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=-5.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 205F0C2D0EC for ; Wed, 8 Apr 2020 02:25:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E11EA206BE for ; Wed, 8 Apr 2020 02:25:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Mr+jmsXp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726444AbgDHCZU (ORCPT ); Tue, 7 Apr 2020 22:25:20 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:33908 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726416AbgDHCZT (ORCPT ); Tue, 7 Apr 2020 22:25:19 -0400 Received: by mail-pg1-f193.google.com with SMTP id l14so2664374pgb.1 for ; Tue, 07 Apr 2020 19:25:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:openpgp:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=8YakeIytkCqdHsA7rZz1DKZmmB2+FFdVVFL33CNj1L0=; b=Mr+jmsXpQfi/mJzy+2EkycfrUdnhUWgfbYvF4YE1VRvqyqWUqUD0CAAUNluaH9xwTq I7lT0MhkfVoUKxiuvAJ5Pw8bVvxU0Ih6h/IdGpMAtz2RUsOFpYVFQasvGHmvCI9R1HF5 6JoA86zxqv3HsPPiQlQaxyx3BMQPzJwuK+QCMYHHrdP63zySCxyFiDdHqO3cLDukrDxQ Oto++2ctjS0zDb1+a/ByMx1E7ac9QSfaieerXdaZaWT/Tv7/cbNxzZKIfkqhfDPo01Q8 kJMvEFXK/rto3F3zSswpKiYDpDVefcLeo5NYgeXKLSuyiZWZSI/rdv+0g0hB40WQlFer ZRyA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=8YakeIytkCqdHsA7rZz1DKZmmB2+FFdVVFL33CNj1L0=; b=cdOMJh5KFOlNAAYaUH2QHocbawzcDpD1h6YOPPI84hs+qjmzdv6U4tV2RDko/izXHT cusKABv76BgHe554X5V54890yirnDwG+PVASzxRBMfEJNM6K1Sbi24UkEULH8P8bBkFQ XsG84QWolCiQW0CtMA0PJfff93j9gJF9SkqpA7Tq+zeM49ooNoqYUKxDiP7HHEpMnwCE wkOpzsoYQWMrNAWpmAsYn9dXbrwEgXo5bo/RgTH2Sbo4BqgTmAtfJTw0ovJZmorP7Ncq OgAD5foRcs3qg3SzxebCmoOLoukSSwEoS3zv+cYxYt6RD/w2jyFOqtLNaaahWpxF+v3O Jvyw== X-Gm-Message-State: AGi0Pubf3R3yTHS0q5EFfH8ne+mg4RiDP1c6khWPeWo2/v8wEiDqUvBr r/AcCNC1PchEJgEcmyLnAX+c7fZW X-Google-Smtp-Source: APiQypL6VdDS+QFl5RvJkV7nJriuiJr9LDZN0HFfdtzbavKpLrlXwC/lf+htlusZVSAQG07Ucj2hag== X-Received: by 2002:a62:164a:: with SMTP id 71mr632683pfw.273.1586312718894; Tue, 07 Apr 2020 19:25:18 -0700 (PDT) Received: from [0.0.0.0] ([2001:19f0:8001:1c6b:5400:2ff:fe92:fb44]) by smtp.googlemail.com with ESMTPSA id s61sm3017792pjd.33.2020.04.07.19.25.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Apr 2020 19:25:18 -0700 (PDT) Subject: Re: [PATCH net 2/2] net/rds: Fix MR reference counting problem To: santosh.shilimkar@oracle.com, Ka-Cheong Poon , netdev@vger.kernel.org Cc: davem@davemloft.net, rds-devel@oss.oracle.com References: <4b96ea99c3f0ccd5cc0683a5c944a1c4da41cc38.1586275373.git.ka-cheong.poon@oracle.com> <96f17f7d-365c-32ec-2efe-a6a5d9d306b7@oracle.com> From: zerons Openpgp: preference=signencrypt Message-ID: Date: Wed, 8 Apr 2020 10:25:11 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <96f17f7d-365c-32ec-2efe-a6a5d9d306b7@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/8/20 03:30, santosh.shilimkar@oracle.com wrote: > On 4/7/20 9:08 AM, Ka-Cheong Poon wrote: >> In rds_free_mr(), it calls rds_destroy_mr(mr) directly.  But this >> defeats the purpose of reference counting and makes MR free handling >> impossible.  It means that holding a reference does not guarantee that >> it is safe to access some fields.  For example, In >> rds_cmsg_rdma_dest(), it increases the ref count, unlocks and then >> calls mr->r_trans->sync_mr().  But if rds_free_mr() (and >> rds_destroy_mr()) is called in between (there is no lock preventing >> this to happen), r_trans_private is set to NULL, causing a panic. >> Similar issue is in rds_rdma_unuse(). >> >> Reported-by: zerons >> Signed-off-by: Ka-Cheong Poon >> --- > Thanks for getting this out on the list. > > Hi zerons, > Can you please review it and see it addresses your concern ? > Yes, the MR gets freed only when the ref count decreases to zero does address my concern. I think it make the logic cleaner as well. Fantastic! Regards, zerons