> -----Original Message-----
> From: Myklebust, Trond
> Sent: Thursday, June 04, 2009 12:55 PM
> To: Benny Halevy
> Cc: Adamson, Andy; linux-nfs@xxxxxxxxxxxxxxx; pnfs@xxxxxxxxxxxxx
> Subject: Re: [pnfs] [RFC 10/39] nfs41: Add backchannel processing
support
> to RPC state machine
>
> On Fri, 2009-05-01 at 02:20 +0300, Benny Halevy wrote:
> > From: Ricardo Labiaga <Ricardo.Labiaga@xxxxxxxxxx>
> >
> > Adds rpc_run_bc_task() which is called by the NFS callback service
to
> > process backchannel requests. It performs similar work to
> rpc_run_task()
> > though "schedules" the backchannel task to be executed starting at
the
> > call_trasmit state in the RPC state machine.
> >
> > It also introduces some miscellaneous updates to the argument
> validation,
> > call_transmit, and transport cleanup functions to take into account
> > that there are now forechannel and backchannel tasks.
> >
> > Backchannel requests do not carry an RPC message structure, since
the
> > payload has already been XDR encoded using the existing NFSv4
callback
> > mechanism.
> >
> > Introduce a new transmit state for the client to reply on to
backchannel
> > requests. This new state simply reserves the transport and issues
the
> > reply. In case of a connection related error, disconnects the
transport
> and
> > drops the reply. It requires the forechannel to re-establish the
> connection
> > and the server to retransmit the request, as stated in NFSv4.1
section
> > 2.9.2 "Client and Server Transport Behavior".
> >
> > Note: There is no need to loop attempting to reserve the transport.
If
> EAGAIN
> > is returned by xprt_prepare_transmit(), return with tk_status == 0,
> > setting tk_action to call_bc_transmit. rpc_execute() will invoke it
> again
> > after the task is taken off the sleep queue.
> >
> > [nfs41: rpc_run_bc_task() need not be exported outside RPC module]
> > [nfs41: New call_bc_transmit RPC state]
> > Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@xxxxxxxxxx>
> > Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
> > [nfs41: Backchannel: No need to loop in call_bc_transmit()]
> > Signed-off-by: Andy Adamson <andros@xxxxxxxxxx>
> > Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@xxxxxxxxxx>
> > Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
> > ---
> > include/linux/sunrpc/sched.h | 2 +
> > include/linux/sunrpc/xprt.h | 12 ++++
> > net/sunrpc/clnt.c | 117
> +++++++++++++++++++++++++++++++++++++++++-
> > net/sunrpc/stats.c | 6 ++-
> > net/sunrpc/sunrpc.h | 35 +++++++++++++
> > net/sunrpc/xprt.c | 36 +++++++++++--
> > 6 files changed, 199 insertions(+), 9 deletions(-)
> > create mode 100644 net/sunrpc/sunrpc.h
> >
> > diff --git a/include/linux/sunrpc/sched.h
b/include/linux/sunrpc/sched.h
> > index 1773768..4010977 100644
> > --- a/include/linux/sunrpc/sched.h
> > +++ b/include/linux/sunrpc/sched.h
> > @@ -210,6 +210,8 @@ struct rpc_wait_queue {
> > */
> > struct rpc_task *rpc_new_task(const struct rpc_task_setup *);
> > struct rpc_task *rpc_run_task(const struct rpc_task_setup *);
> > +struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req,
> > + const struct rpc_call_ops *ops);
> > void rpc_put_task(struct rpc_task *);
> > void rpc_exit_task(struct rpc_task *);
> > void rpc_release_calldata(const struct rpc_call_ops
*, void *);
> > diff --git a/include/linux/sunrpc/xprt.h
b/include/linux/sunrpc/xprt.h
> > index 6b37724..1531abe 100644
> > --- a/include/linux/sunrpc/xprt.h
> > +++ b/include/linux/sunrpc/xprt.h
> > @@ -215,6 +215,18 @@ struct rpc_xprt {
> > /* buffer in use */
> > #endif /* CONFIG_NFS_V4_1 */
> >
> > +#if defined(CONFIG_NFS_V4_1)
> > +static inline int bc_prealloc(struct rpc_rqst *req)
> > +{
