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Tue, 20 Aug 2024 04:59:54 -0700 (PDT) Received: from blackdock.suse.cz ([193.86.92.181]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a83839470ebsm755475766b.159.2024.08.20.04.59.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Aug 2024 04:59:53 -0700 (PDT) Date: Tue, 20 Aug 2024 13:59:52 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Kinsey Ho Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Yosry Ahmed , Roman Gushchin , Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , Tejun Heo , Zefan Li Subject: Re: [PATCH mm-unstable v2 4/5] mm: restart if multiple traversals raced Message-ID: References: <20240813204716.842811-1-kinseyho@google.com> <20240813204716.842811-5-kinseyho@google.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ajk7qmdwnuv6drcb" Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: A2F3040026 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: k8qc1gb44zfae8t3ueu5nt8jq7sj1ges X-HE-Tag: 1724155196-279629 X-HE-Meta: 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 rBBZ/qIg bxbgn9G3TQrhKz/HlxLFq2ItD/ouStj9VdM9Z33gNzA2qBN4dTsluY+OdSWgyeaMMAoO39w3Ac/vw1w5gTJiN6iIhNFE/I6V3IXQk0UU3pru+Dty6OSDp25KosFCURYN48VbiHvWnO5qLWknmcfVTcnEileUD3VkOpeEwUjsQYX23V6DJtLlytH8BgA/8/uQDAD2/6KfmZIa69UYK9W4geFDBGYyXlvg1QZPeFPbyaWX4RGHrYB8lmEW6iRJbD0IiIfxeh5kqiB3I5OXkwwq0Rr3xxCjarEjIdIXh+E9ymxNUA+ytg7GGR9i8ngRwv1mdegEshhufnhF7BNUSUb0GZG0SweOiSZmcNY8KkQN1slO8Ea4aMzJspKoLu26r1/Ij6ZvxCYm7juz1L39ZQ1asceVPXHOVByIDLq2DuXXSwQ6JvP6o99NIjPaDsw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --ajk7qmdwnuv6drcb Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 16, 2024 at 12:27:27PM GMT, Kinsey Ho wro= te: > Hi Michal, >=20 > > I may be missing (literal) context but I'd suggest not moving the memcg > > assignment and leverage > > if (memcg !=3D NULL) > > css_put(memcg->css) > > so that the is-root comparison needn't be repeated. >=20 > I might also be misunderstanding you with respect to the is-root > comparison =E2=80=93 the reason the memcg assignment is moved is because = it is > possible that on the restart added in this patch, css could be NULL. I've played with this applied up to 4/5 and I see more changes would be needed to preserve the function. Please disregard my initial suggestion ':-) Michal --ajk7qmdwnuv6drcb Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTd6mfF2PbEZnpdoAkt3Wney77BSQUCZsSFNQAKCRAt3Wney77B Sbe0AQCqKc678v6xKlFe6veLAdsc1gPRVpg9yKjZ3q02OmMDAAD+KpFdcpw2LANz Y88ecO/8A4H/9QQ8MQ4PqwfNql79bgA= =znwP -----END PGP SIGNATURE----- --ajk7qmdwnuv6drcb--