Hi,
On 2/4/2023 3:45 AM, Bart Van Assche wrote:
> On 2/2/23 17:48, Hou Tao wrote:
>> I don't get it on how to remove IOPRIO_POL_PROMOTION when calculating the final
>> ioprio for bio. IOPRIO_POL_PROMOTION is not used for IOPRIO_CLASS values but
>> used to determinate on how to calculate the final ioprio for bio: choosing the
>> maximum or minimum between blkcg ioprio and original bio bi_ioprio.
>
> Do the block layer code changes shown below implement the functionality that you
> need?
Yes, something like that. The reason for introducing IOPRIO_POL_PROMOTION is to
support other promotion policy (e.g., promote-to-be), but now I think the
possibility of adding other promotion policies is low, so the code below is fine
to me.
>
> Thanks,
>
> Bart.
>
>
>
> diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
> index 8bb6b8eba4ce..4a56da95168e 100644
> --- a/block/blk-ioprio.c
> +++ b/block/blk-ioprio.c
> @@ -27,6 +27,8 @@
> * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
> * IOPRIO_CLASS_BE.
> * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
> + * @POLICY_PROMOTE_TO_RT: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_BE into
> + * IOPRIO_CLASS_RT.
> *
> * See also <linux/ioprio.h>.
> */
> @@ -35,6 +37,7 @@ enum prio_policy {
> POLICY_NONE_TO_RT = 1,
> POLICY_RESTRICT_TO_BE = 2,
> POLICY_ALL_TO_IDLE = 3,
> + POLICY_PROMOTE_TO_RT,
> };
>
> static const char *policy_name[] = {
> @@ -42,6 +45,7 @@ static const char *policy_name[] = {
> [POLICY_NONE_TO_RT] = "none-to-rt",
> [POLICY_RESTRICT_TO_BE] = "restrict-to-be",
> [POLICY_ALL_TO_IDLE] = "idle",
> + [POLICY_PROMOTE_TO_RT] = "promote-to-rt",
> };
>
> static struct blkcg_policy ioprio_policy;
> @@ -189,17 +193,23 @@ void blkcg_set_ioprio(struct bio *bio)
> if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
> return;
>
> - /*
> - * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
> - * correspond to a lower priority. Hence, the max_t() below selects
> - * the lower priority of bi_ioprio and the cgroup I/O priority class.
> - * If the bio I/O priority equals IOPRIO_CLASS_NONE, the cgroup I/O
> - * priority is assigned to the bio.
> - */
> - prio = max_t(u16, bio->bi_ioprio,
> - IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
> - if (prio > bio->bi_ioprio)
> - bio->bi_ioprio = prio;
> + if (blkcg->prio_policy == PROMOTE_TO_RT) {
> + if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT)
> + bio->bi_ioprio = IOPRIO_CLASS_RT;
> + } else {
> + /*
> + * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
> + * correspond to a lower priority. Hence, the max_t() below
> + * selects the lower priority of bi_ioprio and the cgroup I/O
> + * priority class. If the bio I/O priority equals
> + * IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the
> + * bio.
> + */
> + prio = max_t(u16, bio->bi_ioprio,
> + IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
> + if (prio > bio->bi_ioprio)
> + bio->bi_ioprio = prio;
> + }
> }
>
> void blk_ioprio_exit(struct gendisk *disk)
>