> > + return test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
> > +}
> > +#else
> > +static inline int bc_prealloc(struct rpc_rqst *req)
> > +{
> > + return 0;
> > +}
> > +#endif /* CONFIG_NFS_V4_1 */
> > +
> > struct xprt_create {
> > int ident; /* XPRT_TRANSPORT
identifier */
> > struct sockaddr * srcaddr; /* optional local
address */
> > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> > index 76d7d46..349b4d6 100644
> > --- a/net/sunrpc/clnt.c
> > +++ b/net/sunrpc/clnt.c
> > @@ -36,7 +36,9 @@
> > #include <linux/sunrpc/clnt.h>
> > #include <linux/sunrpc/rpc_pipe_fs.h>
> > #include <linux/sunrpc/metrics.h>
> > +#include <linux/sunrpc/bc_xprt.h>
> >
> > +#include "sunrpc.h"
> >
> > #ifdef RPC_DEBUG
> > # define RPCDBG_FACILITY RPCDBG_CALL
> > @@ -63,6 +65,9 @@ static void call_decode(struct rpc_task
*task);
> > static void call_bind(struct rpc_task *task);
> > static void call_bind_status(struct rpc_task *task);
> > static void call_transmit(struct rpc_task *task);
> > +#if defined(CONFIG_NFS_V4_1)
> > +static void call_bc_transmit(struct rpc_task *task);
> > +#endif /* CONFIG_NFS_V4_1 */
> > static void call_status(struct rpc_task *task);
> > static void call_transmit_status(struct rpc_task *task);
> > static void call_refresh(struct rpc_task *task);
> > @@ -613,6 +618,50 @@ rpc_call_async(struct rpc_clnt *clnt, const
struct
> rpc_message *msg, int flags,
> > }
> > EXPORT_SYMBOL_GPL(rpc_call_async);
> >
> > +#if defined(CONFIG_NFS_V4_1)
> > +/**
> > + * rpc_run_bc_task - Allocate a new RPC task for backchannel use,
then
> run
> > + * rpc_execute against it
> > + * @ops: RPC call ops
> > + */
> > +struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req,
> > + const struct rpc_call_ops
*tk_ops)
> > +{
> > + struct rpc_task *task;
> > + struct xdr_buf *xbufp = &req->rq_snd_buf;
> > + struct rpc_task_setup task_setup_data = {
> > + .callback_ops = tk_ops,
> > + };
> > +
> > + dprintk("RPC: rpc_run_bc_task req= %p\n", req);
> > + /*
> > + * Create an rpc_task to send the data
> > + */
> > + task = rpc_new_task(&task_setup_data);
> > + if (!task) {
> > + xprt_free_bc_request(req);
> > + goto out;
> > + }
> > + task->tk_rqstp = req;
> > +
> > + /*
> > + * Set up the xdr_buf length.
> > + * This also indicates that the buffer is XDR encoded already.
> > + */
> > + xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
> > + xbufp->tail[0].iov_len;
> > +
> > + task->tk_action = call_bc_transmit;
> > + atomic_inc(&task->tk_count);
> > + BUG_ON(atomic_read(&task->tk_count) != 2);
> > + rpc_execute(task);
> > +
> > +out:
> > + dprintk("RPC: rpc_run_bc_task: task= %p\n", task);
> > + return task;
> > +}
> > +#endif /* CONFIG_NFS_V4_1 */
> > +
> > void
> > rpc_call_start(struct rpc_task *task)
> > {
> > @@ -1098,7 +1147,7 @@ call_transmit(struct rpc_task *task)
> > * in order to allow access to the socket to other RPC requests.
> > */
> > call_transmit_status(task);
> > - if (task->tk_msg.rpc_proc->p_decode != NULL)
> > + if (rpc_reply_expected(task))
> > return;
> > task->tk_action = rpc_exit_task;
> > rpc_wake_up_queued_task(&task->tk_xprt->pending, task);
> > @@ -1133,6 +1182,72 @@ call_transmit_status(struct rpc_task *task)
> > }
> > }
> >
> > +#if defined(CONFIG_NFS_V4_1)
> > +/*
> > + * 5b. Send the backchannel RPC reply. On error, drop the
reply. In
> > + * addition, disconnect on connectivity errors.
> > + */
> > +static void
> > +call_bc_transmit(struct rpc_task *task)
> > +{
> > + struct rpc_rqst *req = task->tk_rqstp;
> > +
> > + BUG_ON(task->tk_status != 0);
> > + task->tk_status = xprt_prepare_transmit(task);
> > + if (task->tk_status == -EAGAIN) {
> > + /*
> > + * Could not reserve the transport. Try again after the
> > + * transport is released.
