Pull s390 updates from Martin Schwidefsky:

 - A larger update for the zcrypt / AP bus code:
    + Update two inline assemblies in the zcrypt driver to make gcc happy
    + Add a missing reply code for invalid special commands for zcrypt
    + Allow AP device reset to be triggered from user space
    + Split the AP scan function into smaller, more readable functions

 - Updates for vfio-ccw and vfio-ap
    + Add maintainers and reviewer for vfio-ccw
    + Include facility.h in vfio_ap_drv.c to avoid fragile include chain
    + Simplicy vfio-ccw state machine

 - Use the common code version of bust_spinlocks

 - Make use of the DEFINE_SHOW_ATTRIBUTE

 - Fix three incorrect file permissions in the DASD driver

 - Remove bit spin-lock from the PCI interrupt handler

 - Fix GFP_ATOMIC vs GFP_KERNEL in the PCI code

* tag 's390-4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/zcrypt: rework ap scan bus code
  s390/zcrypt: make sysfs reset attribute trigger queue reset
  s390/pci: fix sleeping in atomic during hotplug
  s390/pci: remove bit_lock usage in interrupt handler
  s390/drivers: fix proc/debugfs file permissions
  s390: convert to DEFINE_SHOW_ATTRIBUTE
  MAINTAINERS/vfio-ccw: add Farhan and Eric, make Halil Reviewer
  vfio: ccw: Merge BUSY and BOXED states
  s390: use common bust_spinlocks()
  s390/zcrypt: improve special ap message cmd handling
  s390/ap: rework assembler functions to use unions for in/out register variables
  s390: vfio-ap: include <asm/facility> for test_facility()

Pull NFS client updates from Anna Schumaker:
 "Stable bugfixes:
   - xprtrdma: Yet another double DMA-unmap # v4.20

  Features:
   - Allow some /proc/sys/sunrpc entries without CONFIG_SUNRPC_DEBUG
   - Per-xprt rdma receive workqueues
   - Drop support for FMR memory registration
   - Make port= mount option optional for RDMA mounts

  Other bugfixes and cleanups:
   - Remove unused nfs4_xdev_fs_type declaration
   - Fix comments for behavior that has changed
   - Remove generic RPC credentials by switching to 'struct cred'
   - Fix crossing mountpoints with different auth flavors
   - Various xprtrdma fixes from testing and auditing the close code
   - Fixes for disconnect issues when using xprtrdma with krb5
   - Clean up and improve xprtrdma trace points
   - Fix NFS v4.2 async copy reboot recovery"

* tag 'nfs-for-4.21-1' of git://git.linux-nfs.org/projects/anna/linux-nfs: (63 commits)
  sunrpc: convert to DEFINE_SHOW_ATTRIBUTE
  sunrpc: Add xprt after nfs4_test_session_trunk()
  sunrpc: convert unnecessary GFP_ATOMIC to GFP_NOFS
  sunrpc: handle ENOMEM in rpcb_getport_async
  NFS: remove unnecessary test for IS_ERR(cred)
  xprtrdma: Prevent leak of rpcrdma_rep objects
  NFSv4.2 fix async copy reboot recovery
  xprtrdma: Don't leak freed MRs
  xprtrdma: Add documenting comment for rpcrdma_buffer_destroy
  xprtrdma: Replace outdated comment for rpcrdma_ep_post
  xprtrdma: Update comments in frwr_op_send
  SUNRPC: Fix some kernel doc complaints
  SUNRPC: Simplify defining common RPC trace events
  NFS: Fix NFSv4 symbolic trace point output
  xprtrdma: Trace mapping, alloc, and dereg failures
  xprtrdma: Add trace points for calls to transport switch methods
  xprtrdma: Relocate the xprtrdma_mr_map trace points
  xprtrdma: Clean up of xprtrdma chunk trace points
  xprtrdma: Remove unused fields from rpcrdma_ia
  xprtrdma: Cull dprintk() call sites
  ...

