XArray: Fix xa_reserve for 2-byte aligned entries

If we reserve index 0, the next entry to be stored there might be 2-byte
aligned.  That means we have to create the root xa_node at the time of
reserving the initial entry.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index bc202d468a6b..5d4bad8bd96a 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -1355,6 +1355,10 @@ static void check_align_1(struct xarray *xa, char *name)
         xa_destroy(xa);
 }
 
+/*
+ * We should always be able to store without allocating memory after
+ * reserving a slot.
+ */
 static void check_align_2(struct xarray *xa, char *name)
 {
         int i;
@@ -1366,6 +1370,12 @@ static void check_align_2(struct xarray *xa, char *name)
                 xa_erase(xa, 0);
         }
 
+        for (i = 0; i < 8; i++) {
+                XA_BUG_ON(xa, xa_reserve(xa, 0, GFP_KERNEL) != 0);
+                XA_BUG_ON(xa, xa_store(xa, 0, name + i, 0) != NULL);
+                xa_erase(xa, 0);
+        }
+
         XA_BUG_ON(xa, !xa_empty(xa));
 }