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btrfs, block: move REQ_CGROUP_PUNT to btrfs

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REQ_CGROUP_PUNT is a bit annoying as it is hard to follow and adds
a branch to the bio submission hot path.  To fix this, export
blkcg_punt_bio_submit and let btrfs call it directly.  Add a new
REQ_FS_PRIVATE flag for btrfs to indicate to it's own low-level
bio submission code that a punt to the cgroup submission helper
is required.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Christoph Hellwig
2023-03-27 09:49:51 +09:00
committed by David Sterba
parent 0a0596fbbe
commit 3480373ebd
9 changed files with 40 additions and 48 deletions
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31
block/blk-cgroup.c
View File

@@ -1688,24 +1688,27 @@ out_unlock:
}
EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
bool __blkcg_punt_bio_submit(struct bio *bio)
/*
* When a shared kthread issues a bio for a cgroup, doing so synchronously can
* lead to priority inversions as the kthread can be trapped waiting for that
* cgroup. Use this helper instead of submit_bio to punt the actual issuing to
* a dedicated per-blkcg work item to avoid such priority inversions.
*/
void blkcg_punt_bio_submit(struct bio *bio)
{
struct blkcg_gq *blkg = bio->bi_blkg;
/* consume the flag first */
bio->bi_opf &= ~REQ_CGROUP_PUNT;
/* never bounce for the root cgroup */
if (!blkg->parent)
return false;
spin_lock_bh(&blkg->async_bio_lock);
bio_list_add(&blkg->async_bios, bio);
spin_unlock_bh(&blkg->async_bio_lock);
queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
return true;
if (blkg->parent) {
spin_lock_bh(&blkg->async_bio_lock);
bio_list_add(&blkg->async_bios, bio);
spin_unlock_bh(&blkg->async_bio_lock);
queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
} else {
/* never bounce for the root cgroup */
submit_bio(bio);
}
}
EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit);
/*
* Scale the accumulated delay based on how long it has been since we updated

12
block/blk-cgroup.h
View File

@@ -375,16 +375,6 @@ static inline void blkg_put(struct blkcg_gq *blkg)
if (((d_blkg) = blkg_lookup(css_to_blkcg(pos_css), \
(p_blkg)->q)))
bool __blkcg_punt_bio_submit(struct bio *bio);
static inline bool blkcg_punt_bio_submit(struct bio *bio)
{
if (bio->bi_opf & REQ_CGROUP_PUNT)
return __blkcg_punt_bio_submit(bio);
else
return false;
}
static inline void blkcg_bio_issue_init(struct bio *bio)
{
bio_issue_init(&bio->bi_issue, bio_sectors(bio));
@@ -506,8 +496,6 @@ static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return
static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
static inline void blkg_get(struct blkcg_gq *blkg) { }
static inline void blkg_put(struct blkcg_gq *blkg) { }
static inline bool blkcg_punt_bio_submit(struct bio *bio) { return false; }
static inline void blkcg_bio_issue_init(struct bio *bio) { }
static inline void blk_cgroup_bio_start(struct bio *bio) { }
static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }

3
block/blk-core.c
View File

@@ -830,9 +830,6 @@ EXPORT_SYMBOL(submit_bio_noacct);
*/
void submit_bio(struct bio *bio)
{
if (blkcg_punt_bio_submit(bio))
return;
if (bio_op(bio) == REQ_OP_READ) {
task_io_account_read(bio->bi_iter.bi_size);
count_vm_events(PGPGIN, bio_sectors(bio));