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blk-ioprio: don't set bio priority if not needed 

We don't need to write to the bio if:

1) No ioprio value has ever been assigned to the blkcg
2) We wouldn't anyway, depending on bio and blkcg IO priority

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-11-13 13:37:38 -07:00
parent 1e9c23034d
commit 25c4b5e058
1 changed files with 10 additions and 3 deletions
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13
block/blk-ioprio.c
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@ -62,6 +62,7 @@ struct ioprio_blkg {
struct ioprio_blkcg {
struct blkcg_policy_data cpd;
enum prio_policy prio_policy;
bool prio_set;
};
static inline struct ioprio_blkg *pd_to_ioprio(struct blkg_policy_data *pd)
@ -112,7 +113,7 @@ static ssize_t ioprio_set_prio_policy(struct kernfs_open_file *of, char *buf,
if (ret < 0)
return ret;
blkcg->prio_policy = ret;
blkcg->prio_set = true;
return nbytes;
}
@ -190,6 +191,10 @@ static void blkcg_ioprio_track(struct rq_qos *rqos, struct request *rq,
struct bio *bio)
{
struct ioprio_blkcg *blkcg = ioprio_blkcg_from_bio(bio);
u16 prio;
if (!blkcg->prio_set)
return;
/*
* Except for IOPRIO_CLASS_NONE, higher I/O priority numbers
@ -199,8 +204,10 @@ static void blkcg_ioprio_track(struct rq_qos *rqos, struct request *rq,
* bio I/O priority is not modified. If the bio I/O priority equals
* IOPRIO_CLASS_NONE, the cgroup I/O priority is assigned to the bio.
*/
bio->bi_ioprio = max_t(u16, bio->bi_ioprio,
IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
prio = max_t(u16, bio->bi_ioprio,
IOPRIO_PRIO_VALUE(blkcg->prio_policy, 0));
if (prio > bio->bi_ioprio)
bio->bi_ioprio = prio;
}
static void blkcg_ioprio_exit(struct rq_qos *rqos)