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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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