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Mon, 6 Oct 2025 12:29:55 +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 xwdACUO242gfdwAAD6G6ig (envelope-from ); Mon, 06 Oct 2025 12:29:55 +0000 Date: Mon, 6 Oct 2025 14:29:53 +0200 From: Oscar Salvador To: Ryan Roberts Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm: Consistently use current->mm in mm_get_unmapped_area() Message-ID: References: <20251003155306.2147572-1-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251003155306.2147572-1-ryan.roberts@arm.com> X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Queue-Id: 546DF18000C X-Rspamd-Server: rspam03 X-Stat-Signature: y8tbtf1jgzbt1zaqwp418i6cn86jx8pt X-HE-Tag: 1759753797-836184 X-HE-Meta: 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 j+PlmoFv Q5sqHKBaWMy5a/cgITG2C7UAOoRxJFr7l+8og572dZsQIAvxzBiALWyGeBNJRYeyEjor6VSGu7L/j7jlKElPYQKEa4QzIOpAA+7gQLMW+2874dHiYhQAFWAHQejVbbWfGB7apKr16PlhyxVEg8bARHQpMxsqg3FueHWxSS9HCiEeRCirFgT/8E1z4VLhVVWdN550ZYO4r7Lnu1SoUA5o++FTT33U1g9QECSyS2j9mmgZvPgm/7c6fr/nu3OQR+EPXM1Ic/mfUSrkl7gsBnQJ49e16ehkp6DG1MXlpjO7iNCrUQJ+XqzroDFfhPXXz7RQEaks/2RM1PVWYxNk= 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 Fri, Oct 03, 2025 at 04:53:04PM +0100, Ryan Roberts wrote: > mm_get_unmapped_area() is a wrapper around arch_get_unmapped_area() / > arch_get_unmapped_area_topdown(), both of which search current->mm for > some free space. Neither take an mm_struct - they implicitly operate on > current->mm. > > But the wrapper takes an mm_struct and uses it to decide whether to > search bottom up or top down. All callers pass in current->mm for this, > so everything is working consistently. But it feels like an accident > waiting to happen; eventually someone will call that function with a > different mm, expecting to find free space in it, but what gets returned > is free space in the current mm. > > So let's simplify by removing the parameter and have the wrapper use > current->mm to decide which end to start at. Now everything is > consistent and self-documenting. > > Signed-off-by: Ryan Roberts I think it looks cleaner: Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE Labs