rxrpc: Allow the app to store private data on peer structs

Provide a way for the application (e.g. the afs filesystem) to store
private data on the rxrpc_peer structs for later retrieval via the cal

rxrpc: Allow the app to store private data on peer structs

Provide a way for the application (e.g. the afs filesystem) to store
private data on the rxrpc_peer structs for later retrieval via the call
object.

This will allow afs to store a pointer to the afs_server object on the
rxrpc_peer struct, thereby obviating the need for afs to keep lookup tables
by which it can associate an incoming call with server that transmitted it.

Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: Simon Horman <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/ # v1
Link: https://lore.kernel.org/r/[email protected]/ # v4

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rxrpc, afs: Allow afs to pin rxrpc_peer objects

Change rxrpc's API such that:

(1) A new function, rxrpc_kernel_lookup_peer(), is provided to look up an
rxrpc_peer record for a remote address

rxrpc, afs: Allow afs to pin rxrpc_peer objects

Change rxrpc's API such that:

(1) A new function, rxrpc_kernel_lookup_peer(), is provided to look up an
rxrpc_peer record for a remote address and a corresponding function,
rxrpc_kernel_put_peer(), is provided to dispose of it again.

(2) When setting up a call, the rxrpc_peer object used during a call is
now passed in rather than being set up by rxrpc_connect_call(). For
afs, this meenat passing it to rxrpc_kernel_begin_call() rather than
the full address (the service ID then has to be passed in as a
separate parameter).

(3) A new function, rxrpc_kernel_remote_addr(), is added so that afs can
get a pointer to the transport address for display purposed, and
another, rxrpc_kernel_remote_srx(), to gain a pointer to the full
rxrpc address.

(4) The function to retrieve the RTT from a call, rxrpc_kernel_get_srtt(),
is then altered to take a peer. This now returns the RTT or -1 if
there are insufficient samples.

(5) Rename rxrpc_kernel_get_peer() to rxrpc_kernel_call_get_peer().

(6) Provide a new function, rxrpc_kernel_get_peer(), to get a ref on a
peer the caller already has.

This allows the afs filesystem to pin the rxrpc_peer records that it is
using, allowing faster lookups and pointer comparisons rather than
comparing sockaddr_rxrpc contents. It also makes it easier to get hold of
the RTT. The following changes are made to afs:

(1) The addr_list struct's addrs[] elements now hold a peer struct pointer
and a service ID rather than a sockaddr_rxrpc.

(2) When displaying the transport address, rxrpc_kernel_remote_addr() is
used.

(3) The port arg is removed from afs_alloc_addrlist() since it's always
overridden.

(4) afs_merge_fs_addr4() and afs_merge_fs_addr6() do peer lookup and may
now return an error that must be handled.

(5) afs_find_server() now takes a peer pointer to specify the address.

(6) afs_find_server(), afs_compare_fs_alists() and afs_merge_fs_addr[46]{}
now do peer pointer comparison rather than address comparison.

Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]

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rxrpc: Fix timeout of a call that hasn't yet been granted a channel

afs_make_call() calls rxrpc_kernel_begin_call() to begin a call (which may
get stalled in the background waiting for a connection

rxrpc: Fix timeout of a call that hasn't yet been granted a channel

afs_make_call() calls rxrpc_kernel_begin_call() to begin a call (which may
get stalled in the background waiting for a connection to become
available); it then calls rxrpc_kernel_set_max_life() to set the timeouts -
but that starts the call timer so the call timer might then expire before
we get a connection assigned - leading to the following oops if the call
stalled:

BUG: kernel NULL pointer dereference, address: 0000000000000000
...
CPU: 1 PID: 5111 Comm: krxrpcio/0 Not tainted 6.3.0-rc7-build3+ #701
RIP: 0010:rxrpc_alloc_txbuf+0xc0/0x157
...
Call Trace:
<TASK>
rxrpc_send_ACK+0x50/0x13b
rxrpc_input_call_event+0x16a/0x67d
rxrpc_io_thread+0x1b6/0x45f
? _raw_spin_unlock_irqrestore+0x1f/0x35
? rxrpc_input_packet+0x519/0x519
kthread+0xe7/0xef
? kthread_complete_and_exit+0x1b/0x1b
ret_from_fork+0x22/0x30

Fix this by noting the timeouts in struct rxrpc_call when the call is
created. The timer will be started when the first packet is transmitted.

It shouldn't be possible to trigger this directly from userspace through
AF_RXRPC as sendmsg() will return EBUSY if the call is in the
waiting-for-conn state if it dropped out of the wait due to a signal.

