This is a rework of the following patch sent almost a year back:
http://www.mail-archive.com/linux-rdma%40vger.kernel.org/msg20730.html

In presence of active mount if someone tries to rmmod vendor-driver, the
command remains stuck forever waiting for destruction of all rdma-cm-id.
in worst case client can crash during shutdown with active mounts.

The existing code assumes that ia->ri_id->device cannot change during
the lifetime of a transport. xprtrdma do not have support for
DEVICE_REMOVAL event either. Lifting that assumption and adding support
for DEVICE_REMOVAL event is a long chain of work, and is in plan.

The community decided that preventing the hang right now is more
important than waiting for architectural changes.

Thus, this patch introduces a temporary workaround to acquire HCA driver
module reference count during the mount of a nfs-rdma mount point.
Signed-off-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

RDMA_MSGP type calls insert a zero pad in the middle of the RPC
message to align the RPC request's data payload to the server's
alignment preferences. A server can then "page flip" the payload
into place to avoid a data copy in certain circumstances. However:

1. The client has to have a priori knowledge of the server's
   preferred alignment

2. Requests eligible for RDMA_MSGP are requests that are small
   enough to have been sent inline, and convey a data payload
   at the _end_ of the RPC message

Today 1. is done with a sysctl, and is a global setting that is
copied during mount. Linux does not support CCP to query the
server's preferences (RFC 5666, Section 6).

A small-ish NFSv3 WRITE might use RDMA_MSGP, but no NFSv4
compound fits bullet 2.

Thus the Linux client currently leaves RDMA_MSGP disabled. The
Linux server handles RDMA_MSGP, but does not use any special
page flipping, so it confers no benefit.

Clean up the marshaling code by removing the logic that constructs
RDMA_MSGP type calls. This also reduces the maximum send iovec size
from four to just two elements.

/proc/sys/sunrpc/rdma_inline_write_padding is a kernel API, and
thus is left in place.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Untangle the end of rpcrdma_ia_open() by moving DMA MR set-up, which
is different for each registration method, to the .ro_open functions.

This is refactoring only. No behavior change is expected.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

All HCA providers have an ib_get_dma_mr() verb. Thus
rpcrdma_ia_open() will either grab the device's local_dma_key if one
is available, or it will call ib_get_dma_mr(). If ib_get_dma_mr()
fails, rpcrdma_ia_open() fails and no transport is created.

Therefore execution never reaches the ib_reg_phys_mr() call site in
rpcrdma_register_internal(), so it can be removed.

The remaining logic in rpcrdma_{de}register_internal() is folded
into rpcrdma_{alloc,free}_regbuf().

This is clean up only. No behavior change is expected.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-By: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

PHYSICAL memory registration uses a single rkey for all of the
client's memory, thus is insecure. It is still useful in some cases
for testing.

Retain the ability to select PHYSICAL memory registration capability
via /proc/sys/sunrpc/rdma_memreg_strategy, but don't fall back to it
if the HCA does not support FRWR or FMR.

This means amso1100 no longer works out of the box with NFS/RDMA.
When using amso1100 HCAs, set the memreg_strategy sysctl to 6 before
performing NFS/RDMA mounts.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Currently, ib_create_cq uses cqe and comp_vecotr instead
of the extendible ib_cq_init_attr struct.

Earlier patches already changed the vendors to work with
ib_cq_init_attr. This patch changes the consumers too.
Signed-off-by: NMatan Barak <matanb@mellanox.com>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

/proc/lock_stat showed contention between rpcrdma_buffer_get/put
and the MR allocation functions during I/O intensive workloads.

Now that MRs are no longer allocated in rpcrdma_buffer_get(),
there's no reason the rb_mws list has to be managed using the
same lock as the send/receive buffers. Split that lock. The
new lock does not need to disable interrupts because buffer
get/put is never called in an interrupt context.

struct rpcrdma_buffer is re-arranged to ensure rb_mwlock and rb_mws
are always in a different cacheline than rb_lock and the buffer
pointers.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: This field is no longer used.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Reviewed-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

An RPC can exit at any time. When it does so, xprt_rdma_free() is
called, and it calls ->op_unmap().

If ->ro_reset() is running due to a transport disconnect, the two
methods can race while processing the same rpcrdma_mw. The results
are unpredictable.

