test_maple_tree: test exhausted upper limit of mtree_alloc_cyclic()

When the upper bound of the search is exhausted, the maple state may be
returned in an error state of -EBUSY.  This means maple state needs to be
reset before the second search in mas_alloc_cylic() to ensure the search
happens.  This test ensures the issue is not recreated.

Link: https://lkml.kernel.org/r/20241216190113.1226145-3-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Yang Erkun <yangerkun@huawei.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com> says:
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index 72bda304b595252230bc590ded14cf552108140f..13e2a10d7554d6b1de5ffbda59f3a5bc4039a8c8 100644 (file)
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -3738,6 +3738,34 @@ static noinline void __init alloc_cyclic_testing(struct maple_tree *mt)
        }
 
        mtree_destroy(mt);
+
+       /*
+        * Issue with reverse search was discovered
+        * https://lore.kernel.org/all/20241216060600.287B4C4CED0@smtp.kernel.org/
+        * Exhausting the allocation area and forcing the search to wrap needs a
+        * mas_reset() in mas_alloc_cyclic().
+        */
+       next = 0;
+       mt_init_flags(mt, MT_FLAGS_ALLOC_RANGE);
+       for (int i = 0; i < 1023; i++) {
+               mtree_alloc_cyclic(mt, &location, mt, 2, 1024, &next, GFP_KERNEL);
+               MT_BUG_ON(mt, i != location - 2);
+               MT_BUG_ON(mt, i != next - 3);
+               MT_BUG_ON(mt, mtree_load(mt, location) != mt);
+       }
+       mtree_erase(mt, 123);
+       MT_BUG_ON(mt, mtree_load(mt, 123) != NULL);
+       mtree_alloc_cyclic(mt, &location, mt, 2, 1024, &next, GFP_KERNEL);
+       MT_BUG_ON(mt, 123 != location);
+       MT_BUG_ON(mt, 124 != next);
+       MT_BUG_ON(mt, mtree_load(mt, location) != mt);
+       mtree_erase(mt, 100);
+       mtree_alloc_cyclic(mt, &location, mt, 2, 1024, &next, GFP_KERNEL);
+       MT_BUG_ON(mt, 100 != location);
+       MT_BUG_ON(mt, 101 != next);
+       MT_BUG_ON(mt, mtree_load(mt, location) != mt);
+       mtree_destroy(mt);
+
        /* Overflow test */
        next = ULONG_MAX - 1;
        ret = mtree_alloc_cyclic(mt, &location, mt, 2, ULONG_MAX, &next, GFP_KERNEL);