Fixes: 9d35d880e0e4 ("rxrpc: Move client call connection to the I/O thread")
Reported-by: Marc Dionne <[email protected]>
Signed-off-by: David Howells <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: David S. Miller <[email protected]>

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rxrpc: Fix potential race in error handling in afs_make_call()

If the rxrpc call set up by afs_make_call() receives an error whilst it is
transmitting the request, there's the possibility that it ma

rxrpc: Fix potential race in error handling in afs_make_call()

If the rxrpc call set up by afs_make_call() receives an error whilst it is
transmitting the request, there's the possibility that it may get to the
point the rxrpc call is ended (after the error_kill_call label) just as the
call is queued for async processing.

This could manifest itself as call->rxcall being seen as NULL in
afs_deliver_to_call() when it tries to lock the call.

Fix this by splitting rxrpc_kernel_end_call() into a function to shut down
an rxrpc call and a function to release the caller's reference and calling
the latter only when we get to afs_put_call().

Reported-by: Jeffrey Altman <[email protected]>
Signed-off-by: David Howells <[email protected]>
Tested-by: [email protected]
cc: Marc Dionne <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: [email protected]
cc: [email protected]
Signed-off-by: David S. Miller <[email protected]>

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rxrpc: Tidy up abort generation infrastructure

Tidy up the abort generation infrastructure in the following ways:

(1) Create an enum and string mapping table to list the reasons an abort
migh

rxrpc: Tidy up abort generation infrastructure

Tidy up the abort generation infrastructure in the following ways:

(1) Create an enum and string mapping table to list the reasons an abort
might be generated in tracing.

(2) Replace the 3-char string with the values from (1) in the places that
use that to log the abort source. This gets rid of a memcpy() in the
tracepoint.

(3) Subsume the rxrpc_rx_eproto tracepoint with the rxrpc_abort tracepoint
and use values from (1) to indicate the trace reason.

(4) Always make a call to an abort function at the point of the abort
rather than stashing the values into variables and using goto to get
to a place where it reported. The C optimiser will collapse the calls
together as appropriate. The abort functions return a value that can
be returned directly if appropriate.

Note that this extends into afs also at the points where that generates an
abort. To aid with this, the afs sources need to #define
RXRPC_TRACE_ONLY_DEFINE_ENUMS before including the rxrpc tracing header
because they don't have access to the rxrpc internal structures that some
of the tracepoints make use of.

Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]

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rxrpc: Remove decl for rxrpc_kernel_call_is_complete()

rxrpc_kernel_call_is_complete() has been removed, so remove its declaration
too.

Signed-off-by: David Howells <[email protected]>
cc: Marc D

rxrpc: Remove decl for rxrpc_kernel_call_is_complete()

rxrpc_kernel_call_is_complete() has been removed, so remove its declaration
too.

Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]

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rxrpc: Implement an in-kernel rxperf server for testing purposes

Implement an in-kernel rxperf server to allow kernel-based rxrpc services
to be tested directly, unlike with AFS where they're access

rxrpc: Implement an in-kernel rxperf server for testing purposes

Implement an in-kernel rxperf server to allow kernel-based rxrpc services
to be tested directly, unlike with AFS where they're accessed by the
fileserver when the latter decides it wants to.

This is implemented as a module that, if loaded, opens UDP port 7009
(afs3-rmtsys) and listens on it for incoming calls. Calls can be generated
using the rxperf command shipped with OpenAFS, for example.

Changes
=======
ver #2)
- Use min_t() instead of min().

Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]
cc: Jakub Kicinski <[email protected]>

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rxrpc: Remove rxrpc_get_reply_time() which is no longer used

Remove rxrpc_get_reply_time() as that is no longer used now that the call
issue time is used instead of the reply time.

Signed-off-by: D

rxrpc: Remove rxrpc_get_reply_time() which is no longer used

Remove rxrpc_get_reply_time() as that is no longer used now that the call
issue time is used instead of the reply time.

Signed-off-by: David Howells <[email protected]>

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afs: Don't truncate iter during data fetch

Don't truncate the iterator to correspond to the actual data size when
fetching the data from the server - rather, pass the length we want to read
to rxrpc

afs: Don't truncate iter during data fetch

Don't truncate the iterator to correspond to the actual data size when
fetching the data from the server - rather, pass the length we want to read
to rxrpc.

This will allow the clear-after-read code in future to simply clear the
remaining iterator capacity rather than having to reinitialise the
iterator.

