For the synchronous I/O path case (read(), write() etc system calls), a BIO I/O priority is not initialized until the execution of blk_init_request_from_bio() when the BIO is submitted and a request initialized for the BIO execution. This is due to the ki_ioprio field of the struct kiocb defined on stack being always initialized to IOPRIO_CLASS_NONE, regardless of the calling process I/O context ioprio value set with ioprio_set(). This late initialization can result in the BIO being merged to pending requests even when the I/O priorities differ.
Fix this by initializing the ki_iopriority field of on stack struct kiocb using the get_current_ioprio() helper, ensuring that all BIOs allocated and submitted for the system call execution see the correct intended I/O priority early. With this, since a BIO I/O priority is always set to the intended effective value for both the sync and async path, blk_init_request_from_bio() can be simplified. Signed-off-by: Damien Le Moal <[email protected]> --- block/blk-core.c | 5 +---- include/linux/fs.h | 2 +- 2 files changed, 2 insertions(+), 5 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index dde30b08aa14..04f5be473638 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -814,10 +814,7 @@ void blk_init_request_from_bio(struct request *req, struct bio *bio) req->cmd_flags |= REQ_FAILFAST_MASK; req->__sector = bio->bi_iter.bi_sector; - if (ioprio_valid(bio_prio(bio))) - req->ioprio = bio_prio(bio); - else - req->ioprio = get_current_ioprio(); + req->ioprio = bio_prio(bio); req->write_hint = bio->bi_write_hint; blk_rq_bio_prep(req->q, req, bio); } diff --git a/include/linux/fs.h b/include/linux/fs.h index c95c0807471f..a1ab233e6469 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2021,7 +2021,7 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp) .ki_filp = filp, .ki_flags = iocb_flags(filp), .ki_hint = ki_hint_validate(file_write_hint(filp)), - .ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0), + .ki_ioprio = get_current_ioprio(), }; } -- 2.19.1
