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/mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds.patch
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@xxxxxxx>
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@xxxxxxx
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>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxx 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
