From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52148) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zc81l-0003Y3-IQ for qemu-devel@nongnu.org; Wed, 16 Sep 2015 04:25:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zc81i-0003Sk-Dt for qemu-devel@nongnu.org; Wed, 16 Sep 2015 04:25:17 -0400 References: <1441878905-5272-1-git-send-email-wency@cn.fujitsu.com> <1441878905-5272-2-git-send-email-wency@cn.fujitsu.com> <87r3m1krdl.fsf@blackfin.pond.sub.org> <55F6EBF5.2090101@redhat.com> <55F776CC.3050601@cn.fujitsu.com> <87fv2g876a.fsf@blackfin.pond.sub.org> <55F7D06D.1080205@cn.fujitsu.com> <87mvwo3phm.fsf@blackfin.pond.sub.org> <55F9054F.1000001@cn.fujitsu.com> <87r3lyzsef.fsf@blackfin.pond.sub.org> From: Wen Congyang Message-ID: <55F92745.6040904@cn.fujitsu.com> Date: Wed, 16 Sep 2015 16:24:37 +0800 MIME-Version: 1.0 In-Reply-To: <87r3lyzsef.fsf@blackfin.pond.sub.org> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 1/5] support nbd driver in blockdev-add List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: Kevin Wolf , Alberto Garcia , zhanghailiang , qemu block , Jiang Yunhong , Dong Eddie , qemu devel , "Dr. David Alan Gilbert" , Gonglei , Stefan Hajnoczi , Yang Hongyang On 09/16/2015 04:21 PM, Markus Armbruster wrote: > Wen Congyang writes: > >> On 09/15/2015 07:12 PM, Markus Armbruster wrote: >>> Wen Congyang writes: >>> >>>> On 09/15/2015 03:37 PM, Markus Armbruster wrote: >>>>> Wen Congyang writes: >>>>> >>>>>> On 09/14/2015 11:47 PM, Eric Blake wrote: >>>>>>> On 09/14/2015 08:27 AM, Markus Armbruster wrote: >>>>>>>> Wen Congyang writes: >>>>>>>> >>>>>>>>> The NBD driver needs: filename, path or (host, port, exportname). >>>>>>>>> It checks which key exists and decides use unix or inet socket. >>>>>>>>> It doesn't recognize the key type, so we can't use union, and >>>>>>>>> can't reuse InetSocketAddress. >>>>>>>>> >>>>>>>>> Signed-off-by: Wen Congyang >>>>>>>>> Signed-off-by: zhanghailiang >>>>>>>>> Signed-off-by: Gonglei >>>>>>>>> --- >>>>>>>>> qapi/block-core.json | 42 ++++++++++++++++++++++++++++++++++++++++-- >>>>>>>>> 1 file changed, 40 insertions(+), 2 deletions(-) >>>>>>>>> >>>>>>> >>>>>>>>> ## >>>>>>>>> +# @BlockdevOptionsNBD >>>>>>>>> +# >>>>>>>>> +# Driver specific block device options for NBD >>>>>>>>> +# >>>>>>>>> +# @filename: #optional unix or inet path. The format is: >>>>>>>>> +# unix: nbd+unix:///export?socket=path or >>>>>>>>> +# nbd:unix:path:exportname=export >>>>>>>>> +# inet: nbd[+tcp]://host[:port]/export or >>>>>>>>> +# nbd:host[:port]:exportname=export >>>>>>> >>>>>>> Yuck. You are passing structured data through a single 'str', when you >>>>>>> SHOULD be passing it through structured JSON. Just because we have a >>>>>>> filename shorthand for convenience does NOT mean that we want to expose >>>>>>> that convenience in QMP. Instead, we really want the breakdown of the >>>>>>> pieces (here, using abbreviated syntax of an inline base, since there >>>>>>> are pending qapi patches that will allow it): >>>>>> >>>>>> Do you mean that: there is no need to support filename? >>>>> >>>>> Rule of thumb: if the QMP command handler needs to parse a string >>>>> argument, that argument should be a complex QAPI type instead. >>>>> >>>>> Example: @filename needs to be parsed into its components, either >>>>> >>>>> * protocol unix, socket path, export name, or >>>>> * protocol tcp, host, port, export name >>>>> >>>>> Since there's an either/or, the complex QAPI type should be a union. >>>>> >>>>>>> { 'enum': 'NBDTransport', 'data': ['unix', 'tcp', 'udp'] } >>>>>> >>>>>> NBD only uses tcp, it doesn't support udp. >>>>>> >>>>>>> { 'union': 'BlockdevOptionsNBD', >>>>>>> 'base': { 'transport': 'NBDTransport', 'export': 'str' }, >>>>>>> 'discriminator': 'transport', >>>>>>> 'data': { 'unix': 'NBDUnix', 'tcp': 'NBDInet', 'udp': 'NBDInet' } } >>>>>>> { 'struct': 'NBDUnix', 'data': { 'socket': 'str' } } >>>>>> >>>>>> unix socket needs a path, and I think we can use UnixSocketAddress here. >>>>> >>>>> Yes, we should try to reuse common types like SocketAddress, >>>>> InetSocketAddress, UnixSocketAddress. >>>>> >>>>> Perhaps it could be as simple as >>>>> >>>>> { 'struct': 'BlockdevOptionsNBD', >>>>> 'data': { 'addr: 'SocketAddress', 'export': 'str' } } >>>> >>>> The problem is that: NBD doesn't use the fd. >>> >>> Is that fundamental, or just a matter of implementation? > > Question still open. > >>>> Another question is: what key will we see in nbd_open()? "addr.host" >>>> or "host"? >>> >>> As long as nbd_config() looks for "host" in the options QDict, we need >>> to put "host". >> >> Yes, we need "host" in nbd_config(), but we pass "addr.data.host" to it. >> >> How to avoid this problem? > > Where is the code constructing the QDict? The QDict is constructed in qmp_blockdev_add(): visit_type_BlockdevOptions(qmp_output_get_visitor(ov), &options, NULL, &local_err); if (local_err) { error_propagate(errp, local_err); goto fail; } obj = qmp_output_get_qobject(ov); qdict = qobject_to_qdict(obj); qdict_flatten(qdict); Thanks Wen Congyang > . >