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b=cQuaEnvyIVzF1iyxdJAkXqhmxDCZYMNY9j2eYZJ07Mb6eI4uuD6iCsTsS+XpIax5b wX76OJsUvCoHl44rzpGGKNbDUnkQZdxlMma60wLmSTyYPzGIgHgsFm1eUQU//wGMlD XkLaNUmR9cJYUhhJcYebFLcWjw6QOfQ2MYSbJYY0ycp+xgVXdunHq6/e+yfNYiUdxE E6pJrCmbnIC1vM+8lUjIKIleVNO8CY3bc05B66ou/M/Pr3PYwIiSk/KWDfEyynFjl4 Cymr2wIIm3yXem2ANvwX2ZqgPbMUlLxxmycHSORHJHSC2b7YT6yQ8S03CF/Yj4r8FR 9HL8UnSyELE5A== Date: Tue, 15 Sep 2026 11:21:53 +0100 From: Harry Yoo To: SJ Park Cc: 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 Message-ID: References: <20260914-test-zswap-wb-ignore-eagain-v1-1-6fb715c22cd8@kernel.org> <20260915001817.101713-1-sj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260915001817.101713-1-sj@kernel.org> X-Stat-Signature: kt7yxdpxfw48a9xcknownc9j8nedrndx X-Rspam-User: X-Rspamd-Queue-Id: A64A240008 X-Rspamd-Server: rspam03 X-HE-Tag: 1789467716-258836 X-HE-Meta: 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 WanZEc+c t06oMhf2K85hQUvj3sd5lfgWhCwzbADMG8Z57FOluykJQsg5ahVf1YnRmvW/Cd6QYpMZsSm90hEdsYeHULaoq+yFDFdBsT1cwZRAlqz3Bi341rp14c/SbFLHFrX/vlzM79fjCXjYHVnnHxiHOT1oBUgtbe8BQ4gUKMr/LaA+pnGU5LNFJyTIDrGsu6+KDzYV5h+NGUcIyIY9H9FCjcx2sv4gxAvcUS2XWdbL3V//2kLFNbR6mh6ukVkpuW4Qhvvv1mr0uH6DmFfT9rs+IcEhsi/3aK3pSq+r3wWM1aXFPhj3SXNGpjQac7jUSMXLX8/t6fVkKtqF76UKUeU82QgSkQ4BP96TlssBL5OT4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Not sure we can reduce that to one line of code. > out: > free(mem); > ''' -- Cheers, Harry / Hyeonggon