Re: [PATCH V6 12/12] dm: support IO polling for bio-based dm device

[JeffleXu <jefflexu@linux.alibaba.com>]

On 4/22/21 8:20 PM, Ming Lei wrote:
> From: Jeffle Xu <jefflexu@linux.alibaba.com>
> 
> IO polling is enabled when all underlying target devices are capable
> of IO polling. The sanity check supports the stacked device model, in
> which one dm device may be build upon another dm device. In this case,
> the mapped device will check if the underlying dm target device
> supports IO polling.
> 
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Reviewed-by: Mike Snitzer <snitzer@redhat.com>
> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/md/dm-table.c         | 24 ++++++++++++++++++++++++
>  drivers/md/dm.c               |  2 ++
>  include/linux/device-mapper.h |  1 +
>  3 files changed, 27 insertions(+)
> 
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 95391f78b8d5..a8f3575fb118 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -1509,6 +1509,12 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
>  	return &t->targets[(KEYS_PER_NODE * n) + k];
>  }
>  
> +static int device_not_poll_capable(struct dm_target *ti, struct dm_dev *dev,
> +				   sector_t start, sector_t len, void *data)
> +{
> +	return !blk_queue_poll(bdev_get_queue(dev->bdev));
> +}
> +
>  /*
>   * type->iterate_devices() should be called when the sanity check needs to
>   * iterate and check all underlying data devices. iterate_devices() will
> @@ -1559,6 +1565,11 @@ static int count_device(struct dm_target *ti, struct dm_dev *dev,
>  	return 0;
>  }
>  
> +int dm_table_supports_poll(struct dm_table *t)
> +{
> +	return !dm_table_any_dev_attr(t, device_not_poll_capable, NULL);
> +}
> +

Since .poll_capable() has been dropped, dm_table_supports_poll() can be
declared as 'static' here.

>  /*
>   * Check whether a table has no data devices attached using each
>   * target's iterate_devices method.
> @@ -2079,6 +2090,19 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
>  
>  	dm_update_keyslot_manager(q, t);
>  	blk_queue_update_readahead(q);
> +
> +	/*
> +	 * Check for request-based device is remained to
> +	 * dm_mq_init_request_queue()->blk_mq_init_allocated_queue().
> +	 * For bio-based device, only set QUEUE_FLAG_POLL when all underlying
> +	 * devices supporting polling.
> +	 */
> +	if (__table_type_bio_based(t->type)) {
> +		if (dm_table_supports_poll(t))
> +			blk_queue_flag_set(QUEUE_FLAG_POLL, q);
> +		else
> +			blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
> +	}
>  }
>  
>  unsigned int dm_table_get_num_targets(struct dm_table *t)
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 50b693d776d6..1b160e4e6446 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2175,6 +2175,8 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
>  		}
>  		break;
>  	case DM_TYPE_BIO_BASED:
> +		/* tell block layer we are capable of bio polling */
> +		md->disk->flags |= GENHD_FL_CAP_BIO_POLL;
>  	case DM_TYPE_DAX_BIO_BASED:
>  		break;
>  	case DM_TYPE_NONE:


> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 7f4ac87c0b32..31bfd6f70013 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -538,6 +538,7 @@ unsigned int dm_table_get_num_targets(struct dm_table *t);
>  fmode_t dm_table_get_mode(struct dm_table *t);
>  struct mapped_device *dm_table_get_md(struct dm_table *t);
>  const char *dm_table_device_name(struct dm_table *t);
> +int dm_table_supports_poll(struct dm_table *t);

Similarly, dm_table_supports_poll() doesn't need to be exported.

-- 
Thanks,
Jeffle