The patch titled
Subject: mm: do not lose dirty and accessed bits in pmdp_invalidate()
has been added to the -mm tree. Its filename is
mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: do not lose dirty and accessed bits in pmdp_invalidate()
Vlastimil noted that pmdp_invalidate() is not atomic and we can lose dirty
and access bits if CPU sets them after pmdp dereference, but before
set_pmd_at().
The patch change pmdp_invalidate() to make the entry non-present
atomically and return previous value of the entry. This value can be used
to check if CPU set dirty/accessed bits under us.
The race window is very small and I haven't seen any reports that can be
attributed to the bug. For this reason, I don't think backporting to
stable trees needed.
Link: http://lkml.kernel.org/r/20171213105756.69879-11-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: David Daney <david.daney@xxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Nitin Gupta <nitin.m.gupta@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/asm-generic/pgtable.h | 2 +-
mm/pgtable-generic.c | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
diff -puN include/asm-generic/pgtable.h~mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate include/asm-generic/pgtable.h
--- a/include/asm-generic/pgtable.h~mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate
+++ a/include/asm-generic/pgtable.h
@@ -325,7 +325,7 @@ static inline pmd_t generic_pmdp_establi
#endif
#ifndef __HAVE_ARCH_PMDP_INVALIDATE
-extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+extern pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp);
#endif
diff -puN mm/pgtable-generic.c~mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate mm/pgtable-generic.c
--- a/mm/pgtable-generic.c~mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate
+++ a/mm/pgtable-generic.c
@@ -181,12 +181,12 @@ pgtable_t pgtable_trans_huge_withdraw(st
#endif
#ifndef __HAVE_ARCH_PMDP_INVALIDATE
-void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
- pmd_t entry = *pmdp;
- set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry));
+ pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mknotpresent(*pmdp));
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
+ return old;
}
#endif
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
asm-generic-provide-generic_pmdp_establish.patch
arc-use-generic_pmdp_establish-as-pmdp_establish.patch
arm-mm-provide-pmdp_establish-helper.patch
mips-use-generic_pmdp_establish-as-pmdp_establish.patch
x86-mm-provide-pmdp_establish-helper.patch
mm-do-not-lose-dirty-and-access-bits-in-pmdp_invalidate.patch
mm-use-updated-pmdp_invalidate-interface-to-track-dirty-accessed-bits.patch
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