On Sun, May 30, 2083 at 09:51:06AM +0530, Nitesh Shetty wrote:
> This removes the dependency on interrupts to wake up task. Set task
> state as TASK_RUNNING, if need_resched() returns true,
> while polling for IO completion.
> Earlier, polling task used to sleep, relying on interrupt to wake it up.
> This made some IO take very long when interrupt-coalescing is enabled in
> NVMe.
This is a horrible Changelog.. it does not in fact explain why the patch
works or is correct.
Also, set_current_state(TASK_RUNNING) is dodgy (similarly in
__blk_mq_poll), why do you need that memory barrier?
> Signed-off-by: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
> ---
> fs/block_dev.c | 16 ++++++++++++----
> fs/direct-io.c | 8 ++++++--
> fs/iomap.c | 10 +++++++---
> 3 files changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 4a181fc..a87d8b7 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -236,9 +236,13 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
> set_current_state(TASK_UNINTERRUPTIBLE);
> if (!READ_ONCE(bio.bi_private))
> break;
> - if (!(iocb->ki_flags & IOCB_HIPRI) ||
> - !blk_poll(bdev_get_queue(bdev), qc))
> + if (!(iocb->ki_flags & IOCB_HIPRI))
> io_schedule();
> + else if (!blk_poll(bdev_get_queue(bdev), qc)) {
> + if (need_resched())
> + set_current_state(TASK_RUNNING);
> + io_schedule();
> + }
> }
> __set_current_state(TASK_RUNNING);
>
