damon_new_region() is supposed to be called with only valid address
range arguments.  Do the check under DAMON_DEBUG_SANITY.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index f1a97e85824ac..0c1353164ec81 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -109,6 +109,17 @@ int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id)
 	return err;
 }
 
+#ifdef CONFIG_DAMON_DEBUG_SANITY
+static void damon_verify_new_region(unsigned long start, unsigned long end)
+{
+	WARN_ONCE(start >= end, "start %lu >= end %lu\n", start, end);
+}
+#else
+static void damon_verify_new_region(unsigned long start, unsigned long end)
+{
+}
+#endif
+
 /*
  * Construct a damon_region struct
  *
@@ -118,6 +129,7 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 {
 	struct damon_region *region;
 
+	damon_verify_new_region(start, end);
 	region = kmem_cache_alloc(damon_region_cache, GFP_KERNEL);
 	if (!region)
 		return NULL;
-- 
2.47.3