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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 CCECDC433E0 for ; Mon, 1 Jun 2020 11:30:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 98B06206E2 for ; Mon, 1 Jun 2020 11:30:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 98B06206E2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 364FE80007; Mon, 1 Jun 2020 07:30:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 315298E0006; Mon, 1 Jun 2020 07:30:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 22A9580007; Mon, 1 Jun 2020 07:30:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0235.hostedemail.com [216.40.44.235]) by kanga.kvack.org (Postfix) with ESMTP id 089D28E0006 for ; Mon, 1 Jun 2020 07:30:04 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B1395181AC9CB for ; Mon, 1 Jun 2020 11:30:03 +0000 (UTC) X-FDA: 76880423886.17.blade65_7810c28e242 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 91BCC180D0180 for ; Mon, 1 Jun 2020 11:30:03 +0000 (UTC) X-HE-Tag: blade65_7810c28e242 X-Filterd-Recvd-Size: 3448 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Mon, 1 Jun 2020 11:30:03 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id ED343AC7D; Mon, 1 Jun 2020 11:30:02 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 43BC21E0948; Mon, 1 Jun 2020 13:30:00 +0200 (CEST) Date: Mon, 1 Jun 2020 13:30:00 +0200 From: Jan Kara To: John Hubbard Cc: Andrew Morton , "Michael S . Tsirkin" , 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: <20200601113000.GE3960@quack2.suse.cz> 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> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 91BCC180D0180 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Fri 29-05-20 16:43:09, 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 Looks good to me. You can add: Reviewed-by: Jan Kara Honza > --- > 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 > -- Jan Kara SUSE Labs, CR