If we're part way through transmitting a TCP request, and the client
errors, then we need to disconnect and reconnect the TCP socket in order to
avoid confusing the server.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
(cherry picked from 031a50c8b9ea82616abd4a4e18021a25848941ce commit)

Signed-off-by: NPanagiotis Issaris <takis@issaris.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Make the RPC client select privileged ephemeral source ports at
random.  This improves DRC behavior on the server by using the
same port when reconnecting for the same mount point, but using
a different port for fresh mounts.

The Linux TCP implementation already does this for nonprivileged
ports.  Note that TCP sockets in TIME_WAIT will prevent quick reuse
of a random ephemeral port number by leaving the port INUSE until
the connection transitions out of TIME_WAIT.

Test plan:
Connectathon against every known server implementation using multiple
mount points.  Locking especially.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Account for various things that occur while an RPC task is executed.
Separate timers for RPC round trip and RPC execution time show how
long RPC requests wait in queue before being sent.  Eventually these
will be accumulated at xprt_release time in one place where they can
be viewed from userland.

Test plan:
Compile kernel with CONFIG_NFS enabled.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Monitor generic transport events.  Add a transport switch callout to
format transport counters for export to user-land.

Test plan:
Compile kernel with CONFIG_NFS enabled.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 If the server decides to close the RPC socket, we currently don't actually
 respond until either another RPC call is scheduled, or until xprt_autoclose()
 gets called by the socket expiry timer (which may be up to 5 minutes
 later).

 This patch ensures that xprt_autoclose() is called much sooner if the
 server closes the socket.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 At some point, transport endpoint addresses will no longer be IPv4.  To hide
 the structure of the rpc_xprt's address field from ULPs and port mappers,
 add an API for setting the port number during an RPC bind operation.

 Test-plan:
 Destructive testing (unplugging the network temporarily).  Connectathon
 with UDP and TCP.  NFSv2/3 and NFSv4 mounting should be carefully checked.
 Probably need to rig a server where certain services aren't running, or
 that returns an error for some typical operation.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Add RPC client transport switch support for replacing buffer management
 on a per-transport basis.

 In the current IPv4 socket transport implementation, RPC buffers are
 allocated as needed for each RPC message that is sent.  Some transport
 implementations may choose to use pre-allocated buffers for encoding,
 sending, receiving, and unmarshalling RPC messages, however.  For
 transports capable of direct data placement, the buffers can be carved
 out of a pre-registered area of memory rather than from a slab cache.

 Test-plan:
 Millions of fsx operations.  Performance characterization with "sio" and
 "iozone".  Use oprofile and other tools to look for significant regression
 in CPU utilization.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 If we get something like the following,
 [  125.300636]  [<c04086e1>] schedule_timeout+0x54/0xa5
 [  125.305931]  [<c040866e>] io_schedule_timeout+0x29/0x33
 [  125.311495]  [<c02880c4>] blk_congestion_wait+0x70/0x85
 [  125.317058]  [<c014136b>] throttle_vm_writeout+0x69/0x7d
 [  125.322720]  [<c014714d>] shrink_zone+0xe0/0xfa
 [  125.327560]  [<c01471d4>] shrink_caches+0x6d/0x6f
 [  125.332581]  [<c01472a6>] try_to_free_pages+0xd0/0x1b5
 [  125.338056]  [<c013fa4b>] __alloc_pages+0x135/0x2e8
 [  125.343258]  [<c03b74ad>] tcp_sendmsg+0xaa0/0xb78
 [  125.348281]  [<c03d4666>] inet_sendmsg+0x48/0x53
 [  125.353212]  [<c0388716>] sock_sendmsg+0xb8/0xd3
 [  125.358147]  [<c0388773>] kernel_sendmsg+0x42/0x4f
 [  125.363259]  [<c038bc00>] sock_no_sendpage+0x5e/0x77
 [  125.368556]  [<c03ee7af>] xs_tcp_send_request+0x2af/0x375
 then the socket is blocked until memory is reclaimed, and no
 progress can ever be made.