Pull nfsd updates from Bruce Fields:
 "Thanks to Vasily Averin for fixing a use-after-free in the
  containerized NFSv4.2 client, and cleaning up some convoluted
  backchannel server code in the process.

  Otherwise, miscellaneous smaller bugfixes and cleanup"

* tag 'nfsd-4.21' of git://linux-nfs.org/~bfields/linux: (25 commits)
  nfs: fixed broken compilation in nfs_callback_up_net()
  nfs: minor typo in nfs4_callback_up_net()
  sunrpc: fix debug message in svc_create_xprt()
  sunrpc: make visible processing error in bc_svc_process()
  sunrpc: remove unused xpo_prep_reply_hdr callback
  sunrpc: remove svc_rdma_bc_class
  sunrpc: remove svc_tcp_bc_class
  sunrpc: remove unused bc_up operation from rpc_xprt_ops
  sunrpc: replace svc_serv->sv_bc_xprt by boolean flag
  sunrpc: use-after-free in svc_process_common()
  sunrpc: use SVC_NET() in svcauth_gss_* functions
  nfsd: drop useless LIST_HEAD
  lockd: Show pid of lockd for remote locks
  NFSD remove OP_CACHEME from 4.2 op_flags
  nfsd: Return EPERM, not EACCES, in some SETATTR cases
  sunrpc: fix cache_head leak due to queued request
  nfsd: clean up indentation, increase indentation in switch statement
  svcrdma: Optimize the logic that selects the R_key to invalidate
  nfsd: fix a warning in __cld_pipe_upcall()
  nfsd4: fix crash on writing v4_end_grace before nfsd startup
  ...

Pull 9p updates from Dominique Martinet:
 "Missing prototype warning fix and a syzkaller fix when a 9p server
  advertises a too small msize"

* tag '9p-for-4.21' of git://github.com/martinetd/linux:
  9p/net: put a lower bound on msize
  net/9p: include trans_common.h to fix missing prototype warning.

Pull cifs updates from Steve French:

 - four fixes for stable

 - improvements to DFS including allowing failover to alternate targets

 - some small performance improvements

* tag '4.21-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6: (39 commits)
  cifs: update internal module version number
  cifs: we can not use small padding iovs together with encryption
  cifs: Minor Kconfig clarification
  cifs: Always resolve hostname before reconnecting
  cifs: Add support for failover in cifs_reconnect_tcon()
  cifs: Add support for failover in smb2_reconnect()
  cifs: Only free DFS target list if we actually got one
  cifs: start DFS cache refresher in cifs_mount()
  cifs: Use GFP_ATOMIC when a lock is held in cifs_mount()
  cifs: Add support for failover in cifs_reconnect()
  cifs: Add support for failover in cifs_mount()
  cifs: remove set but not used variable 'sep'
  cifs: Make use of DFS cache to get new DFS referrals
  cifs: minor updates to documentation
  cifs: check kzalloc return
  cifs: remove set but not used variable 'server'
  cifs: Use kzfree() to free password
  cifs: Fix to use kmem_cache_free() instead of kfree()
  cifs: update for current_kernel_time64() removal
  cifs: Add DFS cache routines
  ...

Pull TPM updates from James Morris:

 - Support for partial reads of /dev/tpm0.

 - Clean up for TPM 1.x code: move the commands to tpm1-cmd.c and make
   everything to use the same data structure for building TPM commands
   i.e. struct tpm_buf.

* 'next-tpm' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (25 commits)
  tpm: add support for partial reads
  tpm: tpm_ibmvtpm: fix kdoc warnings
  tpm: fix kdoc for tpm2_flush_context_cmd()
  tpm: tpm_try_transmit() refactor error flow.
  tpm: use u32 instead of int for PCR index
  tpm1: reimplement tpm1_continue_selftest() using tpm_buf
  tpm1: reimplement SAVESTATE using tpm_buf
  tpm1: rename tpm1_pcr_read_dev to tpm1_pcr_read()
  tpm1: implement tpm1_pcr_read_dev() using tpm_buf structure
  tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure
  tpm: tpm-space.c remove unneeded semicolon
  tpm: tpm-interface.c drop unused macros
  tpm: add tpm_auto_startup() into tpm-interface.c
  tpm: factor out tpm_startup function
  tpm: factor out tpm 1.x pm suspend flow into tpm1-cmd.c
  tpm: move tpm 1.x selftest code from tpm-interface.c tpm1-cmd.c
  tpm: factor out tpm1_get_random into tpm1-cmd.c
  tpm: move tpm_getcap to tpm1-cmd.c
  tpm: move tpm1_pcr_extend to tpm1-cmd.c
  tpm: factor out tpm_get_timeouts()
  ...

