X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=mm%2Fhuge_memory.c;h=8e791a3db6b6804987ae587feff95c79ac940480;hb=e944fd67b625c02bda4a78ddf85e413c5e401474;hp=cb9b3e847dac65ad9d0695c42e606a2ae74df743;hpb=21d9ee3eda7792c45880b2f11bff8e95c9a061fb;p=deliverable%2Flinux.git

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index cb9b3e847dac..8e791a3db6b6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1471,7 +1471,7 @@ out:
  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
  */
 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
-		unsigned long addr, pgprot_t newprot)
+		unsigned long addr, pgprot_t newprot, int prot_numa)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	spinlock_t *ptl;
@@ -1479,6 +1479,17 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 
 	if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
 		pmd_t entry;
+
+		/*
+		 * Avoid trapping faults against the zero page. The read-only
+		 * data is likely to be read-cached on the local CPU and
+		 * local/remote hits to the zero page are not interesting.
+		 */
+		if (prot_numa && is_huge_zero_pmd(*pmd)) {
+			spin_unlock(ptl);
+			return 0;
+		}
+
 		ret = 1;
 		entry = pmdp_get_and_clear_notify(mm, addr, pmd);
 		entry = pmd_modify(entry, newprot);