Return-Path: Received: from mail-iw0-f174.google.com ([209.85.214.174]:45983 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754454Ab0LQTzM convert rfc822-to-8bit (ORCPT ); Fri, 17 Dec 2010 14:55:12 -0500 Received: by iwn9 with SMTP id 9so1078277iwn.19 for ; Fri, 17 Dec 2010 11:55:11 -0800 (PST) In-Reply-To: <20101217193324.GC14510@fieldses.org> References: <1292610010-19084-1-git-send-email-andros@netapp.com> <1292610010-19084-2-git-send-email-andros@netapp.com> <20101217184047.GD11515@fieldses.org> <20101217191037.GA14510@fieldses.org> <20101217193324.GC14510@fieldses.org> Date: Fri, 17 Dec 2010 14:55:11 -0500 Message-ID: Subject: Re: [PATCH_V4 1/9] SUNRPC new transport for the NFSv4.1 shared back channel From: "William A. (Andy) Adamson" To: "J. Bruce Fields" Cc: trond.myklebust@netapp.com, bfields@redhat.com, linux-nfs@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Fri, Dec 17, 2010 at 2:33 PM, J. Bruce Fields wrote: > On Fri, Dec 17, 2010 at 02:16:35PM -0500, William A. (Andy) Adamson wrote: >> On Fri, Dec 17, 2010 at 2:10 PM, J. Bruce Fields wrote: >> > On Fri, Dec 17, 2010 at 01:57:50PM -0500, William A. (Andy) Adamson wrote: >> >> On Fri, Dec 17, 2010 at 1:54 PM, William A. (Andy) Adamson >> >> wrote: >> >> > On Fri, Dec 17, 2010 at 1:40 PM, J. Bruce Fields wrote: >> >> >> On Fri, Dec 17, 2010 at 01:20:02PM -0500, andros@netapp.com wrote: >> >> >>> From: Andy Adamson >> >> >>> >> >> >>> Create a new transport for the shared back channel.l Move the current sock >> >> >>> create and destroy routines into the new transport ops. >> >> >>> >> >> >>> Reference the back channel transport across message processing (recv/send). >> >> >>> >> >> >>> Signed-off-by: Andy Adamson >> >> >>> --- >> >> >>> ?include/linux/sunrpc/svcsock.h | ? ?1 + >> >> >>> ?net/sunrpc/svc.c ? ? ? ? ? ? ? | ? 18 +++--- >> >> >>> ?net/sunrpc/svcsock.c ? ? ? ? ? | ?122 +++++++++++++++++++++++++++++++++------- >> >> >>> ?3 files changed, 112 insertions(+), 29 deletions(-) >> >> >>> >> >> >>> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h >> >> >>> index 1b353a7..3a45a80 100644 >> >> >>> --- a/include/linux/sunrpc/svcsock.h >> >> >>> +++ b/include/linux/sunrpc/svcsock.h >> >> >>> @@ -45,6 +45,7 @@ int ? ? ? ? svc_sock_names(struct svc_serv *serv, char *buf, >> >> >>> ?int ? ? ? ? ?svc_addsock(struct svc_serv *serv, const int fd, >> >> >>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? char *name_return, const size_t len); >> >> >>> ?void ? ? ? ? svc_init_xprt_sock(void); >> >> >>> +void ? ? ? ? svc_init_bc_xprt_sock(void); >> >> >>> ?void ? ? ? ? svc_cleanup_xprt_sock(void); >> >> >>> ?struct svc_xprt *svc_sock_create(struct svc_serv *serv, int prot); >> >> >>> ?void ? ? ? ? svc_sock_destroy(struct svc_xprt *); >> >> >>> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c >> >> >>> index 6359c42..3520cb3 100644 >> >> >>> --- a/net/sunrpc/svc.c >> >> >>> +++ b/net/sunrpc/svc.c >> >> >>> @@ -488,10 +488,6 @@ svc_destroy(struct svc_serv *serv) >> >> >>> ? ? ? if (svc_serv_is_pooled(serv)) >> >> >>> ? ? ? ? ? ? ? svc_pool_map_put(); >> >> >>> >> >> >>> -#if defined(CONFIG_NFS_V4_1) >> >> >>> - ? ? svc_sock_destroy(serv->bc_xprt); >> >> >>> -#endif /* CONFIG_NFS_V4_1 */ >> >> >>> - >> >> >>> ? ? ? svc_unregister(serv); >> >> >>> ? ? ? kfree(serv->sv_pools); >> >> >>> ? ? ? kfree(serv); >> >> >>> @@ -1264,7 +1260,7 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req, >> >> >>> ?{ >> >> >>> ? ? ? struct kvec ? ? *argv = &rqstp->rq_arg.head[0]; >> >> >>> ? ? ? struct kvec ? ? *resv = &rqstp->rq_res.head[0]; >> >> >>> - ? ? int ? ? ? ? ? ? error; >> >> >>> + ? ? int ? ? ? ? ? ? ret; >> >> >>> >> >> >>> ? ? ? /* Build the svc_rqst used by the common processing routine */ >> >> >>> ? ? ? rqstp->rq_xprt = serv->bc_xprt; >> >> >>> @@ -1292,12 +1288,16 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req, >> >> >>> ? ? ? svc_getu32(argv); ? ? ? /* XID */ >> >> >>> ? ? ? svc_getnl(argv); ? ? ? ?/* CALLDIR */ >> >> >>> >> >> >>> - ? ? error = svc_process_common(rqstp, argv, resv); >> >> >>> - ? ? if (error <= 0) >> >> >>> - ? ? ? ? ? ? return error; >> >> >>> + ? ? /* Hold a reference to the back channel socket across the call */ >> >> >>> + ? ? svc_xprt_get(serv->bc_xprt); >> >> >> >> >> >> Either we already have a reference, in which case this is unnecessary, >> >> >> or we don't, in which case this is risky. >> >> > >> >> > This is done so that when svc_xprt_put is called due to an svc_drop >> >> > (svc_xprt_release, svc_xprt_put) it is not freed. ?It's not risky >> >> > because AFAICS it's the way the rpc server code is intended to work. >> >> > Note that svc_recv calls svc_xprt_get, and svc_send calls svc_xprt_put >> >> > for the same reason. >> > >> > The svc_xprt_put()'s in svc_send/svc_drop balance the get in svc_recv(). >> > They're needed because on a normal server connections can come and go >> > (because clients come and go) during the lifetime of the server. >> > >> > As I understand it, the client is just creating a new server for each >> > backchannel. ?So the server will never outlive the one connection it >> > uses. ?So you don't need that stuff. ?It's harmless--just leave it >> > alone--but definitely don't try to add additional reference counting >> > during the processing. >> >> If I don't add an svc_xprt_get prior to the svc_process_call, the >> svc_xprt_put called in the svc_drop case will free the bc_xprt, which >> is not what I want. > > Looking at the code some more.... ?Oh, right, because the backchannel > doesn't call svc_recv, it calls its own bc_send, which doesn't do a put. > > Oh, yuch, I see: svc_process_common returns "1" to mean send, "0" to > mean drop, and leaves it up to the caller to do the put in the send > case. ?That's confusing. > > Maybe it would be simpler to have the caller be made responsible for > both cases? ?So: > > ? ? ? ?if (svc_process_common(rqstp)) > ? ? ? ? ? ? ? ?send it > ? ? ? ?else > ? ? ? ? ? ? ? ?drop it That would work well. I'll send a patch -->Andy > > ? > > --b. >