Backchannel doesn't have the rq_task->tk_clientid pointer set.

Otherwise can lead to the following oops:
ocalhost login: [  111.385319] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
[  111.388073] #PF error: [normal kernel read fault]
[  111.389452] PGD 80000000290d8067 P4D 80000000290d8067 PUD 75f25067 PMD 0
[  111.391224] Oops: 0000 [#1] SMP PTI
[  111.392151] CPU: 0 PID: 3533 Comm: NFSv4 callback Not tainted 5.0.0-rc7+ #1
[  111.393787] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
[  111.396340] RIP: 0010:trace_event_raw_event_xprt_enq_xmit+0x6f/0xf0 [sunrpc]
[  111.397974] Code: 00 00 00 48 89 ee 48 89 e7 e8 bd 0a 85 d7 48 85 c0 74 4a 41 0f b7 94 24 e0 00 00 00 48 89 e7 89 50 08 49 8b 94 24 a8 00 00 00 <8b> 52 04 89 50 0c 49 8b 94 24 c0 00 00 00 8b 92 a8 00 00 00 0f ca
[  111.402215] RSP: 0018:ffffb98743263cf8 EFLAGS: 00010286
[  111.403406] RAX: ffffa0890fc3bc88 RBX: 0000000000000003 RCX: 0000000000000000
[  111.405057] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffb98743263cf8
[  111.406656] RBP: ffffa0896f5368f0 R08: 0000000000000246 R09: 0000000000000000
[  111.408437] R10: ffffe19b01c01500 R11: 0000000000000000 R12: ffffa08977d28a00
[  111.410210] R13: 0000000000000004 R14: ffffa089315303f0 R15: ffffa08931530000
[  111.411856] FS:  0000000000000000(0000) GS:ffffa0897bc00000(0000) knlGS:0000000000000000
[  111.413699] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  111.415068] CR2: 0000000000000004 CR3: 000000002ac90004 CR4: 00000000001606f0
[  111.416745] Call Trace:
[  111.417339]  xprt_request_enqueue_transmit+0x2b6/0x4a0 [sunrpc]
[  111.418709]  ? rpc_task_need_encode+0x40/0x40 [sunrpc]
[  111.419957]  call_bc_transmit+0xd5/0x170 [sunrpc]
[  111.421067]  __rpc_execute+0x7e/0x3f0 [sunrpc]
[  111.422177]  rpc_run_bc_task+0x78/0xd0 [sunrpc]
[  111.423212]  bc_svc_process+0x281/0x340 [sunrpc]
[  111.424325]  nfs41_callback_svc+0x130/0x1c0 [nfsv4]
[  111.425430]  ? remove_wait_queue+0x60/0x60
[  111.426398]  kthread+0xf5/0x130
[  111.427155]  ? nfs_callback_authenticate+0x50/0x50 [nfsv4]
[  111.428388]  ? kthread_bind+0x10/0x10
[  111.429270]  ret_from_fork+0x1f/0x30

localhost login: [  467.462259] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
[  467.464411] #PF error: [normal kernel read fault]
[  467.465445] PGD 80000000728c1067 P4D 80000000728c1067 PUD 728c0067 PMD 0
[  467.466980] Oops: 0000 [#1] SMP PTI
[  467.467759] CPU: 0 PID: 3517 Comm: NFSv4 callback Not tainted 5.0.0-rc7+ #1
[  467.469393] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
[  467.471840] RIP: 0010:trace_event_raw_event_xprt_transmit+0x7c/0xf0 [sunrpc]
[  467.473392] Code: f6 48 85 c0 74 4b 49 8b 94 24 98 00 00 00 48 89 e7 0f b7 92 e0 00 00 00 89 50 08 49 8b 94 24 98 00 00 00 48 8b 92 a8 00 00 00 <8b> 52 04 89 50 0c 41 8b 94 24 a8 00 00 00 0f ca 89 50 10 41 8b 94
[  467.477605] RSP: 0018:ffffabe7434fbcd0 EFLAGS: 00010282
[  467.478793] RAX: ffff99720fc3bce0 RBX: 0000000000000003 RCX: 0000000000000000
[  467.480409] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffabe7434fbcd0
[  467.482011] RBP: ffff99726f631948 R08: 0000000000000246 R09: 0000000000000000
[  467.483591] R10: 0000000070000000 R11: 0000000000000000 R12: ffff997277dfcc00
[  467.485226] R13: 0000000000000000 R14: 0000000000000000 R15: ffff99722fecdca8
[  467.486830] FS:  0000000000000000(0000) GS:ffff99727bc00000(0000) knlGS:0000000000000000
[  467.488596] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  467.489931] CR2: 0000000000000004 CR3: 00000000270e6006 CR4: 00000000001606f0
[  467.491559] Call Trace:
[  467.492128]  xprt_transmit+0x303/0x3f0 [sunrpc]
[  467.493143]  ? rpc_task_need_encode+0x40/0x40 [sunrpc]
[  467.494328]  call_bc_transmit+0x49/0x170 [sunrpc]
[  467.495379]  __rpc_execute+0x7e/0x3f0 [sunrpc]
[  467.496451]  rpc_run_bc_task+0x78/0xd0 [sunrpc]
[  467.497467]  bc_svc_process+0x281/0x340 [sunrpc]
[  467.498507]  nfs41_callback_svc+0x130/0x1c0 [nfsv4]
[  467.499751]  ? remove_wait_queue+0x60/0x60
[  467.500686]  kthread+0xf5/0x130
[  467.501438]  ? nfs_callback_authenticate+0x50/0x50 [nfsv4]
[  467.502640]  ? kthread_bind+0x10/0x10
[  467.503454]  ret_from_fork+0x1f/0x30
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Before trying to bind a port, ensure we grab the send lock to
ensure that we don't change the port while another task is busy
transmitting requests.
The connect code already takes the send lock in xprt_connect(),
but it is harmless to take it before that.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

