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Tue, 28 Nov 2023 14:07:40 +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 +hArHCz0ZWUHNwAAD6G6ig (envelope-from ); Tue, 28 Nov 2023 14:07:40 +0000 Date: Tue, 28 Nov 2023 15:07:38 +0100 From: Michal Hocko To: Gregory Price Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, arnd@arndb.de, tglx@linutronix.de, luto@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, tj@kernel.org, ying.huang@intel.com, Gregory Price Subject: Re: [RFC PATCH 05/11] mm/mempolicy: modify set_mempolicy_home_node to take a task argument Message-ID: References: <20231122211200.31620-1-gregory.price@memverge.com> <20231122211200.31620-6-gregory.price@memverge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231122211200.31620-6-gregory.price@memverge.com> X-Spamd-Bar: +++++++++++++++ X-Spam: Yes X-Rspamd-Queue-Id: 8338480057 X-Rspam-User: X-Stat-Signature: 8w1yprp5tei88i9b4ywpd6agxonw6jyk X-Rspamd-Server: rspam03 X-HE-Tag: 1701180462-173073 X-HE-Meta: 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 FlTTukj6 B1hP5G59RUKTof+0Qb1q/BQewEOFqNaIh0Vr2bQZVrcRwsgACZJB5B5B0Ix+mN7p3+vtyDbKQGelYmF3pyKw6WqoQp4JGc0CWqEBm2ndf43T9OyvfK1f1PYrHbX0qwJkU5FxjPaNcobCpvknWaqbuXGnBDxBX68sIv4MqTQNjIhJm2xF4UpQj6eTRPDqG+M+PIXygMw/MEAXXZCg/3XtBD2Z1x/bDW2D0JQckQ6cyz3MK60Jt2yjA9gtrOuiaHLGjHjC0UKW459g/NSLltyZF0OKqgaUJLEXV+JmC 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 22-11-23 16:11:54, Gregory Price wrote: [...] > + > + /* > + * Behavior when task == current allows a task modifying itself > + * to bypass the check in get_task_mm and acquire the mm directly > + */ > + if (task == current) { > + mm = task->mm; > + mmget(mm); > + } else > + mm = get_task_mm(task); Similar question as in the previous patch. When is a kthread legit to do manipulate borrowed mm memory policy? > + > + if (!mm) > + return -ENODEV; Is this an expected error? No mm means task dying and mm has been already released. Should we simply return ESRCH wouldbe a better error code IMO. This should never happen for the current task so it sould be safe to add. -- Michal Hocko SUSE Labs