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Date: Tue, 29 Aug 2017 19:46:07 -0700 From: Nadav Amit <nadav.amit@...il.com> To: Jérôme Glisse <jglisse@...hat.com> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>, Dan Williams <dan.j.williams@...el.com>, Ross Zwisler <ross.zwisler@...ux.intel.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Bernhard Held <berny156@....de>, Adam Borowski <kilobyte@...band.pl>, Andrea Arcangeli <aarcange@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, Wanpeng Li <kernellwp@...il.com>, Paolo Bonzini <pbonzini@...hat.com>, Takashi Iwai <tiwai@...e.de>, Mike Galbraith <efault@....de>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, axie <axie@....com>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH 02/13] mm/rmap: update to new mmu_notifier semantic Jérôme Glisse <jglisse@...hat.com> wrote: > Replacing all mmu_notifier_invalidate_page() by mmu_notifier_invalidat_range() > and making sure it is bracketed by call to mmu_notifier_invalidate_range_start/ > end. > > Note that because we can not presume the pmd value or pte value we have to > assume the worse and unconditionaly report an invalidation as happening. > > Signed-off-by: Jérôme Glisse <jglisse@...hat.com> > Cc: Dan Williams <dan.j.williams@...el.com> > Cc: Ross Zwisler <ross.zwisler@...ux.intel.com> > Cc: Linus Torvalds <torvalds@...ux-foundation.org> > Cc: Bernhard Held <berny156@....de> > Cc: Adam Borowski <kilobyte@...band.pl> > Cc: Andrea Arcangeli <aarcange@...hat.com> > Cc: Radim Krčmář <rkrcmar@...hat.com> > Cc: Wanpeng Li <kernellwp@...il.com> > Cc: Paolo Bonzini <pbonzini@...hat.com> > Cc: Takashi Iwai <tiwai@...e.de> > Cc: Nadav Amit <nadav.amit@...il.com> > Cc: Mike Galbraith <efault@....de> > Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> > Cc: axie <axie@....com> > Cc: Andrew Morton <akpm@...ux-foundation.org> > --- > mm/rmap.c | 44 +++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 41 insertions(+), 3 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index c8993c63eb25..da97ed525088 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -887,11 +887,21 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, > .address = address, > .flags = PVMW_SYNC, > }; > + unsigned long start = address, end; > int *cleaned = arg; > > + /* > + * We have to assume the worse case ie pmd for invalidation. Note that > + * the page can not be free from this function. > + */ > + end = min(vma->vm_end, (start & PMD_MASK) + PMD_SIZE); > + mmu_notifier_invalidate_range_start(vma->vm_mm, start, end); > + > while (page_vma_mapped_walk(&pvmw)) { > + unsigned long cstart, cend; > int ret = 0; > - address = pvmw.address; > + > + cstart = address = pvmw.address; > if (pvmw.pte) { > pte_t entry; > pte_t *pte = pvmw.pte; > @@ -904,6 +914,7 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, > entry = pte_wrprotect(entry); > entry = pte_mkclean(entry); > set_pte_at(vma->vm_mm, address, pte, entry); > + cend = cstart + PAGE_SIZE; > ret = 1; > } else { > #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE > @@ -918,6 +929,8 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, > entry = pmd_wrprotect(entry); > entry = pmd_mkclean(entry); > set_pmd_at(vma->vm_mm, address, pmd, entry); > + cstart &= PMD_MASK; > + cend = cstart + PMD_SIZE; > ret = 1; > #else > /* unexpected pmd-mapped page? */ > @@ -926,11 +939,13 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, > } > > if (ret) { > - mmu_notifier_invalidate_page(vma->vm_mm, address); > + mmu_notifier_invalidate_range(vma->vm_mm, cstart, cend); > (*cleaned)++; > } > } > > + mmu_notifier_invalidate_range_end(vma->vm_mm, start, end); > + > return true; > } > > @@ -1324,6 +1339,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > pte_t pteval; > struct page *subpage; > bool ret = true; > + unsigned long start = address, end; > enum ttu_flags flags = (enum ttu_flags)arg; > > /* munlock has nothing to gain from examining un-locked vmas */ > @@ -1335,6 +1351,14 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > flags & TTU_MIGRATION, page); > } > > + /* > + * We have to assume the worse case ie pmd for invalidation. Note that > + * the page can not be free in this function as call of try_to_unmap() > + * must hold a reference on the page. > + */ > + end = min(vma->vm_end, (start & PMD_MASK) + PMD_SIZE); > + mmu_notifier_invalidate_range_start(vma->vm_mm, start, end); > + > while (page_vma_mapped_walk(&pvmw)) { > /* > * If the page is mlock()d, we cannot swap it out. > @@ -1408,6 +1432,8 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > set_huge_swap_pte_at(mm, address, > pvmw.pte, pteval, > vma_mmu_pagesize(vma)); > + mmu_notifier_invalidate_range(mm, address, > + address + vma_mmu_pagesize(vma)); I don’t think that the notifier should be called after the PTE is set, but after the PTE is cleared, PTE permissions are demoted (e.g., RW->RO) or access/dirty bits are cleared. [There is an exception: if the PFN in the PTE is changed without clearing the PTE before, but it does not apply here, and there is a different notifier for this case.] Therefore, IIUC, try_to_umap_one() should only call mmu_notifier_invalidate_range() after ptep_get_and_clear() and ptep_clear_flush() are called. All the other calls to mmu_notifier_invalidate_range() in this function can be removed. Regards, Nadav
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