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=-12.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 B38BDC433E3 for ; Mon, 24 Aug 2020 09:40:35 +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 7F72C2075B for ; Mon, 24 Aug 2020 09:40:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RRD/9U2V" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F72C2075B 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]:49900 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kA8xu-0001Kv-P5 for qemu-devel@archiver.kernel.org; Mon, 24 Aug 2020 05:40:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44552) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kA8xJ-0000in-8B for qemu-devel@nongnu.org; Mon, 24 Aug 2020 05:39:57 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:26335 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 1kA8xG-0003hg-Ti for qemu-devel@nongnu.org; Mon, 24 Aug 2020 05:39:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598261992; h=from:from:reply-to: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=ijKyWWKGEqvFzU0U4/PA3+BDVILm7DfOymVz0lFxVJQ=; b=RRD/9U2VY/WDbbSsW6Aslh6lK3DoFhlSFlJ09OjSPbLbogKJ6+knuAZ4GeAydxZBqOWs5x aspubamufnpV/aM14A8jWEUaVM45l3q4fG/EqR7Y58Vs01bnZ7FHcu7Zem5/Gr3VoBEqWY RSTt5OXysxixKSNPqQ3+CJZEKNlN0OI= 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-219-TfnGYRUAOK-Fh7jF8pf30Q-1; Mon, 24 Aug 2020 05:39:50 -0400 X-MC-Unique: TfnGYRUAOK-Fh7jF8pf30Q-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 83A2681F006; Mon, 24 Aug 2020 09:39:49 +0000 (UTC) Received: from redhat.com (ovpn-114-223.ams2.redhat.com [10.36.114.223]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B0D495D9DD; Mon, 24 Aug 2020 09:39:44 +0000 (UTC) Date: Mon, 24 Aug 2020 10:39:41 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: =?utf-8?B?5byg5L2z6L6w?= Subject: Re: [External] Re: [PATCH] virtiofsd: add -o allow_directio|no_directio option Message-ID: <20200824093941.GD10011@redhat.com> References: <20200821034126.8004-1-zhangjiachen.jaycee@bytedance.com> <20200821115829.GJ348677@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=berrange@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/24 05:27:06 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.959, 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=-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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Yongji Xie , "Dr . David Alan Gilbert" , Stefan Hajnoczi , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sat, Aug 22, 2020 at 01:51:04AM +0800, 张佳辰 wrote: > On Fri, Aug 21, 2020 at 7:58 PM Daniel P. Berrangé > wrote: > > > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > > > Due to the commit 65da4539803373ec4eec97ffc49ee90083e56efd, the O_DIRECT > > > open flag of guest applications will be discarded by virtiofsd. While > > > this behavior makes it consistent with the virtio-9p scheme when guest > > > applications using direct I/O, we no longer have any chance to bypass > > > the host page cache. > > > > > > Therefore, we add a flag 'allow_directio' to lo_data. If '-o no_directio' > > > option is added, or none of '-o no_directio' or '-o allow_directio' is > > > added, the 'allow_directio' will be set to 0, and virtiofsd discards > > > O_DIRECT as before. If '-o allow_directio' is added to the stariting > > > command-line, 'allow_directio' will be set to 1, so that the O_DIRECT > > > flags will be retained and host page cache can be bypassed. > > > > > > Signed-off-by: Jiachen Zhang > > > --- > > > tools/virtiofsd/helper.c | 4 ++++ > > > tools/virtiofsd/passthrough_ll.c | 20 ++++++++++++++------ > > > 2 files changed, 18 insertions(+), 6 deletions(-) > > > > > > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > > > index 3105b6c23a..534ff52c64 100644 > > > --- a/tools/virtiofsd/helper.c > > > +++ b/tools/virtiofsd/helper.c > > > @@ -180,6 +180,10 @@ void fuse_cmdline_help(void) > > > " (0 leaves rlimit > > unchanged)\n" > > > " default: min(1000000, > > fs.file-max - 16384)\n" > > > " if the current > > rlimit is lower\n" > > > + " -o allow_directio|no_directio\n" > > > + " retain/discard O_DIRECT > > flags passed down\n" > > > + " to virtiofsd from guest > > applications.\n" > > > + " default: no_directio\n" > > > ); > > > > The standard naming convention from existing options is to use > > $OPTNAME and no_$OPTNAME. > > > > IOW, don't use the "allow_" prefix. The options should be just > > "directio" and "no_directio" > > > > Thanks, Daniel. I did consider using "directio" instead of "allow_directio" > before I send out this patch. Although "-o directio" makes it consistent > with other option names, it may confuse the users of virtiofsd. > Because currently, virtiofsd will not add an O_DIRECT to the open flag, > it will just retain or discard the O_DIRECT added by guest applications. > But "-o direct" may make the users think that virtiofsd will do direct IO > all > the time. Then -o allow_direct_io and -o no_allow_direct_io Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|