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[70.53.122.15]) by smtp.gmail.com with ESMTPSA id o4sm10218609qkk.75.2020.09.21.15.30.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Sep 2020 15:30:06 -0700 (PDT) Date: Mon, 21 Sep 2020 18:30:04 -0400 From: Peter Xu To: Jann Horn Cc: Linux-MM , kernel list , Jason Gunthorpe , Andrew Morton , Jan Kara , Michal Hocko , Kirill Tkhai , Kirill Shutemov , Hugh Dickins , Christoph Hellwig , Andrea Arcangeli , John Hubbard , Oleg Nesterov , Leon Romanovsky , Linus Torvalds Subject: Re: [PATCH 1/5] mm: Introduce mm_struct.has_pinned Message-ID: <20200921223004.GB19098@xz-x1> References: <20200921211744.24758-1-peterx@redhat.com> <20200921211744.24758-2-peterx@redhat.com> 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-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 Mon, Sep 21, 2020 at 11:43:38PM +0200, Jann Horn wrote: > On Mon, Sep 21, 2020 at 11:17 PM Peter Xu wrote: > > > > (Commit message collected from Jason Gunthorpe) > > > > Reduce the chance of false positive from page_maybe_dma_pinned() by keeping > > track if the mm_struct has ever been used with pin_user_pages(). mm_structs > > that have never been passed to pin_user_pages() cannot have a positive > > page_maybe_dma_pinned() by definition. > > There are some caveats here, right? E.g. this isn't necessarily true > for pagecache pages, I think? Sorry I didn't follow here. Could you help explain with some details? Thanks, -- Peter Xu