Re: [RFC PATCH v3 3/3] blk-cgroup: move async bio punt state to blkcg

在 2026/8/18 15:06, Yu Kuai 写道:

blkcg_punt_bio_submit() currently queues punted bios on blkg->async_bios,
so it has to call bio_blkg() to find or create a queue-local blkg.  Bios
now carry and pin the blkcg css, so punted bio lifetime no longer needs to
be anchored by a blkg.

Keeping the punt state in blkg can instantiate a blkg even when no blkcg
policy is enabled, just to bounce submission from a shared kthread.  Move
async_bio_lock, async_bios and async_bio_work to struct blkcg, and queue
punted bios on bio_blkcg() for non-root cgroups.  Root or unassociated bios
are submitted directly.

This preserves the priority-inversion avoidance while preventing
blkcg_punt_bio_submit() from creating blkgs that are not needed by any
policy.

Reviewed-by: Tao Cui <redacted>