On Tue, Dec 21, 2021 at 12:06 PM Vishal Verma <vverma@xxxxxxxxxxxxxxxx> wrote:
>
> This adds nowait support to the RAID10 driver. Very similar to
> raid1 driver changes. It makes RAID10 driver return with EAGAIN
> for situations where it could wait for eg:
>
> - Waiting for the barrier,
> - Too many pending I/Os to be queued,
> - Reshape operation,
> - Discard operation.
>
> wait_barrier() and regular_request_wait() fn are modified to return bool
> to support error for wait barriers. They returns true in case of wait
> or if wait is not required and returns false if wait was required
> but not performed to support nowait.
>
> Signed-off-by: Vishal Verma <vverma@xxxxxxxxxxxxxxxx>
> ---
> drivers/md/raid10.c | 90 +++++++++++++++++++++++++++++++--------------
> 1 file changed, 62 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index dde98f65bd04..7ceae00e863e 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -952,8 +952,9 @@ static void lower_barrier(struct r10conf *conf)
> wake_up(&conf->wait_barrier);
> }
>
> -static void wait_barrier(struct r10conf *conf)
> +static bool wait_barrier(struct r10conf *conf, bool nowait)
> {
> + bool ret = true;
> spin_lock_irq(&conf->resync_lock);
> if (conf->barrier) {
> struct bio_list *bio_list = current->bio_list;
> @@ -968,26 +969,33 @@ static void wait_barrier(struct r10conf *conf)
> * count down.
> */
> raid10_log(conf->mddev, "wait barrier");
> - wait_event_lock_irq(conf->wait_barrier,
> - !conf->barrier ||
> - (atomic_read(&conf->nr_pending) &&
> - bio_list &&
> - (!bio_list_empty(&bio_list[0]) ||
> - !bio_list_empty(&bio_list[1]))) ||
> - /* move on if recovery thread is
> - * blocked by us
> - */
> - (conf->mddev->thread->tsk == current &&
> - test_bit(MD_RECOVERY_RUNNING,
> - &conf->mddev->recovery) &&
> - conf->nr_queued > 0),
> - conf->resync_lock);
> + /* Return false when nowait flag is set */
> + if (nowait)
> + ret = false;
> + else
> + wait_event_lock_irq(conf->wait_barrier,
> + !conf->barrier ||
> + (atomic_read(&conf->nr_pending) &&
> + bio_list &&
> + (!bio_list_empty(&bio_list[0]) ||
> + !bio_list_empty(&bio_list[1]))) ||
> + /* move on if recovery thread is
> + * blocked by us
> + */
> + (conf->mddev->thread->tsk == current &&
> + test_bit(MD_RECOVERY_RUNNING,
> + &conf->mddev->recovery) &&
> + conf->nr_queued > 0),
> + conf->resync_lock);
> conf->nr_waiting--;
> if (!conf->nr_waiting)
> wake_up(&conf->wait_barrier);
> }
> - atomic_inc(&conf->nr_pending);
> + /* Only increment nr_pending when we wait */
> + if (ret)
> + atomic_inc(&conf->nr_pending);
> spin_unlock_irq(&conf->resync_lock);
> + return ret;
> }
>
> static void allow_barrier(struct r10conf *conf)
> @@ -1098,21 +1106,30 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
> * currently.
> * 2. If IO spans the reshape position. Need to wait for reshape to pass.
> */
> -static void regular_request_wait(struct mddev *mddev, struct r10conf *conf,
> +static bool regular_request_wait(struct mddev *mddev, struct r10conf *conf,
> struct bio *bio, sector_t sectors)
This doesn't sound right: regular_request_wait() is called in two
places. But we are
not checking the return value in either of them.
Song
[...]