> > + */
> > + task->tk_status = 0;
> > + task->tk_action = call_bc_transmit;
> > + return;
> > + }
> > +
> > + task->tk_action = rpc_exit_task;
> > + if (task->tk_status < 0) {
> > + printk(KERN_NOTICE "RPC: Could not send backchannel
reply "
> > + "error: %d\n", task->tk_status);
> > + return;
> > + }
> > +
> > + xprt_transmit(task);
> > + xprt_end_transmit(task);
> > + dprint_status(task);
> > + switch (task->tk_status) {
> > + case 0:
> > + /* Success */
> > + break;
> > + case -EHOSTDOWN:
> > + case -EHOSTUNREACH:
> > + case -ENETUNREACH:
> > + case -ETIMEDOUT:
> > + /*
> > + * Problem reaching the server. Disconnect and let the
> > + * forechannel reestablish the connection. The server
will
> > + * have to retransmit the backchannel request and we'll
> > + * reprocess it. Since these ops are idempotent,
there's no
> > + * need to cache our reply at this time.
> > + */
> > + printk(KERN_NOTICE "RPC: Could not send backchannel
reply "
> > + "error: %d\n", task->tk_status);
> > + xprt_conditional_disconnect(task->tk_xprt,
> > + req->rq_connect_cookie);
> > + break;
> > + default:
> > + /*
> > + * We were unable to reply and will have to drop the
> > + * request. The server should reconnect and retransmit.
> > + */
> > + BUG_ON(task->tk_status == -EAGAIN);
> > + printk(KERN_NOTICE "RPC: Could not send backchannel
reply "
> > + "error: %d\n", task->tk_status);
> > + break;
> > + }
> > + rpc_wake_up_queued_task(&req->rq_xprt->pending, task);
> > +}
> > +#endif /* CONFIG_NFS_V4_1 */
> > +
> > /*
> > * 6. Sort out the RPC call status
> > */
> > diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c
> > index 1ef6e46..a0e3d97 100644
> > --- a/net/sunrpc/stats.c
> > +++ b/net/sunrpc/stats.c
> > @@ -141,12 +141,14 @@ EXPORT_SYMBOL_GPL(rpc_free_iostats);
> > void rpc_count_iostats(struct rpc_task *task)
> > {
> > struct rpc_rqst *req = task->tk_rqstp;
> > - struct rpc_iostats *stats = task->tk_client->cl_metrics;
> > + struct rpc_iostats *stats;
> > struct rpc_iostats *op_metrics;
> > long rtt, execute, queue;
> >
> > - if (!stats || !req)
> > + if (!task->tk_client || task->tk_client->cl_metrics || !req)
>
> When are we going to have a tk_client without metrics?
>
The original code checked for stats being non-null, so we're doing the
same thing. Having said that, I don't see when cl_metrics could be null
either, since rpc_new_client() guarantees its allocation.
I can remove it, but it's not strictly due to functionality in this
patch.
> > return;
> > +
> > + stats = task->tk_client->cl_metrics;
> > op_metrics = &stats[task->tk_msg.rpc_proc->p_statidx];
> >
> > op_metrics->om_ops++;
> > diff --git a/net/sunrpc/sunrpc.h b/net/sunrpc/sunrpc.h
> > new file mode 100644
> > index 0000000..b462de4
> > --- /dev/null
> > +++ b/net/sunrpc/sunrpc.h
> > @@ -0,0 +1,35 @@
> >
>
+/**********************************************************************
**
> ******
> > +
> > +(c) 2008 Network Appliance, Inc. All Rights Reserved.
> > +
>
> Ditto...
Will fix.
> > +Network Appliance provides this source code under the GPL v2
License.
> > +The GPL v2 license is available at
> > +http://opensource.org/licenses/gpl-license.php.
> > +
> > +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> > +"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> > +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR
> > +A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT
> OWNER OR
> > +CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL,
> > +EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
> > +PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
> > +PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
OF
> > +LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING
> > +NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
> > +SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
> > +
> >
>
+***********************************************************************
**
> *****/
> > +
> > +/*
> > + * Functions and macros used internally by RPC
> > + */
> > +
> > +#ifndef _NET_SUNRPC_SUNRPC_H
> > +#define _NET_SUNRPC_SUNRPC_H
> > +
> > +#define rpc_reply_expected(task) \
> > + (((task)->tk_msg.rpc_proc != NULL) && \
> > + ((task)->tk_msg.rpc_proc->p_decode != NULL))
>
> Why is this a macro instead of being an inlined function?