In cases where we know the task is not sleeping, try to optimise
away the indirect call to task->tk_action() by replacing it with
a direct call.
Only change tail calls, to allow gcc to perform tail call
elimination.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Before initiating transport actions that require putting the task to sleep,
such as rebinding or reconnecting, we should check whether or not the task
was already transmitted.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

The RPC task wakeup calls all check for RPC_IS_QUEUED() before taking any
locks. In addition, rpc_exit() already calls rpc_wake_up_queued_task().
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Replace remaining callers of call_timeout() with rpc_check_timeout().
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Fix a regression where soft and softconn requests are not timing out
as expected.

Fixes: 89f90fe1 ("SUNRPC: Allow calls to xprt_transmit() to drain...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Now that transmissions happen through a queue, we require the RPC tasks
to handle error conditions that may have been set while they were
sleeping. The back channel does not currently do this, but assumes
that any error condition happens during its own call to xprt_transmit().

The solution is to ensure that the back channel splits out the
error handling just like the forward channel does.

Fixes: 89f90fe1 ("SUNRPC: Allow calls to xprt_transmit() to drain...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

If the socket is not connected, then we want to initiate a reconnect
rather that trying to transmit requests. If there is a large number
of requests queued and waiting for the lock in call_transmit(),
then it can take a while for one of the to loop back and retake
the lock in call_connect.

Fixes: 89f90fe1 ("SUNRPC: Allow calls to xprt_transmit() to drain...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Now that the reads happen in a process context rather than a softirq,
it is safe to allocate back channel slots using a reclaiming
allocation.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Users can still control this value explicitly using the
max_session_cb_slots module parameter, but let's bump the default
up to 16 for now.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Convert the remaining gfp_flags arguments in sunrpc to standard reclaiming
allocations, now that we set memalloc_nofs_save() as appropriate.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Get rid of the redundant parameter and rename the function
ff_layout_mirror_valid() to ff_layout_init_mirror_ds() for clarity.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

nfs4_ff_alloc_deviceid_node() guarantees that if mirror->mirror_ds is
a valid pointer, then so is mirror->mirror_ds->ds.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Pass in a pointer to the mirror rather than forcing another
array access.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Pass in a pointer to the mirror rather than forcing another
array access.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Pass in a pointer to the mirror rather than forcing another
array access.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Pass in a pointer to the mirror rather than forcing another
array access.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Pass in a pointer to the mirror rather than having to retrieve it from
the array and then verify the resulting pointer.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

If we notice that a DS may be down, we should attempt to read from the
other mirrors first before we go back to retry the dead DS.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

If the DS is unresponsive, we want to just mark it as such, while
reporting the errors. If the server later returns the same deviceid
in a new layout, then we don't want to have to look it up again.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

We already check the deviceids before we start the RPC call.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

In ff_layout_mirror_valid() we may not want to invalidate the layout
segment despite the call to GETDEVICEINFO failing. The reason is that
a read may still be able to make progress on another mirror.

