This is a note to let you know that I've just added the patch titled
mm/damon/ops-common: atomically test and clear young on ptes and pmds
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c11d34fa139e4b0fb4249a30f37b178353533fa1 Mon Sep 17 00:00:00 2001
From: Ryan Roberts <ryan.roberts@xxxxxxx>
Date: Fri, 2 Jun 2023 10:29:47 +0100
Subject: mm/damon/ops-common: atomically test and clear young on ptes and pmds
From: Ryan Roberts <ryan.roberts@xxxxxxx>
commit c11d34fa139e4b0fb4249a30f37b178353533fa1 upstream.
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@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>
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/damon/vaddr.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -393,7 +393,7 @@ static struct page *damon_get_page(unsig
return page;
}
-static void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm,
+static void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma,
unsigned long addr)
{
bool referenced = false;
@@ -402,13 +402,11 @@ static void damon_ptep_mkold(pte_t *pte,
if (!page)
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 */
@@ -419,7 +417,7 @@ static void damon_ptep_mkold(pte_t *pte,
put_page(page);
}
-static void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm,
+static void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma,
unsigned long addr)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -429,13 +427,11 @@ static void damon_pmdp_mkold(pmd_t *pmd,
if (!page)
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,
+ if (mmu_notifier_clear_young(vma->vm_mm, addr,
addr + ((1UL) << HPAGE_PMD_SHIFT)))
referenced = true;
#endif /* CONFIG_MMU_NOTIFIER */
@@ -462,7 +458,7 @@ static int damon_mkold_pmd_entry(pmd_t *
}
if (pmd_huge(*pmd)) {
- damon_pmdp_mkold(pmd, walk->mm, addr);
+ damon_pmdp_mkold(pmd, walk->vma, addr);
spin_unlock(ptl);
return 0;
}
@@ -474,7 +470,7 @@ 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 stable-queue which might be from ryan.roberts@xxxxxxx are
queue-5.15/mm-damon-ops-common-atomically-test-and-clear-young-on-ptes-and-pmds.patch
