mm: Convert workingset to XArray

We construct an XA_STATE and use it to delete the node with
xas_store() rather than adding a special function for this unique
use case.  Includes a test that simulates this usage for the
test suite.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index a752e6a37e6f..128c6489082f 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -863,6 +863,67 @@ static noinline void check_create_range(struct xarray *xa)
         check_create_range_3();
 }
 
+static LIST_HEAD(shadow_nodes);
+
+static void test_update_node(struct xa_node *node)
+{
+        if (node->count && node->count == node->nr_values) {
+                if (list_empty(&node->private_list))
+                        list_add(&shadow_nodes, &node->private_list);
+        } else {
+                if (!list_empty(&node->private_list))
+                        list_del_init(&node->private_list);
+        }
+}
+
+static noinline void shadow_remove(struct xarray *xa)
+{
+        struct xa_node *node;
+
+        xa_lock(xa);
+        while ((node = list_first_entry_or_null(&shadow_nodes,
+                                        struct xa_node, private_list))) {
+                XA_STATE(xas, node->array, 0);
+                XA_BUG_ON(xa, node->array != xa);
+                list_del_init(&node->private_list);
+                xas.xa_node = xa_parent_locked(node->array, node);
+                xas.xa_offset = node->offset;
+                xas.xa_shift = node->shift + XA_CHUNK_SHIFT;
+                xas_set_update(&xas, test_update_node);
+                xas_store(&xas, NULL);
+        }
+        xa_unlock(xa);
+}
+
+static noinline void check_workingset(struct xarray *xa, unsigned long index)
+{
+        XA_STATE(xas, xa, index);
+        xas_set_update(&xas, test_update_node);
+
+        do {
+                xas_lock(&xas);
+                xas_store(&xas, xa_mk_value(0));
+                xas_next(&xas);
+                xas_store(&xas, xa_mk_value(1));
+                xas_unlock(&xas);
+        } while (xas_nomem(&xas, GFP_KERNEL));
+
+        XA_BUG_ON(xa, list_empty(&shadow_nodes));
+
+        xas_lock(&xas);
+        xas_next(&xas);
+        xas_store(&xas, &xas);
+        XA_BUG_ON(xa, !list_empty(&shadow_nodes));
+
+        xas_store(&xas, xa_mk_value(2));
+        xas_unlock(&xas);
+        XA_BUG_ON(xa, list_empty(&shadow_nodes));
+
+        shadow_remove(xa);
+        XA_BUG_ON(xa, !list_empty(&shadow_nodes));
+        XA_BUG_ON(xa, !xa_empty(xa));
+}
+
 static noinline void check_destroy(struct xarray *xa)
 {
         unsigned long index;
@@ -916,6 +977,10 @@ static int xarray_checks(void)
         check_create_range(&array);
         check_store_iter(&array);
 
+        check_workingset(&array, 0);
+        check_workingset(&array, 64);
+        check_workingset(&array, 4096);
+
         printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);
         return (tests_run == tests_passed) ? 0 : -EINVAL;
 }