 Try to access the emergency pools by using GFP_ATOMIC.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 The sunrpc module should build properly even when CONFIG_SYSCTL is
 disabled.

 Reported by Jan-Benedict Glaw.

 Test plan:
 Compile kernel with CONFIG_NFS as a module and built-in, and CONFIG_SYSCTL
 enabled and disabled.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 In fact, ->set_buffer_size should be completely functionless for non-UDP.

 Test-plan:
 Check socket buffer size on UDP sockets over time.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Each transport implementation can now set unique bind, connect,
 reestablishment, and idle timeout values.  These are variables,
 allowing the values to be modified dynamically.  This permits
 exponential backoff of any of these values, for instance.

 As an example, we implement exponential backoff for the connection
 reestablishment timeout.

 Test-plan:
 Destructive testing (unplugging the network temporarily).  Connectathon
 with UDP and TCP.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Implement a best practice: if the remote end drops our connection, try to
 reconnect using the same port number.  This is important because the NFS
 server's Duplicate Reply Cache often hashes on the source port number.
 If the client reuses the port number when it reconnects, the server's DRC
 will be more effective.

 Based on suggestions by Mike Eisler, Olaf Kirch, and Alexey Kuznetsky.

 Test-plan:
 Destructive testing.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Select an RPC client source port between 650 and 1023 instead of between
 1 and 800.  The old range conflicts with a number of network services.
 Provide sysctls to allow admins to select a different port range.

 Note that this doesn't affect user-level RPC library behavior, which
 still uses 1 to 800.

 Based on a suggestion by Olaf Kirch <okir@suse.de>.

 Test-plan:
 Repeated mount and unmount.  Destructive testing.  Idle timeouts.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Clean-up:  Move some macros that are specific to the Van Jacobson
 implementation into xprt.c.  Get rid of the cong_wait field in
 rpc_xprt, which is no longer used.  Get rid of xprt_clear_backlog.

 Test-plan:
 Compile with CONFIG_NFS enabled.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Get rid of the "xprt->nocong" variable.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss with UDP mounts.
 Look for significant regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 The final place where congestion control state is adjusted is in
 xprt_release, where each request is finally released.  Add a callout
 there to allow transports to perform additional processing when a
 request is about to be released.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for significant
 regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 A new interface that allows transports to adjust their congestion window
 using the Van Jacobson implementation in xprt.c is provided.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for
 significant regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Allow transports to hook the retransmit timer interrupt.  Some transports
 calculate their congestion window here so that a retransmit timeout has
 immediate effect on the congestion window.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for significant
 regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 The next method we abstract is the one that releases a transport,
 allowing another task to have access to the transport.

 Again, one generic version of this is provided for transports that
 don't need the RPC client to perform congestion control, and one
 version is for transports that can use the original Van Jacobson
 implementation in xprt.c.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for
 significant regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 The next several patches introduce an API that allows transports to
 choose whether the RPC client provides congestion control or whether
 the transport itself provides it.

 The first method we abstract is the one that serializes access to the
 RPC transport to prevent the bytes from different requests from mingling
 together.  This method provides proper request serialization and the
 opportunity to prevent new requests from being started because the
 transport is congested.

 The normal situation is for the transport to handle congestion control
 itself.  Although NFS over UDP was first, it has been recognized after
 years of experience that having the transport provide congestion control
 is much better than doing it in the RPC client.  Thus TCP, and probably
 every future transport implementation, will use the default method,
 xprt_lock_write, provided in xprt.c, which does not provide any kind
 of congestion control.  UDP can continue using the xprt.c-provided
 Van Jacobson congestion avoidance implementation.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for significant
 regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Prepare the way to remove the "xprt->nocong" variable by adding a callout
 to the RPC client transport switch API to handle setting RPC retransmit
 timeouts.

 Add a pair of generic helper functions that provide the ability to set a
 simple fixed timeout, or to set a timeout based on the state of a round-
 trip estimator.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for significant
 regression in performance or client stability.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Now we can fix up the last few places that use the "xprt->stream"
 variable, and get rid of it from the rpc_xprt structure.

