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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id s19sm19059776qks.130.2021.04.07.15.51.08 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Wed, 07 Apr 2021 15:51:10 -0700 (PDT) Date: Wed, 7 Apr 2021 15:50:54 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Axel Rasmussen cc: Hugh Dickins , Alexander Viro , Andrea Arcangeli , Andrew Morton , Jerome Glisse , Joe Perches , Lokesh Gidra , Mike Rapoport , Peter Xu , Shaohua Li , Shuah Khan , Stephen Rothwell , Wang Qing , LKML , linux-fsdevel@vger.kernel.org, Linux MM , linux-kselftest@vger.kernel.org, Brian Geffon , Cannon Matthews , "Dr . David Alan Gilbert" , David Rientjes , Michel Lespinasse , Mina Almasry , Oliver Upton Subject: Re: [PATCH v4] userfaultfd/shmem: fix MCOPY_ATOMIC_CONTINUE behavior In-Reply-To: Message-ID: References: <20210401183701.1774159-1-axelrasmussen@google.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 7A36AC0007C2 X-Stat-Signature: wmaxnxopgueowoe6wrndk754tgwi9ygp Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf22; identity=mailfrom; envelope-from=""; helo=mail-qk1-f172.google.com; client-ip=209.85.222.172 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617835869-209730 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, 7 Apr 2021, Axel Rasmussen wrote: > Agreed about taking one direction or the other further. > > I get the sense that Peter prefers the mcopy_atomic_install_ptes() > version, and would thus prefer to just expose that and let > shmem_mcopy_atomic_pte() use it. > > But, I get the sense that you (Hugh) slightly prefer the other way - > just letting shmem_mcopy_atomic_pte() deal with both the VM_SHARED and > !VM_SHARED cases. No, either direction seems plausible to me: start from whichever end you prefer. > > I was planning to write "I prefer option X because (reasons), and > objections?" but I'm realizing that it isn't really clear to me which > route would end up being cleaner. I think I have to just pick one, > write it out, and see where I end up. If it ends up gross, I don't > mind backtracking and taking the other route. :) To that end, I'll > proceed by having shmem_mcopy_atomic_pte() call the new > mcopy_atomic_install_ptes() helper, and see how it looks (unless there > are objections). I am pleased to read that: it's exactly how I would approach it - so it must be right :-) Hugh