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=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 72F49C433E2 for ; Wed, 9 Sep 2020 08:21:55 +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 A3E092076C for ; Wed, 9 Sep 2020 08:21:54 +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="CNyA/3kS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A3E092076C 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]:52846 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kFvMX-0007dX-NW for qemu-devel@archiver.kernel.org; Wed, 09 Sep 2020 04:21:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34010) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kFvLU-00066z-AC for qemu-devel@nongnu.org; Wed, 09 Sep 2020 04:20:48 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:21946 helo=us-smtp-delivery-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 1kFvLR-0004BM-Sd for qemu-devel@nongnu.org; Wed, 09 Sep 2020 04:20:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599639644; 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=ow03md1dmzJNtknAHHuWn8qCqgl0QtY+YMweXygRRAY=; b=CNyA/3kSknQxw7hoixYWUxjDU8csNC1O3xC8+39n610g7g+ceF5LacIK+FiskVVwNTb2Nw kzPWeqN3O5PlR9m3C6C5vk25txlcHUyDfbFSZgmpdCCCnv9w/AUKgBOM/9RI29Mi1+qDbF s1szhoYHLOzJZ3usWT5af6EfiNowOG0= 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-580-bTWBYleBNYav420tElujIg-1; Wed, 09 Sep 2020 04:20:39 -0400 X-MC-Unique: bTWBYleBNYav420tElujIg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D8E2818BA285; Wed, 9 Sep 2020 08:20:38 +0000 (UTC) Received: from starship (unknown [10.35.206.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id 917E75C230; Wed, 9 Sep 2020 08:20:25 +0000 (UTC) Message-ID: Subject: Re: [PATCH v4 9/9] scsi/scsi_bus: fix races in REPORT LUNS From: Maxim Levitsky To: Stefan Hajnoczi Date: Wed, 09 Sep 2020 11:20:24 +0300 In-Reply-To: <20200908152740.GF7154@stefanha-x1.localdomain> References: <20200831150124.206267-1-mlevitsk@redhat.com> <20200831150124.206267-10-mlevitsk@redhat.com> <20200908152740.GF7154@stefanha-x1.localdomain> User-Agent: Evolution 3.36.3 (3.36.3-1.fc32) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlevitsk@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=mlevitsk@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/09 03:20:45 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 Tue, 2020-09-08 at 16:27 +0100, Stefan Hajnoczi wrote: > On Mon, Aug 31, 2020 at 06:01:24PM +0300, Maxim Levitsky wrote: > > Currently scsi_target_emulate_report_luns iterates > > over child devices list twice, and there is guarantee, that > > it will not be changed meanwhile. > > > > This reason for two loops is that it needs to know how much memory > > to allocate. > > > > Avoid this by iterating once, and allocating the memory for the output > > dynamically with reserving enought memory so that in practice it won't > > be reallocated often. > > > > Bugzilla for reference: https://bugzilla.redhat.com/show_bug.cgi?id=1866707 > > "Buglink:" is the tag name documented in > https://wiki.qemu.org/Contribute/SubmitAPatch#Write_a_meaningful_commit_message Noted > > > static bool scsi_target_emulate_report_luns(SCSITargetReq *r) > > { > > BusChild *kid; > > - int i, len, n; > > int channel, id; > > - bool found_lun0; > > + uint8_t tmp[8] = {0}; > > + int len = 0; > > + > > + /* reserve space for 63 LUNs*/ > > + GByteArray *buf = g_byte_array_sized_new(512); > > > > if (r->req.cmd.xfer < 16) { > > return false; > > buf is leaked. Oops, will fix > > > @@ -460,46 +466,36 @@ static bool scsi_target_emulate_report_luns(SCSITargetReq *r) > > } > > channel = r->req.dev->channel; > > id = r->req.dev->id; > > - found_lun0 = false; > > - n = 0; > > > > - rcu_read_lock(); > > > > - QTAILQ_FOREACH_RCU(kid, &r->req.bus->qbus.children, sibling) { > > - DeviceState *qdev = kid->child; > > - SCSIDevice *dev = SCSI_DEVICE(qdev); > > + /* add size (will be updated later to correct value */ > > + g_byte_array_append(buf, tmp, 8); > > + len += 8; > > Can g_byte_array_size() be used instead of keeping a len local variable? Glib don't seem to have this function, I checked the docs. Its seems that they want to convert it to GBytes which is basically immutible verion of GByteArray and it does have g_bytes_get_size. I decided that a local variable while ugly is still better that this. I haven't wrote much code that uses Glib, so I might have missed something though. I had read this reference: https://developer.gnome.org/glib/stable/glib-Byte-Arrays.html > > Reviewed-by: Stefan Hajnoczi Best regards, Maxim Levitsky