shmem: Convert find_swap_entry to XArray

This is a 1:1 conversion.  The major part of this patch is converting
the test framework from userspace to kernel space and mirroring the
algorithm now used in find_swap_entry().
Signed-off-by: Matthew Wilcox <willy@infradead.org>

lib/test_xarray.c

@@ -631,6 +631,61 @@ static noinline void check_find(struct xarray *xa)
 	check_multi_find_2(xa);
 }
 
+/* See find_swap_entry() in mm/shmem.c */
+static noinline unsigned long xa_find_entry(struct xarray *xa, void *item)
+{
+	XA_STATE(xas, xa, 0);
+	unsigned int checked = 0;
+	void *entry;
+
+	rcu_read_lock();
+	xas_for_each(&xas, entry, ULONG_MAX) {
+		if (xas_retry(&xas, entry))
+			continue;
+		if (entry == item)
+			break;
+		checked++;
+		if ((checked % 4) != 0)
+			continue;
+		xas_pause(&xas);
+	}
+	rcu_read_unlock();
+
+	return entry ? xas.xa_index : -1;
+}
+
+static noinline void check_find_entry(struct xarray *xa)
+{
+#ifdef CONFIG_XARRAY_MULTI
+	unsigned int order;
+	unsigned long offset, index;
+
+	for (order = 0; order < 20; order++) {
+		for (offset = 0; offset < (1UL << (order + 3));
+		     offset += (1UL << order)) {
+			for (index = 0; index < (1UL << (order + 5));
+			     index += (1UL << order)) {
+				xa_store_order(xa, index, order,
+						xa_mk_value(index), GFP_KERNEL);
+				XA_BUG_ON(xa, xa_load(xa, index) !=
+						xa_mk_value(index));
+				XA_BUG_ON(xa, xa_find_entry(xa,
+						xa_mk_value(index)) != index);
+			}
+			XA_BUG_ON(xa, xa_find_entry(xa, xa) != -1);
+			xa_destroy(xa);
+		}
+	}
+#endif
+
+	XA_BUG_ON(xa, xa_find_entry(xa, xa) != -1);
+	xa_store_index(xa, ULONG_MAX, GFP_KERNEL);
+	XA_BUG_ON(xa, xa_find_entry(xa, xa) != -1);
+	XA_BUG_ON(xa, xa_find_entry(xa, xa_mk_value(LONG_MAX)) != -1);
+	xa_erase_index(xa, ULONG_MAX);
+	XA_BUG_ON(xa, !xa_empty(xa));
+}
+
 static noinline void check_move_small(struct xarray *xa, unsigned long idx)
 {
 	XA_STATE(xas, xa, 0);
@@ -972,6 +1027,7 @@ static int xarray_checks(void)
 	check_multi_store(&array);
 	check_xa_alloc();
 	check_find(&array);
+	check_find_entry(&array);
 	check_destroy(&array);
 	check_move(&array);
 	check_create_range(&array);

mm/shmem.c

@@ -1100,34 +1100,27 @@ static void shmem_evict_inode(struct inode *inode)
 	clear_inode(inode);
 }
 
-static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
+static unsigned long find_swap_entry(struct xarray *xa, void *item)
 {
-	struct radix_tree_iter iter;
-	void __rcu **slot;
-	unsigned long found = -1;
+	XA_STATE(xas, xa, 0);
 	unsigned int checked = 0;
+	void *entry;
 
 	rcu_read_lock();
-	radix_tree_for_each_slot(slot, root, &iter, 0) {
-		void *entry = radix_tree_deref_slot(slot);
-
-		if (radix_tree_deref_retry(entry)) {
-			slot = radix_tree_iter_retry(&iter);
+	xas_for_each(&xas, entry, ULONG_MAX) {
+		if (xas_retry(&xas, entry))
 			continue;
-		}
-		if (entry == item) {
-			found = iter.index;
+		if (entry == item)
 			break;
-		}
 		checked++;
-		if ((checked % 4096) != 0)
+		if ((checked % XA_CHECK_SCHED) != 0)
 			continue;
-		slot = radix_tree_iter_resume(slot, &iter);
+		xas_pause(&xas);
 		cond_resched_rcu();
 	}
-
 	rcu_read_unlock();
-	return found;
+
+	return entry ? xas.xa_index : -1;
 }
 
