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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 C5B9FC47082 for ; Tue, 8 Jun 2021 17:35:54 +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 62E5361360 for ; Tue, 8 Jun 2021 17:35:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 62E5361360 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]:42730 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lqfdp-0007JO-Ft for qemu-devel@archiver.kernel.org; Tue, 08 Jun 2021 13:35:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47718) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lqfce-0005vk-Gi for qemu-devel@nongnu.org; Tue, 08 Jun 2021 13:34:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:58888) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lqfcb-00072g-Up for qemu-devel@nongnu.org; Tue, 08 Jun 2021 13:34:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623173676; 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: in-reply-to:in-reply-to:references:references; bh=1K3Mt1COvbU6Z7SeutUI2IrnkeVJy75H3B8MyB0CgA4=; b=fNOHe8/3Z9QQkcGuIzpSNRriQi6K5wMaenlkFp/eXQ/WBPp2uHO/JJD8QcYQ0S7lfpRJWQ XIVhfEZKmXR+mq1IExyJwkyMcshVuoGI8EKvlun3ekGQ7S71K1lzGYuLV0nCD+ZBYwydiD 1dmW+xsQgksbEAdB7OXwSA4vvTl/3BA= 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-126-8RVBd4cuOUmw-aym8N0C4Q-1; Tue, 08 Jun 2021 13:34:32 -0400 X-MC-Unique: 8RVBd4cuOUmw-aym8N0C4Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 58EF7805740; Tue, 8 Jun 2021 17:34:14 +0000 (UTC) Received: from redhat.com (ovpn-113-53.phx2.redhat.com [10.3.113.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B19B25D6A8; Tue, 8 Jun 2021 17:34:13 +0000 (UTC) Date: Tue, 8 Jun 2021 12:34:12 -0500 From: Eric Blake To: Paolo Bonzini Subject: Re: [PATCH v4 1/7] file-posix: fix max_iov for /dev/sg devices Message-ID: <20210608173412.mmkelvozgl6uxmya@redhat.com> References: <20210608131634.423904-1-pbonzini@redhat.com> <20210608131634.423904-2-pbonzini@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210608131634.423904-2-pbonzini@redhat.com> User-Agent: NeoMutt/20210205 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.197, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=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: kwolf@redhat.com, vsementsov@virtuozzo.com, qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jun 08, 2021 at 03:16:28PM +0200, Paolo Bonzini wrote: > Even though it was only called for devices that have bs->sg set (which > must be character devices), sg_get_max_segments looked at /sys/dev/block > which only works for block devices. > > On Linux the sg driver has its own way to provide the maximum number of > iovecs in a scatter/gather list, so add support for it. The block device > path is kept because it will be reinstated in the next patches. > > Signed-off-by: Paolo Bonzini > --- > block/file-posix.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/block/file-posix.c b/block/file-posix.c > index f37dfc10b3..536998a1d6 100644 > --- a/block/file-posix.c > +++ b/block/file-posix.c > @@ -1180,6 +1180,17 @@ static int sg_get_max_segments(int fd) > goto out; > } > > + if (S_ISCHR(st.st_mode)) { > + if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) { Do we need to do any conditional compilation based on whether SG_GET_SG_TABLESIZE is a known ioctl, or is it old enough to be assumed present on all platforms we care about? > + return ret; > + } > + return -ENOTSUP; > + } > + > + if (!S_ISBLK(st.st_mode)) { > + return -ENOTSUP; > + } > + > sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments", > major(st.st_rdev), minor(st.st_rdev)); > sysfd = open(sysfspath, O_RDONLY); Otherwise looks good to me. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org