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 385E9C43381 for ; Tue, 19 Mar 2019 08:13:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 02F2420850 for ; Tue, 19 Mar 2019 08:13:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="uAsQ6DLq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727208AbfCSINo (ORCPT ); Tue, 19 Mar 2019 04:13:44 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:60006 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726916AbfCSINo (ORCPT ); Tue, 19 Mar 2019 04:13:44 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2J8Bkvm089146; Tue, 19 Mar 2019 08:13:38 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=cRL02KRukfO1/OeuxBvZoGs2Fz7pvakqOJl/MZ/jAQo=; b=uAsQ6DLqW3CT6QmVypZTFWV2k1lBNPKIAGokPDlQxZeaoKn6RbrSkKvHJU2ayEiT3+mO qatUvAWFuCsX+Absn+m4TByQRj/fOACwhu5u4GtWWufwH36HQk8PTI2aDMm19tQV1waM 5W41CN1Rokl2z7hofCLg6Om2+FKfrrXgHmN/suoeqTij17j4o64cM7WD+hVuTtoRbawB N+OqTSVbppFU2IjHa3npaD1U0dUuz+J34kVmvwemZMsdYgBu+Uvnjpa71hebQwR3IS/R Vi9UlWFsFaSgIAdZwx5gxDbP8eKYSIzNPJ92NGuTTSEk9hvmRoroKsKfPWfFMiXb+Xt8 Wg== Received: from aserv0021.oracle.com (aserv0021.oracle.com [141.146.126.233]) by userp2130.oracle.com with ESMTP id 2r8rjuk0nf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 19 Mar 2019 08:13:38 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x2J8DWRb006426 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 19 Mar 2019 08:13:32 GMT Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x2J8DVHl029511; Tue, 19 Mar 2019 08:13:32 GMT Received: from [10.182.69.118] (/10.182.69.118) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 19 Mar 2019 01:13:31 -0700 Subject: Re: [PATCH] sbitmap: order RW on old associated instance and setting clear bit To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, Omar Sandoval , Yi Zhang References: <20190319042447.27580-1-ming.lei@redhat.com> <9e784c48-2865-a14a-d8f4-e6c74f258f48@oracle.com> <20190319075815.GA28327@ming.t460p> From: "jianchao.wang" Message-ID: <4b2ac159-a42b-b410-e0ba-19ec86681f48@oracle.com> Date: Tue, 19 Mar 2019 16:16:40 +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: <20190319075815.GA28327@ming.t460p> 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=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=827 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903190062 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 3:58 PM, Ming Lei wrote: > On Tue, Mar 19, 2019 at 01:17:31PM +0800, jianchao.wang wrote: >> 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 ? > > test_and_set_bit_lock() in __sbitmap_get_word(). Yes, thanks for your pointing out. Would you perhaps detail this in the comment ? Thanks Jianchao > >> >>> + */ >>> + smp_mb(); >> >> smp_mb_before_atomic should be enough. > > Right, will change to it in V2. > > Thanks, > Ming >