diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2017-11-27 06:21:25 +0300 |
|---|---|---|
| committer | Sasha Levin <alexander.levin@verizon.com> | 2017-12-08 18:01:15 -0500 |
| commit | 88c251ffb80e140339cbe74f320d6cba38360ab5 (patch) | |
| tree | aa0d82b208eb54a83c393d81b51aeab523835382 /mm | |
| parent | 82cf23e1b0ca95ef53afead81d9563081d8bc431 (diff) | |
mm, thp: Do not make page table dirty unconditionally in touch_p[mu]d()
[ Upstream commit a8f97366452ed491d13cf1e44241bc0b5740b1f0 ]
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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/huge_memory.c | 14 |
1 files changed, 4 insertions, 10 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index bdd6a8dd5797..4aa31c77cbab 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1235,17 +1235,11 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 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_POPULATE) && (vma->vm_flags & VM_LOCKED)) { |