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.
Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces").
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>
Reviewed-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
---
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(-)
diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index cc63cf953636..acc264b97903 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -37,7 +37,7 @@ struct folio *damon_get_folio(unsigned long pfn)
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 mm_struct *mm, unsigned long addr)
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 mm_struct *mm, unsigned long addr)
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 mm_struct *mm, unsigned long addr)
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 */
diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h
index 14f4bc69f29b..18d837d11bce 100644
--- a/mm/damon/ops-common.h
+++ b/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);
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 467b99166b43..5b3a3463d078 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -24,9 +24,9 @@ static bool __damon_pa_mkold(struct folio *folio, struct vm_area_struct *vma,
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;
}
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 1fec16d7263e..37994fb6120c 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -311,7 +311,7 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
}
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 *pmd, unsigned long addr,
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;
--
2.25.1
