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 <[email protected]> Signed-off-by: Tal Zussman <[email protected]> --- block/fops.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/fops.c b/block/fops.c index 15783a6180de..8b39c53b6393 100644 --- a/block/fops.c +++ b/block/fops.c @@ -941,7 +941,7 @@ 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) -- 2.39.5
