From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23D11C77B7A for ; Fri, 26 May 2023 08:34:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236850AbjEZIe4 (ORCPT ); Fri, 26 May 2023 04:34:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242730AbjEZIep (ORCPT ); Fri, 26 May 2023 04:34:45 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA0CE18D for ; Fri, 26 May 2023 01:33:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685090036; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HZdbB846VP2Mif8vkzLshswwvIDgJcVcn/Vxjtn6SVU=; b=iKea04jW38VtApRpESOwMuC1Xdm8YTzVdkVnRdSCFf+CbY7Dx49+qAZ3Kya6JUwzqNnhGL ev2ajUzZiq0i3VxDD/1vXOwXxKsAQUF9ZOeKqM+m2TSEm8ObHH3zpR6nxT/KbBqUHEOWgs GJtV8Dl4QmZODWhgi8xyy4FEctdGOd0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-31-7sMtwyH8MCSL5zzDtp_gYw-1; Fri, 26 May 2023 04:33:51 -0400 X-MC-Unique: 7sMtwyH8MCSL5zzDtp_gYw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 626FE1C04180; Fri, 26 May 2023 08:33:50 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.39.192.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id E3E5C200AD47; Fri, 26 May 2023 08:33:47 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. 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 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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