Pull smack updates from James Morris:
 "Two Smack patches for 4.21.

  Jose's patch adds missing documentation and Zoran's fleshes out the
  access checks on keyrings"

* 'next-smack' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  Smack: Improve Documentation
  smack: fix access permissions for keyring

This mostly reverts commit 849a3700 ("block: avoid ordered task
state change for polled IO").  It was wrongly claiming that the ordering
wasn't necessary.  The memory barrier _is_ necessary.

If something is truly polling and not going to sleep, it's the whole
state setting that is unnecessary, not the memory barrier.  Whenever you
set your state to a sleeping state, you absolutely need the memory
barrier.

Note that sometimes the memory barrier can be elsewhere.  For example,
the ordering might be provided by an external lock, or by setting the
process state to sleeping before adding yourself to the wait queue list
that is used for waking up (where the wait queue lock itself will
guarantee that any wakeup will correctly see the sleeping state).

But none of those cases were true here.

NOTE! Some of the polling paths may indeed be able to drop the state
setting entirely, at which point the memory barrier also goes away.

(Also note that this doesn't revert the TASK_RUNNING cases: there is no
race between a wakeup and setting the process state to TASK_RUNNING,
since the end result doesn't depend on ordering).

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull seccomp updates from James Morris:

 - Add SECCOMP_RET_USER_NOTIF

 - seccomp fixes for sparse warnings and s390 build (Tycho)

* 'next-seccomp' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  seccomp, s390: fix build for syscall type change
  seccomp: fix poor type promotion
  samples: add an example of seccomp user trap
  seccomp: add a return code to trap to userspace
  seccomp: switch system call argument type to void *
  seccomp: hoist struct seccomp_data recalculation higher

Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

Pull integrity updates from James Morris:
 "In Linux 4.19, a new LSM hook named security_kernel_load_data was
  upstreamed, allowing LSMs and IMA to prevent the kexec_load syscall.
  Different signature verification methods exist for verifying the
  kexec'ed kernel image. This adds additional support in IMA to prevent
  loading unsigned kernel images via the kexec_load syscall,
  independently of the IMA policy rules, based on the runtime "secure
  boot" flag. An initial IMA kselftest is included.

  In addition, this pull request defines a new, separate keyring named
  ".platform" for storing the preboot/firmware keys needed for verifying
  the kexec'ed kernel image's signature and includes the associated IMA
  kexec usage of the ".platform" keyring.

  (David Howell's and Josh Boyer's patches for reading the
  preboot/firmware keys, which were previously posted for a different
  use case scenario, are included here)"

* 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  integrity: Remove references to module keyring
  ima: Use inode_is_open_for_write
  ima: Support platform keyring for kernel appraisal
  efi: Allow the "db" UEFI variable to be suppressed
  efi: Import certificates from UEFI Secure Boot
  efi: Add an EFI signature blob parser
  efi: Add EFI signature data types
  integrity: Load certs to the platform keyring
  integrity: Define a trusted platform keyring
  selftests/ima: kexec_load syscall test
  ima: don't measure/appraise files on efivarfs
  x86/ima: retry detecting secure boot mode
  docs: Extend trusted keys documentation for TPM 2.0
  x86/ima: define arch_get_ima_policy() for x86
  ima: add support for arch specific policies
  ima: refactor ima_init_policy()
  ima: prevent kexec_load syscall based on runtime secureboot flag
  x86/ima: define arch_ima_get_secureboot
  integrity: support new struct public_key_signature encoding field

Use DEFINE_SHOW_ATTRIBUTE macro to simplify the code.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Multipathing: In case of NFSv3, rpc_clnt_test_and_add_xprt() adds
the xprt to xprt switch (i.e. xps) if rpc_call_null_helper() returns
success. But in case of NFSv4.1, it needs to do EXCHANGEID to verify
the path along with check for session trunking.

