Messages in this thread Patch in this message | | | Date | Wed, 19 Nov 2014 15:08:42 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 17/19] mlock, thp: HACK: split all pages in VM_LOCKED vma |
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On Wed, Nov 19, 2014 at 09:02:42AM +0000, Naoya Horiguchi wrote: > On Wed, Nov 05, 2014 at 04:49:52PM +0200, Kirill A. Shutemov wrote: > > We don't yet handle mlocked pages properly with new THP refcounting. > > For now we split all pages in VMA on mlock and disallow khugepaged > > collapse pages in the VMA. If split failed on mlock() we fail the > > syscall with -EBUSY. > > --- > ... > > > @@ -542,6 +530,60 @@ next: > > } > > } > > > > +static int thp_split(pmd_t *pmd, unsigned long addr, unsigned long end, > > + struct mm_walk *walk) > > +{ > > + spinlock_t *ptl; > > + struct page *page = NULL; > > + pte_t *pte; > > + int err = 0; > > + > > +retry: > > + if (pmd_none(*pmd)) > > + return 0; > > + if (pmd_trans_huge(*pmd)) { > > + if (is_huge_zero_pmd(*pmd)) { > > + split_huge_pmd(walk->vma, pmd, addr); > > + return 0; > > + } > > + ptl = pmd_lock(walk->mm, pmd); > > + if (!pmd_trans_huge(*pmd)) { > > + spin_unlock(ptl); > > + goto retry; > > + } > > + page = pmd_page(*pmd); > > + VM_BUG_ON_PAGE(!PageHead(page), page); > > + get_page(page); > > + spin_unlock(ptl); > > + err = split_huge_page(page); > > + put_page(page); > > + return err; > > + } > > + pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > > + do { > > + if (!pte_present(*pte)) > > + continue; > > + page = vm_normal_page(walk->vma, addr, *pte); > > + if (!page) > > + continue; > > + if (PageTransCompound(page)) { > > + page = compound_head(page); > > + get_page(page); > > + spin_unlock(ptl); > > + err = split_huge_page(page); > > + spin_lock(ptl); > > + put_page(page); > > + if (!err) { > > + VM_BUG_ON_PAGE(compound_mapcount(page), page); > > + VM_BUG_ON_PAGE(PageTransCompound(page), page); > > If split_huge_page() succeeded, we don't have to continue the iteration, > so break this loop here?
We may want to skip to the next huge page region, but the patch is crap anyway -- don't bother.
-- Kirill A. Shutemov
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