diff --git a/mm/memory.c b/mm/memory.c
index a40e4b1..24ba688 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1219,6 +1219,30 @@
 EXPORT_SYMBOL(remap_pfn_range);
 
 /*
+ * handle_pte_fault chooses page fault handler according to an entry
+ * which was read non-atomically.  Before making any commitment, on
+ * those architectures or configurations (e.g. i386 with PAE) which
+ * might give a mix of unmatched parts, do_swap_page and do_file_page
+ * must check under lock before unmapping the pte and proceeding
+ * (but do_wp_page is only called after already making such a check;
+ * and do_anonymous_page and do_no_page can safely check later on).
+ */
+static inline int pte_unmap_same(struct mm_struct *mm,
+				pte_t *page_table, pte_t orig_pte)
+{
+	int same = 1;
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
+	if (sizeof(pte_t) > sizeof(unsigned long)) {
+		spin_lock(&mm->page_table_lock);
+		same = pte_same(*page_table, orig_pte);
+		spin_unlock(&mm->page_table_lock);
+	}
+#endif
+	pte_unmap(page_table);
+	return same;
+}
+
+/*
  * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
  * servicing faults for write access.  In the normal case, do always want
  * pte_mkwrite.  But get_user_pages can cause write faults for mappings
@@ -1245,12 +1269,13 @@
  * change only once the write actually happens. This avoids a few races,
  * and potentially makes it more efficient.
  *
- * We hold the mm semaphore and the page_table_lock on entry and exit
- * with the page_table_lock released.
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), with pte both mapped and locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
-		pte_t orig_pte)
+		spinlock_t *ptl, pte_t orig_pte)
 {
 	struct page *old_page, *new_page;
 	unsigned long pfn = pte_pfn(orig_pte);
@@ -1288,8 +1313,7 @@
 	 * Ok, we need to copy. Oh, well..
 	 */
 	page_cache_get(old_page);
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	pte_unmap_unlock(page_table, ptl);
 
 	if (unlikely(anon_vma_prepare(vma)))
 		goto oom;
@@ -1307,8 +1331,7 @@
 	/*
 	 * Re-check the pte - we dropped the lock
 	 */
-	spin_lock(&mm->page_table_lock);
-	page_table = pte_offset_map(pmd, address);
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
 	if (likely(pte_same(*page_table, orig_pte))) {
 		page_remove_rmap(old_page);
 		if (!PageAnon(old_page)) {
@@ -1321,7 +1344,6 @@
 		ptep_establish(vma, address, page_table, entry);
 		update_mmu_cache(vma, address, entry);
 		lazy_mmu_prot_update(entry);
-
 		lru_cache_add_active(new_page);
 		page_add_anon_rmap(new_page, vma, address);
 
@@ -1332,8 +1354,7 @@
 	page_cache_release(new_page);
 	page_cache_release(old_page);
 unlock:
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	pte_unmap_unlock(page_table, ptl);
 	return ret;
 oom:
 	page_cache_release(old_page);
@@ -1660,20 +1681,22 @@
 }
 
 /*
- * We hold the mm semaphore and the page_table_lock on entry and
- * should release the pagetable lock on exit..
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
 		int write_access, pte_t orig_pte)
 {
+	spinlock_t *ptl;
 	struct page *page;
 	swp_entry_t entry;
 	pte_t pte;
 	int ret = VM_FAULT_MINOR;
 
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	if (!pte_unmap_same(mm, page_table, orig_pte))
+		goto out;
 
 	entry = pte_to_swp_entry(orig_pte);
 	page = lookup_swap_cache(entry);
@@ -1682,11 +1705,10 @@
  		page = read_swap_cache_async(entry, vma, address);
 		if (!page) {
 			/*
-			 * Back out if somebody else faulted in this pte while
-			 * we released the page table lock.
+			 * Back out if somebody else faulted in this pte
+			 * while we released the pte lock.
 			 */
-			spin_lock(&mm->page_table_lock);
-			page_table = pte_offset_map(pmd, address);
+			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
 			if (likely(pte_same(*page_table, orig_pte)))
 				ret = VM_FAULT_OOM;
 			goto unlock;
@@ -1702,11 +1724,9 @@
 	lock_page(page);
 
 	/*
-	 * Back out if somebody else faulted in this pte while we
-	 * released the page table lock.
+	 * Back out if somebody else already faulted in this pte.
 	 */
-	spin_lock(&mm->page_table_lock);
-	page_table = pte_offset_map(pmd, address);
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
 	if (unlikely(!pte_same(*page_table, orig_pte)))
 		goto out_nomap;
 
@@ -1735,7 +1755,7 @@
 
 	if (write_access) {
 		if (do_wp_page(mm, vma, address,
-				page_table, pmd, pte) == VM_FAULT_OOM)
+				page_table, pmd, ptl, pte) == VM_FAULT_OOM)
 			ret = VM_FAULT_OOM;
 		goto out;
 	}
@@ -1744,37 +1764,32 @@
 	update_mmu_cache(vma, address, pte);
 	lazy_mmu_prot_update(pte);
 unlock:
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	pte_unmap_unlock(page_table, ptl);
 out:
 	return ret;
 out_nomap:
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	pte_unmap_unlock(page_table, ptl);
 	unlock_page(page);
 	page_cache_release(page);
 	return ret;
 }
 
 /*
- * We are called with the MM semaphore and page_table_lock
- * spinlock held to protect against concurrent faults in
- * multithreaded programs. 
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
 		int write_access)
 {
-	struct page *page = ZERO_PAGE(addr);
+	struct page *page;
+	spinlock_t *ptl;
 	pte_t entry;
 
