| Message ID | 20181119035131.11255-8-damien.lemoal@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Improve I/O priority handling | expand |
On Mon, Nov 19, 2018 at 12:51:31PM +0900, Damien Le Moal wrote: > 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 <damien.lemoal@wdc.com> Looks good, Reviewed-by: Christoph Hellwig <hch@lst.de>
On Mon, 2018-11-19 at 12:51 +0900, Damien Le Moal wrote: > 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 <damien.lemoal@wdc.com> Nice cleanup, looks good. Thanks Damien. Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com> > --- > 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(), > }; > } >
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(), }; }
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 <damien.lemoal@wdc.com> --- block/blk-core.c | 5 +---- include/linux/fs.h | 2 +- 2 files changed, 2 insertions(+), 5 deletions(-)