[RFC PATCH 08/14] mm/damon/core: add kdamond_call() debug_sanity check

[SeongJae Park <sj@kernel.org>]

kdamond_call() is the place where DAMON API callers are allowed to
access the DAMON context's public internal state including the
monitoring results. Hence it is important to ensure it is called with
the expected DAMON context state.  Do the check under
DAMON_DEBUG_SANITY.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 8a9202937781c..22327a23c7e57 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -3331,6 +3331,37 @@ static void kdamond_usleep(unsigned long usecs)
 		usleep_range_idle(usecs, usecs + 1);
 }
 
+#ifdef CONFIG_DAMON_DEBUG_SANITY
+static void damon_verify_ctx(struct damon_ctx *c)
+{
+	struct damon_target *t;
+	struct damon_region *r;
+
+	damon_for_each_target(t, c) {
+		struct damon_region *prev_r = NULL;
+		unsigned int nr_regions = 0;
+
+		damon_for_each_region(r, t) {
+			WARN_ONCE(r->ar.start <= r->ar.end,
+					"region start (%lu) <= end (%lu)\n",
+					r->ar.start, r->ar.end);
+			WARN_ONCE(prev_r && prev_r->ar.end > r->ar.start,
+					"region overlap (%lu > %lu)\n",
+					prev_r->ar.end, r->ar.start);
+			prev_r = r;
+			nr_regions++;
+		}
+		WARN_ONCE(damon_nr_regions(t) != nr_regions,
+				"nr_regions mismatch: %u != %u\n",
+				damon_nr_regions(t), nr_regions);
+	}
+}
+#else
+static void damon_verify_ctx(struct damon_ctx *c)
+{
+}
+#endif
+
 /*
  * kdamond_call() - handle damon_call_control objects.
  * @ctx:	The &struct damon_ctx of the kdamond.
@@ -3346,6 +3377,8 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel)
 	struct damon_call_control *control, *next;
 	LIST_HEAD(controls);
 
+	damon_verify_ctx(ctx);
+
 	mutex_lock(&ctx->call_controls_lock);
 	list_splice_tail_init(&ctx->call_controls, &controls);
 	mutex_unlock(&ctx->call_controls_lock);
-- 
2.47.3