 /*

tools/testing/radix-tree/main.c

@@ -236,63 +236,6 @@ void copy_tag_check(void)
 	item_kill_tree(&tree);
 }
 
-static void __locate_check(struct radix_tree_root *tree, unsigned long index,
-			unsigned order)
-{
-	struct item *item;
-	unsigned long index2;
-
-	item_insert_order(tree, index, order);
-	item = item_lookup(tree, index);
-	index2 = find_item(tree, item);
-	if (index != index2) {
-		printv(2, "index %ld order %d inserted; found %ld\n",
-			index, order, index2);
-		abort();
-	}
-}
-
-static void __order_0_locate_check(void)
-{
-	RADIX_TREE(tree, GFP_KERNEL);
-	int i;
-
-	for (i = 0; i < 50; i++)
-		__locate_check(&tree, rand() % INT_MAX, 0);
-
-	item_kill_tree(&tree);
-}
-
-static void locate_check(void)
-{
-	RADIX_TREE(tree, GFP_KERNEL);
-	unsigned order;
-	unsigned long offset, index;
-
-	__order_0_locate_check();
-
-	for (order = 0; order < 20; order++) {
-		for (offset = 0; offset < (1 << (order + 3));
-		     offset += (1UL << order)) {
-			for (index = 0; index < (1UL << (order + 5));
-			     index += (1UL << order)) {
-				__locate_check(&tree, index + offset, order);
-			}
-			if (find_item(&tree, &tree) != -1)
-				abort();
-
-			item_kill_tree(&tree);
-		}
-	}
-
-	if (find_item(&tree, &tree) != -1)
-		abort();
-	__locate_check(&tree, -1, 0);
-	if (find_item(&tree, &tree) != -1)
-		abort();
-	item_kill_tree(&tree);
-}
-
 static void single_thread_tests(bool long_run)
 {
 	int i;
@@ -303,10 +246,6 @@ static void single_thread_tests(bool long_run)
 	rcu_barrier();
 	printv(2, "after multiorder_check: %d allocated, preempt %d\n",
 		nr_allocated, preempt_count);
-	locate_check();
-	rcu_barrier();
-	printv(2, "after locate_check: %d allocated, preempt %d\n",
-		nr_allocated, preempt_count);
 	tag_check();
 	rcu_barrier();
 	printv(2, "after tag_check: %d allocated, preempt %d\n",

tools/testing/radix-tree/test.c

@@ -209,28 +209,6 @@ int tag_tagged_items(struct radix_tree_root *root, pthread_mutex_t *lock,
 	return tagged;
 }
 
-/* Use the same pattern as find_swap_entry() in mm/shmem.c */
-unsigned long find_item(struct radix_tree_root *root, void *item)
-{
-	struct radix_tree_iter iter;
-	void **slot;
-	unsigned long found = -1;
-	unsigned long checked = 0;
-
-	radix_tree_for_each_slot(slot, root, &iter, 0) {
-		if (*slot == item) {
-			found = iter.index;
-			break;
-		}
-		checked++;
-		if ((checked % 4) != 0)
-			continue;
-		slot = radix_tree_iter_resume(slot, &iter);
-	}
-
-	return found;
-}
-
 static int verify_node(struct radix_tree_node *slot, unsigned int tag,
 			int tagged)
 {

tools/testing/radix-tree/test.h

@@ -32,7 +32,6 @@ void item_kill_tree(struct radix_tree_root *root);
 int tag_tagged_items(struct radix_tree_root *, pthread_mutex_t *,
 			unsigned long start, unsigned long end, unsigned batch,
 			unsigned iftag, unsigned thentag);
-unsigned long find_item(struct radix_tree_root *, void *item);
 
 void xarray_tests(void);
 void tag_check(void);