Re: [PATCH 5/9] md: raid10 nowait support

[Shaohua Li <shli@kernel.org>]

On Wed, Jul 26, 2017 at 06:58:02PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Bail and status to EAGAIN if raid10 is going to wait for:
>  + barriers
>  + reshape operation
>  + Too many queued requests
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  drivers/md/raid10.c | 62 ++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 47 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 5026e7ad51d3..6d80438c5040 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -978,8 +978,9 @@ 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) {
>  		conf->nr_waiting++;
> @@ -993,19 +994,23 @@ 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) &&
> -				     current->bio_list &&
> -				     (!bio_list_empty(&current->bio_list[0]) ||
> -				      !bio_list_empty(&current->bio_list[1]))),
> -				    conf->resync_lock);
> +		if (!nowait)
> +			wait_event_lock_irq(conf->wait_barrier,
> +					    !conf->barrier ||
> +				            (atomic_read(&conf->nr_pending) &&
> +				             current->bio_list &&
> +				             (!bio_list_empty(&current->bio_list[0]) ||
> +				              !bio_list_empty(&current->bio_list[1]))),
> +					    conf->resync_lock);
> +		else
> +			ret = false;
same here, nr_pending shouldn't be increased

>  		conf->nr_waiting--;
>  		if (!conf->nr_waiting)
>  			wake_up(&conf->wait_barrier);
>  	}
>  	atomic_inc(&conf->nr_pending);
>  	spin_unlock_irq(&conf->resync_lock);
> +	return ret;
>  }
>  
>  static void allow_barrier(struct r10conf *conf)
> @@ -1158,7 +1163,10 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>  	 * thread has put up a bar for new requests.
>  	 * Continue immediately if no resync is active currently.
>  	 */
> -	wait_barrier(conf);
> +	if (!wait_barrier(conf, bio->bi_opf & REQ_NOWAIT)) {
> +		bio_wouldblock_error(bio);
> +		return;
> +	}
>  
>  	sectors = r10_bio->sectors;
>  	while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
> @@ -1169,12 +1177,16 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>  		 * pass
>  		 */
>  		raid10_log(conf->mddev, "wait reshape");
> +		if (bio->bi_opf & REQ_NOWAIT) {
> +			bio_wouldblock_error(bio);
> +			return;
> +		}
>  		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);
>  	}
>  
>  	rdev = read_balance(conf, r10_bio, &max_sectors);
> @@ -1308,7 +1320,10 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
>  	 * thread has put up a bar for new requests.
>  	 * Continue immediately if no resync is active currently.
>  	 */
> -	wait_barrier(conf);
> +	if (!wait_barrier(conf, bio->bi_opf & REQ_NOWAIT)) {
> +		bio_wouldblock_error(bio);
> +		return;
> +	}
>  
>  	sectors = r10_bio->sectors;
>  	while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
> @@ -1319,12 +1334,16 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
>  		 * pass
>  		 */
>  		raid10_log(conf->mddev, "wait reshape");
> +		if (bio->bi_opf & REQ_NOWAIT) {
> +			bio_wouldblock_error(bio);
> +			return;
> +		}
>  		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);
>  	}
>  
>  	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
> @@ -1339,6 +1358,10 @@ 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));
>  
> @@ -1348,6 +1371,10 @@ 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");
> +		if (bio->bi_opf & REQ_NOWAIT) {
> +			bio_wouldblock_error(bio);
> +			return;
> +		}
>  		wait_event(conf->wait_barrier,
>  			   conf->pending_count < max_queued_requests);
>  	}
> @@ -1454,6 +1481,11 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
>  		int j;
>  		int d;
>  
> +		if (bio->bi_opf & REQ_NOWAIT) {
> +			bio_wouldblock_error(bio);
> +			return;
> +		}
> +
>  		for (j = 0; j < i; j++) {
>  			if (r10_bio->devs[j].bio) {
>  				d = r10_bio->devs[j].devnum;
> @@ -1474,7 +1506,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
>  		allow_barrier(conf);
>  		raid10_log(conf->mddev, "wait rdev %d blocked", blocked_rdev->raid_disk);
>  		md_wait_for_blocked_rdev(blocked_rdev, mddev);
> -		wait_barrier(conf);
> +		wait_barrier(conf, false);
>  		goto retry_write;
>  	}
>  
> @@ -1703,7 +1735,7 @@ 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_destroy(conf->r10buf_pool);
> @@ -4347,7 +4379,7 @@ 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)
> -- 
> 2.12.3
> 
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