From a1dc162e3f7f0c34d66981ffbcc83a2d78bc49b9 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 7 Jan 2014 14:00:40 +0000 Subject: [PATCH] mm: numa: do not clear PTE for pte_numa update commit 0c5f83c23ca703d32f930393825487257a5cde6d upstream. The TLB must be flushed if the PTE is updated but change_pte_range is clearing the PTE while marking PTEs pte_numa without necessarily flushing the TLB if it reinserts the same entry. Without the flush, it's conceivable that two processors have different TLBs for the same virtual address and at the very least it would generate spurious faults. This patch only unmaps the pages in change_pte_range for a full protection change. [riel@redhat.com: write pte_numa pte back to the page tables] Signed-off-by: Mel Gorman Signed-off-by: Rik van Riel Reviewed-by: Rik van Riel Cc: Alex Thorlton Cc: Chegu Vinod Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mprotect.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 6c3f56f..3277121 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -54,13 +54,14 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, pte_t ptent; bool updated = false; - ptent = ptep_modify_prot_start(mm, addr, pte); if (!prot_numa) { + ptent = ptep_modify_prot_start(mm, addr, pte); ptent = pte_modify(ptent, newprot); updated = true; } else { struct page *page; + ptent = *pte; page = vm_normal_page(vma, addr, oldpte); if (page) { int this_nid = page_to_nid(page); @@ -73,6 +74,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, if (!pte_numa(oldpte) && page_mapcount(page) == 1) { ptent = pte_mknuma(ptent); + set_pte_at(mm, addr, pte, ptent); updated = true; } } @@ -89,7 +91,10 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, if (updated) pages++; - ptep_modify_prot_commit(mm, addr, pte, ptent); + + /* Only !prot_numa always clears the pte */ + if (!prot_numa) + ptep_modify_prot_commit(mm, addr, pte, ptent); } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) { swp_entry_t entry = pte_to_swp_entry(oldpte); -- 2.7.4