| Message ID | 20241122072609.29429-1-daikunhai@didiglobal.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | block: iocost: ensure hweight_inuse is at least 1 | expand |
Hi, 在 2024/11/22 15:26, Kunhai Dai 写道: > 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@didiglobal.com> > --- > 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); I'm confused, how could DIV64_U64_Round_UP() end up less than 1? #define DIV64_U64_ROUND_UP(ll, d) \ ({ u64 _tmp = (d); div64_u64((ll) + _tmp - 1, _tmp); }) AFAIK, the only case that could happen is that iocg->hweight_active - iocg->hweight_donating is 0, then I don't get it now how cound active iocg donate all the hweight, if this really happend perhaps the better solution is to avoid such case. Thanks, Kuai > > /* w' = s' * b' / b'_p */ > inuse = DIV64_U64_ROUND_UP( >
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(
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@didiglobal.com> --- block/blk-iocost.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)