Messages in this thread Patch in this message | | | From | Baolin Wang <> | Subject | [PATCH v2 1/2] mm/damon: validate if the pmd entry is present before accessing | Date | Thu, 18 Aug 2022 15:37:43 +0800 |
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The pmd_huge() is used to validate if the pmd entry is mapped by a huge page, also including the case of non-present (migration or hwpoisoned) pmd entry on arm64 or x86 architectures. That means the pmd_pfn() can not get the correct pfn number for the non-present pmd entry, which will cause damon_get_page() to get an incorrect page struct (also may be NULL by pfn_to_online_page()) to make the access statistics incorrect.
Moreover it does not make sense that we still waste time to get the page of the non-present entry, just treat it as not-accessed and skip it, that keeps consistent with non-present pte level entry.
Thus adding a pmd entry present validation to fix above issues.
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: SeongJae Park <sj@kernel.org> --- Changes from v1: - Update the commit message to make it more clear. - Add reviewed tag from SeongJae. --- mm/damon/vaddr.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 3c7b9d6..1d16c6c 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -304,6 +304,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr, if (pmd_huge(*pmd)) { ptl = pmd_lock(walk->mm, pmd); + if (!pmd_present(*pmd)) { + spin_unlock(ptl); + return 0; + } + if (pmd_huge(*pmd)) { damon_pmdp_mkold(pmd, walk->mm, addr); spin_unlock(ptl); @@ -431,6 +436,11 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr, #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (pmd_huge(*pmd)) { ptl = pmd_lock(walk->mm, pmd); + if (!pmd_present(*pmd)) { + spin_unlock(ptl); + return 0; + } + if (!pmd_huge(*pmd)) { spin_unlock(ptl); goto regular_page; -- 1.8.3.1
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