This is a note to let you know that I've just added the patch titled
mm, thp: Do not make page table dirty unconditionally in touch_p[mu]d()
to the 4.4-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-thp-do-not-make-page-table-dirty-unconditionally-in-touch_pd.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a8f97366452ed491d13cf1e44241bc0b5740b1f0 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Mon, 27 Nov 2017 06:21:25 +0300
Subject: mm, thp: Do not make page table dirty unconditionally in touch_p[mu]d()
From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
commit a8f97366452ed491d13cf1e44241bc0b5740b1f0 upstream.
Currently, we unconditionally make page table dirty in touch_pmd().
It may result in false-positive can_follow_write_pmd().
We may avoid the situation, if we would only make the page table entry
dirty if caller asks for write access -- FOLL_WRITE.
The patch also changes touch_pud() in the same way.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[Salvatore Bonaccorso: backport for 3.16:
- Adjust context
- Drop specific part for PUD-sized transparent hugepages. Support
for PUD-sized transparent hugepages was added in v4.11-rc1
]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1304,17 +1304,11 @@ struct page *follow_trans_huge_pmd(struc
VM_BUG_ON_PAGE(!PageHead(page), page);
if (flags & FOLL_TOUCH) {
pmd_t _pmd;
- /*
- * We should set the dirty bit only for FOLL_WRITE but
- * for now the dirty bit in the pmd is meaningless.
- * And if the dirty bit will become meaningful and
- * we'll only set it with FOLL_WRITE, an atomic
- * set_bit will be required on the pmd to set the
- * young bit, instead of the current set_pmd_at.
- */
- _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
+ _pmd = pmd_mkyoung(*pmd);
+ if (flags & FOLL_WRITE)
+ _pmd = pmd_mkdirty(_pmd);
if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
- pmd, _pmd, 1))
+ pmd, _pmd, flags & FOLL_WRITE))
update_mmu_cache_pmd(vma, addr, pmd);
}
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-4.4/mm-thp-do-not-make-page-table-dirty-unconditionally-in-touch_pd.patch
queue-4.4/mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch