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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1777003378; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VcJ71eB0Ct26LCodBxWEDWyUKWisA2ZlGgHlF6yt2M8=; b=u2UUUdOLq/sTdbKir0hjZ104Y8LIJpS74cn7qDT1LzGQvC8x59z4JKTAYYFv+Mi2wy77jP 0erlRvbTWrp6xVDva3XA8Q9mWdOuWMDPKHx9XMzdrSkIVihGcR7+omGvoVjKtNcjcQJGTn HOhQ3z3hpFynAlwnZwurAZ3K3oZ/krY= From: Li Wang To: akpm@linux-foundation.org, tj@kernel.org, longman@redhat.com, roman.gushchin@linux.dev, hannes@cmpxchg.org, yosry@kernel.org, jiayuan.chen@linux.dev, nphamcs@gmail.com, chengming.zhou@linux.dev, mkoutny@suse.com, shuah@kernel.org Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Michal Hocko , Muchun Song , Shakeel Butt , Yosry Ahmed Subject: [PATCH v7 8/8] selftests/cgroup: test_zswap: wait for asynchronous writeback Date: Fri, 24 Apr 2026 12:00:59 +0800 Message-ID: <20260424040059.12940-9-li.wang@linux.dev> In-Reply-To: <20260424040059.12940-1-li.wang@linux.dev> References: <20260424040059.12940-1-li.wang@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 9i8b4q34n6tdr1dtqkzao8e7hz9cnxpe X-Rspam-User: X-Rspamd-Queue-Id: 9E09980014 X-Rspamd-Server: rspam05 X-HE-Tag: 1777003379-791100 X-HE-Meta: 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 WUZTilBI yQCyAqJ9ucaw5PXaB4C7pjzQ90/DwsCq7alrzcCKBmCJ1GGGsm9H4kMrGEAMLo0CHyEfgEtoh/evQ1/0E6YTdFVDk4yJdX3/EYmWqD6V7ZHmE7QYy71fDGIcppv0C6HH9jzXYzraYFEcskpvN23epBl73GkLL/lV45tVhGchJOHwT/1BttLqbjH6Lfo/+ZR0vkqYLWZW1bNi5OZiB9XXJ9qhjLryBzXqaL0oo4WMqbrpwaP2zDyNKFWypdgwG0l2vQzYy8CX5I9Eebo+Y0zpcvJczcswp5Cmvsq33ff+aXq0tBbUlLGGCQ8bdKxoednZPQjVlZ2FR0e2BcSl0YVfAUom/H5RjG4APbxM4XRUX6JTZarUoGqmXDeeFqsvCOx1aw4hRK11N/qNBPXHq8VNuOBvrik7PiPmqEx65KadRa4OvVusqqjaqXg0n9JqdjUP+Wh24MyNTqwu43/JKanHjDKISiQ== 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 Acked-by: Nhat Pham --- 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 5fe0cffb557..49b36ee7916 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -120,6 +120,27 @@ 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. */ @@ -345,7 +366,10 @@ 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; @@ -476,7 +500,7 @@ 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