-	/* Mapping of ZERO_PAGE - vm_page_prot is readonly */
-	entry = mk_pte(page, vma->vm_page_prot);
-
 	if (write_access) {
 		/* Allocate our own private page. */
 		pte_unmap(page_table);
-		spin_unlock(&mm->page_table_lock);
 
 		if (unlikely(anon_vma_prepare(vma)))
 			goto oom;
@@ -1782,23 +1797,28 @@
 		if (!page)
 			goto oom;
 
-		spin_lock(&mm->page_table_lock);
-		page_table = pte_offset_map(pmd, address);
-
-		if (!pte_none(*page_table)) {
-			page_cache_release(page);
-			goto unlock;
-		}
-		inc_mm_counter(mm, anon_rss);
 		entry = mk_pte(page, vma->vm_page_prot);
 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+
+		page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+		if (!pte_none(*page_table))
+			goto release;
+		inc_mm_counter(mm, anon_rss);
 		lru_cache_add_active(page);
 		SetPageReferenced(page);
 		page_add_anon_rmap(page, vma, address);
 	} else {
+		/* Map the ZERO_PAGE - vm_page_prot is readonly */
+		page = ZERO_PAGE(address);
+		page_cache_get(page);
+		entry = mk_pte(page, vma->vm_page_prot);
+
+		ptl = &mm->page_table_lock;
+		spin_lock(ptl);
+		if (!pte_none(*page_table))
+			goto release;
 		inc_mm_counter(mm, file_rss);
 		page_add_file_rmap(page);
-		page_cache_get(page);
 	}
 
 	set_pte_at(mm, address, page_table, entry);
@@ -1807,9 +1827,11 @@
 	update_mmu_cache(vma, address, entry);
 	lazy_mmu_prot_update(entry);
 unlock:
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	pte_unmap_unlock(page_table, ptl);
 	return VM_FAULT_MINOR;
+release:
+	page_cache_release(page);
+	goto unlock;
 oom:
 	return VM_FAULT_OOM;
 }
@@ -1823,13 +1845,15 @@
  * As this is called only for pages that do not currently exist, we
  * do not need to flush old virtual caches or the TLB.
  *
- * This is called with the MM semaphore held and the page table
- * spinlock held. Exit with the spinlock released.
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
 static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
 		int write_access)
 {
+	spinlock_t *ptl;
 	struct page *new_page;
 	struct address_space *mapping = NULL;
 	pte_t entry;
@@ -1838,7 +1862,6 @@
 	int anon = 0;
 
 	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
 
 	if (vma->vm_file) {
 		mapping = vma->vm_file->f_mapping;
@@ -1878,21 +1901,20 @@
 		anon = 1;
 	}
 
-	spin_lock(&mm->page_table_lock);
+	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
 	/*
 	 * For a file-backed vma, someone could have truncated or otherwise
 	 * invalidated this page.  If unmap_mapping_range got called,
 	 * retry getting the page.
 	 */
 	if (mapping && unlikely(sequence != mapping->truncate_count)) {
-		spin_unlock(&mm->page_table_lock);
+		pte_unmap_unlock(page_table, ptl);
 		page_cache_release(new_page);
 		cond_resched();
 		sequence = mapping->truncate_count;
 		smp_rmb();
 		goto retry;
 	}
-	page_table = pte_offset_map(pmd, address);
 
 	/*
 	 * This silly early PAGE_DIRTY setting removes a race
@@ -1929,8 +1951,7 @@
 	update_mmu_cache(vma, address, entry);
 	lazy_mmu_prot_update(entry);
 unlock:
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	pte_unmap_unlock(page_table, ptl);
 	return ret;
 oom:
 	page_cache_release(new_page);
@@ -1941,6 +1962,10 @@
  * Fault of a previously existing named mapping. Repopulate the pte
  * from the encoded file_pte if possible. This enables swappable
  * nonlinear vmas.
+ *
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
 static int do_file_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pte_t *page_table, pmd_t *pmd,
@@ -1949,8 +1974,8 @@
 	pgoff_t pgoff;
 	int err;
 
-	pte_unmap(page_table);
-	spin_unlock(&mm->page_table_lock);
+	if (!pte_unmap_same(mm, page_table, orig_pte))
+		return VM_FAULT_MINOR;
 
 	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
 		/*
@@ -1989,8 +2014,8 @@
 		pte_t *pte, pmd_t *pmd, int write_access)
 {
 	pte_t entry;
+	spinlock_t *ptl;
 
-	spin_lock(&mm->page_table_lock);
 	entry = *pte;
 	if (!pte_present(entry)) {
 		if (pte_none(entry)) {
@@ -2007,17 +2032,22 @@
 					pte, pmd, write_access, entry);
 	}
 
+	ptl = &mm->page_table_lock;
+	spin_lock(ptl);
+	if (unlikely(!pte_same(*pte, entry)))
+		goto unlock;
 	if (write_access) {
 		if (!pte_write(entry))
-			return do_wp_page(mm, vma, address, pte, pmd, entry);
+			return do_wp_page(mm, vma, address,
+					pte, pmd, ptl, entry);
 		entry = pte_mkdirty(entry);
 	}
 	entry = pte_mkyoung(entry);
 	ptep_set_access_flags(vma, address, pte, entry, write_access);
 	update_mmu_cache(vma, address, entry);
 	lazy_mmu_prot_update(entry);
-	pte_unmap(pte);
-	spin_unlock(&mm->page_table_lock);
+unlock:
+	pte_unmap_unlock(pte, ptl);
 	return VM_FAULT_MINOR;
 }