Add the xprt in nfs4_test_session_trunk() only when
nfs4_detect_session_trunking() returns success. Also release refcount
hold by rpc_clnt_setup_test_and_add_xprt().
Signed-off-by: Santosh kumar pradhan <santoshkumar.pradhan@wdc.com>
Tested-by: Suresh Jayaraman <suresh.jayaraman@wdc.com>
Reported-by: Aditya Agnihotri <aditya.agnihotri@wdc.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

It's OK to sleep here, we just don't want to recurse into the filesystem
as a writeout could be waiting on this.

Future work: the documentation for GFP_NOFS says "Please try to avoid
using this flag directly and instead use memalloc_nofs_{save,restore} to
mark the whole scope which cannot/shouldn't recurse into the FS layer
with a short explanation why. All allocation requests will inherit
GFP_NOFS implicitly."

But I'm not sure where to do this.  Should the workqueue be arranging
that for us in the case of workqueues created with WQ_MEM_RECLAIM?
Reported-by: Trond Myklebust <trondmy@hammer.space>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

If we ignore the error we'll hit a null dereference a little later.

Reported-by: syzbot+4b98281f2401ab849f4b@syzkaller.appspotmail.com
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

As gte_current_cred() cannot return an error,
this test is not necessary.
It hasn't been necessary for years, but it wasn't so obvious
before.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

If a reply has been processed but the RPC is later retransmitted
anyway, the req->rl_reply field still contains the only pointer to
the old rpcrdma rep. When the next reply comes in, the reply handler
will stomp on the rl_reply field, leaking the old rep.

A trace event is added to capture such leaks.

This problem seems to be worsened by the restructuring of the RPC
Call path in v4.20. Fully addressing this issue will require at
least a re-architecture of the disconnect logic, which is not
appropriate during -rc.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Original commit (e4648aa4 "NFS recover from destination server
reboot for copies") used memcmp() and then it was changed to use
nfs4_stateid_match_other() but that function returns opposite of
memcmp. As the result, recovery can't find the copy leading
to copy hanging.

Fixes: 80f42368 ("NFSv4: Split out NFS v4.2 copy completion functions")
Fixes: cb7a8384 ("NFS: Split out the body of nfs4_reclaim_open_state")
Signed-of-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Defensive clean up. Don't set frwr->fr_mr until we know that the
scatterlist allocation has succeeded.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Make a note of the function's dependency on an earlier ib_drain_qp.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Since commit 7c8d9e7c ("xprtrdma: Move Receive posting to
Receive handler"), rpcrdma_ep_post is no longer responsible for
posting Receive buffers. Update the documenting comment to reflect
this change.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Commit f2877623 ("xprtrdma: Chain Send to FastReg WRs") was
written before commit ce5b3717 ("xprtrdma: Replace all usage of
"frmr" with "frwr""), but was merged afterwards. Thus it still
refers to FRMR and MWs.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Clean up some warnings observed when building with "make W=1".
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Clean up, no functional change is expected.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

These symbolic values were not being displayed in string form.
TRACE_DEFINE_ENUM was missing in many cases. It also turns out that
__print_symbolic wants an unsigned long in the first field...
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

These are rare, but can be helpful at tracking down DMAR and other
problems.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Name them "trace_xprtrdma_op_*" so they can be easily enabled as a
group. No trace point is added where the generic layer already has
observability.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

The mr_map trace points were capturing information about the previous
use of the MR rather than about the segment that was just mapped.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

The chunk-related trace points capture nearly the same information
as the MR-related trace points.

