The patch titled Subject: mm/damon/ops-common: atomically test and clear young on ptes and pmds has been added to the -mm mm-unstable branch. Its filename is mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Ryan Roberts ryan.roberts@arm.com Subject: mm/damon/ops-common: atomically test and clear young on ptes and pmds Date: Fri, 2 Jun 2023 10:29:47 +0100

It is racy to non-atomically read a pte, then clear the young bit, then write it back as this could discard dirty information. Further, it is bad practice to directly set a pte entry within a table. Instead clearing young must go through the arch-provided helper, ptep_test_and_clear_young() to ensure it is modified atomically and to give the arch code visibility and allow it to check (and potentially modify) the operation.

Link: https://lkml.kernel.org/r/20230602092949.545577-3-ryan.roberts@arm.com Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces"). Signed-off-by: Ryan Roberts ryan.roberts@arm.com Reviewed-by: Zi Yan ziy@nvidia.com Reviewed-by: SeongJae Park sj@kernel.org Reviewed-by: Mike Rapoport (IBM) rppt@kernel.org Cc: Christoph Hellwig hch@infradead.org Cc: Christoph Hellwig hch@lst.de Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Lorenzo Stoakes lstoakes@gmail.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Uladzislau Rezki (Sony) urezki@gmail.com Cc: Yu Zhao yuzhao@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/damon/ops-common.c | 16 ++++++---------- mm/damon/ops-common.h | 4 ++-- mm/damon/paddr.c | 4 ++-- mm/damon/vaddr.c | 4 ++-- 4 files changed, 12 insertions(+), 16 deletions(-)

--- a/mm/damon/ops-common.c~mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds +++ a/mm/damon/ops-common.c @@ -37,7 +37,7 @@ struct folio *damon_get_folio(unsigned l return folio; }

-void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr) +void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr) { bool referenced = false; struct folio *folio = damon_get_folio(pte_pfn(*pte)); @@ -45,13 +45,11 @@ void damon_ptep_mkold(pte_t *pte, struct if (!folio) return;

- if (pte_young(*pte)) { + if (ptep_test_and_clear_young(vma, addr, pte)) referenced = true; - *pte = pte_mkold(*pte); - }

#ifdef CONFIG_MMU_NOTIFIER - if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE)) + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE)) referenced = true; #endif /* CONFIG_MMU_NOTIFIER */

@@ -62,7 +60,7 @@ void damon_ptep_mkold(pte_t *pte, struct folio_put(folio); }

-void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr) +void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE bool referenced = false; @@ -71,13 +69,11 @@ void damon_pmdp_mkold(pmd_t *pmd, struct if (!folio) return;

- if (pmd_young(*pmd)) { + if (pmdp_test_and_clear_young(vma, addr, pmd)) referenced = true; - *pmd = pmd_mkold(*pmd); - }

#ifdef CONFIG_MMU_NOTIFIER - if (mmu_notifier_clear_young(mm, addr, addr + HPAGE_PMD_SIZE)) + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + HPAGE_PMD_SIZE)) referenced = true; #endif /* CONFIG_MMU_NOTIFIER */

--- a/mm/damon/ops-common.h~mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds +++ a/mm/damon/ops-common.h @@ -9,8 +9,8 @@

struct folio *damon_get_folio(unsigned long pfn);

-void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr); -void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr); +void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr); +void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr);

int damon_cold_score(struct damon_ctx *c, struct damon_region *r, struct damos *s); --- a/mm/damon/paddr.c~mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds +++ a/mm/damon/paddr.c @@ -24,9 +24,9 @@ static bool __damon_pa_mkold(struct foli while (page_vma_mapped_walk(&pvmw)) { addr = pvmw.address; if (pvmw.pte) - damon_ptep_mkold(pvmw.pte, vma->vm_mm, addr); + damon_ptep_mkold(pvmw.pte, vma, addr); else - damon_pmdp_mkold(pvmw.pmd, vma->vm_mm, addr); + damon_pmdp_mkold(pvmw.pmd, vma, addr); } return true; } --- a/mm/damon/vaddr.c~mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds +++ a/mm/damon/vaddr.c @@ -311,7 +311,7 @@ static int damon_mkold_pmd_entry(pmd_t * }

if (pmd_trans_huge(*pmd)) { - damon_pmdp_mkold(pmd, walk->mm, addr); + damon_pmdp_mkold(pmd, walk->vma, addr); spin_unlock(ptl); return 0; } @@ -323,7 +323,7 @@ static int damon_mkold_pmd_entry(pmd_t * pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); if (!pte_present(*pte)) goto out; - damon_ptep_mkold(pte, walk->mm, addr); + damon_ptep_mkold(pte, walk->vma, addr); out: pte_unmap_unlock(pte, ptl); return 0; _

Patches currently in -mm which might be from ryan.roberts@arm.com are

mm-vmalloc-must-set-pte-via-arch-code.patch mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds.patch mm-damon-ops-common-refactor-to-use-ptepmdp_clear_young_notify.patch mm-fix-failure-to-unmap-pte-on-highmem-systems.patch