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[70.52.228.144]) by smtp.gmail.com with ESMTPSA id o5-20020a05620a2a0500b006fc2f74ad12sm22803013qkp.92.2023.01.03.09.09.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Jan 2023 09:09:25 -0800 (PST) Date: Tue, 3 Jan 2023 12:09:23 -0500 From: Peter Xu To: James Houghton Cc: Mike Kravetz , Muchun Song , David Hildenbrand , David Rientjes , Axel Rasmussen , Mina Almasry , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 34/47] hugetlb: userfaultfd: add support for high-granularity UFFDIO_CONTINUE Message-ID: References: <20221021163703.3218176-1-jthoughton@google.com> <20221021163703.3218176-35-jthoughton@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 27, 2022 at 11:38:31AM -0500, James Houghton wrote: > On Fri, Dec 23, 2022 at 1:38 PM Peter Xu wrote: > > > > James, > > > > On Fri, Oct 21, 2022 at 04:36:50PM +0000, James Houghton wrote: > > > + bool use_hgm = uffd_ctx_has_hgm(&dst_vma->vm_userfaultfd_ctx) && > > > + mode == MCOPY_ATOMIC_CONTINUE; > > > > Do you think in your new version use_hgm can work even for MISSING by > > default? > > I don't think so -- UFFDIO_COPY will allocate a hugepage, so I'm not > sure if it makes sense to allow it at high-granularity. If UFFDIO_COPY > didn't allocate a new page, then it could make sense (maybe we'd need > a new ioctl or new UFFDIO_COPY mode?). I think it makes most sense to > add this with another series. I forgot again on how the page cache is managed for the split pages, sorry.. Yeah let's stick with minor mode for now. -- Peter Xu