Most of this code should also be reusable with other socket types.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Treat socket write space handling in the same way we now treat transport
congestion: by denying the XPRT_LOCK until the transport signals that it
has free buffer space.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

The theory was that we would need to grab the socket lock anyway, so we
might as well use it to gate the allocation of RPC slots for a TCP
socket.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Both RDMA and UDP transports require the request to get a "congestion control"
credit before they can be transmitted. Right now, this is done when
the request locks the socket. We'd like it to happen when a request attempts
to be transmitted for the first time.
In order to support retransmission of requests that already hold such
credits, we also want to ensure that they get queued first, so that we
don't deadlock with requests that have yet to obtain a credit.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

When we shift to using the transmit queue, then the task that holds the
write lock will not necessarily be the same as the one being transmitted.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

We will use the same lock to protect both the transmit and receive queues.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

If the previous message was only partially transmitted, we need to close
the socket in order to avoid corruption of the message stream. To do so,
we currently hijack the unlocking of the socket in order to schedule
the close.
Now that we track the message offset in the socket state, we can move
that kind of checking out of the socket lock code, which is needed to
allow messages to remain queued after dropping the socket lock.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Rather than resetting state variables in socket state_change() callback,
do it in the sunrpc TCP connect function itself.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Since we will want to introduce similar TCP state variables for the
transmission of requests, let's rename the existing ones to label
that they are for the receive side.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

Remove trailing whitespace and blank line at EOF
Signed-off-by: NStephen Hemminger <stephen@networkplumber.org>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Refactor: xprtrdma needs to have better control over when RPCs are
awoken from the backlog queue, so replace xprt_free_slot with a
transport op callout.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Some RPC transports have more overhead in their send_request
callouts than others. For example, for RPC-over-RDMA:

- Marshaling an RPC often has to DMA map the RPC arguments

- Registration methods perform memory registration as part of
  marshaling

To capture just server and network latencies more precisely: when
sending a Call, capture the rq_xtime timestamp _after_ the transport
header has been marshaled.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Since commit 33849792 ("xprtrdma: Detect unreachable NFS/RDMA
servers more reliably"), the xprtrdma transport now has a ->timer
callout. But xprtrdma does not need to compute RTT data, only UDP
needs that. Move the xprt_update_rtt call into the UDP transport
implementation.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Changes since v1:
Added changes in these files:
    drivers/infiniband/hw/usnic/usnic_transport.c
    drivers/staging/lustre/lnet/lnet/lib-socket.c
    drivers/target/iscsi/iscsi_target_login.c
    drivers/vhost/net.c
    fs/dlm/lowcomms.c
    fs/ocfs2/cluster/tcp.c
    security/tomoyo/network.c

Before:
All these functions either return a negative error indicator,
or store length of sockaddr into "int *socklen" parameter
and return zero on success.

"int *socklen" parameter is awkward. For example, if caller does not
care, it still needs to provide on-stack storage for the value
it does not need.

None of the many FOO_getname() functions of various protocols
ever used old value of *socklen. They always just overwrite it.

This change drops this parameter, and makes all these functions, on success,
return length of sockaddr. It's always >= 0 and can be differentiated
from an error.

Tests in callers are changed from "if (err)" to "if (err < 0)", where needed.

rpc_sockname() lost "int buflen" parameter, since its only use was
to be passed to kernel_getsockname() as &buflen and subsequently
not used in any way.

Userspace API is not changed.

    text    data     bss      dec     hex filename
30108430 2633624  873672 33615726 200ef6e vmlinux.before.o
30108109 2633612  873672 33615393 200ee21 vmlinux.o
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
CC: David S. Miller <davem@davemloft.net>
CC: linux-kernel@vger.kernel.org
CC: netdev@vger.kernel.org
CC: linux-bluetooth@vger.kernel.org
CC: linux-decnet-user@lists.sourceforge.net
CC: linux-wireless@vger.kernel.org
CC: linux-rdma@vger.kernel.org
CC: linux-sctp@vger.kernel.org
CC: linux-nfs@vger.kernel.org
CC: linux-x25@vger.kernel.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Calling __UDPX_INC_STATS() from a preemptible context leads to a
warning of the form:

 BUG: using __this_cpu_add() in preemptible [00000000] code: kworker/u5:0/31
 caller is xs_udp_data_receive_workfn+0x194/0x270
 CPU: 1 PID: 31 Comm: kworker/u5:0 Not tainted 4.15.0-rc8-00076-g90ea9f1b #2
 Workqueue: xprtiod xs_udp_data_receive_workfn
 Call Trace:
  dump_stack+0x85/0xc1
  check_preemption_disabled+0xce/0xe0
  xs_udp_data_receive_workfn+0x194/0x270
  process_one_work+0x318/0x620
  worker_thread+0x20a/0x390
  ? process_one_work+0x620/0x620
  kthread+0x120/0x130
  ? __kthread_bind_mask+0x60/0x60
  ret_from_fork+0x24/0x30

