On 2/26/25 02:20, Darrick J. Wong wrote:
On Wed, Feb 26, 2025 at 02:06:51AM +0000, Pavel Begunkov wrote:
On 2/26/25 01:53, Darrick J. Wong wrote:
On Wed, Feb 26, 2025 at 01:33:58AM +0000, Pavel Begunkov wrote:
There are reports of high io_uring submission latency for ext4 and xfs,
which is due to iomap not propagating nowait flag to the block layer
resulting in waiting for IO during tag allocation.
Cc: stable@xxxxxxxxxxxxxxx
Link: https://github.com/axboe/liburing/issues/826#issuecomment-2674131870
Reported-by: wu lei <uwydoc@xxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/iomap/direct-io.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index b521eb15759e..25c5e87dbd94 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -81,6 +81,9 @@ static void iomap_dio_submit_bio(const struct iomap_iter *iter,
WRITE_ONCE(iocb->private, bio);
}
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ bio->bi_opf |= REQ_NOWAIT;
Shouldn't this go in iomap_dio_bio_opflags?
It can, if that's the preference, but iomap_dio_zero() would need
to have a separate check. It also affects 5.4, and I'm not sure
which version would be easier to back port.
Yes, please don't go scattering the bi_opf setting code all around the
Sure, even though the function already adjusts bi_opf through
bio_set_polled.
file. Also, do you need to modify iomap_dio_zero?
Is there a reason why it can't be hit? It's in the same path, and
from a quick look ending up there seems as easy as writing just a
little beyond the file size.
--
Pavel Begunkov
