From 2441774f2d2890940f2db21bbc264c7e2f56d1ae Mon Sep 17 00:00:00 2001 From: Qi Zheng Date: Thu, 26 Sep 2024 14:46:25 +0800 Subject: [PATCH] mm: multi-gen LRU: walk_pte_range() use pte_offset_map_rw_nolock() In walk_pte_range(), we may modify the pte entry after holding the ptl, so convert it to using pte_offset_map_rw_nolock(). At this time, the pte_same() check is not performed after the ptl held, so we should get pmdval and do pmd_same() check to ensure the stability of pmd entry. Link: https://lkml.kernel.org/r/7e9c194a5efacc9609cfd31abb9c7df88b53b530.1727332572.git.zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Reviewed-by: Muchun Song Acked-by: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Mike Rapoport (Microsoft) Cc: Peter Xu Cc: Ryan Roberts Cc: Vishal Moola (Oracle) Signed-off-by: Andrew Morton --- mm/vmscan.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 20dd72c98813..8f25dd6cec54 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3386,8 +3386,10 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); DEFINE_MAX_SEQ(walk->lruvec); int old_gen, new_gen = lru_gen_from_seq(max_seq); + pmd_t pmdval; - pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl); + pte = pte_offset_map_rw_nolock(args->mm, pmd, start & PMD_MASK, &pmdval, + &ptl); if (!pte) return false; if (!spin_trylock(ptl)) { @@ -3395,6 +3397,11 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, return false; } + if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) { + pte_unmap_unlock(pte, ptl); + return false; + } + arch_enter_lazy_mmu_mode(); restart: for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) { -- 2.25.1