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Fri, 13 Mar 2026 01:00:03 -0700 (PDT) X-Received: by 2002:a17:903:2ace:b0:2ae:ba41:55 with SMTP id d9443c01a7336-2aecab1f315mr23814895ad.26.1773388803242; Fri, 13 Mar 2026 01:00:03 -0700 (PDT) Received: from redhat.com ([209.132.188.88]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2aece825aaesm12117585ad.73.2026.03.13.01.00.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 01:00:02 -0700 (PDT) Date: Fri, 13 Mar 2026 16:00:00 +0800 From: Li Wang To: Yosry Ahmed Cc: yosryahmed@google.com, nphamcs@gmail.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Michal Hocko , Michal =?utf-8?Q?Koutn=C3=BD?= , Muchun Song , Tejun Heo , Roman Gushchin , Shakeel Butt Subject: Re: [PATCH v3 1/7] selftests/cgroup: skip test_zswap if zswap is globally disabled Message-ID: References: <20260313043532.103987-1-liwang@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: gnUFgBUZT34sxc5gSHxUTDVYov3HmJH6ZPFJKaL0uBY_1773388804 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D716640012 X-Stat-Signature: g6u3obhgyxbwffkw9dsutpa334yhzj4w X-Rspam-User: X-HE-Tag: 1773388806-593541 X-HE-Meta: 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 390/xUAU r0wRQoNAKBgz4YPut9EnX9Zf/OytRaY0aARLFMviuTj3dMpkXtXJknU6uFMPmDVqYvY6JXbJQlZ/UjOx83a+Cig1z0I0GI9RJomRg5hnJGpfYJeTZGvyvFFfu9LDOwvk23IbP1Pq7x3/UqAiv8k5P2bAM1N/zJyHM34CuWD7rXjtFKmZuWwMjVqAjJIk1xr1giykXv9QJXdkduVeCqO3ZRxURYVDqnM3ALf0t9H8qVrdpobhvfgpdxWcwwGN0zlw8kfXWvb0IdB1F5hNNcv0U7vtmpiH0mPUsYtT26M/ZGs3la9wwnhckXagtZrpVRzJ/ybl9AlG1af/0cx6AoReyA8vvMJF3an3KTU3oE3KkAjcvlZ3jb/CDTcg1JgnFKY2RzALabD63t2jkVjKE7OaQ9oY2dbqLurKT44jUhRhALliSStLxfqwiKwkjUMRKdHb5Zxr2oTi41Ni5rhTz4axFY/dILYwlaNQnVOuG Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 12, 2026 at 11:34:41PM -0700, Yosry Ahmed wrote: > > diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c > > index 64ebc3f3f203..e69d845d3592 100644 > > --- a/tools/testing/selftests/cgroup/test_zswap.c > > +++ b/tools/testing/selftests/cgroup/test_zswap.c > > @@ -589,9 +589,21 @@ struct zswap_test { > > }; > > #undef T > > > > -static bool zswap_configured(void) > > +static void check_zswap_enabled(void) > > { > > - return access("/sys/module/zswap", F_OK) == 0; > > + char value[2]; > > Please wait for discussions on the previous version to conclude and > give people a little bit of time to respond before sending the next > version. Sorry for the rush. I thought that I had clarified the issue there. > I think this can just be be: > > char value; > ... > > if (read_text(.., &value, sizeof(value)) < 0) This actuall introduce a problem to the code, as in read_text() that achivement is: len = read(fd, buf, max_len - 1); When 'sizeof(value) == 1' pass in that makes read(fd, &value, 0); read zero, after that, the value is set to '\0'. With your < 0 check, this is treated as success, then value == 'N' is false, the check_zswap_enabled will report wrong status (enabled) on disabled. -- Regards, Li Wang