From: SeongJae Park <sj@kernel.org>
Date: Fri, 6 Mar 2026 15:29:07 +0000 (-0800)
Subject: mm/damon/core: add damon_nr_regions() debug_sanity check
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=242a764abe149f297273be18fdb66cfeaf27dec2;p=thirdparty%2Fkernel%2Flinux.git

mm/damon/core: add damon_nr_regions() debug_sanity check

damon_target->nr_regions is introduced to get the number quickly without
having to iterate regions always.  Add a sanity check for that under
CONFIG_DAMON_DEBUG_SANITY.

Link: https://lkml.kernel.org/r/20260306152914.86303-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/damon/core.c b/mm/damon/core.c
index c499a02ac44eb..16bedde920f03 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -545,8 +545,27 @@ void damon_destroy_target(struct damon_target *t, struct damon_ctx *ctx)
 	damon_free_target(t);
 }
 
+#ifdef CONFIG_DAMON_DEBUG_SANITY
+static void damon_verify_nr_regions(struct damon_target *t)
+{
+	struct damon_region *r;
+	unsigned int count = 0;
+
+	damon_for_each_region(r, t)
+		count++;
+	WARN_ONCE(count != t->nr_regions, "t->nr_regions (%u) != count (%u)\n",
+			t->nr_regions, count);
+}
+#else
+static void damon_verify_nr_regions(struct damon_target *t)
+{
+}
+#endif
+
 unsigned int damon_nr_regions(struct damon_target *t)
 {
+	damon_verify_nr_regions(t);
+
 	return t->nr_regions;
 }