From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33243) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zc5lk-0000ad-0l for qemu-devel@nongnu.org; Wed, 16 Sep 2015 02:00:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zc5lg-0001B1-Oq for qemu-devel@nongnu.org; Wed, 16 Sep 2015 02:00:35 -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> From: Wen Congyang Message-ID: <55F9054F.1000001@cn.fujitsu.com> Date: Wed, 16 Sep 2015 13:59:43 +0800 MIME-Version: 1.0 In-Reply-To: <87mvwo3phm.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 , Eric Blake Cc: Kevin Wolf , Alberto Garcia , zhanghailiang , qemu block , Jiang Yunhong , Dong Eddie , qemu devel , "Dr. David Alan Gilbert" , Gonglei , Stefan Hajnoczi , Yang Hongyang On 09/15/2015 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? > >> 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? Thanks Wen Congyang > >> Thanks >> Wen Congyang >> >>> >>> Eric, what do you think? >>> >>>>> { 'struct': 'NBDInet', 'data': { 'host': 'str', '*port': 'int', >>>>> '*ipv4': 'bool', '*ipv6': 'bool' } } >>>> >>>> Thanks for the above, and I will try it. >>> >>> [...] >>> . >>> > . >