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Thu, 06 Aug 2026 01:33:13 -0700 (PDT) Date: Thu, 6 Aug 2026 10:33:12 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Yosry Ahmed Cc: Wilson Felipe Pereira , Johannes Weiner , Nhat Pham , Chengming Zhou , Tejun Heo , Shuah Khan , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH 1/2] selftests/cgroup: test_zswap: retry subtree_control write on EBUSY in test_zswap_writeback Message-ID: References: <20260804042053.56940-1-wfelipe@google.com> <20260804042053.56940-2-wfelipe@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="nas2iww3rivojx2z" Content-Disposition: inline In-Reply-To: --nas2iww3rivojx2z Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 1/2] selftests/cgroup: test_zswap: retry subtree_control write on EBUSY in test_zswap_writeback MIME-Version: 1.0 On Mon, Aug 03, 2026 at 11:39:14PM -0700, Yosry Ahmed wr= ote: > > diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testin= g/selftests/cgroup/test_zswap.c > > index 49b36ee791606..312d51887a1d8 100644 > > --- a/tools/testing/selftests/cgroup/test_zswap.c > > +++ b/tools/testing/selftests/cgroup/test_zswap.c > > @@ -407,8 +407,11 @@ static int test_zswap_writeback(const char *root, = bool wb) > > * Thus, the parent's setting shall be what's in effect. */ > > if (cg_write(test_group, "memory.zswap.max", "max")) > > goto out; > > - if (cg_write(test_group, "cgroup.subtree_control", "+memory")) > > - goto out; > > + while (cg_write(test_group, "cgroup.subtree_control", "+memory"= )) { > > + if (errno !=3D EBUSY) > > + goto out; > > + usleep(1000); > > + } >=20 > I would honestly rather create a new cgroup here instead of reusing > the leaf cgroup as a parent, to avoid any subtleties like this in the > future, or even split test_zswap_writeback() into two test cases. I > don't feel strongly though if others think the simple wait here is > enough. I somewhat agree, I'm not sure whether the recycling brings any signal to the test. In the case, the recycling and (re-)enablement is needed, I'd suggest an explicit check for emptiness, the best of utils arsenal seems: cg_read_strcmp_wait(test_cgroup, "cgroup.events", "populated 0\n") Thanks, Michal --nas2iww3rivojx2z Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCanRGxBsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMiwyLDIACgkQfj0C55Tb+AgPAAEAnkONm5a6/QU81n89rmaO gX8APeieENGJZExlGWvR9vIBAIX33lBPb1rWjVE6b1pdC7aLDpHTt2AoQfLJFbmA yzkN =sJQx -----END PGP SIGNATURE----- --nas2iww3rivojx2z--