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b=EtH4RCPAGt8eG3YAeogfbeH4uqJlSWBkDjNf+0ldGQu2sW+ZDSssoW4DVtN8vXsci 0TuCYsbHtG0qtsbUZ5LwHtsJ18k/2dBxrJ9MdBXSZHMMZkYpQ5GJJdxc02a+OPMnse e/X2awvw8y6cF12of+7uXMUcE5LsKFhd93XayEtx7fbHboYqBBffGlhkiHf046JwaR n4hz1yqShHSRqdhqsYMKRjR3m2e2SNsNwdsoZumtQu5sXdEWz1ctbIzkqMbfI5iGRf N/FPnYieXVGG58iZ66mMQ3krFQbnFHevuJZ3ZNdGXQ+2eG4X4PU472jaMx8leAFmjl I9mblwyJgh4SA== From: SJ Park To: Harry Yoo Cc: SJ Park , Johannes Weiner , Yosry Ahmed , Nhat Pham , Usama Arif , Chengming Zhou , Tejun Heo , Michal =?utf-8?Q?Koutn=C3=BD?= , Shuah Khan , Andrew Morton , Joshua Hahn , Kiryl Shutsemau , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests/cgroup: ignore memory.reclaim -EAGAIN for zswap writeback test Date: Tue, 15 Sep 2026 07:10:48 -0700 Message-ID: <20260915141049.70696-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: 83b1udyck79hsen6efjmr479axx35jnm X-Rspamd-Queue-Id: 9773B18000C X-Rspamd-Server: rspam07 X-HE-Tag: 1789481457-186188 X-HE-Meta: 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 Hrd/oB/n zX64pRPqmPmd4mJQn0nyMfKtGAZTVncq/cN4e34emFl399RXIwW0ucwMPURUjiN1BIMbYxHt3wTRMMPoH/tupueTySOd1f/dKbZtDPgh6R61n7o8iv8WVFlN5L0QN1pTnn/NDMJW+AtrbZ58v1MapHd0egqNHg2uj8SnXMfsw/S6uAP0yI6C/0mQCP1OFt1YhlrPhNXhF0TJeFOD4zgAsMFfugBZLuu2O+R9vvDsitOw/o1ZuKET/Piw92Oj0JRmwMNRa0+7+9tH1lAX1pCSrupw8b5q2c0xKjIhYbdwWG1lq+nJgjEO3I6Wl5A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 15 Sep 2026 11:21:53 +0100 Harry Yoo wrote: > On Mon, Sep 14, 2026 at 05:18:17PM -0700, SJ Park wrote: > > Hi Harry, > > Hi SJ, thanks for looking into it! > > > On Mon, 14 Sep 2026 21:36:39 +0100 "Harry Yoo (Meta)" wrote: > > Makes sense to me. > > Thanks! > > > [...] > > > --- a/tools/testing/selftests/cgroup/test_zswap.c > > > +++ b/tools/testing/selftests/cgroup/test_zswap.c > > > @@ -346,7 +346,16 @@ static int attempt_writeback(const char *cgroup, void *arg) > > > * it can't writeback to swap. > > > */ > > > ret = cg_write_numeric(cgroup, "memory.reclaim", memsize); > > > - if (!wb_enabled) > > > + > > > + /* > > > + * When writeback is enabled, memory.reclaim may still fail to reclaim > > > + * the requested amount of memory due to a slow swap device. > > > + * Ignore -EAGAIN here. The caller determines pass/fail based on the > > > + * zswap writeback counter. > > > + */ > > > + if (wb_enabled && ret == -EAGAIN) > > > + ret = 0; > > > + else if (!wb_enabled) > > > ret = (ret == -EAGAIN) ? 0 : -1; > > > > My humble eyes were unable to easily understand the change. Is the change > > effectively same to below, and if so, would this be easier to read? > > > > ''' > > @@ -344,10 +344,11 @@ static int attempt_writeback(const char *cgroup, void *arg) > > * writeback as zswap.max is 1/4 of what was needed when reclaim ran the first time. > > * If writeback is disabled, memory reclaim will fail as zswap is limited and > > * it can't writeback to swap. > > + * Even if writeback is enabled, it could return -EAGAIN due to a slow > > + * swap device. > > */ > > ret = cg_write_numeric(cgroup, "memory.reclaim", memsize); > > - if (!wb_enabled) > > - ret = (ret == -EAGAIN) ? 0 : -1; > > + ret = (ret == -EAGAIN) ? 0 : -1; > > Hmm, no. This will mark the test as failed when a write to > memory.reclaim returns zero even when wb_enabled is true. > > It's not the same because when wb_enabled == true we consider > ret == 0 or ret == -EAGAIN as success, while with wb_enabled == false > we consider ret == -EAGAIN as success. Ah, got it. You are right. Sorry for making noise and thank you for kindly correcting me. Reviewed-by: SJ Park Thanks, SJ [...]