mm/damon/core: fix commit_ops_filters by using correct nth function

damos_commit_ops_filters() incorrectly uses damos_nth_filter() which
iterates core_filters.  As a result, performing a commit unintentionally
corrupts ops_filters.

Add damos_nth_ops_filter() which iterates ops_filters.  Use this function
to fix issues caused by wrong iteration.

Link: https://lkml.kernel.org/r/20250810124201.15743-1-ekffu200098@gmail.com
Fixes: 3607cc5 ("mm/damon/core: support committing ops_filters") # 6.15.x
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: hqsz

mm/damon/core.c

@@ -845,6 +845,18 @@ static struct damos_filter *damos_nth_filter(int n, struct damos *s)
 	return NULL;
 }
 
+static struct damos_filter *damos_nth_ops_filter(int n, struct damos *s)
+{
+	struct damos_filter *filter;
+	int i = 0;
+
+	damos_for_each_ops_filter(filter, s) {
+		if (i++ == n)
+			return filter;
+	}
+	return NULL;
+}
+
 static void damos_commit_filter_arg(
 		struct damos_filter *dst, struct damos_filter *src)
 {
@@ -908,7 +920,7 @@ static int damos_commit_ops_filters(struct damos *dst, struct damos *src)
 	int i = 0, j = 0;
 
 	damos_for_each_ops_filter_safe(dst_filter, next, dst) {
-		src_filter = damos_nth_filter(i++, src);
+		src_filter = damos_nth_ops_filter(i++, src);
 		if (src_filter)
 			damos_commit_filter(dst_filter, src_filter);
 		else