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bfq: Get rid of __bio_blkcg() usage

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commit 4e54a2493e582361adc3bfbf06c7d50d19d18837 upstream.

BFQ usage of __bio_blkcg() is a relict from the past. Furthermore if bio
would not be associated with any blkcg, the usage of __bio_blkcg() in
BFQ is prone to races with the task being migrated between cgroups as
__bio_blkcg() calls at different places could return different blkcgs.

Convert BFQ to the new situation where bio->bi_blkg is initialized in
bio_set_dev() and thus practically always valid. This allows us to save
blkcg_gq lookup and noticeably simplify the code.

CC: [email protected]
Fixes: 0fe061b9f0 ("blkcg: fix ref count issue with bio_blkcg() using task_css")
Tested-by: "yukuai (C)" <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Jan Kara 2022-06-07 11:15:12 +02:00 • committed by Greg Kroah-Hartman
commit 8afc13b958
3 changed files with 25 additions and 51 deletions
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10
block/bfq-iosched.c
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@ -5158,14 +5158,7 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
struct bfq_queue *bfqq;
struct bfq_group *bfqg;
rcu_read_lock();
bfqg = bfq_find_set_group(bfqd, __bio_blkcg(bio));
if (!bfqg) {
bfqq = &bfqd->oom_bfqq;
goto out;
}
bfqg = bfq_bio_bfqg(bfqd, bio);
if (!is_sync) {
async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class,
ioprio);
@ -5209,7 +5202,6 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
out:
bfqq->ref++; /* get a process reference to this queue */
bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref);
rcu_read_unlock();
return bfqq;
}