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[174.93.89.182]) by smtp.gmail.com with ESMTPSA id 2sm5165227qtt.24.2021.02.04.11.25.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Feb 2021 11:25:58 -0800 (PST) Date: Thu, 4 Feb 2021 14:25:56 -0500 From: Peter Xu To: Linus Torvalds Cc: Linux-MM , Linux Kernel Mailing List , Kirill Shutemov , Wei Zhang , Mike Rapoport , Matthew Wilcox , Miaohe Lin , Andrea Arcangeli , Gal Pressman , Jan Kara , Jann Horn , Andrew Morton , Kirill Tkhai , Mike Kravetz , Jason Gunthorpe , David Gibson , Christoph Hellwig Subject: Re: [PATCH v2 3/4] mm: Introduce page_needs_cow_for_dma() for deciding whether cow Message-ID: <20210204192556.GT6468@xz-x1> References: <20210204145033.136755-1-peterx@redhat.com> <20210204145033.136755-4-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 Thu, Feb 04, 2021 at 09:54:37AM -0800, Linus Torvalds wrote: > On Thu, Feb 4, 2021 at 6:50 AM Peter Xu wrote: > > > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -1291,6 +1291,27 @@ static inline bool page_maybe_dma_pinned(struct page *page) > > GUP_PIN_COUNTING_BIAS; > > } > > > > +static inline bool is_cow_mapping(vm_flags_t flags) > > +{ > > + return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; > > +} > > Oh, and I just realized: moving this to means that this > patch could/should also get rid of > > - manual copy of this in mm/hugetlb.c: > > cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; > > - private #define for the same thing in fs/proc/task_mmu.c > > #define is_cow_mapping(flags) (((flags) & (VM_SHARED | > VM_MAYWRITE)) == VM_MAYWRITE) > > - manual copy in drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c: > > bool is_cow_mapping = > (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; > > I guess it could be a later cleanup patch too, but maybe best done in > this series just to not forget about it. Will do in v3 if there is. Or I'll post a standalone patch to not disturb Gal just in case he's kicked a test. Thanks, -- Peter Xu