mm/damon/core: remove damon_verify_nr_regions()

When CONFIG_DAMON_DEBUG_SANITY is enabled, damon_verify_nr_regions() is
called for each damon_nr_regions() invocation.  damon_veify_nr_regions()
iterates all regions.  damon_nr_regions() is called for each region in
kdamond_reset_aggregated() and damos_apply_scheme().  Hence it imposes
O(n**2) overhead where n is the number of regions.

Though the verification is enabled only under DAMON_DEBUG_SANITY, which is
not for production use cases, it could be too high overhead.  Meanwhile,
damon_verify_ctx() is doing the damon_nr_regions() test.  Because
damon_verify_ctx() is called for each kdamond_call(), the test coverage
from damon_verify_ctx() could be sufficient.  Remove damon_nr_regions()
verification.

Link: https://lore.kernel.org/20260522154026.80546-10-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 0 insertions, 19 deletions

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 00e2997524ec..b33920873871 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -686,27 +686,8 @@ 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;
 }