mm: numa: Do not mark PTEs pte_numa when splitting huge pages
commitabc40bd2ee
upstream. This patch reverts1ba6e0b50b
("mm: numa: split_huge_page: transfer the NUMA type from the pmd to the pte"). If a huge page is being split due a protection change and the tail will be in a PROT_NONE vma then NUMA hinting PTEs are temporarily created in the protected VMA. VM_RW|VM_PROTNONE |-----------------| ^ split here In the specific case above, it should get fixed up by change_pte_range() but there is a window of opportunity for weirdness to happen. Similarly, if a huge page is shrunk and split during a protection update but before pmd_numa is cleared then a pte_numa can be left behind. Instead of adding complexity trying to deal with the case, this patch will not mark PTEs NUMA when splitting a huge page. NUMA hinting faults will not be triggered which is marginal in comparison to the complexity in dealing with the corner cases during THP split. Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1826,14 +1826,17 @@ static int __split_huge_page_map(struct page *page,
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for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
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for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
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pte_t *pte, entry;
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pte_t *pte, entry;
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BUG_ON(PageCompound(page+i));
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BUG_ON(PageCompound(page+i));
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/*
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* Note that pmd_numa is not transferred deliberately
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* to avoid any possibility that pte_numa leaks to
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* a PROT_NONE VMA by accident.
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*/
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entry = mk_pte(page + i, vma->vm_page_prot);
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entry = mk_pte(page + i, vma->vm_page_prot);
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entry = maybe_mkwrite(pte_mkdirty(entry), vma);
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entry = maybe_mkwrite(pte_mkdirty(entry), vma);
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if (!pmd_write(*pmd))
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if (!pmd_write(*pmd))
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entry = pte_wrprotect(entry);
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entry = pte_wrprotect(entry);
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if (!pmd_young(*pmd))
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if (!pmd_young(*pmd))
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entry = pte_mkold(entry);
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entry = pte_mkold(entry);
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if (pmd_numa(*pmd))
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entry = pte_mknuma(entry);
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pte = pte_offset_map(&_pmd, haddr);
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pte = pte_offset_map(&_pmd, haddr);
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BUG_ON(!pte_none(*pte));
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BUG_ON(!pte_none(*pte));
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set_pte_at(mm, haddr, pte, entry);
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set_pte_at(mm, haddr, pte, entry);
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