xarray: Add xas_create_range

This hopefully temporary function is useful for users who have not yet
been converted to multi-index entries.
Signed-off-by: NMatthew Wilcox <willy@infradead.org>

include/linux/xarray.h

@@ -822,6 +822,17 @@ static inline bool xas_valid(const struct xa_state *xas)
 	return !xas_invalid(xas);
 }
 
+/**
+ * xas_is_node() - Does the xas point to a node?
+ * @xas: XArray operation state.
+ *
+ * Return: %true if the xas currently references a node.
+ */
+static inline bool xas_is_node(const struct xa_state *xas)
+{
+	return xas_valid(xas) && xas->xa_node;
+}
+
 /* True if the pointer is something other than a node */
 static inline bool xas_not_node(struct xa_node *node)
 {
@@ -889,6 +900,8 @@ void xas_init_marks(const struct xa_state *);
 bool xas_nomem(struct xa_state *, gfp_t);
 void xas_pause(struct xa_state *);
 
+void xas_create_range(struct xa_state *);
+
 /**
  * xas_reload() - Refetch an entry from the xarray.
  * @xas: XArray operation state.

lib/test_xarray.c

@@ -646,6 +646,124 @@ static noinline void check_move(struct xarray *xa)
 		check_move_small(xa, (1UL << i) - 1);
 }
 
+static noinline void xa_store_many_order(struct xarray *xa,
+		unsigned long index, unsigned order)
+{
+	XA_STATE_ORDER(xas, xa, index, order);
+	unsigned int i = 0;
+
+	do {
+		xas_lock(&xas);
+		XA_BUG_ON(xa, xas_find_conflict(&xas));
+		xas_create_range(&xas);
+		if (xas_error(&xas))
+			goto unlock;
+		for (i = 0; i < (1U << order); i++) {
+			XA_BUG_ON(xa, xas_store(&xas, xa_mk_value(index + i)));
+			xas_next(&xas);
+		}
+unlock:
+		xas_unlock(&xas);
+	} while (xas_nomem(&xas, GFP_KERNEL));
+
+	XA_BUG_ON(xa, xas_error(&xas));
+}
+
+static noinline void check_create_range_1(struct xarray *xa,
+		unsigned long index, unsigned order)
+{
+	unsigned long i;
+
+	xa_store_many_order(xa, index, order);
+	for (i = index; i < index + (1UL << order); i++)
+		xa_erase_index(xa, i);
+	XA_BUG_ON(xa, !xa_empty(xa));
+}
+
+static noinline void check_create_range_2(struct xarray *xa, unsigned order)
+{
+	unsigned long i;
+	unsigned long nr = 1UL << order;
+
+	for (i = 0; i < nr * nr; i += nr)
+		xa_store_many_order(xa, i, order);
+	for (i = 0; i < nr * nr; i++)
+		xa_erase_index(xa, i);
+	XA_BUG_ON(xa, !xa_empty(xa));
+}
+
+static noinline void check_create_range_3(void)
+{
+	XA_STATE(xas, NULL, 0);
+	xas_set_err(&xas, -EEXIST);
+	xas_create_range(&xas);
+	XA_BUG_ON(NULL, xas_error(&xas) != -EEXIST);
+}
+
+static noinline void check_create_range_4(struct xarray *xa,
+		unsigned long index, unsigned order)
+{
+	XA_STATE_ORDER(xas, xa, index, order);
+	unsigned long base = xas.xa_index;
+	unsigned long i = 0;
+
+	xa_store_index(xa, index, GFP_KERNEL);
+	do {
+		xas_lock(&xas);
+		xas_create_range(&xas);
+		if (xas_error(&xas))
+			goto unlock;
+		for (i = 0; i < (1UL << order); i++) {
+			void *old = xas_store(&xas, xa_mk_value(base + i));
+			if (xas.xa_index == index)
+				XA_BUG_ON(xa, old != xa_mk_value(base + i));
+			else
+				XA_BUG_ON(xa, old != NULL);
+			xas_next(&xas);
+		}
+unlock:
+		xas_unlock(&xas);
+	} while (xas_nomem(&xas, GFP_KERNEL));
+
+	XA_BUG_ON(xa, xas_error(&xas));
+
+	for (i = base; i < base + (1UL << order); i++)
+		xa_erase_index(xa, i);
+	XA_BUG_ON(xa, !xa_empty(xa));
+}
+
+static noinline void check_create_range(struct xarray *xa)
+{
+	unsigned int order;
+	unsigned int max_order = IS_ENABLED(CONFIG_XARRAY_MULTI) ? 12 : 1;
+
+	for (order = 0; order < max_order; order++) {
+		check_create_range_1(xa, 0, order);
+		check_create_range_1(xa, 1U << order, order);
+		check_create_range_1(xa, 2U << order, order);
+		check_create_range_1(xa, 3U << order, order);
+		check_create_range_1(xa, 1U << 24, order);
+		if (order < 10)
+			check_create_range_2(xa, order);
+
+		check_create_range_4(xa, 0, order);
+		check_create_range_4(xa, 1U << order, order);
+		check_create_range_4(xa, 2U << order, order);
+		check_create_range_4(xa, 3U << order, order);
+		check_create_range_4(xa, 1U << 24, order);
+
+		check_create_range_4(xa, 1, order);
+		check_create_range_4(xa, (1U << order) + 1, order);
+		check_create_range_4(xa, (2U << order) + 1, order);
+		check_create_range_4(xa, (2U << order) - 1, order);
+		check_create_range_4(xa, (3U << order) + 1, order);
+		check_create_range_4(xa, (3U << order) - 1, order);
+		check_create_range_4(xa, (1U << 24) + 1, order);
+	}
+
+	check_create_range_3();
+}
+
 static noinline void check_destroy(struct xarray *xa)
 {
 	unsigned long index;
@@ -694,6 +812,7 @@ static int xarray_checks(void)
 	check_find(&array);
 	check_destroy(&array);
 	check_move(&array);
+	check_create_range(&array);
 	check_store_iter(&array);
 
