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)
> {
> - wait_barrier(conf);
> + /* Bail out if REQ_NOWAIT is set for the bio */
> + if (!wait_barrier(conf, bio->bi_opf & REQ_NOWAIT)) {
> + bio_wouldblock_error(bio);
> + return false;
> + }
> while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
> bio->bi_iter.bi_sector < conf->reshape_progress &&
> bio->bi_iter.bi_sector + sectors > conf->reshape_progress) {
> raid10_log(conf->mddev, "wait reshape");
> + if (bio->bi_opf & REQ_NOWAIT) {
> + bio_wouldblock_error(bio);
> + return false;
> + }
> allow_barrier(conf);
> wait_event(conf->wait_barrier,
> conf->reshape_progress <= bio->bi_iter.bi_sector ||
> conf->reshape_progress >= bio->bi_iter.bi_sector +
> sectors);
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> }
> + return true;
> }
>
> static void raid10_read_request(struct mddev *mddev, struct bio *bio,
> @@ -1179,7 +1196,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
> bio_chain(split, bio);
> allow_barrier(conf);
> submit_bio_noacct(bio);
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> bio = split;
> r10_bio->master_bio = bio;
> r10_bio->sectors = max_sectors;
> @@ -1338,7 +1355,7 @@ static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
> raid10_log(conf->mddev, "%s wait rdev %d blocked",
> __func__, blocked_rdev->raid_disk);
> md_wait_for_blocked_rdev(blocked_rdev, mddev);
I think we need more handling here.
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> goto retry_wait;
> }
> }
> @@ -1356,6 +1373,11 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
> bio->bi_iter.bi_sector,
> bio_end_sector(bio)))) {
> DEFINE_WAIT(w);
> + /* Bail out if REQ_NOWAIT is set for the bio */
> + if (bio->bi_opf & REQ_NOWAIT) {
> + bio_wouldblock_error(bio);
> + return;
> + }
> for (;;) {
> prepare_to_wait(&conf->wait_barrier,
> &w, TASK_IDLE);
> @@ -1381,6 +1403,10 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
> BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
> md_wakeup_thread(mddev->thread);
> raid10_log(conf->mddev, "wait reshape metadata");
> + if (bio->bi_opf & REQ_NOWAIT) {
> + bio_wouldblock_error(bio);
> + return;
> + }
> wait_event(mddev->sb_wait,
> !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
>
> @@ -1390,6 +1416,10 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
> if (conf->pending_count >= max_queued_requests) {
> md_wakeup_thread(mddev->thread);
> raid10_log(mddev, "wait queued");
We need the check before logging "wait queued".
> + if (bio->bi_opf & REQ_NOWAIT) {
> + bio_wouldblock_error(bio);
> + return;
> + }
> wait_event(conf->wait_barrier,
> conf->pending_count < max_queued_requests);
> }
> @@ -1482,7 +1512,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
> bio_chain(split, bio);
> allow_barrier(conf);
> submit_bio_noacct(bio);
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> bio = split;
> r10_bio->master_bio = bio;
> }
> @@ -1607,7 +1637,11 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
> if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
> return -EAGAIN;
>
> - wait_barrier(conf);
> + if (bio->bi_opf & REQ_NOWAIT) {
> + bio_wouldblock_error(bio);
> + return 0;
Shall we return -EAGAIN here?
> + }
> + wait_barrier(conf, false);
>
> /*
> * Check reshape again to avoid reshape happens after checking
> @@ -1649,7 +1683,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
> allow_barrier(conf);
> /* Resend the fist split part */
> submit_bio_noacct(split);
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> }
> div_u64_rem(bio_end, stripe_size, &remainder);
> if (remainder) {
> @@ -1660,7 +1694,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
> /* Resend the second split part */
> submit_bio_noacct(bio);
> bio = split;
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> }
>
> bio_start = bio->bi_iter.bi_sector;
> @@ -1816,7 +1850,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
> end_disk_offset += geo->stride;
> atomic_inc(&first_r10bio->remaining);
> raid_end_discard_bio(r10_bio);
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> goto retry_discard;
> }
>
> @@ -2011,7 +2045,7 @@ static void print_conf(struct r10conf *conf)
>
> static void close_sync(struct r10conf *conf)
> {
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> allow_barrier(conf);
>
> mempool_exit(&conf->r10buf_pool);
> @@ -4819,7 +4853,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
> if (need_flush ||
> time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
> /* Need to update reshape_position in metadata */
> - wait_barrier(conf);
> + wait_barrier(conf, false);
> mddev->reshape_position = conf->reshape_progress;
> if (mddev->reshape_backwards)
> mddev->curr_resync_completed = raid10_size(mddev, 0, 0)
> --
> 2.17.1
>
