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%3Ba=su...

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@vger.kernel.org know about it.

From a8f97366452ed491d13cf1e44241bc0b5740b1f0 Mon Sep 17 00:00:00 2001

From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com 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@linux.intel.com

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@linux.intel.com Cc: Michal Hocko mhocko@suse.com Cc: Hugh Dickins hughd@google.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [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@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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@linux.intel.com 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