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blkcg: associate blkg when associating a device

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Previously, blkg association was handled by controller specific code in
blk-throttle and blk-iolatency. However, because a blkg represents a
relationship between a blkcg and a request_queue, it makes sense to keep
the blkg->q and bio->bi_disk->queue consistent.

This patch moves association into the bio_set_dev macro(). This should
cover the majority of cases where the device is set/changed keeping the
two pointers consistent. Fallback code is added to
blkcg_bio_issue_check() to catch any missing paths.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dennis Zhou 2018-12-05 12:10:31 -05:00 • committed by Jens Axboe
parent 892ad71f62
commit 5cdf2e3fea
5 changed files with 14 additions and 12 deletions
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18
include/linux/blk-cgroup.h
View file

@ -21,6 +21,7 @@
#include <linux/blkdev.h>
#include <linux/atomic.h>
#include <linux/kthread.h>
#include <linux/fs.h>
/* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
#define BLKG_STAT_CPU_BATCH (INT_MAX / 2)
@ -802,21 +803,23 @@ static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg
static inline bool blkcg_bio_issue_check(struct request_queue *q,
struct bio *bio)
{
struct blkcg *blkcg;
struct blkcg_gq *blkg;
bool throtl = false;
rcu_read_lock();
if (!bio->bi_blkg) {
char b[BDEVNAME_SIZE];
/* associate blkcg if bio hasn't attached one */
bio_associate_blkcg(bio, NULL);
blkcg = bio_blkcg(bio);
blkg = blkg_lookup_create(blkcg, q);
WARN_ONCE(1,
"no blkg associated for bio on block-device: %s\n",
bio_devname(bio, b));
bio_associate_blkg(bio);
}
blkg = bio->bi_blkg;
throtl = blk_throtl_bio(q, blkg, bio);
if (!throtl) {
blkg = blkg ?: q->root_blkg;
/*
* If the bio is flagged with BIO_QUEUE_ENTERED it means this
* is a split bio and we would have already accounted for the
@ -828,7 +831,6 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,
blkg_rwstat_add(&blkg->stat_ios, bio->bi_opf, 1);
}
rcu_read_unlock();
return !throtl;
}