From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47311) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZboAb-0003nh-PB for qemu-devel@nongnu.org; Tue, 15 Sep 2015 07:13:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZboAa-0003SS-LQ for qemu-devel@nongnu.org; Tue, 15 Sep 2015 07:13:05 -0400 From: Markus Armbruster 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> Date: Tue, 15 Sep 2015 13:12:53 +0200 In-Reply-To: <55F7D06D.1080205@cn.fujitsu.com> (Wen Congyang's message of "Tue, 15 Sep 2015 16:01:49 +0800") Message-ID: <87mvwo3phm.fsf@blackfin.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain 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: Wen Congyang Cc: Kevin Wolf , Alberto Garcia , zhanghailiang , qemu block , Jiang Yunhong , Dong Eddie , qemu devel , "Dr. David Alan Gilbert" , Gonglei , Stefan Hajnoczi , Yang Hongyang 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". > 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. >> >> [...] >> . >>