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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id d206-20020a814fd7000000b0054605c23114sm3346760ywb.66.2023.05.23.18.57.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 May 2023 18:57:20 -0700 (PDT) Date: Tue, 23 May 2023 18:57:17 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Alistair Popple cc: Hugh Dickins , Andrew Morton , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 02/31] mm/migrate: remove cruft from migration_entry_wait()s In-Reply-To: <87bkib95uj.fsf@nvidia.com> Message-ID: <8bc94098-8a57-b62f-a26c-7c73bf945b41@google.com> References: <68a97fbe-5c1e-7ac6-72c-7b9c6290b370@google.com> <1659568-468a-6d36-c26-6a52a335ab59@google.com> <87bkib95uj.fsf@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Stat-Signature: 6zz8wgand5qji7tzhh1boonnmmdds79g X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3E9C520002 X-HE-Tag: 1684893442-636884 X-HE-Meta: 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 +kiVUZiT Nin9SOl6ZM+pbnJgjxwLiW/ZLKMM3G9D6Gy1ZGc2m76oJ9Y1XELRN8cD9n6z8kt9lwtEPCXM0H/ZC/DAZZSY7MrLLv+4oF2MkY/h2UC03ytczVpYybU0zq3wBZhJ73Tmz0KOln6eQTwuuj2UYc7PHYZtVMzPMzFLanHl5hXeFEUzin0Cltq+1txuRpe03xnm1iJUKpQeZ3xOkLkPMWa4Ggx+/lnS6NKWUhW9av0y287q4w+43ZM9RyQ/ZGGWwveUqC3zk1QVcvN+yVW89tay2/qOd+irvVU3zdIMOTljVSpGFNbiAK+JbD8Y0ljEfQDC7oKikd6n2XG57lsNviUdvUQXmZcrSGlwaJ7hUzBtvRv8hkKr+czU1gua4z0vDIHeem65EO/LLSqnrJBT1P7JuiGUzvf09pXUMQmo0QPZbxSb92dozNXBKQs4T5d+WqbWkh4sVuUXWUZwPtpnpNMbYIrvcIcn6b0OAmEhh 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 Tue, 23 May 2023, Alistair Popple wrote: > > Hugh Dickins writes: > > > migration_entry_wait_on_locked() does not need to take a mapped pte > > pointer, its callers can do the unmap first. Annotate it with > > __releases(ptl) to reduce sparse warnings. > > Thanks Hugh, I debated doing something similar when I reworked this to > not take a pageref. However I was unsure if the pte unmap/unlock > ordering mattered as this reverses the order of operations (from unlock > then unmap to unmap then unlock). > > I never found any reason why that would be a problem though so please > add: > > Reviewed-by: Alistair Popple Thanks Alistair. Right, the ordering doesn't matter: you might briefly think that because I'm going to put the rcu_read_unlock() into the pte_unmap(), that there's something wrong with doing that early; but you'd quickly realize that holding on to the spinlock is good enough. Hugh