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* [PATCH v3] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO
@ 2020-11-23  8:45 Hao Xu
  2020-11-24  2:11 ` JeffleXu
  0 siblings, 1 reply; 2+ messages in thread
From: Hao Xu @ 2020-11-23  8:45 UTC (permalink / raw)
  To: Alexander Viro, Christoph Hellwig
  Cc: Darrick J. Wong, linux-fsdevel, Jeffle Xu, Konstantin Khlebnikov,
	Joseph Qi

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.

Suggested-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---

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.:)

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..f3e9e13a9a9f 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);
 
@@ -424,6 +428,9 @@ static void blkdev_bio_end_io(struct bio *bio)
 		if (!nr_pages) {
 			bool polled = false;
 
+			if (iocb->ki_flags & IOCB_NOWAIT)
+				bio->bi_opf |= REQ_NOWAIT;
+
 			if (iocb->ki_flags & IOCB_HIPRI) {
 				bio_set_polled(bio, iocb);
 				polled = true;
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);
 
-- 
1.8.3.1


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH v3] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO
  2020-11-23  8:45 [PATCH v3] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO Hao Xu
@ 2020-11-24  2:11 ` JeffleXu
  0 siblings, 0 replies; 2+ messages in thread
From: JeffleXu @ 2020-11-24  2:11 UTC (permalink / raw)
  To: Hao Xu, Alexander Viro, Christoph Hellwig
  Cc: Darrick J. Wong, linux-fsdevel, Konstantin Khlebnikov, Joseph Qi


On 11/23/20 4:45 PM, 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.
>
> Suggested-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
> ---
>
> 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.:)
>
> 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..f3e9e13a9a9f 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);
>   
> @@ -424,6 +428,9 @@ static void blkdev_bio_end_io(struct bio *bio)
>   		if (!nr_pages) {
>   			bool polled = false;
>   
> +			if (iocb->ki_flags & IOCB_NOWAIT)
> +				bio->bi_opf |= REQ_NOWAIT;
> +

This should be moved outside the "if (!nr_pages) {}" clause. One direct 
IO can be split

into several bios, among which only the last split bio will get into 
this conditional clause.


Thanks,

Jeffle


>   			if (iocb->ki_flags & IOCB_HIPRI) {
>   				bio_set_polled(bio, iocb);
>   				polled = true;
> 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);
>   

-- 
Thanks,
Jeffle


^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2020-11-24  2:12 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
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2020-11-23  8:45 [PATCH v3] iomap: set REQ_NOWAIT according to IOCB_NOWAIT in Direct IO Hao Xu
2020-11-24  2:11 ` JeffleXu

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