block: enable RWF_DONTCACHE for block devices

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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, writeback goes through buffer_head's
__bh_submit() which sets BIO_COMPLETE_IN_TASK on dropbehind folios. For
CONFIG_BUFFER_HEAD=n, writeback goes through iomap which handles it via
BIO_COMPLETE_IN_TASK on the ioend bio.

This support is useful for databases that operate on raw block devices,
among other userspace applications.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260730-blk-dontcache-v7-5-3e8e6850068d@columbia.edu
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Tal Zussman 2026-07-30 02:57:55 -04:00 • committed by Jens Axboe

parent a2c924c240

commit 8b5ffb43ae

1 changed files with 1 additions and 1 deletions

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block/fops.c

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