 Test-plan:
 Destructive testing (unplugging the network temporarily).  Connectathon
 with UDP and TCP.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Add a generic mechanism for skipping over transport-specific headers
 when constructing an RPC request.  This removes another "xprt->stream"
 dependency.

 Test-plan:
 Write-intensive workload on a single mount point (try both UDP and
 TCP).
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Split the RPC client's main socket write path into a TCP version and a UDP
 version to eliminate another dependency on the "xprt->stream" variable.

 Compiler optimization removes unneeded code from xs_sendpages, as this
 function is now called with some constant arguments.

 We can now cleanly perform transport protocol-specific return code testing
 and error recovery in each path.

 Test-plan:
 Millions of fsx operations.  Performance characterization such as
 "sio" or "iozone".  Examine oprofile results for any changes before and
 after this patch is applied.

 Version: Thu, 11 Aug 2005 16:08:46 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Create separate connection worker functions for managing UDP and TCP
 transport sockets.  This eliminates several dependencies on "xprt->stream".

 Test-plan:
 Destructive testing (unplugging the network temporarily).  Connectathon with
 v2, v3, and v4.

 Version: Thu, 11 Aug 2005 16:08:18 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Split the socket write space callback function into a TCP version and UDP
 version, eliminating one dependence on the "xprt->stream" variable.

 Keep the common pieces of this path in xprt.c so other transports can use
 it too.

 Test-plan:
 Write-intensive workload on a single mount point.

 Version: Thu, 11 Aug 2005 16:07:51 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Clean-up: change some comments to reflect the realities of the new RPC
 transport switch mechanism.  Get rid of unused xprt_receive() prototype.

 Also, organize function prototypes in xprt.h by usage and scope.

 Test-plan:
 Compile kernel with CONFIG_NFS enabled.

 Version: Thu, 11 Aug 2005 16:07:21 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Clean-up: remove only reference to xprt->pending from the socket transport
 implementation.  This makes a cleaner interface for other transport
 implementations as well.

 Test-plan:
 Compile kernel with CONFIG_NFS enabled.

 Version: Thu, 11 Aug 2005 16:06:52 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Clean-up: get rid of a name reference to sockets in the generic parts of the
 RPC client by renaming the sockstate field in the rpc_xprt structure.

 Test-plan:
 Compile kernel with CONFIG_NFS enabled.

 Version: Thu, 11 Aug 2005 16:05:53 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Clean-up: replace a name reference to sockets in the generic parts of the RPC
 client by renaming sock_lock in the rpc_xprt structure.

 Test-plan:
 Compile kernel with CONFIG_NFS enabled.

 Version: Thu, 11 Aug 2005 16:05:00 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Reduce stack utilization of the RPC socket transport's send path.

 A couple of unlikely()s are added to ensure the compiler places the
 tail processing at the end of the csect.

 Test-plan:
 Millions of fsx operations.  Performance characterization such as "sio" or
 "iozone".

 Version: Thu, 11 Aug 2005 16:04:30 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Introduce block header comments and a function naming convention to the
 socket transport implementation.  Provide a debug setting for transports
 that is separate from RPCDBG_XPRT.  Eliminate xprt_default_timeout().

 Provide block comments for exposed interfaces in xprt.c, and eliminate
 the useless obvious comments.

 Convert printk's to dprintk's.

 Test-plan:
 Compile kernel with CONFIG_NFS enabled.

 Version: Thu, 11 Aug 2005 16:04:04 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

 Move the bulk of client-side socket-specific code into a separate source
 file, net/sunrpc/xprtsock.c.

 Test-plan:
 Millions of fsx operations.  Performance characterization such as "sio" or
 "iozone".  Destructive testing (unplugging the network temporarily, server
 reboots).  Connectathon with v2, v3, and v4.

 Version: Thu, 11 Aug 2005 16:03:38 -0400
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>