Also, rename them so globbing can be used to enable or disable
these trace points more easily.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Clean up. The last use of these fields was in commit 173b8f49
("xprtrdma: Demote "connect" log messages") .
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: Remove dprintk() call sites that report rare or impossible
errors. Leave a few that display high-value low noise status
information.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: There's little chance of contention between the use of
rb_lock and rb_reqslock, so merge the two. This avoids having to
take both in some (possibly future) cases.

Transport tear-down is already serialized, thus there is no need for
locking at all when destroying rpcrdma_reqs.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

For better observability of parsing errors, return the error code
generated in the decoders to the upper layer consumer.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Since commit ffe1f0df ("rpcrdma: Merge svcrdma and xprtrdma
modules into one"), the forward and backchannel components are part
of the same kernel module. A separate request_module() call in the
backchannel code is no longer necessary.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Commit 431f6eb3 ("SUNRPC: Add a label for RPC calls that require
allocation on receive") didn't update similar logic in rpc_rdma.c.
I don't think this is a bug, per-se; the commit just adds more
careful checking for broken upper layer behavior.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Having to specify "proto=rdma,port=20049" is cumbersome.

RFC 8267 Section 6.3 requires NFSv4 clients to use "the alternative
well-known port number", which is 20049. Make the use of the well-
known port number automatic, just as it is for NFS/TCP and port
2049.

For NFSv2/3, Section 4.2 allows clients to simply choose 20049 as
the default or use rpcbind. I don't know of an NFS/RDMA server
implementation that registers it's NFS/RDMA service with rpcbind,
so automatically choosing 20049 seems like the better choice. The
other widely-deployed NFS/RDMA client, Solaris, also uses 20049
as the default port.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Place the associated RPC transaction's XID in the upper 32 bits of
each RDMA segment's rdma_offset field. There are two reasons to do
this:

- The R_key only has 8 bits that are different from registration to
  registration. The XID adds more uniqueness to each RDMA segment to
  reduce the likelihood of a software bug on the server reading from
  or writing into memory it's not supposed to.

- On-the-wire RDMA Read and Write requests do not otherwise carry
  any identifier that matches them up to an RPC. The XID in the
  upper 32 bits will act as an eye-catcher in network captures.
Suggested-by: Tom Talpey <ttalpey@microsoft.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: Now that there is only FRWR, there is no need for a memory
registration switch. The indirect calls to the memreg operations can
be replaced with faster direct calls.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

FMR is not supported on most recent RDMA devices. It is also less
secure than FRWR because an FMR memory registration can expose
adjacent bytes to remote reading or writing. As discussed during the
RDMA BoF at LPC 2018, it is time to remove support for FMR in the
NFS/RDMA client stack.

Note that NFS/RDMA server-side uses either local memory registration
or FRWR. FMR is not used.

There are a few Infiniband/RoCE devices in the kernel tree that do
not appear to support MEM_MGT_EXTENSIONS (FRWR), and therefore will
not support client-side NFS/RDMA after this patch. These are:

 - mthca
 - qib
 - hns (RoCE)

Users of these devices can use NFS/TCP on IPoIB instead.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Some devices advertise a large max_fast_reg_page_list_len
capability, but perform optimally when MRs are significantly smaller
than that depth -- probably when the MR itself is no larger than a
page.

By default, the RDMA R/W core API uses max_sge_rd as the maximum
page depth for MRs. For some devices, the value of max_sge_rd is
1, which is also not optimal. Thus, when max_sge_rd is larger than
1, use that value. Otherwise use the value of the
max_fast_reg_page_list_len attribute.

I've tested this with CX-3 Pro, FastLinq, and CX-5 devices. It
reproducibly improves the throughput of large I/Os by several
percent.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

With certain combinations of krb5i/p, MR size, and r/wsize, I/O can
fail with EMSGSIZE. This is because the calculated value of
ri_max_segs (the max number of MRs per RPC) exceeded
RPCRDMA_MAX_HDR_SEGS, which caused Read or Write list encoding to
walk off the end of the transport header.

Once that was addressed, the ro_maxpages result has to be corrected
to account for the number of MRs needed for Reply chunks, which is
2 MRs smaller than a normal Read or Write chunk.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>