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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6365C433DF for ; Tue, 2 Jun 2020 04:22:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B87C02074B for ; Tue, 2 Jun 2020 04:22:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="X8FnC/x9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725966AbgFBEWl (ORCPT ); Tue, 2 Jun 2020 00:22:41 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:34725 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725957AbgFBEWh (ORCPT ); Tue, 2 Jun 2020 00:22:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591071755; 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=YDfsRlwfRR1nDcp4wd5hK1KujxFVRibBNSbBOaOrz2Q=; b=X8FnC/x9SCa5vJY15Os/NgB6nawcFpKJaDXreIB8m84EPDlTy9XHLAWv/Zny3K0FHi4Nb3 8LdpUU/8m/eOLIxkEiiX9UFoTyhOTFaK/KJFTZMPWNZ3Let1L3FvT3iSJVQSnPTVqcc4R7 i1c1lgV4k52xxGtwe+/HGiSPJXPtk+c= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-502-ke-FVvXQOJi2LjjeUPm_Dg-1; Tue, 02 Jun 2020 00:22:30 -0400 X-MC-Unique: ke-FVvXQOJi2LjjeUPm_Dg-1 Received: by mail-wm1-f70.google.com with SMTP id h25so498402wmb.0 for ; Mon, 01 Jun 2020 21:22:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=YDfsRlwfRR1nDcp4wd5hK1KujxFVRibBNSbBOaOrz2Q=; b=Z9caD32gkn74SS3fbh5oZjr4lt2KxgShALa7ktLkcSM0fZNs5Ci6++ipHwqNCctXV9 BcaZLgW6lKXi+nek4TIkSsYenBL8Oocec7KfjPiOYYp4Xrj7ZVKsPSiRZky9CDCe9Nkg o0Qh28NUjjpS4rHXEnEZeBMs9xq44LcXdgz5eVKp8zo9+FeKSCMpadPsluL+pLGSG+eX wrkH0DhPsG2rJaNb4ClpSN4rWn3B7kscsavoOCMR5hdU+1vP+f7eI/S6pJCOlTkTBcMV UZESDDJUiN7De45Usz+XJyjfWy3LA1rkSjrBW0qHcvnhH/UTt/NmKX4IKVjjlPehqYoc z+VA== X-Gm-Message-State: AOAM53224LhD2cqb6LMRCSndXBQJ4SIqBlis6Qu6rAYUp7ftyWcqNPen 3ypTKd1O2z5ETEZ4NKo7F+//dSeNqsPi0FV2XDgxY90wAkLGiemgwEjbuK7IMUv2fkobtsi+NUs r/anceiQ05OdsOmZljteLNOF9KA== X-Received: by 2002:a05:6000:1083:: with SMTP id y3mr23714190wrw.425.1591071749222; Mon, 01 Jun 2020 21:22:29 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx2SKrCnIib4b4OHp9esqIfnn8bX4FrOHyf8lEFnkhypfH/4sW2rsrN9doierFMkcN8evfSkA== X-Received: by 2002:a05:6000:1083:: with SMTP id y3mr23714174wrw.425.1591071749030; Mon, 01 Jun 2020 21:22:29 -0700 (PDT) Received: from redhat.com (bzq-109-64-41-91.red.bezeqint.net. [109.64.41.91]) by smtp.gmail.com with ESMTPSA id z2sm1731263wrs.87.2020.06.01.21.22.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Jun 2020 21:22:28 -0700 (PDT) Date: Tue, 2 Jun 2020 00:22:25 -0400 From: "Michael S. Tsirkin" To: John Hubbard Cc: Andrew Morton , Jason Wang , Vlastimil Babka , =?iso-8859-1?B?Suly9G1l?= Glisse , Jan Kara , Dave Chinner , Souptick Joarder , Jonathan Corbet , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, LKML , linux-mm@kvack.org Subject: Re: [PATCH 2/2] vhost: convert get_user_pages() --> pin_user_pages() Message-ID: <20200602002212-mutt-send-email-mst@kernel.org> References: <20200529234309.484480-1-jhubbard@nvidia.com> <20200529234309.484480-3-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200529234309.484480-3-jhubbard@nvidia.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, May 29, 2020 at 04:43:09PM -0700, John Hubbard wrote: > This code was using get_user_pages*(), in approximately a "Case 5" > scenario (accessing the data within a page), using the categorization > from [1]. That means that it's time to convert the get_user_pages*() + > put_page() calls to pin_user_pages*() + unpin_user_pages() calls. > > There is some helpful background in [2]: basically, this is a small > part of fixing a long-standing disconnect between pinning pages, and > file systems' use of those pages. > > [1] Documentation/core-api/pin_user_pages.rst > > [2] "Explicit pinning of user-space pages": > https://lwn.net/Articles/807108/ > > Cc: Michael S. Tsirkin > Cc: Jason Wang > Cc: kvm@vger.kernel.org > Cc: virtualization@lists.linux-foundation.org > Cc: netdev@vger.kernel.org > Signed-off-by: John Hubbard Acked-by: Michael S. Tsirkin > --- > drivers/vhost/vhost.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 21a59b598ed8..596132a96cd5 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1762,15 +1762,14 @@ static int set_bit_to_user(int nr, void __user *addr) > int bit = nr + (log % PAGE_SIZE) * 8; > int r; > > - r = get_user_pages_fast(log, 1, FOLL_WRITE, &page); > + r = pin_user_pages_fast(log, 1, FOLL_WRITE, &page); > if (r < 0) > return r; > BUG_ON(r != 1); > base = kmap_atomic(page); > set_bit(bit, base); > kunmap_atomic(base); > - set_page_dirty_lock(page); > - put_page(page); > + unpin_user_pages_dirty_lock(&page, 1, true); > return 0; > } > > -- > 2.26.2