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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS autolearn=ham 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 040F4C43381 for ; Tue, 19 Mar 2019 05:14:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C10CE20989 for ; Tue, 19 Mar 2019 05:14:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="D1kLBlyR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725978AbfCSFOd (ORCPT ); Tue, 19 Mar 2019 01:14:33 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:38842 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725287AbfCSFOd (ORCPT ); Tue, 19 Mar 2019 01:14:33 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2J5ELmT155178; Tue, 19 Mar 2019 05:14:28 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=DwSnNDqnPUTXk4dmngFX+rC699NjHiw/SGofjgeXANc=; b=D1kLBlyR1Oc4OaVTPN4eVDW2vXsk7WJKLuZLckfza9YnbOO1GaVpYPMHsvh/rJxj25Hd BrIvW2EMaxg5kEFbeRqlI33AhOw/aq4sWC412eXgdDaZq5SBkYtkr/J3fXmb6tbSdEt8 MHyQn7EHlEzo/AD+HA66xFlvA/itf9WUWTpMoUaqu8pAbx49kfaqVQZlSVIf3cmojx9K 1c+UG00GHglu16R6OgIZa3vhKSfDIv440Nb4zUaM/pOqdFILktEeOghw6FKEM/fG0aKX ULBEqx4kMz7g6zK82Pz3W0auOwEgPwHAQuaMrzrlkYH1oyBSPE2y342Ny+wvFkvLsTsS HQ== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by userp2120.oracle.com with ESMTP id 2r8ssra7bn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 19 Mar 2019 05:14:28 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x2J5EMAP010354 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 19 Mar 2019 05:14:22 GMT Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x2J5EMBp017489; Tue, 19 Mar 2019 05:14:22 GMT Received: from [10.182.69.118] (/10.182.69.118) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 18 Mar 2019 22:14:22 -0700 Subject: Re: [PATCH] sbitmap: order RW on old associated instance and setting clear bit To: Ming Lei , Jens Axboe Cc: linux-block@vger.kernel.org, Omar Sandoval , Yi Zhang References: <20190319042447.27580-1-ming.lei@redhat.com> From: "jianchao.wang" Message-ID: <9e784c48-2865-a14a-d8f4-e6c74f258f48@oracle.com> Date: Tue, 19 Mar 2019 13:17:31 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190319042447.27580-1-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9199 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=904 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903190039 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Ming On 3/19/19 12:24 PM, Ming Lei wrote: > @@ -591,6 +591,15 @@ EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up); > void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, > unsigned int cpu) > { > + /* > + * Once the clear bit is set, it will be visible to allocation > + * side. > + * > + * This memory barrier orders any READ/WRITE on the to-be-freed > + * asssociated instance for avoiding potential use-after-free, and > + * its pair is the memory barrier implied in sbitmap_get(). which one ? > + */ > + smp_mb(); smp_mb_before_atomic should be enough. > sbitmap_deferred_clear_bit(&sbq->sb, nr); Thanks Jianchao