diff --git a/mm/shmem.c b/mm/shmem.c
index 585bd220a21ee4e5eefaec2b9c46dc9ae68fde98..a15a466d0d1d14b21bd82de2bfd3df31654420db 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -683,10 +683,21 @@ static int shmem_unuse_inode(struct shmem_inode_info *info,
 		mutex_lock(&shmem_swaplist_mutex);
 		/*
 		 * We needed to drop mutex to make that restrictive page
-		 * allocation; but the inode might already be freed by now,
-		 * and we cannot refer to inode or mapping or info to check.
-		 * However, we do hold page lock on the PageSwapCache page,
-		 * so can check if that still has our reference remaining.
+		 * allocation, but the inode might have been freed while we
+		 * dropped it: although a racing shmem_evict_inode() cannot
+		 * complete without emptying the radix_tree, our page lock
+		 * on this swapcache page is not enough to prevent that -
+		 * free_swap_and_cache() of our swap entry will only
+		 * trylock_page(), removing swap from radix_tree whatever.
+		 *
+		 * We must not proceed to shmem_add_to_page_cache() if the
+		 * inode has been freed, but of course we cannot rely on
+		 * inode or mapping or info to check that.  However, we can
+		 * safely check if our swap entry is still in use (and here
+		 * it can't have got reused for another page): if it's still
+		 * in use, then the inode cannot have been freed yet, and we
+		 * can safely proceed (if it's no longer in use, that tells
+		 * nothing about the inode, but we don't need to unuse swap).
 		 */
 		if (!page_swapcount(*pagep))
 			error = -ENOENT;
@@ -730,9 +741,9 @@ int shmem_unuse(swp_entry_t swap, struct page *page)
 
 	/*
 	 * There's a faint possibility that swap page was replaced before
-	 * caller locked it: it will come back later with the right page.
+	 * caller locked it: caller will come back later with the right page.
 	 */
-	if (unlikely(!PageSwapCache(page)))
+	if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
 		goto out;
 
 	/*
@@ -995,21 +1006,15 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 	newpage = shmem_alloc_page(gfp, info, index);
 	if (!newpage)
 		return -ENOMEM;
-	VM_BUG_ON(shmem_should_replace_page(newpage, gfp));
 
-	*pagep = newpage;
 	page_cache_get(newpage);
 	copy_highpage(newpage, oldpage);
+	flush_dcache_page(newpage);
 
-	VM_BUG_ON(!PageLocked(oldpage));
 	__set_page_locked(newpage);
-	VM_BUG_ON(!PageUptodate(oldpage));
 	SetPageUptodate(newpage);
-	VM_BUG_ON(!PageSwapBacked(oldpage));
 	SetPageSwapBacked(newpage);
-	VM_BUG_ON(!swap_index);
 	set_page_private(newpage, swap_index);
-	VM_BUG_ON(!PageSwapCache(oldpage));
 	SetPageSwapCache(newpage);
 
 	/*
@@ -1019,13 +1024,24 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 	spin_lock_irq(&swap_mapping->tree_lock);
 	error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
 								   newpage);
-	__inc_zone_page_state(newpage, NR_FILE_PAGES);
-	__dec_zone_page_state(oldpage, NR_FILE_PAGES);
+	if (!error) {
+		__inc_zone_page_state(newpage, NR_FILE_PAGES);
+		__dec_zone_page_state(oldpage, NR_FILE_PAGES);
+	}
 	spin_unlock_irq(&swap_mapping->tree_lock);
-	BUG_ON(error);
 
-	mem_cgroup_replace_page_cache(oldpage, newpage);
-	lru_cache_add_anon(newpage);
+	if (unlikely(error)) {
+		/*
+		 * Is this possible?  I think not, now that our callers check
+		 * both PageSwapCache and page_private after getting page lock;
+		 * but be defensive.  Reverse old to newpage for clear and free.
+		 */
+		oldpage = newpage;
+	} else {
+		mem_cgroup_replace_page_cache(oldpage, newpage);
+		lru_cache_add_anon(newpage);
+		*pagep = newpage;
+	}
 
 	ClearPageSwapCache(oldpage);
 	set_page_private(oldpage, 0);
@@ -1033,7 +1049,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 	unlock_page(oldpage);
 	page_cache_release(oldpage);
 	page_cache_release(oldpage);
-	return 0;
+	return error;
 }
 
 /*
@@ -1107,7 +1123,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 
 		/* We have to do this with page locked to prevent races */
 		lock_page(page);
-		if (!PageSwapCache(page) || page->mapping) {
+		if (!PageSwapCache(page) || page_private(page) != swap.val ||
+		    page->mapping) {
 			error = -EEXIST;	/* try again */
 			goto failed;
 		}