From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2a07:de40:b251:101:10:150:64:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 75A02D64; Tue, 28 Nov 2023 06:07:42 -0800 (PST) Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 01DF81F74B; Tue, 28 Nov 2023 14:07:41 +0000 (UTC) Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 81EC31343E; 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> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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-Score: 15.00 X-Rspamd-Server: rspamd1 Authentication-Results: smtp-out2.suse.de; dkim=none; spf=fail (smtp-out2.suse.de: domain of mhocko@suse.com does not designate 2a07:de40:b281:104:10:150:64:97 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=suse.com (policy=quarantine) X-Rspamd-Queue-Id: 01DF81F74B X-Spamd-Result: default: False [15.00 / 50.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_SPF_FAIL(1.00)[-all]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; DMARC_POLICY_QUARANTINE(1.50)[suse.com : No valid SPF, No valid DKIM,quarantine]; BAYES_HAM(-0.00)[43.15%]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_COUNT_THREE(0.00)[3]; MID_RHS_NOT_FQDN(0.50)[]; MX_GOOD(-0.01)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCPT_COUNT_TWELVE(0.00)[19]; FREEMAIL_TO(0.00)[gmail.com]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(2.20)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; SUSPICIOUS_RECIPS(1.50)[] X-Spam: Yes 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