xarray: Add xa_reserve and xa_release
This function reserves a slot in the XArray for users which need
to acquire multiple locks before storing their entry in the tree and
so cannot use a plain xa_store().
Signed-off-by: Matthew Wilcox <[email protected]>
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index 7033700..6aafd411 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -259,6 +259,45 @@ static noinline void check_cmpxchg(struct xarray *xa)
XA_BUG_ON(xa, !xa_empty(xa));
}
+static noinline void check_reserve(struct xarray *xa)
+{
+ void *entry;
+ unsigned long index = 0;
+
+ /* An array with a reserved entry is not empty */
+ XA_BUG_ON(xa, !xa_empty(xa));
+ xa_reserve(xa, 12345678, GFP_KERNEL);
+ XA_BUG_ON(xa, xa_empty(xa));
+ XA_BUG_ON(xa, xa_load(xa, 12345678));
+ xa_release(xa, 12345678);
+ XA_BUG_ON(xa, !xa_empty(xa));
+
+ /* Releasing a used entry does nothing */
+ xa_reserve(xa, 12345678, GFP_KERNEL);
+ XA_BUG_ON(xa, xa_store_index(xa, 12345678, GFP_NOWAIT) != NULL);
+ xa_release(xa, 12345678);
+ xa_erase_index(xa, 12345678);
+ XA_BUG_ON(xa, !xa_empty(xa));
+
+ /* cmpxchg sees a reserved entry as NULL */
+ xa_reserve(xa, 12345678, GFP_KERNEL);
+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, NULL, xa_mk_value(12345678),
+ GFP_NOWAIT) != NULL);
+ xa_release(xa, 12345678);
+ xa_erase_index(xa, 12345678);
+ XA_BUG_ON(xa, !xa_empty(xa));
+
+ /* Can iterate through a reserved entry */
+ xa_store_index(xa, 5, GFP_KERNEL);
+ xa_reserve(xa, 6, GFP_KERNEL);
+ xa_store_index(xa, 7, GFP_KERNEL);
+
+ xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
+ XA_BUG_ON(xa, index != 5 && index != 7);
+ }
+ xa_destroy(xa);
+}
+
static noinline void check_xas_erase(struct xarray *xa)
{
XA_STATE(xas, xa, 0);
@@ -808,6 +847,7 @@ static int xarray_checks(void)
check_xa_shrink(&array);
check_xas_erase(&array);
check_cmpxchg(&array);
+ check_reserve(&array);
check_multi_store(&array);
check_find(&array);
check_destroy(&array);
