linux-kernel - [PATCH v3 3/3] selftests: cgroup: make sure reclaim target memcg is unprotected

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Date:   Fri,  2 Dec 2022 03:15:12 +0000
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>, Yu Zhao <yuzhao@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Tejun Heo <tj@...nel.org>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vasily Averin <vasily.averin@...ux.dev>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chris Down <chris@...isdown.name>,
        David Rientjes <rientjes@...gle.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: [PATCH v3 3/3] selftests: cgroup: make sure reclaim target memcg is unprotected

Make sure that we ignore protection of a memcg that is the target of
memcg reclaim.

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>
---
 tools/testing/selftests/cgroup/test_memcontrol.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index a8f4700353a4..1e616a8c6a9c 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -238,6 +238,8 @@ static int cg_test_proc_killed(const char *cgroup)
 	return -1;
 }
 
+static bool reclaim_until(const char *memcg, long goal);
+
 /*
  * First, this test creates the following hierarchy:
  * A       memory.min = 0,    memory.max = 200M
@@ -266,6 +268,12 @@ static int cg_test_proc_killed(const char *cgroup)
  * unprotected memory in A available, and checks that:
  * a) memory.min protects pagecache even in this case,
  * b) memory.low allows reclaiming page cache with low events.
+ *
+ * Then we try to reclaim from A/B/C using memory.reclaim until its
+ * usage reaches 10M.
+ * This makes sure that:
+ * (a) We ignore the protection of the reclaim target memcg.
+ * (b) The previously calculated emin value (~29M) should be dismissed.
  */
 static int test_memcg_protection(const char *root, bool min)
 {
@@ -385,6 +393,9 @@ static int test_memcg_protection(const char *root, bool min)
 	if (!values_close(cg_read_long(parent[1], "memory.current"), MB(50), 3))
 		goto cleanup;
 
+	if (!reclaim_until(children[0], MB(10)))
+		goto cleanup;
+
 	if (min) {
 		ret = KSFT_PASS;
 		goto cleanup;
-- 
2.39.0.rc0.267.gcb52ba06e7-goog