linux-kernel - [PATCH mm-unstable 2/2] mm/damon/sysfs-schemes: Return an error for filter memcg path id lookup failure

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Date:   Mon, 19 Dec 2022 17:18:07 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     damon@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, SeongJae Park <sj@...nel.org>
Subject: [PATCH mm-unstable 2/2] mm/damon/sysfs-schemes: Return an error for filter memcg path id lookup failure

Commit f36f860207ef ("mm/damon/sysfs-schemes: implement scheme filters")
on mm-unstable introduced damon_sysfs_memcg_path_to_id(), which returns
non-error even if it didn't find the memcg of the given path.  Caller
could check the failure by seeing if the 'id' has really set or not, but
it's unnecessarily complicated.  Return an error for the case instead.

Fixes: f36f860207ef ("mm/damon/sysfs-schemes: implement scheme filters") on mm-unstable
Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/damon/sysfs-schemes.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 5d3ac3107927..f0dabe3e2dc0 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1418,6 +1418,7 @@ static int damon_sysfs_memcg_path_to_id(char *memcg_path, unsigned short *id)
 {
 	struct mem_cgroup *memcg;
 	char *path;
+	bool found = false;
 
 	if (!memcg_path)
 		return -EINVAL;
@@ -1433,12 +1434,13 @@ static int damon_sysfs_memcg_path_to_id(char *memcg_path, unsigned short *id)
 			continue;
 		if (damon_sysfs_memcg_path_eq(memcg, path, memcg_path)) {
 			*id = mem_cgroup_id(memcg);
+			found = true;
 			break;
 		}
 	}
 
 	kfree(path);
-	return 0;
+	return found ? 0 : -EINVAL;
 }
 
 static int damon_sysfs_set_scheme_filters(struct damos *scheme,
-- 
2.25.1