On Tue, Nov 2, 2021 at 5:52 AM Vishal Verma <vverma@xxxxxxxxxxxxxxxx> wrote:
>
> commit 021a24460dc2 ("block: add QUEUE_FLAG_NOWAIT") added support
> for checking whether a given bdev supports handling of REQ_NOWAIT or not.
> Since then commit 6abc49468eea ("dm: add support for REQ_NOWAIT and enable
> it for linear target") added support for REQ_NOWAIT for dm. This uses
> a similar approach to incorporate REQ_NOWAIT for md based bios.
>
> Signed-off-by: Vishal Verma <vverma@xxxxxxxxxxxxxxxx>
> ---
> drivers/md/md.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 5111ed966947..51b2df32aed5 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -419,6 +419,12 @@ void md_handle_request(struct mddev *mddev, struct bio *bio)
> if (is_suspended(mddev, bio)) {
> DEFINE_WAIT(__wait);
> for (;;) {
> + /* Bail out if REQ_NOWAIT is set for the bio */
> + if (bio->bi_opf & REQ_NOWAIT) {
> + bio_wouldblock_error(bio);
> + break;
> + }
> +
> prepare_to_wait(&mddev->sb_wait, &__wait,
> TASK_UNINTERRUPTIBLE);
> if (!is_suspended(mddev, bio))
> @@ -5792,6 +5798,7 @@ int md_run(struct mddev *mddev)
> int err;
> struct md_rdev *rdev;
> struct md_personality *pers;
> + bool nowait = true;
>
> if (list_empty(&mddev->disks))
> /* cannot run an array with no devices.. */
> @@ -5862,8 +5869,14 @@ int md_run(struct mddev *mddev)
> }
> }
> sysfs_notify_dirent_safe(rdev->sysfs_state);
> + if (!blk_queue_nowait(bdev_get_queue(rdev->bdev)))
> + nowait = false;
I think this is more clear:
nowait = blk_queue_nowait(bdev_get_queue(rdev->bdev));
> }
>
> + /* Set the NOWAIT flags if all underlying devices support it */
> + if (nowait)
> + blk_queue_flag_set(QUEUE_FLAG_NOWAIT, mddev->queue);
> +
> if (!bioset_initialized(&mddev->bio_set)) {
> err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
> if (err)
> @@ -7007,6 +7020,14 @@ static int hot_add_disk(struct mddev *mddev, dev_t dev)
> set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
> if (!mddev->thread)
> md_update_sb(mddev, 1);
> + /* If the new disk does not support REQ_NOWAIT,
> + * disable on the whole MD.
> + */
> + if (!blk_queue_nowait(bdev_get_queue(rdev->bdev))) {
> + pr_info("%s: Disabling nowait because %s does not support nowait\n",
> + mdname(mddev), bdevname(rdev->bdev, b));
> + blk_queue_flag_clear(QUEUE_FLAG_NOWAIT, mddev->queue);
> + }
> /*
> * Kick recovery, maybe this spare has to be added to the
> * array immediately.
> --
> 2.17.1
>