Signed-off-by: David Howells <[email protected]>
Tested-By: Marc Dionne <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/158861249201.340223.13035445866976590375.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/159465825061.1377938.14403904452300909320.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/160588531418.3465195.10712005940763063144.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161118148567.1232039.13380313332292947956.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161161044610.2537118.17908520793806837792.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/161340407907.1303470.6501394859511712746.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/161539551721.286939.14655713136572200716.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/161653807790.2770958.14034599989374173734.stgit@warthog.procyon.org.uk/ # v5
Link: https://lore.kernel.org/r/161789090823.6155.15673999934535049102.stgit@warthog.procyon.org.uk/ # v6

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rxrpc: Make rxrpc_kernel_get_srtt() indicate validity

Fix rxrpc_kernel_get_srtt() to indicate the validity of the returned
smoothed RTT. If we haven't had any valid samples yet, the SRTT isn't
usef

rxrpc: Make rxrpc_kernel_get_srtt() indicate validity

Fix rxrpc_kernel_get_srtt() to indicate the validity of the returned
smoothed RTT. If we haven't had any valid samples yet, the SRTT isn't
useful.

Fixes: c410bf01933e ("rxrpc: Fix the excessive initial retransmission timeout")
Signed-off-by: David Howells <[email protected]>

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rxrpc: add rxrpc_sock_set_min_security_level

Add a helper to directly set the RXRPC_MIN_SECURITY_LEVEL sockopt from
kernel space without going through a fake uaccess.

Thanks to David Howells for th

rxrpc: add rxrpc_sock_set_min_security_level

Add a helper to directly set the RXRPC_MIN_SECURITY_LEVEL sockopt from
kernel space without going through a fake uaccess.

Thanks to David Howells for the documentation updates.

Signed-off-by: Christoph Hellwig <[email protected]>
Acked-by: David Howells <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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rxrpc: Fix the excessive initial retransmission timeout

rxrpc currently uses a fixed 4s retransmission timeout until the RTT is
sufficiently sampled. This can cause problems with some fileservers w

rxrpc: Fix the excessive initial retransmission timeout

rxrpc currently uses a fixed 4s retransmission timeout until the RTT is
sufficiently sampled. This can cause problems with some fileservers with
calls to the cache manager in the afs filesystem being dropped from the
fileserver because a packet goes missing and the retransmission timeout is
greater than the call expiry timeout.

Fix this by:

(1) Copying the RTT/RTO calculation code from Linux's TCP implementation
and altering it to fit rxrpc.

(2) Altering the various users of the RTT to make use of the new SRTT
value.

(3) Replacing the use of rxrpc_resend_timeout to use the calculated RTO
value instead (which is needed in jiffies), along with a backoff.

Notes:

(1) rxrpc provides RTT samples by matching the serial numbers on outgoing
DATA packets that have the RXRPC_REQUEST_ACK set and PING ACK packets
against the reference serial number in incoming REQUESTED ACK and
PING-RESPONSE ACK packets.

(2) Each packet that is transmitted on an rxrpc connection gets a new
per-connection serial number, even for retransmissions, so an ACK can
be cross-referenced to a specific trigger packet. This allows RTT
information to be drawn from retransmitted DATA packets also.

(3) rxrpc maintains the RTT/RTO state on the rxrpc_peer record rather than
on an rxrpc_call because many RPC calls won't live long enough to
generate more than one sample.

(4) The calculated SRTT value is in units of 8ths of a microsecond rather
than nanoseconds.

The (S)RTT and RTO values are displayed in /proc/net/rxrpc/peers.

Fixes: 17926a79320a ([AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both"")
Signed-off-by: David Howells <[email protected]>

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afs: Fix client call Rx-phase signal handling

Fix the handling of signals in client rxrpc calls made by the afs
filesystem. Ignore signals completely, leaving call abandonment or
connection loss to

afs: Fix client call Rx-phase signal handling

Fix the handling of signals in client rxrpc calls made by the afs
filesystem. Ignore signals completely, leaving call abandonment or
connection loss to be detected by timeouts inside AF_RXRPC.

Allowing a filesystem call to be interrupted after the entire request has
been transmitted and an abort sent means that the server may or may not
have done the action - and we don't know. It may even be worse than that
for older servers.

Fixes: bc5e3a546d55 ("rxrpc: Use MSG_WAITALL to tell sendmsg() to temporarily ignore signals")
Signed-off-by: David Howells <[email protected]>

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rxrpc: Fix call interruptibility handling

Fix the interruptibility of kernel-initiated client calls so that they're
either only interruptible when they're waiting for a call slot to come
available o

rxrpc: Fix call interruptibility handling

Fix the interruptibility of kernel-initiated client calls so that they're
either only interruptible when they're waiting for a call slot to come
available or they're not interruptible at all. Either way, they're not
interruptible during transmission.

