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Wong" , Carlos Maiolino , Al Viro , Jan Kara Cc: Dave Chinner , Bart Van Assche , Gao Xiang , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 3/8] block: enable RWF_DONTCACHE for block devices Date: Thu, 9 Apr 2026 18:02:16 +0200 Message-ID: <20260409160243.1008358-4-hch@lst.de> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260409160243.1008358-1-hch@lst.de> References: <20260409160243.1008358-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 2A6781A001A X-Stat-Signature: ujgquo1g4cfxfucsfn4shay5k6mjwjj9 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1775750604-384401 X-HE-Meta: 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 QpMVbnzz 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Tal Zussman 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=y 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. Set BIO_COMPLETE_IN_TASK in submit_bh_wbc() when the folio has dropbehind so that buffer_head writeback completions get deferred to task context. CONFIG_BUFFER_HEAD=n paths are handled by the previously added iomap BIO_COMPLETE_IN_TASK support. 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 | 22 +++++++++++++++++++--- include/linux/buffer_head.h | 3 +++ 3 files changed, 25 insertions(+), 5 deletions(-) diff --git a/block/fops.c b/block/fops.c index bb6642b45937..31b073181d87 100644 --- a/block/fops.c +++ b/block/fops.c @@ -504,7 +504,8 @@ 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, @@ -966,7 +967,7 @@ 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 d6e062c42a8d..289ab33fe3fd 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2131,14 +2131,19 @@ 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); @@ -2153,6 +2158,13 @@ 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, @@ -2481,7 +2493,8 @@ 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); @@ -2711,6 +2724,9 @@ static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh, if (IS_ENABLED(CONFIG_FS_ENCRYPTION)) buffer_set_crypto_ctx(bio, bh, GFP_NOIO); + if (folio_test_dropbehind(bh->b_folio)) + bio_set_flag(bio, BIO_COMPLETE_IN_TASK); + bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9); bio->bi_write_hint = write_hint; diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index e4939e33b4b5..4ce50882d621 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 *); -- 2.47.3