1 files changed, 15 insertions, 31 deletions

diff --git a/mm/mprotect.c b/mm/mprotect.c
index f9c07f54dd62..a45b4dc6a7f5 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -33,34 +33,6 @@
 
 #include "internal.h"
 
-/*
- * For a prot_numa update we only hold mmap_sem for read so there is a
- * potential race with faulting where a pmd was temporarily none. This
- * function checks for a transhuge pmd under the appropriate lock. It
- * returns a pte if it was successfully locked or NULL if it raced with
- * a transhuge insertion.
- */
-static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd,
-			unsigned long addr, int prot_numa, spinlock_t **ptl)
-{
-	pte_t *pte;
-	spinlock_t *pmdl;
-
-	/* !prot_numa is protected by mmap_sem held for write */
-	if (!prot_numa)
-		return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
-
-	pmdl = pmd_lock(vma->vm_mm, pmd);
-	if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) {
-		spin_unlock(pmdl);
-		return NULL;
-	}
-
-	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
-	spin_unlock(pmdl);
-	return pte;
-}
-
 static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long addr, unsigned long end, pgprot_t newprot,
 		int dirty_accountable, int prot_numa)
@@ -71,7 +43,21 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 	unsigned long pages = 0;
 	int target_node = NUMA_NO_NODE;
 
-	pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl);
+	/*
+	 * Can be called with only the mmap_sem for reading by
+	 * prot_numa so we must check the pmd isn't constantly
+	 * changing from under us from pmd_none to pmd_trans_huge
+	 * and/or the other way around.
+	 */
+	if (pmd_trans_unstable(pmd))
+		return 0;
+
+	/*
+	 * The pmd points to a regular pte so the pmd can't change
+	 * from under us even if the mmap_sem is only hold for
+	 * reading.
+	 */
+	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	if (!pte)
 		return 0;
 
@@ -177,8 +163,6 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 		if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 			if (next - addr != HPAGE_PMD_SIZE) {
 				__split_huge_pmd(vma, pmd, addr, false, NULL);
-				if (pmd_trans_unstable(pmd))
-					continue;
 			} else {
 				int nr_ptes = change_huge_pmd(vma, pmd, addr,
 						newprot, prot_numa);