 	printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);

lib/xarray.c

@@ -637,6 +637,56 @@ static void *xas_create(struct xa_state *xas)
 	return entry;
 }
 
+/**
+ * xas_create_range() - Ensure that stores to this range will succeed
+ * @xas: XArray operation state.
+ *
+ * Creates all of the slots in the range covered by @xas.  Sets @xas to
+ * create single-index entries and positions it at the beginning of the
+ * range.  This is for the benefit of users which have not yet been
+ * converted to use multi-index entries.
+ */
+void xas_create_range(struct xa_state *xas)
+{
+	unsigned long index = xas->xa_index;
+	unsigned char shift = xas->xa_shift;
+	unsigned char sibs = xas->xa_sibs;
+
+	xas->xa_index |= ((sibs + 1) << shift) - 1;
+	if (xas_is_node(xas) && xas->xa_node->shift == xas->xa_shift)
+		xas->xa_offset |= sibs;
+	xas->xa_shift = 0;
+	xas->xa_sibs = 0;
+
+	for (;;) {
+		xas_create(xas);
+		if (xas_error(xas))
+			goto restore;
+		if (xas->xa_index <= (index | XA_CHUNK_MASK))
+			goto success;
+		xas->xa_index -= XA_CHUNK_SIZE;
+
+		for (;;) {
+			struct xa_node *node = xas->xa_node;
+			xas->xa_node = xa_parent_locked(xas->xa, node);
+			xas->xa_offset = node->offset - 1;
+			if (node->offset != 0)
+				break;
+		}
+	}
+
+restore:
+	xas->xa_shift = shift;
+	xas->xa_sibs = sibs;
+	xas->xa_index = index;
+	return;
+success:
+	xas->xa_index = index;
+	if (xas->xa_node)
+		xas_set_offset(xas);
+}
+EXPORT_SYMBOL_GPL(xas_create_range);
+
 static void update_node(struct xa_state *xas, struct xa_node *node,
 		int count, int values)
 {