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Thu, 2 Apr 2026 06:38:43 +0000 (UTC) Received: from fedora-laptop-x1.redhat.com (unknown [10.72.112.158]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BC9491800361; Thu, 2 Apr 2026 06:38:34 +0000 (UTC) From: Li Wang To: akpm@linux-foundation.org, rppt@kernel.org, david@kernel.org, hannes@cmpxchg.org, yosry@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, mhocko@suse.com, shuah@kernel.org, chengming.zhou@linux.dev, longman@redhat.com, nphamcs@gmail.com Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Michal Hocko , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Muchun Song , Tejun Heo , Roman Gushchin , Shakeel Butt , Yosry Ahmed Subject: [PATCH v6 8/8] selftests/cgroup: test_zswap: wait for asynchronous writeback Date: Thu, 2 Apr 2026 14:37:14 +0800 Message-ID: <20260402063714.55124-9-liwang@redhat.com> In-Reply-To: <20260402063714.55124-1-liwang@redhat.com> References: <20260402063714.55124-1-liwang@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-MFC-PROC-ID: lwVrHRoZY4p_mRD6yuQ7PZ1r1n3QQ2e_QO_z93WEANo_1775111924 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 39CCE2000A X-Stat-Signature: wk65ke44i1g6jweddm3hamo4ek1g4bh1 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1775111931-990500 X-HE-Meta: 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 DMOhmfNv 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: zswap writeback is asynchronous, but test_zswap.c checks writeback counters immediately after reclaim/trigger paths. On some platforms (e.g. ppc64le), this can race with background writeback and cause spurious failures even when behavior is correct. Add wait_for_writeback() to poll get_cg_wb_count() with a bounded timeout, and use it in: test_zswap_writeback_one() when writeback is expected test_no_invasive_cgroup_shrink() for the wb_group check This keeps the original before/after assertion style while making the tests robust against writeback completion latency. No test behavior change, selftest stability improvement only. Signed-off-by: Li Wang Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Koutný Cc: Muchun Song Cc: Nhat Pham Cc: Tejun Heo Cc: Roman Gushchin Cc: Shakeel Butt Cc: Yosry Ahmed --- Notes: v6: - Declear long type for elapsed and count variables. tools/testing/selftests/cgroup/test_zswap.c | 28 +++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index ffc037922e1b..8656130961a3 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -118,6 +118,27 @@ static char *setup_test_group_1M(const char *root, const char *name) return NULL; } +/* + * Writeback is asynchronous; poll until at least one writeback has + * been recorded for @cg, or until @timeout_ms has elapsed. + */ +static long wait_for_writeback(const char *cg, int timeout_ms) +{ + long elapsed, count; + for (elapsed = 0; elapsed < timeout_ms; elapsed += 100) { + count = get_cg_wb_count(cg); + + if (count < 0) + return -1; + if (count > 0) + return count; + + usleep(100000); + } + + return 0; +} + /* * Sanity test to check that pages are written into zswap. */ @@ -343,7 +364,10 @@ static int test_zswap_writeback_one(const char *cgroup, bool wb) return -1; /* Verify that zswap writeback occurred only if writeback was enabled */ - zswpwb_after = get_cg_wb_count(cgroup); + if (wb) + zswpwb_after = wait_for_writeback(cgroup, 5000); + else + zswpwb_after = get_cg_wb_count(cgroup); if (zswpwb_after < 0) return -1; @@ -474,7 +498,7 @@ static int test_no_invasive_cgroup_shrink(const char *root) } /* Verify that only zswapped memory from gwb_group has been written back */ - if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(zw_group) == 0) + if (wait_for_writeback(wb_group, 5000) > 0 && get_cg_wb_count(zw_group) == 0) ret = KSFT_PASS; out: cg_enter_current(root); -- 2.53.0