Since we're taking a spinlock in those functions anyway, let's fix the
issue by moving the call so that it occurs under the spinlock.
Reported-by: Nkernel test robot <fengguang.wu@intel.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Ensure that we release the TCP socket once it is in the TCP_CLOSE or
TCP_TIME_WAIT state (and only then) so that we don't confuse rkhunter
and its ilk.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

When reading the reply from the server, insert an explicit
cond_resched() to avoid starving higher priority tasks.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Read the TCP data in chunks of max 2MB so that we do not hog the
socket lock.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Reported-by: NDmitry Vyukov <dvyukov@google.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Tested-by: NDmitry Vyukov <dvyukov@google.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
Signed-off-by: NGustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: NPhilippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

sock is being initialized and then being almost immediately updated
hence the initialized value is not being used and is redundant. Remove
the initialization. Cleans up clang warning:

warning: Value stored to 'sock' during its initialization is never read
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

This further reduces contention with the transport_lock, and allows us
to convert to using a non-bh-safe spinlock, since the list is now never
accessed from a bh context.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Simplify the code to avoid a full copy of the struct xdr_skb_reader.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Ensure that we don't hog the workqueue thread by requeuing the job
every 64 loops.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

The backchannel request has no associated task, so it is going nowhere
until we call xprt_complete_bc_request().
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Instead add a mechanism to ensure that the request doesn't disappear
from underneath us while copying from the socket. We do this by
preventing xprt_release() from freeing the XDR buffers until the
flag RPC_TASK_MSG_RECV has been cleared from the request.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: NChuck Lever <chuck.lever@oracle.com>

After transport instance creation, these function pointers never
change. Mark them as constant to prevent their use as an attack
vector for code injections.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Commit 3d476263 ("tcp: remove poll() flakes when receiving
RST") in v4.12 changed the order in which ->sk_state_change()
and ->sk_error_report() are called when a socket is shut
down - sk_state_change() is now called first.

This causes xs_tcp_state_change() -> xs_sock_mark_closed() ->
xprt_disconnect_done() to wake all pending tasked with -EAGAIN.
When the ->sk_error_report() callback arrives, it is too late to
pass the error on, and it is lost.

As easy way to demonstrate the problem caused is to try to start
rpc.nfsd while rcpbind isn't running.
nfsd will attempt a tcp connection to rpcbind.  A ECONNREFUSED
error is returned, but sunrpc code loses the error and keeps
retrying.  If it saw the ECONNREFUSED, it would abort.

To fix this, handle the sk->sk_err in the TCP_CLOSE branch of
xs_tcp_state_change().

Fixes: 3d476263 ("tcp: remove poll() flakes when receiving RST")
Cc: stable@vger.kernel.org (v4.12)
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

If you attempt a TCP mount from an host that is unreachable in a way
that triggers an immediate error from kernel_connect(), that error
does not propagate up, instead EAGAIN is reported.

This results in call_connect_status receiving the wrong error.

A case that it easy to demonstrate is to attempt to mount from an
address that results in ENETUNREACH, but first deleting any default
route.
Without this patch, the mount.nfs process is persistently runnable
and is hard to kill.  With this patch it exits as it should.

The problem is caused by the fact that xs_tcp_force_close() eventually
calls
      xprt_wake_pending_tasks(xprt, -EAGAIN);
which causes an error return of -EAGAIN.  so when xs_tcp_setup_sock()
calls
      xprt_wake_pending_tasks(xprt, status);
the status is ignored.

Fixes: 4efdd92c ("SUNRPC: Remove TCP client connection reset hack")
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

Now that %z is standartised in C99 there is no reason to support %Z.
Unlike %L it doesn't even make format strings smaller.

Use BUILD_BUG_ON in a couple ATM drivers.

In case anyone didn't notice lib/vsprintf.o is about half of SLUB which
is in my opinion is quite an achievement.  Hopefully this patch inspires
someone else to trim vsprintf.c more.

Link: http://lkml.kernel.org/r/20170103230126.GA30170@avx2Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kstrtouint() can return a couple different error codes so the check for
"ret == -EINVAL" is wrong and static analysis tools correctly complain
that we can use "num" without initializing it.  It's not super harmful
because we check the bounds.  But it's also easy enough to fix.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The transport lock is needed to protect the xprt_adjust_cwnd() call
in xs_udp_timer, but it is not necessary for accessing the
rq_reply_bytes_recvd or tk_status fields. It is correct to sublimate
the lock into UDP's xs_udp_timer method, where it is required.

The ->timer method has to take the transport lock if needed, but it
can now sleep safely, or even call back into the RPC scheduler.

This is more a clean-up than a fix, but the "issue" was introduced
by my transport switch patches back in 2005.

