xarray: Destroy an XArray

This function frees all the internal memory allocated to the xarray
and reinitialises it to be empty.

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

2 files changed, 62 insertions, 0 deletions

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index e3c2d4d00b15..a96f67caa1c2 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -465,6 +465,39 @@ static noinline void check_find(struct xarray *xa)
         check_multi_find_2(xa);
 }
 
+static noinline void check_destroy(struct xarray *xa)
+{
+        unsigned long index;
+
+        XA_BUG_ON(xa, !xa_empty(xa));
+
+        /* Destroying an empty array is a no-op */
+        xa_destroy(xa);
+        XA_BUG_ON(xa, !xa_empty(xa));
+
+        /* Destroying an array with a single entry */
+        for (index = 0; index < 1000; index++) {
+                xa_store_index(xa, index, GFP_KERNEL);
+                XA_BUG_ON(xa, xa_empty(xa));
+                xa_destroy(xa);
+                XA_BUG_ON(xa, !xa_empty(xa));
+        }
+
+        /* Destroying an array with a single entry at ULONG_MAX */
+        xa_store(xa, ULONG_MAX, xa, GFP_KERNEL);
+        XA_BUG_ON(xa, xa_empty(xa));
+        xa_destroy(xa);
+        XA_BUG_ON(xa, !xa_empty(xa));
+
+#ifdef CONFIG_XARRAY_MULTI
+        /* Destroying an array with a multi-index entry */
+        xa_store_order(xa, 1 << 11, 11, xa, GFP_KERNEL);
+        XA_BUG_ON(xa, xa_empty(xa));
+        xa_destroy(xa);
+        XA_BUG_ON(xa, !xa_empty(xa));
+#endif
+}
+
 static DEFINE_XARRAY(array);
 
 static int xarray_checks(void)
@@ -478,6 +511,7 @@ static int xarray_checks(void)
         check_cmpxchg(&array);
         check_multi_store(&array);
         check_find(&array);
+        check_destroy(&array);
 
         printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);
         return (tests_run == tests_passed) ? 0 : -EINVAL;
diff --git a/lib/xarray.c b/lib/xarray.c
index 70e04810c8c2..057dbe0d3bf6 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1524,6 +1524,34 @@ unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
 }
 EXPORT_SYMBOL(xa_extract);
 
+/**
+ * xa_destroy() - Free all internal data structures.
+ * @xa: XArray.
+ *
+ * After calling this function, the XArray is empty and has freed all memory
+ * allocated for its internal data structures.  You are responsible for
+ * freeing the objects referenced by the XArray.
+ *
+ * Context: Any context.  Takes and releases the xa_lock, interrupt-safe.
+ */
+void xa_destroy(struct xarray *xa)
+{
+        XA_STATE(xas, xa, 0);
+        unsigned long flags;
+        void *entry;
+
+        xas.xa_node = NULL;
+        xas_lock_irqsave(&xas, flags);
+        entry = xa_head_locked(xa);
+        RCU_INIT_POINTER(xa->xa_head, NULL);
+        xas_init_marks(&xas);
+        /* lockdep checks we're still holding the lock in xas_free_nodes() */
+        if (xa_is_node(entry))
+                xas_free_nodes(&xas, xa_to_node(entry));
+        xas_unlock_irqrestore(&xas, flags);
+}
+EXPORT_SYMBOL(xa_destroy);
+
 #ifdef XA_DEBUG
 void xa_dump_node(const struct xa_node *node)
 {