Ignore cgroup without io queued in blk_throtl_cancel_bios for two reasons: 1. Save cpu cycle for trying to dispatch cgroup which is no io queued. 2. Avoid non-consistent state that cgroup is inserted to service queue without THROTL_TG_PENDING set as tg_update_disptime will unconditional re-insert cgroup to service queue. If we are on the default hierarchy, IO dispatched from child in tg_dispatch_one_bio will trigger inserting cgroup to service queue without erase first and ruin the tree. Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> --- block/blk-throttle.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index d516a37e82fb..ee7dc1a0adfd 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -1738,7 +1738,18 @@ void blk_throtl_cancel_bios(struct gendisk *disk) * Set the flag to make sure throtl_pending_timer_fn() won't * stop until all throttled bios are dispatched. */ - blkg_to_tg(blkg)->flags |= THROTL_TG_CANCELING; + tg->flags |= THROTL_TG_CANCELING; + + /* + * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup + * will be inserted to service queue without THROTL_TG_PENDING + * set in tg_update_disptime below. Then IO dispatched from + * child in tg_dispatch_one_bio will trigger double insertion + * and corrupt the tree. + */ + if (!(tg->flags & THROTL_TG_PENDING)) + continue; + /* * Update disptime after setting the above flag to make sure * throtl_select_dispatch() won't exit without dispatching. -- 2.30.0
