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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 4B254C433DF for ; Thu, 9 Jul 2020 10:44:48 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1747B206DF for ; Thu, 9 Jul 2020 10:44:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="irFcnii/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1747B206DF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59344 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jtU2p-0002Fs-BH for qemu-devel@archiver.kernel.org; Thu, 09 Jul 2020 06:44:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34214) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jtU2H-0001r3-IU for qemu-devel@nongnu.org; Thu, 09 Jul 2020 06:44:13 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:43854 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jtU2F-00020E-UF for qemu-devel@nongnu.org; Thu, 09 Jul 2020 06:44:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594291451; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Yis14YisU5x4HNb8WFQH7xcJgGklH8B3Hss5/8/NyoY=; b=irFcnii/YmxnJPknaKGXPc0Tw+6DX5+Afofj4ENzvEKhXTDdp89tOjD2BjT5maDH26iv/m u6Wo4Hu9uApraANILIvDZPR5yqi2lJKkPtgsOwF8jxQpNrHVp+mtIvctO7kO3p6knWFDIW enEr7PgjumH35ZXtWiCbO4/qDIXEf3I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-22-rwqsfE9GNL6Yk9uTwYiDMw-1; Thu, 09 Jul 2020 06:44:07 -0400 X-MC-Unique: rwqsfE9GNL6Yk9uTwYiDMw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8C1691DE1; Thu, 9 Jul 2020 10:44:05 +0000 (UTC) Received: from starship (unknown [10.35.206.232]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3695060F8D; Thu, 9 Jul 2020 10:44:00 +0000 (UTC) Message-ID: <394d6c7d7ca6008152593e7b592f19a41baf1fee.camel@redhat.com> Subject: Re: [PATCH v2 7/7] virtio-scsi: use scsi_device_get From: Maxim Levitsky To: Stefan Hajnoczi Date: Thu, 09 Jul 2020 13:43:58 +0300 In-Reply-To: <20200527155010.GM29137@stefanha-x1.localdomain> References: <20200511160951.8733-1-mlevitsk@redhat.com> <20200511160951.8733-8-mlevitsk@redhat.com> <20200527155010.GM29137@stefanha-x1.localdomain> User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlevitsk@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=mlevitsk@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/09 01:47:04 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , "Daniel P. =?ISO-8859-1?Q?Berrang=E9?=" , Eduardo Habkost , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 2020-05-27 at 16:50 +0100, Stefan Hajnoczi wrote: > On Mon, May 11, 2020 at 07:09:51PM +0300, Maxim Levitsky wrote: > > This will help us to avoid the scsi device disappearing > > after we took a reference to it. > > > > It doesn't by itself forbid case when we try to access > > an unrealized device > > > > Suggested-by: Stefan Hajnoczi > > Signed-off-by: Maxim Levitsky > > --- > > hw/scsi/virtio-scsi.c | 23 +++++++++++++++-------- > > 1 file changed, 15 insertions(+), 8 deletions(-) > > I'm not very familiar with the SCSI emulation code, but this looks > correct. My understanding of what this patch does: > > This patch keeps SCSIDevice alive between scsi_device_find() and > scsi_req_new(). Previously no SCSIDevice ref was taken so the device > could have been freed before scsi_req_new() had a chance to take a ref. Yep, I also verified now that this is what happens. > > The TMF case is similar: the SCSIDevice ref must be held during > virtio_scsi_do_tmf(). We don't need to worry about the async cancel > notifiers because the request being canceled already holds a ref. This code I understand less to be honest, but in the worst case, the patch shoudn't make it worse. Best regards, Maxim Levitsky