The quilt patch titled Subject: mm/mglru: fix div-by-zero in vmpressure_calc_level() has been removed from the -mm tree. Its filename was mm-mglru-fix-div-by-zero-in-vmpressure_calc_level.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Yu Zhao <yuzhao@xxxxxxxxxx> Subject: mm/mglru: fix div-by-zero in vmpressure_calc_level() Date: Thu, 11 Jul 2024 13:19:56 -0600 evict_folios() uses a second pass to reclaim folios that have gone through page writeback and become clean before it finishes the first pass, since folio_rotate_reclaimable() cannot handle those folios due to the isolation. The second pass tries to avoid potential double counting by deducting scan_control->nr_scanned. However, this can result in underflow of nr_scanned, under a condition where shrink_folio_list() does not increment nr_scanned, i.e., when folio_trylock() fails. The underflow can cause the divisor, i.e., scale=scanned+reclaimed in vmpressure_calc_level(), to become zero, resulting in the following crash: [exception RIP: vmpressure_work_fn+101] process_one_work at ffffffffa3313f2b Since scan_control->nr_scanned has no established semantics, the potential double counting has minimal risks. Therefore, fix the problem by not deducting scan_control->nr_scanned in evict_folios(). Link: https://lkml.kernel.org/r/20240711191957.939105-1-yuzhao@xxxxxxxxxx Fixes: 359a5e1416ca ("mm: multi-gen LRU: retry folios written back while isolated") Reported-by: Wei Xu <weixugc@xxxxxxxxxx> Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx> Cc: Alexander Motin <mav@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 1 - 1 file changed, 1 deletion(-) --- a/mm/vmscan.c~mm-mglru-fix-div-by-zero-in-vmpressure_calc_level +++ a/mm/vmscan.c @@ -4597,7 +4597,6 @@ retry: /* retry folios that may have missed folio_rotate_reclaimable() */ list_move(&folio->lru, &clean); - sc->nr_scanned -= folio_nr_pages(folio); } spin_lock_irq(&lruvec->lru_lock); _ Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are