On 02/02/2016 08:34 AM, Andrew Morton wrote:

On Wed, 27 Jan 2016 19:25:06 +0100 Alexander Potapenko [off-list ref] wrote:

quoted

depending on which allocator (SLAB or SLUB) is being used

...

--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c

@@ -68,7 +68,22 @@ static noinline void __init kmalloc_node_oob_right(void)
 static noinline void __init kmalloc_large_oob_right(void)
 {
 	char *ptr;
-	size_t size = KMALLOC_MAX_CACHE_SIZE + 10;
+	size_t size;
+
+	if (KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE) {
+		/*
+		 * We're using the SLAB allocator. Allocate a chunk that fits
+		 * into a slab.
+		 */
+		size = KMALLOC_MAX_CACHE_SIZE - 256;
+	} else {
+		/*
+		 * KMALLOC_MAX_SIZE > KMALLOC_MAX_CACHE_SIZE.
+		 * We're using the SLUB allocator. Allocate a chunk that does
+		 * not fit into a slab to trigger the page allocator.
+		 */
+		size = KMALLOC_MAX_CACHE_SIZE + 10;
+	}

This seems a weird way of working out whether we're using SLAB or SLUB.

Can't we use, umm, #ifdef CONFIG_SLAB?  If not that then let's cook up
something standardized rather than a weird just-happens-to-work like
this.

Actually it would be simpler to not use KMALLOC_MAX_CACHE_SIZE at all.
Simply replace it with 2 or 3 PAGE_SIZEs.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>