Because of this, in previous patches I've altered ->ro_map() to
handle MR reset. ->ro_reset() is no longer needed and can be
removed.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Reviewed-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: Remove functions no longer used to recover broken FRMRs.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Reviewed-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Acquiring 64 MRs in rpcrdma_buffer_get() while holding the buffer
pool lock is expensive, and unnecessary because most modern adapters
can transfer 100s of KBs of payload using just a single MR.

Instead, acquire MRs one-at-a-time as chunks are registered, and
return them to rb_mws immediately during deregistration.

Note: commit 539431a4 ("xprtrdma: Don't invalidate FRMRs if
registration fails") is reverted: There is now a valid case where
registration can fail (with -ENOMEM) but the QP is still in RTS.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Acquiring 64 FMRs in rpcrdma_buffer_get() while holding the buffer
pool lock is expensive, and unnecessary because FMR mode can
transfer up to a 1MB payload using just a single ib_fmr.

Instead, acquire ib_fmrs one-at-a-time as chunks are registered, and
return them to rb_mws immediately during deregistration.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

We eventually want to handle allocating MWs one at a time, as
needed, instead of grabbing 64 and throwing them at each RPC in the
pipeline.

Add a helper for grabbing an MW off rb_mws, and a helper for
returning an MW to rb_mws. These will be used in a subsequent patch.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The connect worker can replace ri_id, but prevents ri_id->device
from changing during the lifetime of a transport instance. The old
ID is kept around until a new ID is created and the ->device is
confirmed to be the same.

Cache a copy of ri_id->device in rpcrdma_ia and in rpcrdma_rep.
The cached copy can be used safely in code that does not serialize
with the connect worker.

Other code can use it to save an extra address generation (one
pointer dereference instead of two).
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

A posted rpcrdma_rep never has rr_func set to anything but
rpcrdma_reply_handler.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: Instead of carrying a pointer to the buffer pool and
the rpc_xprt, carry a pointer to the controlling rpcrdma_xprt.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

WARN during transport destruction if ib_dealloc_pd() fails. This is
a sign that xprtrdma orphaned one or more RDMA API objects at some
point, which can pin lower layer kernel modules and cause shutdown
to hang.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Reviewed-by: NDevesh Sharma <devesh.sharma@avagotech.com>
Tested-By: NDevesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: NDoug Ledford <dledford@redhat.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Reviewed-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NSagi Grimberg <sagig@mellanox.com>
Signed-off-by: NAnna Schumaker <anna.schumaker@netapp.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

These functions are called in a loop for each page transferred via
RDMA READ or WRITE. Extract loop invariants and inline them to
reduce CPU overhead.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Allow each memory registration mode to plug in a callout that handles
the completion of a memory registration operation.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The open op determines the size of various transport data structures
based on device capabilities and memory registration mode.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Memory Region objects associated with a transport instance are
destroyed before the instance is shutdown and destroyed.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

This method is invoked when a transport instance is about to be
reconnected. Each Memory Region object is reset to its initial
state.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

This method is used when setting up a new transport instance to
create a pool of Memory Region objects that will be used to register
memory during operation.

Memory Regions are not needed for "physical" registration, since
->prepare and ->release are no-ops for that mode.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

There is very little common processing among the different external
memory deregistration functions.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

There is very little common processing among the different external
memory registration functions. Have rpcrdma_create_chunks() call
the registration method directly. This removes a stack frame and a
switch statement from the external registration path.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The max_payload computation is generalized to ensure that the
payload maximum is the lesser of RPC_MAX_DATA_SEGS and the number of
data segments that can be transmitted in an inline buffer.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Instead of employing switch() statements, let's use the typical
Linux kernel idiom for handling behavioral variation: virtual
functions.

Start by defining a vector of operations for each supported memory
registration mode, and by adding a source file for each mode.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

If a provider advertizes a zero max_fast_reg_page_list_len, FRWR
depth detection loops forever. Instead of just failing the mount,
try other memory registration modes.

Fixes: 0fc6c4e7 ("xprtrdma: mind the device's max fast . . .")
Reported-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The RPC/RDMA transport's FRWR registration logic registers whole
pages. This means areas in the first and last pages that are not
involved in the RDMA I/O are needlessly exposed to the server.

Buffered I/O is typically page-aligned, so not a problem there. But
for direct I/O, which can be byte-aligned, and for reply chunks,
which are nearly always smaller than a page, the transport could
expose memory outside the I/O buffer.

