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Tsirkin" , LKML , linux-mm , Andy Lutomirski , Vlastimil Babka , Andrea Arcangeli , Sonny Rao , Minchan Kim , "Kirill A . Shutemov" , Dmitry Safonov Subject: Re: [PATCH v2 1/2] mm: Allow non-VM_DONTEXPAND and VM_PFNMAP mappings with MREMAP_DONTUNMAP Message-ID: <20210317211857.GN395976@xz-x1> References: <20210303175235.3308220-1-bgeffon@google.com> <20210317191334.564944-1-bgeffon@google.com> <20210317204015.GM395976@xz-x1> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 5946A801914D X-Stat-Signature: dzr3k3s1qkc7ur9rb4r4dkxqpa9mys6e Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616015941-530891 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: On Wed, Mar 17, 2021 at 04:44:25PM -0400, Brian Geffon wrote: > Hi Peter, Hi, Brian, > Thank you as always for taking a look. This change relies on the > existing check in vma_to_resize on line 686: > https://elixir.bootlin.com/linux/v5.12-rc3/source/mm/mremap.c#L686 > which returns -EFAULT when the vma is VM_DONTEXPAND or VM_PFNMAP. Do you mean line 676? https://elixir.bootlin.com/linux/v5.12-rc3/source/mm/mremap.c#L676 I'm not sure whether it'll work for MREMAP_DONTUNMAP, since IIUC MREMAP_DONTUNMAP only works for the remap case with no size change, however in that case in vma_to_resize() we'll bail out even earlier than line 676 when checking against the size: https://elixir.bootlin.com/linux/v5.12-rc3/source/mm/mremap.c#L667 So IIUC we'll still need the change as Hugh suggested previously. Thanks, -- Peter Xu