YqHQhqYCO0Z0hbhQ8ejc /NaBYpCPoMvoetPdYP5Cl9IP0j0iAOR71/12t6kstSLDsReSs2U/oC8HH5QkNVHSWixDwNN+Hkb x7Z6BrEKjGHreJ6Yc7w== X-Authority-Analysis: v=2.4 cv=fu7RpV4f c=1 sm=1 tr=0 ts=69a1c939 cx=c_pps a=wEM5vcRIz55oU/E2lInRtA==:117 a=GaPK54s0Se3oFqK5NkZy0g==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=x7bEGLp0ZPQA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=BpGzv1V74M3SfeTrGa8v:22 a=Kw1KkKa2aV08GXngiw4A:9 a=QEXdDO2ut3YA:10 a=OIgjcC2v60KrkQgK7BGD:22 X-Proofpoint-Virus-Version: vendor=nai engine=6800 definitions=11714 signatures=596818 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=10 malwarescore=0 adultscore=0 suspectscore=0 priorityscore=1501 bulkscore=10 clxscore=1015 lowpriorityscore=10 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2602270148 Block device buffered reads and writes already pass through filemap_read() and iomap_file_buffered_write() respectively, both of which handle IOCB_DONTCACHE. Enable RWF_DONTCACHE for block device files by setting FOP_DONTCACHE in def_blk_fops. For CONFIG_BUFFER_HEAD paths, add block_write_begin_iocb() which threads the kiocb through so that buffer_head-based I/O can use DONTCACHE behavior. The existing block_write_begin() is preserved as a wrapper that passes a NULL iocb. This support is useful for databases that operate on raw block devices, among other userspace applications. Signed-off-by: Tal Zussman --- block/fops.c | 5 +++-- fs/buffer.c | 19 ++++++++++++++++--- include/linux/buffer_head.h | 3 +++ 3 files changed, 22 insertions(+), 5 deletions(-) diff --git a/block/fops.c b/block/fops.c index 4d32785b31d9..d8165f6ba71c 100644 --- a/block/fops.c +++ b/block/fops.c @@ -505,7 +505,8 @@ static int blkdev_write_begin(const struct kiocb *iocb, unsigned len, struct folio **foliop, void **fsdata) { - return block_write_begin(mapping, pos, len, foliop, blkdev_get_block); + return block_write_begin_iocb(iocb, mapping, pos, len, foliop, + blkdev_get_block); } static int blkdev_write_end(const struct kiocb *iocb, @@ -967,7 +968,7 @@ const struct file_operations def_blk_fops = { .splice_write = iter_file_splice_write, .fallocate = blkdev_fallocate, .uring_cmd = blkdev_uring_cmd, - .fop_flags = FOP_BUFFER_RASYNC, + .fop_flags = FOP_BUFFER_RASYNC | FOP_DONTCACHE, }; static __init int blkdev_init(void) diff --git a/fs/buffer.c b/fs/buffer.c index 838c0c571022..18f1d128bb19 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2241,14 +2241,19 @@ EXPORT_SYMBOL(block_commit_write); * * The filesystem needs to handle block truncation upon failure. */ -int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, +int block_write_begin_iocb(const struct kiocb *iocb, + struct address_space *mapping, loff_t pos, unsigned len, struct folio **foliop, get_block_t *get_block) { pgoff_t index = pos >> PAGE_SHIFT; + fgf_t fgp_flags = FGP_WRITEBEGIN; struct folio *folio; int status; - folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN, + if (iocb && iocb->ki_flags & IOCB_DONTCACHE) + fgp_flags |= FGP_DONTCACHE; + + folio = __filemap_get_folio(mapping, index, fgp_flags, mapping_gfp_mask(mapping)); if (IS_ERR(folio)) return PTR_ERR(folio); @@ -2263,6 +2268,13 @@ int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, *foliop = folio; return status; } + +int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, + struct folio **foliop, get_block_t *get_block) +{ + return block_write_begin_iocb(NULL, mapping, pos, len, foliop, + get_block); +} EXPORT_SYMBOL(block_write_begin); int block_write_end(loff_t pos, unsigned len, unsigned copied, @@ -2591,7 +2603,8 @@ int cont_write_begin(const struct kiocb *iocb, struct address_space *mapping, (*bytes)++; } - return block_write_begin(mapping, pos, len, foliop, get_block); + return block_write_begin_iocb(iocb, mapping, pos, len, foliop, + get_block); } EXPORT_SYMBOL(cont_write_begin); diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index b16b88bfbc3e..ddf88ce290f2 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -260,6 +260,9 @@ int block_read_full_folio(struct folio *, get_block_t *); bool block_is_partially_uptodate(struct folio *, size_t from, size_t count); int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, struct folio **foliop, get_block_t *get_block); +int block_write_begin_iocb(const struct kiocb *iocb, + struct address_space *mapping, loff_t pos, unsigned len, + struct folio **foliop, get_block_t *get_block); int __block_write_begin(struct folio *folio, loff_t pos, unsigned len, get_block_t *get_block); int block_write_end(loff_t pos, unsigned len, unsigned copied, struct folio *); -- 2.39.5