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    SubjectRe: [patch] mm: dirty page tracking race fix
    Date
    On Monday 18 August 2008 17:49, Peter Zijlstra wrote:
    > On Mon, 2008-08-18 at 07:38 +0200, Nick Piggin wrote:

    > > It's possible to retain this optimization for page_referenced and
    > > try_to_unmap.
    >
    > s/synch/sync/ ?
    >
    > we use sync all over the kernel to mean synchonous, so why are you
    > inventing a new shorthand?

    Mmm, we also use synch all over the kernel to mean synchronous,
    including in mm/, so I'm not inventing a new shorthand. sync I
    see is more common, but it's not something anybody would get
    confused about is it?

    >
    > Anyway, still
    >
    > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

    Thanks.


    > > Signed-off-by: Nick Piggin <npiggin@suse.de>
    > > ---
    > > Index: linux-2.6/include/linux/rmap.h
    > > ===================================================================
    > > --- linux-2.6.orig/include/linux/rmap.h
    > > +++ linux-2.6/include/linux/rmap.h
    > > @@ -102,7 +102,7 @@ int try_to_unmap(struct page *, int igno
    > > * Called from mm/filemap_xip.c to unmap empty zero page
    > > */
    > > pte_t *page_check_address(struct page *, struct mm_struct *,
    > > - unsigned long, spinlock_t **);
    > > + unsigned long, spinlock_t **, int);
    > >
    > > /*
    > > * Used by swapoff to help locate where page is expected in vma.
    > > Index: linux-2.6/mm/filemap_xip.c
    > > ===================================================================
    > > --- linux-2.6.orig/mm/filemap_xip.c
    > > +++ linux-2.6/mm/filemap_xip.c
    > > @@ -185,7 +185,7 @@ __xip_unmap (struct address_space * mapp
    > > address = vma->vm_start +
    > > ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
    > > BUG_ON(address < vma->vm_start || address >= vma->vm_end);
    > > - pte = page_check_address(page, mm, address, &ptl);
    > > + pte = page_check_address(page, mm, address, &ptl, 1);
    > > if (pte) {
    > > /* Nuke the page table entry. */
    > > flush_cache_page(vma, address, pte_pfn(*pte));
    > > Index: linux-2.6/mm/rmap.c
    > > ===================================================================
    > > --- linux-2.6.orig/mm/rmap.c
    > > +++ linux-2.6/mm/rmap.c
    > > @@ -224,10 +224,14 @@ unsigned long page_address_in_vma(struct
    > > /*
    > > * Check that @page is mapped at @address into @mm.
    > > *
    > > + * If @synch is false, page_check_address may perform a racy check to
    > > avoid + * the page table lock when the pte is not present (helpful when
    > > reclaiming + * highly shared pages).
    > > + *
    > > * On success returns with pte mapped and locked.
    > > */
    > > pte_t *page_check_address(struct page *page, struct mm_struct *mm,
    > > - unsigned long address, spinlock_t **ptlp)
    > > + unsigned long address, spinlock_t **ptlp, int synch)
    > > {
    > > pgd_t *pgd;
    > > pud_t *pud;
    > > @@ -249,7 +253,7 @@ pte_t *page_check_address(struct page *p
    > >
    > > pte = pte_offset_map(pmd, address);
    > > /* Make a quick check before getting the lock */
    > > - if (!pte_present(*pte)) {
    > > + if (!synch && !pte_present(*pte)) {
    > > pte_unmap(pte);
    > > return NULL;
    > > }
    > > @@ -281,7 +285,7 @@ static int page_referenced_one(struct pa
    > > if (address == -EFAULT)
    > > goto out;
    > >
    > > - pte = page_check_address(page, mm, address, &ptl);
    > > + pte = page_check_address(page, mm, address, &ptl, 0);
    > > if (!pte)
    > > goto out;
    > >
    > > @@ -450,7 +454,7 @@ static int page_mkclean_one(struct page
    > > if (address == -EFAULT)
    > > goto out;
    > >
    > > - pte = page_check_address(page, mm, address, &ptl);
    > > + pte = page_check_address(page, mm, address, &ptl, 1);
    > > if (!pte)
    > > goto out;
    > >
    > > @@ -697,7 +701,7 @@ static int try_to_unmap_one(struct page
    > > if (address == -EFAULT)
    > > goto out;
    > >
    > > - pte = page_check_address(page, mm, address, &ptl);
    > > + pte = page_check_address(page, mm, address, &ptl, 0);
    > > if (!pte)
    > > goto out;
    >
    > --
    > To unsubscribe, send a message with 'unsubscribe linux-mm' in
    > the body to majordomo@kvack.org. For more info on Linux MM,
    > see: http://www.linux-mm.org/ .
    > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>


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