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Wed, 20 Mar 2024 17:12:55 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id EghGBBcZ+2VLdwAAD6G6ig (envelope-from ); Wed, 20 Mar 2024 17:12:55 +0000 Date: Wed, 20 Mar 2024 18:12:50 +0100 From: Michal Hocko To: Waiman Long Cc: Pavel Tikhomirov , Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org Subject: Re: [PATCH] mm/memcontrol: stop resize loop if limit was changed again Message-ID: References: <20240320100556.463266-1-ptikhomirov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DFB6A40012 X-Stat-Signature: gxc3brsd89u64ka1h9dksd4wdqp5q9dj X-HE-Tag: 1710954776-542894 X-HE-Meta: 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 0r33GmNB kQtvrJw860rRTJnUOrEvSquyYZ7t9+KC4qaV99QPcFqx/l/A40Kb+YNx1q8SG9ocaCD1FCbrHxBZL8ZiiVXEmq/vYYd5khFc5+Zp2lY73NYIdMHijn0BNnfJgI5fHQNa/T8RKWIQ6Rf0moLKCL0hbS84p+jaxAAB4r/2t4QXWbcNdo2nCYxOJamh1ObIUfWOPqjlwE/61Z6Sn9n64MAlvymNhhKzQrZMEXllPeLbeBag3VIdp4Rqltsg0EawmZd/81AzTeZJSbzX4S/dbr6QaDl22CVcDlNLx0Hu2vVLpsJfju/iDC4vfGocbjw== 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: On Wed 20-03-24 13:09:07, Waiman Long wrote: > > On 3/20/24 06:03, Pavel Tikhomirov wrote: > > In memory_max_write() we first set memcg->memory.max and only then > > try to enforce it in loop. What if while we are in loop someone else > > have changed memcg->memory.max but we are still trying to enforce > > the old value? I believe this can lead to nasty consequence like getting > > an oom on perfectly fine cgroup within it's limits or excess reclaim. > > Concurrent write to the same cgroup control file is not possible as the > underlying kernfs_open_file structure has a mutex that serialize access to > the file. This is good to know and I was not aware of that. Thanks! -- Michal Hocko SUSE Labs