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 4.9-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-4.9 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 4.9: - 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 | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-)

--- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -745,20 +745,15 @@ int vmf_insert_pfn_pmd(struct vm_area_st EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);

static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, - pmd_t *pmd) + pmd_t *pmd, int flags) { 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); }

@@ -787,7 +782,7 @@ struct page *follow_devmap_pmd(struct vm return NULL;

if (flags & FOLL_TOUCH) - touch_pmd(vma, addr, pmd); + touch_pmd(vma, addr, pmd, flags);

/* * device mapped pages can only be returned if the @@ -1158,7 +1153,7 @@ struct page *follow_trans_huge_pmd(struc page = pmd_page(*pmd); VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); if (flags & FOLL_TOUCH) - touch_pmd(vma, addr, pmd); + touch_pmd(vma, addr, pmd, flags); if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { /* * We don't mlock() pte-mapped THPs. This way we can avoid

Patches currently in stable-queue which might be from kirill.shutemov@linux.intel.com are

queue-4.9/mm-thp-do-not-make-page-table-dirty-unconditionally-in-touch_pd.patch queue-4.9/mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch