On Thu, 19 Oct 2023 19:49:19 +0000 SeongJae Park <sj@xxxxxxxxxx> wrote: > The maximum nr_accesses of given DAMON context can be calculated by > dividing the aggregation interval by the sampling interval. Some logics > in DAMON uses the maximum nr_accesses as a divisor. Hence, the value > shouldn't be zero. Such case is avoided since DAMON avoids setting the > agregation interval as samller than the sampling interval. However, > since nr_accesses is unsigned int while the intervals are unsigned long, > the maximum nr_accesses could be zero while casting. Actually, the issue was reported by Jakub, and I didn't add 'Reported-by:' tags for him. I sure Andrew could add that on his own, but I want to minimize Andrew's load, so will send v2 of this patchset. Andrew, please let me know if that doesn't help but only increasing your load. Thanks, SJ > > Avoid the divide-by-zero by implementing a function that handles the > corner case (first patch), and replaces the vulnerable direct max > nr_accesses calculations (remaining patches). > > Note that the patches for the replacements are divided for broken > commits, to make backporting on required tres easier. Especially, the > last patch is for a patch that not yet merged into the mainline but in > mm tree. > > SeongJae Park (5): > mm/damon: implement a function for max nr_accesses safe calculation > mm/damon/core: avoid divide-by-zero during monitoring results update > mm/damon/ops-common: avoid divide-by-zero during region hotness > calculation > mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation > mm/damon/core: avoid divide-by-zero from pseudo-moving window length > calculation > > include/linux/damon.h | 7 +++++++ > mm/damon/core.c | 12 +++--------- > mm/damon/lru_sort.c | 4 +--- > mm/damon/ops-common.c | 5 ++--- > 4 files changed, 13 insertions(+), 15 deletions(-) > > > base-commit: e845524c56a529768a8793e96304db09134eafdf > -- > 2.34.1 > >