So instead we let the caller (in this case nfs4_ff_layout_prepare_ds())
decide whether or not it needs to invalidate.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

While we may want to skip attempting to connect to a downed mirror
when we're deciding which mirror to select for a read, we do not
want to do so once we've committed to attempting the I/O in
ff_layout_read/write_pagelist(), or ff_layout_initiate_commit()
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

If the LAYOUTGET rpc call exits early without an error, convert it to
EAGAIN.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

When a read to the preferred mirror returns an error, the flexfiles
driver records the error in the inode list and currently marks the
layout for return before failing over the attempted read to the next
mirror.
What we actually want to do is fire off a LAYOUTERROR to notify the
MDS that there is an issue with the preferred mirror, then we fail
over. Only once we've failed to read from all mirrors should we
return the layout.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

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

If a layout segment gets invalidated while a pNFS I/O operation
is queued for transmission, then we ideally want to abort
immediately. This is particularly the case when there is a large
number of I/O related RPCs queued in the RPC layer, and the layout
segment gets invalidated due to an ENOSPC error, or an EACCES (because
the client was fenced). We may end up forced to spam the MDS with a
lot of otherwise unnecessary LAYOUTERRORs after that I/O fails.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Fix the memory barriers in nfs4_mark_deviceid_unavailable() and
nfs4_test_deviceid_unavailable().
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

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

If the attempt to instantiate the mirror's layout DS pointer failed,
then that pointer may hold a value of type ERR_PTR(), so we need
to check that before we dereference it.

Fixes: 65990d1a ("pNFS/flexfiles: Fix a deadlock on LAYOUTGET")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

These really should have been there from the beginning, but we never
noticed because there was enough slack in the RPC request for the extra
bytes. Chuck's recent patch to use au_cslack and au_rslack to compute
buffer size shrunk the buffer enough that this was now a problem for
SEEK operations on my test client.

Fixes: f4ac1674 ("nfs: Add ALLOCATE support")
Fixes: 2e72448b ("NFS: Add COPY nfs operation")
Fixes: cb95deea ("NFS OFFLOAD_CANCEL xdr")
Fixes: 624bd5b7 ("nfs: Add DEALLOCATE support")
Fixes: 1c6dcbe5 ("NFS: Implement SEEK")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Ensure that if we call nfs41_sequence_process() a second time for the
same rpc_task, then we only process the results once.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

If we have to retransmit a request, we should ensure that we reinitialise
the sequence results structure, since in the event of a signal
we need to treat the request as if it had not been sent.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: stable@vger.kernel.org

udp_poll() checks the struct file for the O_NONBLOCK flag, so we must not
call it with a NULL file pointer.

Fixes: 0ffe86f4 ("SUNRPC: Use poll() to fix up the socket requeue races")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

NFSoRDMA client updates for 5.1

New features:
- Convert rpc auth layer to use xdr_streams
- Config option to disable insecure enctypes
- Reduce size of RPC receive buffers

Bugfixes and cleanups:
- Fix sparse warnings
- Check inline size before providing a write chunk
- Reduce the receive doorbell rate
- Various tracepoint improvements

[Trond: Fix up merge conflicts]
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

If a bulk layout recall or a metadata server reboot coincides with a
umount, then holding a reference to an inode is unsafe unless we
also hold a reference to the super block.

Fixes: fd9a8d71 ("NFSv4.1: Fix bulk recall and destroy of layouts")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Fix a soft lockup when NFS client delegation recovery is attempted
but the inode is in the process of being freed. When the
igrab(inode) call fails, and we have to restart the recovery process,
we need to ensure that we won't attempt to recover the same delegation
again.

Fixes: 45870d69 ("NFSv4.1: Test delegation stateids when server...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

A 'false retry' in NFSv4.1 occurs when the client attempts to transmit a
new RPC call using a slot+sequence number combination that references an
already cached one. Currently, the Linux NFS client will do this if a
user process interrupts an RPC call that is in progress.
The problem with doing so is that we defeat the main mechanism used by
the server to differentiate between a new call and a replayed one. Even
if the server is able to perfectly cache the arguments of the old call,
it cannot know if the client intended to replay or send a new call.

The obvious fix is to bump the sequence number pre-emptively if an
RPC call is interrupted, but in order to deal with the corner cases
where the interrupted call is not actually received and processed by
the server, we need to interpret the error NFS4ERR_SEQ_MISORDERED
as a sign that we need to either wait or locate a correct sequence
number that lies between the value we sent, and the last value that
was acked by a SEQUENCE call on that slot.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Tested-by: Jason Tibbitts <tibbs@math.uh.edu>

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