From patchwork Fri May 29 23:43:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11579841 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C71D914C0 for ; Fri, 29 May 2020 23:43:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ACE8920810 for ; Fri, 29 May 2020 23:43:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="AIidyHaK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728616AbgE2XnO (ORCPT ); Fri, 29 May 2020 19:43:14 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:4272 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728396AbgE2XnM (ORCPT ); Fri, 29 May 2020 19:43:12 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Fri, 29 May 2020 16:41:39 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 29 May 2020 16:43:11 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 29 May 2020 16:43:11 -0700 Received: from HQMAIL105.nvidia.com (172.20.187.12) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 29 May 2020 23:43:11 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Fri, 29 May 2020 23:43:11 +0000 Received: from sandstorm.nvidia.com (Not Verified[10.2.87.173]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Fri, 29 May 2020 16:43:11 -0700 From: John Hubbard To: Andrew Morton CC: "Michael S . Tsirkin" , Jason Wang , Vlastimil Babka , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Dave Chinner , Souptick Joarder , Jonathan Corbet , , , , , , LKML , , John Hubbard Subject: [PATCH 2/2] vhost: convert get_user_pages() --> pin_user_pages() Date: Fri, 29 May 2020 16:43:09 -0700 Message-ID: <20200529234309.484480-3-jhubbard@nvidia.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200529234309.484480-1-jhubbard@nvidia.com> References: <20200529234309.484480-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1590795699; bh=w393fB7aMdfV2Mn/9DhXAANTn2k/9wVRvrXDZ4wAcPA=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=AIidyHaKCFf7Kb9AMouG61nHIQlapNE9AiLsib0QpCDzLvsTwwBRUeW/4GekCvb7F smypOSFVsFd+3nRh66RM2eztwXbwv34HZFIIxCxH6UUi9Vfk+SuxiFXQ65SN4/Oyec t0wmLYAFAUh8q/OQuepY8cNQQSVBaoRKNXM+2ZyKvm/br5zGAy7GAmhlyThqdzI8F4 gGIm7rRrqWBXbXJDWLRUKD+2zTb2K76ePxs13DoVdpK+OGjEjrJpmQMXEgxYczFvxI h/SDh/NadxwC+Ci7m6OF9cb0f6gLx/1Rhdpx54yYTuyHd+F9BjdY3kDrKXOQg2JVnE /C86UeF1NcgJA== Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 Reviewed-by: Jan Kara 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; }