Fixes: 46c0ee8b ("RPC: separate xprt_timer implementations")
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

When the NFSv4 server tells us the lease period, we usually want
to adjust down the timeout parameters on the TCP connection to
ensure that we don't miss lease renewals due to a faulty connection.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

A new argument is added to __skb_recv_datagram to provide
an explicit skb destructor, invoked under the receive queue
lock.
The UDP protocol uses such argument to perform memory
reclaiming on dequeue, so that the UDP protocol does not
set anymore skb->desctructor.
Instead explicit memory reclaiming is performed at close() time and
when skbs are removed from the receive queue.
The in kernel UDP protocol users now need to call a
skb_recv_udp() variant instead of skb_recv_datagram() to
properly perform memory accounting on dequeue.

Overall, this allows acquiring only once the receive queue
lock on dequeue.

Tested using pktgen with random src port, 64 bytes packet,
wire-speed on a 10G link as sender and udp_sink as the receiver,
using an l4 tuple rxhash to stress the contention, and one or more
udp_sink instances with reuseport.

nr sinks	vanilla		patched
1		440		560
3		2150		2300
6		3650		3800
9		4450		4600
12		6250		6450

v1 -> v2:
 - do rmem and allocated memory scheduling under the receive lock
 - do bulk scheduling in first_packet_length() and in udp_destruct_sock()
 - avoid the typdef for the dequeue callback
Suggested-by: NEric Dumazet <edumazet@google.com>
Acked-by: NHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We've been seeing some crashes in testing that look like this:

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffff8135ce99>] memcpy_orig+0x29/0x110
PGD 212ca2067 PUD 212ca3067 PMD 0
Oops: 0002 [#1] SMP
Modules linked in: rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache ppdev parport_pc i2c_piix4 sg parport i2c_core virtio_balloon pcspkr acpi_cpufreq nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod ata_generic pata_acpi virtio_scsi 8139too ata_piix libata 8139cp mii virtio_pci floppy virtio_ring serio_raw virtio
CPU: 1 PID: 1540 Comm: nfsd Not tainted 4.9.0-rc1 #39
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2007
task: ffff88020d7ed200 task.stack: ffff880211838000
RIP: 0010:[<ffffffff8135ce99>]  [<ffffffff8135ce99>] memcpy_orig+0x29/0x110
RSP: 0018:ffff88021183bdd0  EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff88020d7fa000 RCX: 000000f400000000
RDX: 0000000000000014 RSI: ffff880212927020 RDI: 0000000000000000
RBP: ffff88021183be30 R08: 01000000ef896996 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff880211704ca8
R13: ffff88021473f000 R14: 00000000ef896996 R15: ffff880211704800
FS:  0000000000000000(0000) GS:ffff88021fc80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000212ca1000 CR4: 00000000000006e0
Stack:
 ffffffffa01ea087 ffffffff63400001 ffff880215145e00 ffff880211bacd00
 ffff88021473f2b8 0000000000000004 00000000d0679d67 ffff880211bacd00
 ffff88020d7fa000 ffff88021473f000 0000000000000000 ffff88020d7faa30
Call Trace:
 [<ffffffffa01ea087>] ? svc_tcp_recvfrom+0x5a7/0x790 [sunrpc]
 [<ffffffffa01f84d8>] svc_recv+0xad8/0xbd0 [sunrpc]
 [<ffffffffa0262d5e>] nfsd+0xde/0x160 [nfsd]
 [<ffffffffa0262c80>] ? nfsd_destroy+0x60/0x60 [nfsd]
 [<ffffffff810a9418>] kthread+0xd8/0xf0
 [<ffffffff816dbdbf>] ret_from_fork+0x1f/0x40
 [<ffffffff810a9340>] ? kthread_park+0x60/0x60
Code: 00 00 48 89 f8 48 83 fa 20 72 7e 40 38 fe 7c 35 48 83 ea 20 48 83 ea 20 4c 8b 06 4c 8b 4e 08 4c 8b 56 10 4c 8b 5e 18 48 8d 76 20 <4c> 89 07 4c 89 4f 08 4c 89 57 10 4c 89 5f 18 48 8d 7f 20 73 d4
RIP  [<ffffffff8135ce99>] memcpy_orig+0x29/0x110
 RSP <ffff88021183bdd0>
CR2: 0000000000000000

Both Bruce and Eryu ran a bisect here and found that the problematic
patch was 68778945 (SUNRPC: Separate buffer pointers for RPC Call and
Reply messages).

That patch changed rpc_xdr_encode to use a new rq_rbuffer pointer to
set up the receive buffer, but didn't change all of the necessary
codepaths to set it properly. In particular the backchannel setup was
missing.

We need to set rq_rbuffer whenever rq_buffer is set. Ensure that it is.
Reviewed-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NChuck Lever <chuck.lever@oracle.com>
Reported-by: NEryu Guan <guaneryu@gmail.com>
Tested-by: NEryu Guan <guaneryu@gmail.com>
Fixes: 68778945 "SUNRPC: Separate buffer pointers..."
Reported-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>