diff options
| author | Christoph Hellwig <hch@lst.de> | 2023-03-27 09:49:51 +0900 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2023-04-17 18:01:22 +0200 |
| commit | 3480373ebdf7625ee29bee6508c9fc4ae70c00bf (patch) | |
| tree | dddeb5c65b5a3d8dd35e31347916ac7d4846ce7b /block/blk-cgroup.c | |
| parent | 0a0596fbbe5bddd28b1dfae7e7ecb6d70bdbf059 (diff) | |
btrfs, block: move REQ_CGROUP_PUNT to btrfs
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>
Diffstat (limited to 'block/blk-cgroup.c')
| -rw-r--r-- | block/blk-cgroup.c | 31 |
1 files changed, 17 insertions, 14 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index bd50b55bdb61..9f5f3263c178 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -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 |