On 04/12/2020 09:44, Hao Xu wrote: > Currently, IOCB_NOWAIT is ignored in Direct IO, REQ_NOWAIT is only set > when IOCB_HIPRI is set. But REQ_NOWAIT should be set as well when > IOCB_NOWAIT is set. I believe Jens took my patch fixing that for blkdev_direct_IO*() (but not iomap) a while ago. BTW, even though get_maintainer.pl doesn't think so, AFAIK fs/block_dev.c is managed by linux-block@xxxxxxxxxxxxxxx. Please CC it next time. > Suggested-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx> > --- > > Hi all, > I tested fio io_uring direct read for a file on ext4 filesystem on a > nvme ssd. I found that IOCB_NOWAIT is ignored in iomap layer, which > means REQ_NOWAIT is not set in bio->bi_opf. This makes nowait IO a > normal IO. Since I'm new to iomap and block layer, I sincerely ask > yours opinions in case I misunderstand the code which is very likely > to happen.:) > The example I use: io_uring direct randread, the first try is with > IOCB_NOWAIT but not IOCB_HIPRI, the IOCB_NOWAIT is ignored in block > layer which I think is not the designed behaviour. > > I found that Konstantin found this issue before in May > 2020 (https://www.spinics.net/lists/linux-block/msg53275.html), here add > his signature, add Jeffle's as well since he gave me some help. > > v1->v2: > * add same logic in __blkdev_direct_IO_simple() > v2->v3: > * add same logic in do_blockdev_direct_IO() > > fs/block_dev.c | 7 +++++++ > fs/direct-io.c | 6 ++++-- > fs/iomap/direct-io.c | 3 +++ > 3 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 9e84b1928b94..ca6f365c2f14 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -263,6 +263,10 @@ static void blkdev_bio_end_io_simple(struct bio *bio) > bio.bi_opf = dio_bio_write_op(iocb); > task_io_account_write(ret); > } > + > + if (iocb->ki_flags & IOCB_NOWAIT) > + bio.bi_opf |= REQ_NOWAIT; > + > if (iocb->ki_flags & IOCB_HIPRI) > bio_set_polled(&bio, iocb); > > @@ -417,6 +421,9 @@ static void blkdev_bio_end_io(struct bio *bio) > task_io_account_write(bio->bi_iter.bi_size); > } > > + if (iocb->ki_flags & IOCB_NOWAIT) > + bio->bi_opf |= REQ_NOWAIT; > + > dio->size += bio->bi_iter.bi_size; > pos += bio->bi_iter.bi_size; > > diff --git a/fs/direct-io.c b/fs/direct-io.c > index d53fa92a1ab6..b221ed351c1c 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -1206,11 +1206,13 @@ static inline int drop_refcount(struct dio *dio) > if (iov_iter_rw(iter) == WRITE) { > dio->op = REQ_OP_WRITE; > dio->op_flags = REQ_SYNC | REQ_IDLE; > - if (iocb->ki_flags & IOCB_NOWAIT) > - dio->op_flags |= REQ_NOWAIT; > } else { > dio->op = REQ_OP_READ; > } > + > + if (iocb->ki_flags & IOCB_NOWAIT) > + dio->op_flags |= REQ_NOWAIT; > + > if (iocb->ki_flags & IOCB_HIPRI) > dio->op_flags |= REQ_HIPRI; > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 933f234d5bec..2e897688ed6d 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -64,6 +64,9 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap, > { > atomic_inc(&dio->ref); > > + if (dio->iocb->ki_flags & IOCB_NOWAIT) > + bio->bi_opf |= REQ_NOWAIT; > + > if (dio->iocb->ki_flags & IOCB_HIPRI) > bio_set_polled(bio, dio->iocb); > > -- Pavel Begunkov
