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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20230525223953.225496-1-dhowells@redhat.com> <20230525223953.225496-4-dhowells@redhat.com> To: Christoph Hellwig Cc: dhowells@redhat.com, David Hildenbrand , Jens Axboe , Al Viro , Matthew Wilcox , Jan Kara , Jeff Layton , Jason Gunthorpe , Logan Gunthorpe , Hillf Danton , Christian Brauner , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton Subject: Re: [RFC PATCH v2 3/3] block: Use iov_iter_extract_pages() and page pinning in direct-io.c MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <520476.1685090027.1@warthog.procyon.org.uk> Date: Fri, 26 May 2023 09:33:47 +0100 Message-ID: <520477.1685090027@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Rspamd-Queue-Id: DC7C840016 X-Rspam-User: X-Stat-Signature: ooh1qmk5by3kaaofmkpb4sy7haasoa1z X-Rspamd-Server: rspam01 X-HE-Tag: 1685090035-7505 X-HE-Meta: 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 BidgxlHx X3h8qEhClz2Xcg8M+b2qkX9MfNoAU6/THgpGBAswkIfQ9iY2qvIoL/cUpE53l5bcTYEM9EpZt4vvpAfepisvanaMBF+a3Sndq6wUWn4N9YyfycrlMTIPJkpTG7uI2E6oR1AbgRvV6PoZMbbOkl0jMKiJr5UV9MPqSeKOoj9X2GmLI0HXQ/kdNKSQWUC0RmYXD/UaG1LZJqFZdzg8AK6/x/Y/32Ft1lTXnM4vxoLlE8V/ja2tuoaSnror6lKdFJxgXAd5+lFvIU6qQLrI= 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: Christoph Hellwig wrote: > I'm not seeing where we skip the unpin of the zero page, as commented > in patch 1 (but maybe I'm not reviewing carefully enough as I'm at a > conference right now). It's done by unpin_user_page{,s}(), hidden away in gup.c. See the commit message for patch 1: Make pin_user_pages*() leave a ZERO_PAGE unpinned if it extracts a pointer to it from the page tables and make unpin_user_page*() correspondingly ignore a ZERO_PAGE when unpinning. David