FRWR allows byte-aligned memory registration, so let's use it as
it was intended.
Reported-by: NSagi Grimberg <sagig@mellanox.com>
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSagi Grimberg <sagig@mellanox.com>
Tested-by: NDevesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: NMeghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: NVeeresh U. Kokatnur <veereshuk@chelsio.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

This patch fix spelling typo in printk messages.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

rpcrdma_{de}register_internal() are used only in verbs.c now.

MAX_RPCRDMAHDR is no longer used and can be removed.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Use the new rpcrdma_alloc_regbuf() API to shrink the amount of
contiguous memory needed for a buffer pool by moving the zero
pad buffer into a regbuf.

This is for consistency with the other uses of internally
registered memory.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The rr_base field is currently the buffer where RPC replies land.

An RPC/RDMA reply header lands in this buffer. In some cases an RPC
reply header also lands in this buffer, just after the RPC/RDMA
header.

The inline threshold is an agreed-on size limit for RDMA SEND
operations that pass from server and client. The sum of the
RPC/RDMA reply header size and the RPC reply header size must be
less than this threshold.

The largest RDMA RECV that the client should have to handle is the
size of the inline threshold. The receive buffer should thus be the
size of the inline threshold, and not related to RPCRDMA_MAX_SEGS.

RPC replies received via RDMA WRITE (long replies) are caught in
rq_rcv_buf, which is the second half of the RPC send buffer. Ie,
such replies are not involved in any way with rr_base.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

The rl_base field is currently the buffer where each RPC/RDMA call
header is built.

The inline threshold is an agreed-on size limit to for RDMA SEND
operations that pass between client and server. The sum of the
RPC/RDMA header size and the RPC header size must be less than or
equal to this threshold.

Increasing the r/wsize maximum will require MAX_SEGS to grow
significantly, but the inline threshold size won't change (both
sides agree on it). The server's inline threshold doesn't change.

Since an RPC/RDMA header can never be larger than the inline
threshold, make all RPC/RDMA header buffers the size of the
inline threshold.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Because internal memory registration is an expensive and synchronous
operation, xprtrdma pre-registers send and receive buffers at mount
time, and then re-uses them for each RPC.

A "hardway" allocation is a memory allocation and registration that
replaces a send buffer during the processing of an RPC. Hardway must
be done if the RPC send buffer is too small to accommodate an RPC's
call and reply headers.

For xprtrdma, each RPC send buffer is currently part of struct
rpcrdma_req so that xprt_rdma_free(), which is passed nothing but
the address of an RPC send buffer, can find its matching struct
rpcrdma_req and rpcrdma_rep quickly via container_of / offsetof.

That means that hardway currently has to replace a whole rpcrmda_req
when it replaces an RPC send buffer. This is often a fairly hefty
chunk of contiguous memory due to the size of the rl_segments array
and the fact that both the send and receive buffers are part of
struct rpcrdma_req.

Some obscure re-use of fields in rpcrdma_req is done so that
xprt_rdma_free() can detect replaced rpcrdma_req structs, and
restore the original.

This commit breaks apart the RPC send buffer and struct rpcrdma_req
so that increasing the size of the rl_segments array does not change
the alignment of each RPC send buffer. (Increasing rl_segments is
needed to bump up the maximum r/wsize for NFS/RDMA).

This change opens up some interesting possibilities for improving
the design of xprt_rdma_allocate().

xprt_rdma_allocate() is now the one place where RPC send buffers
are allocated or re-allocated, and they are now always left in place
by xprt_rdma_free().

A large re-allocation that includes both the rl_segments array and
the RPC send buffer is no longer needed. Send buffer re-allocation
becomes quite rare. Good send buffer alignment is guaranteed no
matter what the size of the rl_segments array is.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

There are several spots that allocate a buffer via kmalloc (usually
contiguously with another data structure) and then register that
buffer internally. I'd like to split the buffers out of these data
structures to allow the data structures to scale.

Start by adding functions that can kmalloc and register a buffer,
and can manage/preserve the buffer's associated ib_sge and ib_mr
fields.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Move the details of how to create and destroy rpcrdma_req and
rpcrdma_rep structures into helper functions.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

Clean up: There is one call site for rpcrdma_buffer_create(). All of
the arguments there are fields of an rpcrdma_xprt.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>