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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> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="nas2iww3rivojx2z" Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 993BA1C0002 X-Stat-Signature: t3nurntwdr4zao4pq3b9a5wn9cey3iss X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1786005195-488070 X-HE-Meta: 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 J5T8vzJJ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --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--