From 97cb95d2148835ae86ff916b145aef332d40439d Mon Sep 17 00:00:00 2001 From: Usama Arif Date: Fri, 14 Aug 2026 09:56:38 -0700 Subject: [PATCH] blk-iocost: clear delay state when freeing policy data iocg_kick_delay() turns sufficiently large debt into an explicit block-cgroup delay with blkcg_set_delay(), setting blkg->use_delay to -1 and incrementing blkcg->congestion_count. Clearing it again depends on iocg_kick_delay() running from the period timer, the waitq timer or the issue path. ioc_pd_free() removes the iocg from active_iocgs and cancels its waitq timer, and no further bios can arrive, so once it has run nothing is left which can reduce the debt and clear the delay. The blkcg stays marked congested for the rest of its life. blk_cgroup_congested() then returns true for every task in that cgroup and its descendants: page_cache_sync_ra() cuts readahead to a single page, page_cache_async_ra() skips it altogether, and __folio_throttle_swaprate() takes swap_avail_lock and schedules a throttle on anonymous folio allocation. Clear it explicitly, after the list removal and the synchronous hrtimer_cancel() so that neither timer processing nor an I/O path can re-arm it. The free callback can also see policy data which was never attached to a blkg, hence the pd->blkg check. Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost") Signed-off-by: Usama Arif Acked-by: Tejun Heo Link: https://patch.msgid.link/20260814165712.510132-3-usama.arif@linux.dev Signed-off-by: Jens Axboe --- block/blk-iocost.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index dd7749d59900..2745bffcd5ee 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -3063,6 +3063,7 @@ static void iocg_release(struct rcu_head *rcu) static void ioc_pd_free(struct blkg_policy_data *pd) { struct ioc_gq *iocg = pd_to_iocg(pd); + struct blkcg_gq *blkg = pd_to_blkg(pd); struct ioc *ioc = iocg->ioc; unsigned long flags; @@ -3085,6 +3086,12 @@ static void ioc_pd_free(struct blkg_policy_data *pd) hrtimer_cancel(&iocg->waitq_timer); } + /* off ->active_iocgs and timer gone, so nothing can re-arm the delay */ + iocg->delay = 0; + iocg->indelay_since = 0; + if (blkg) + blkcg_clear_delay(blkg); + call_rcu(&pd->rcu_head, iocg_release); }