>
My fault, I was still getting acquainted with the difference between
macros and inlining. Will change to inlined function.
> > +
> > +#endif /* _NET_SUNRPC_SUNRPC_H */
> > +
> > diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> > index bbaec23..df65d15 100644
> > --- a/net/sunrpc/xprt.c
> > +++ b/net/sunrpc/xprt.c
> > @@ -12,8 +12,9 @@
> > * - Next, the caller puts together the RPC message, stuffs
it into
> > * the request struct, and calls xprt_transmit().
> > * - xprt_transmit sends the message and installs the caller
on the
> > - * transport's wait list. At the same time, it installs a timer
> that
> > - * is run after the packet's timeout has expired.
> > + * transport's wait list. At the same time, if a reply is expected,
> > + * it installs a timer that is run after the packet's timeout has
> > + * expired.
> > * - When a packet arrives, the data_ready handler walks the
list of
> > * pending requests for that transport. If a matching XID is found,
> the
> > * caller is woken up, and the timer removed.
> > @@ -46,6 +47,8 @@
> > #include <linux/sunrpc/clnt.h>
> > #include <linux/sunrpc/metrics.h>
> >
> > +#include "sunrpc.h"
> > +
> > /*
> > * Local variables
> > */
> > @@ -875,7 +878,10 @@ void xprt_transmit(struct rpc_task *task)
> > dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid,
req->rq_slen);
> >
> > if (!req->rq_received) {
> > - if (list_empty(&req->rq_list)) {
> > + if (list_empty(&req->rq_list) &&
rpc_reply_expected(task)) {
> > + /*
> > + * Add to the list only if we're expecting a
reply
> > + */
> > spin_lock_bh(&xprt->transport_lock);
> > /* Update the softirq receive buffer */
> > memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
> > @@ -910,8 +916,13 @@ void xprt_transmit(struct rpc_task *task)
> > /* Don't race with disconnect */
> > if (!xprt_connected(xprt))
> > task->tk_status = -ENOTCONN;
> > - else if (!req->rq_received)
> > + else if (!req->rq_received && rpc_reply_expected(task)) {
> > + /*
> > + * Sleep on the pending queue since
> > + * we're expecting a reply.
> > + */
> > rpc_sleep_on(&xprt->pending, task, xprt_timer);
> > + }
> > spin_unlock_bh(&xprt->transport_lock);
> > }
> >
> > @@ -984,11 +995,15 @@ static void xprt_request_init(struct rpc_task
> *task, struct rpc_xprt *xprt)
> > */
> > void xprt_release(struct rpc_task *task)
> > {
> > - struct rpc_xprt *xprt = task->tk_xprt;
> > + struct rpc_xprt *xprt;
> > struct rpc_rqst *req;
> > + int prealloc;
> >
> > + BUG_ON(atomic_read(&task->tk_count) < 0);
>
> Err?
>
This was useful during early development. Never hit it though :-) So
I'll remove it.
> > if (!(req = task->tk_rqstp))
> > return;
> > + prealloc = bc_prealloc(req); /* Preallocated backchannel
request? */
> > + xprt = req->rq_xprt;
> > rpc_count_iostats(task);
> > spin_lock_bh(&xprt->transport_lock);
> > xprt->ops->release_xprt(xprt, task);
> > @@ -1001,10 +1016,19 @@ void xprt_release(struct rpc_task *task)
> > mod_timer(&xprt->timer,
> > xprt->last_used + xprt->idle_timeout);
> > spin_unlock_bh(&xprt->transport_lock);
> > - xprt->ops->buf_free(req->rq_buffer);
> > + if (!bc_prealloc(req))
> > + xprt->ops->buf_free(req->rq_buffer);
> > task->tk_rqstp = NULL;
> > if (req->rq_release_snd_buf)
> > req->rq_release_snd_buf(req);
> > +
> > + /*
> > + * Early exit if this is a backchannel preallocated request.
> > + * There is no need to have it added to the RPC slot list.
> > + */
> > + if (prealloc)
> > + return;
>
> Could we change the name of 'prealloc' to something along the lines of
> 'is_bc_request'?
>
Yes, will do.
- ricardo
> > +
> > memset(req, 0, sizeof(*req)); /* mark unused */
> >
> > dprintk("RPC: %5u release request %p\n", task->tk_pid, req);
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
> _______________________________________________
> pNFS mailing list
> pNFS@xxxxxxxxxxxxx
> http://linux-nfs.org/cgi-bin/mailman/listinfo/pnfs
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