This should help prevent StoreData calls from being interrupted when
writeback is in progress. It doesn't, however, handle interruption during
the receive phase.

Userspace-initiated calls are still interruptable. After the signal has
been handled, sendmsg() will return the amount of data copied out of the
buffer and userspace can perform another sendmsg() call to continue
transmission.

Fixes: bc5e3a546d55 ("rxrpc: Use MSG_WAITALL to tell sendmsg() to temporarily ignore signals")
Signed-off-by: David Howells <[email protected]>

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treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of th

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Allison Randal <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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rxrpc: Allow the kernel to mark a call as being non-interruptible

Allow kernel services using AF_RXRPC to indicate that a call should be
non-interruptible. This allows kafs to make things like lock

rxrpc: Allow the kernel to mark a call as being non-interruptible

Allow kernel services using AF_RXRPC to indicate that a call should be
non-interruptible. This allows kafs to make things like lock-extension and
writeback data storage calls non-interruptible.

If this is set, signals will be ignored for operations on that call where
possible - such as waiting to get a call channel on an rxrpc connection.

It doesn't prevent UDP sendmsg from being interrupted, but that will be
handled by packet retransmission.

rxrpc_kernel_recv_data() isn't affected by this since that never waits,
preferring instead to return -EAGAIN and leave the waiting to the caller.

Userspace initiated calls can't be set to be uninterruptible at this time.

Signed-off-by: David Howells <[email protected]>

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rxrpc: Provide kernel interface to set max lifespan on a call

Provide an interface to set max lifespan on a call from inside of the
kernel without having to call kernel_sendmsg().

Signed-off-by: Da

rxrpc: Provide kernel interface to set max lifespan on a call

Provide an interface to set max lifespan on a call from inside of the
kernel without having to call kernel_sendmsg().

Signed-off-by: David Howells <[email protected]>

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rxrpc: Make rxrpc_kernel_check_life() indicate if call completed

Make rxrpc_kernel_check_life() pass back the life counter through the
argument list and return true if the call has not yet completed

rxrpc: Make rxrpc_kernel_check_life() indicate if call completed

Make rxrpc_kernel_check_life() pass back the life counter through the
argument list and return true if the call has not yet completed.

Suggested-by: Marc Dionne <[email protected]>
Signed-off-by: David Howells <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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Revert "rxrpc: Allow failed client calls to be retried"

The changes introduced to allow rxrpc calls to be retried creates an issue
when it comes to refcounting afs_call structs. The problem is that

Revert "rxrpc: Allow failed client calls to be retried"

The changes introduced to allow rxrpc calls to be retried creates an issue
when it comes to refcounting afs_call structs. The problem is that when
rxrpc_send_data() queues the last packet for an asynchronous call, the
following sequence can occur:

(1) The notify_end_tx callback is invoked which causes the state in the
afs_call to be changed from AFS_CALL_CL_REQUESTING or
AFS_CALL_SV_REPLYING.

(2) afs_deliver_to_call() can then process event notifications from rxrpc
on the async_work queue.

(3) Delivery of events, such as an abort from the server, can cause the
afs_call state to be changed to AFS_CALL_COMPLETE on async_work.

(4) For an asynchronous call, afs_process_async_call() notes that the call
is complete and tried to clean up all the refs on async_work.

(5) rxrpc_send_data() might return the amount of data transferred
(success) or an error - which could in turn reflect a local error or a
received error.

Synchronising the clean up after rxrpc_kernel_send_data() returns an error
with the asynchronous cleanup is then tricky to get right.

Mostly revert commit c038a58ccfd6704d4d7d60ed3d6a0fca13cf13a4. The two API
functions the original commit added aren't currently used. This makes
rxrpc_kernel_send_data() always return successfully if it queued the data
it was given.

Note that this doesn't affect synchronous calls since their Rx notification
function merely pokes a wait queue and does not refcounting. The
asynchronous call notification function *has* to do refcounting and pass a
ref over the work item to avoid the need to sync the workqueue in call
cleanup.

Signed-off-by: David Howells <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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rxrpc: Fix life check

The life-checking function, which is used by kAFS to make sure that a call
is still live in the event of a pending signal, only samples the received
packet serial number counte

rxrpc: Fix life check

The life-checking function, which is used by kAFS to make sure that a call
is still live in the event of a pending signal, only samples the received
packet serial number counter; it doesn't actually provoke a change in the
counter, rather relying on the server to happen to give us a packet in the
time window.

