In fact, we did encounter such a special situation where the kernel printed out `iocg: invalid donation weights in /a/b/c: active=1 donating=1 after=0`, and then it immediately panic. I analyzed the code but could not figure out how this happened; it might be a concurrency issue or some other hidden bug. Our kernel is not the latest, but it includes the patch edaa26334c117a584add6053f48d63a988d25a6e (iocost: Fix divide-by-zero on donation from low hweight cgroup). 在 2024/11/22 15:26，“戴坤海 Tony Dai”<daikunhai@xxxxxxxxxxxxxx <mailto:daikunhai@xxxxxxxxxxxxxx>> 写入: The hweight_inuse calculation in transfer_surpluses() could potentially result in a value of 0, which would lead to division by zero errors in subsequent calculations that use this value as a divisor. Signed-off-by: Kunhai Dai <daikunhai@xxxxxxxxxxxxxx <mailto:daikunhai@xxxxxxxxxxxxxx>> --- block/blk-iocost.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 384aa15e8260..65cdb55d30cc 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -1999,9 +1999,10 @@ static void transfer_surpluses(struct list_head *surpluses, struct ioc_now *now) parent = iocg->ancestors[iocg->level - 1]; /* b' = gamma * b_f + b_t' */ - iocg->hweight_inuse = DIV64_U64_ROUND_UP( - (u64)gamma * (iocg->hweight_active - iocg->hweight_donating), - WEIGHT_ONE) + iocg->hweight_after_donation; + iocg->hweight_inuse = max_t(u64, 1, + DIV64_U64_ROUND_UP( + (u64)gamma * (iocg->hweight_active - iocg->hweight_donating), + WEIGHT_ONE) + iocg->hweight_after_donation); /* w' = s' * b' / b'_p */ inuse = DIV64_U64_ROUND_UP( -- 2.27.0
