[dm-devel] [PATCH RFC 7/7] dm: add support for IO polling
JeffleXu
jefflexu at linux.alibaba.com
Fri Jan 8 03:12:26 UTC 2021
On 12/23/20 7:26 PM, Jeffle Xu wrote:
> Enable iopoll when all underlying target devices supports iopoll.
>
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
> drivers/md/dm-table.c | 28 ++++++++++++++++++++++++++++
> drivers/md/dm.c | 1 +
> 2 files changed, 29 insertions(+)
>
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 188f41287f18..b0cd5bf58c3c 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -1791,6 +1791,31 @@ static bool dm_table_requires_stable_pages(struct dm_table *t)
> return false;
> }
>
> +static int device_supports_poll(struct dm_target *ti, struct dm_dev *dev,
> + sector_t start, sector_t len, void *data)
> +{
> + struct request_queue *q = bdev_get_queue(dev->bdev);
> +
> + return q && test_bit(QUEUE_FLAG_POLL, &q->queue_flags);
> +}
> +
> +static bool dm_table_supports_poll(struct dm_table *t)
> +{
> + struct dm_target *ti;
> + unsigned int i;
> +
> + /* Ensure that all targets support iopoll. */
> + for (i = 0; i < dm_table_get_num_targets(t); i++) {
> + ti = dm_table_get_target(t, i);
> +
> + if (!ti->type->iterate_devices ||
> + !ti->type->iterate_devices(ti, device_supports_poll, NULL))
> + return false;
> + }
> +
> + return true;
> +}
> +
> void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
> struct queue_limits *limits)
> {
> @@ -1883,6 +1908,9 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
> #endif
>
> blk_queue_update_readahead(q);
> +
> + if (dm_table_supports_poll(t))
> + blk_queue_flag_set(QUEUE_FLAG_POLL, q);
> }
>
This works in arbitrary bio-based DM stacking. Suppose the following
device stack:
dm0
dm1
nvme0 nvme1
dm 0 will check if dm1 has QUEUE_FLAG_POLL flag set.
> unsigned int dm_table_get_num_targets(struct dm_table *t)
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 03c2b867acaa..ffd2c5ead256 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -3049,6 +3049,7 @@ static const struct pr_ops dm_pr_ops = {
> };
>
> static const struct block_device_operations dm_blk_dops = {
> + .iopoll = blk_bio_poll,
> .submit_bio = dm_submit_bio,
> .open = dm_blk_open,
> .release = dm_blk_close,
>
--
Thanks,
Jeffle
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