Fix this by adding a function to force a ping to be transmitted.

kAFS then keeps track of whether there's been a stall, and if so, uses the
new function to ping the server, resetting the timeout to allow the reply
to come back.

If there's a stall, a ping and the call is *still* stalled in the same
place after another period, then the call will be aborted.

Fixes: bc5e3a546d55 ("rxrpc: Use MSG_WAITALL to tell sendmsg() to temporarily ignore signals")
Fixes: f4d15fb6f99a ("rxrpc: Provide functions for allowing cleaner handling of signals")
Signed-off-by: David Howells <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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rxrpc: Allow the reply time to be obtained on a client call

Allow the epoch value to be queried on a server connection. This is in the
rxrpc header of every packet for use in routing and is derived

rxrpc: Allow the reply time to be obtained on a client call

Allow the epoch value to be queried on a server connection. This is in the
rxrpc header of every packet for use in routing and is derived from the
client's state. It's also not supposed to change unless the client gets
restarted.

AFS can make use of this information to deduce whether a fileserver has
been restarted because the fileserver makes client calls to the filesystem
driver's cache manager to send notifications (ie. callback breaks) about
conflicting changes from other clients. These convey the fileserver's own
epoch value back to the filesystem.

Signed-off-by: David Howells <[email protected]>

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rxrpc: Allow the reply time to be obtained on a client call

Allow the timestamp on the sk_buff holding the first DATA packet of a reply
to be queried. This can then be used as a base for the expiry

rxrpc: Allow the reply time to be obtained on a client call

Allow the timestamp on the sk_buff holding the first DATA packet of a reply
to be queried. This can then be used as a base for the expiry time
calculation on the callback promise duration indicated by an operation
result.

Signed-off-by: David Howells <[email protected]>

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rxrpc: Push iov_iter up from rxrpc_kernel_recv_data() to caller

Push iov_iter up from rxrpc_kernel_recv_data() to its caller to allow
non-contiguous iovs to be passed down, thereby permitting file r

rxrpc: Push iov_iter up from rxrpc_kernel_recv_data() to caller

Push iov_iter up from rxrpc_kernel_recv_data() to its caller to allow
non-contiguous iovs to be passed down, thereby permitting file reading to
be simplified in the AFS filesystem in a future patch.

Signed-off-by: David Howells <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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rxrpc, afs: Use debug_ids rather than pointers in traces

In rxrpc and afs, use the debug_ids that are monotonically allocated to
various objects as they're allocated rather than pointers as kernel
p

rxrpc, afs: Use debug_ids rather than pointers in traces

In rxrpc and afs, use the debug_ids that are monotonically allocated to
various objects as they're allocated rather than pointers as kernel
pointers are now hashed making them less useful. Further, the debug ids
aren't reused anywhere nearly as quickly.

In addition, allow kernel services that use rxrpc, such as afs, to take
numbers from the rxrpc counter, assign them to their own call struct and
pass them in to rxrpc for both client and service calls so that the trace
lines for each will have the same ID tag.

Signed-off-by: David Howells <[email protected]>

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rxrpc: Provide functions for allowing cleaner handling of signals

Provide a couple of functions to allow cleaner handling of signals in a
kernel service. They are:

(1) rxrpc_kernel_get_rtt()

rxrpc: Provide functions for allowing cleaner handling of signals

Provide a couple of functions to allow cleaner handling of signals in a
kernel service. They are:

(1) rxrpc_kernel_get_rtt()

This allows the kernel service to find out the RTT time for a call, so
as to better judge how large a timeout to employ.

Note, though, that whilst this returns a value in nanoseconds, the
timeouts can only actually be in jiffies.

(2) rxrpc_kernel_check_life()

This returns a number that is updated when ACKs are received from the
peer (notably including PING RESPONSE ACKs which we can elicit by
sending PING ACKs to see if the call still exists on the server).

The caller should compare the numbers of two calls to see if the call
is still alive.

These can be used to provide an extending timeout rather than returning
immediately in the case that a signal occurs that would otherwise abort an
RPC operation. The timeout would be extended if the server is still
responsive and the call is still apparently alive on the server.

For most operations this isn't that necessary - but for FS.StoreData it is:
OpenAFS writes the data to storage as it comes in without making a backup,
so if we immediately abort it when partially complete on a CTRL+C, say, we
have no idea of the state of the file after the abort.

Signed-off-by: David Howells <[email protected]>

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