Smatch warns that:

    fs/afs/rxrpc.c:922 afs_extract_data()
    error: uninitialized symbol 'remote_abort'.

Smatch is right that "remote_abort" might be uninitialized when we pass
it to afs_set_call_complete().  I don't know if that function uses the
uninitialized variable.  Anyway, the comment for rxrpc_kernel_recv_data(),
says that "*_abort should also be initialised to 0." and this patch does
that.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Protect call->state changes against the call being prematurely terminated
due to a signal.

What can happen is that a signal causes afs_wait_for_call_to_complete() to
abort an afs_call because it's not yet complete whilst afs_deliver_to_call()
is delivering data to that call.

If the data delivery causes the state to change, this may overwrite the state
of the afs_call, making it not-yet-complete again - but no further
notifications will be forthcoming from AF_RXRPC as the rxrpc call has been
aborted and completed, so kAFS will just hang in various places waiting for
that call or on page bits that need clearing by that call.

A tracepoint to monitor call state changes is also provided.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

It is not required that the afs client operate on port 7001.
The port could be in use because another kernel or userspace
client has already bound to it.

If the port is in use, just fallback to using a dynamic port.
Signed-off-by: NMarc Dionne <marc.dionne@auristor.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Add a pair of tracepoints to log the sending of pages for an FS.StoreData
or FS.StoreData64 operation.

Tracepoint afs_send_pages notes each set of pages added to the operation.
There may be several of these per operation as we get up at most 8
contiguous pages in one go because the bvec we're using is on the stack.

Tracepoint afs_sent_pages notes the end of adding data from a whole run of
pages to the operation and the completion of the request phase.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Add tracepoints to trace the initiation and completion of client calls
within the kafs filesystem.

The afs_make_vl_call tracepoint watches calls to the volume location
database server.

The afs_make_fs_call tracepoint watches calls to the file server.

The afs_call_done tracepoint watches for call completion.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Fix the total-length calculation in afs_make_call() when the operation
being dispatched has data from a series of pages attached.

Despite the patched code looking like that it should reduce mathematically
to the current code, it doesn't because the 32-bit unsigned arithmetic
being used to calculate the page-offset-difference doesn't correctly extend
to a 64-bit value when the result is effectively negative.

Without this, some FS.StoreData operations that span multiple pages fail,
reporting too little or too much data.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Only progress the AFS call state at the end of Tx phase from the callback
passed to rxrpc_kernel_send_data() rather than setting it before the last
data send call.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

The current code assumes that volumes and servers are per-cell and are
never shared, but this is not enforced, and, indeed, public cells do exist
that are aliases of each other.  Further, an organisation can, say, set up
a public cell and a private cell with overlapping, but not identical, sets
of servers.  The difference is purely in the database attached to the VL
servers.

The current code will malfunction if it sees a server in two cells as it
assumes global address -> server record mappings and that each server is in
just one cell.

Further, each server may have multiple addresses - and may have addresses
of different families (IPv4 and IPv6, say).

To this end, the following structural changes are made:

 (1) Server record management is overhauled:

     (a) Server records are made independent of cell.  The namespace keeps
     	 track of them, volume records have lists of them and each vnode
     	 has a server on which its callback interest currently resides.

     (b) The cell record no longer keeps a list of servers known to be in
     	 that cell.

     (c) The server records are now kept in a flat list because there's no
     	 single address to sort on.

     (d) Server records are now keyed by their UUID within the namespace.

     (e) The addresses for a server are obtained with the VL.GetAddrsU
     	 rather than with VL.GetEntryByName, using the server's UUID as a
     	 parameter.

     (f) Cached server records are garbage collected after a period of
     	 non-use and are counted out of existence before purging is allowed
     	 to complete.  This protects the work functions against rmmod.

     (g) The servers list is now in /proc/fs/afs/servers.

 (2) Volume record management is overhauled:

     (a) An RCU-replaceable server list is introduced.  This tracks both
     	 servers and their coresponding callback interests.

     (b) The superblock is now keyed on cell record and numeric volume ID.

     (c) The volume record is now tied to the superblock which mounts it,
     	 and is activated when mounted and deactivated when unmounted.
     	 This makes it easier to handle the cache cookie without causing a
     	 double-use in fscache.

     (d) The volume record is loaded from the VLDB using VL.GetEntryByNameU
     	 to get the server UUID list.

     (e) The volume name is updated if it is seen to have changed when the
     	 volume is updated (the update is keyed on the volume ID).

 (3) The vlocation record is got rid of and VLDB records are no longer
     cached.  Sufficient information is stored in the volume record, though
     an update to a volume record is now no longer shared between related
     volumes (volumes come in bundles of three: R/W, R/O and backup).

and the following procedural changes are made:

 (1) The fileserver cursor introduced previously is now fleshed out and
     used to iterate over fileservers and their addresses.

 (2) Volume status is checked during iteration, and the server list is
     replaced if a change is detected.

 (3) Server status is checked during iteration, and the address list is
     replaced if a change is detected.

 (4) The abort code is saved into the address list cursor and -ECONNABORTED
     returned in afs_make_call() if a remote abort happened rather than
     translating the abort into an error message.  This allows actions to
     be taken depending on the abort code more easily.

     (a) If a VMOVED abort is seen then this is handled by rechecking the
     	 volume and restarting the iteration.

     (b) If a VBUSY, VRESTARTING or VSALVAGING abort is seen then this is
         handled by sleeping for a short period and retrying and/or trying
         other servers that might serve that volume.  A message is also
         displayed once until the condition has cleared.

     (c) If a VOFFLINE abort is seen, then this is handled as VBUSY for the
     	 moment.

     (d) If a VNOVOL abort is seen, the volume is rechecked in the VLDB to
     	 see if it has been deleted; if not, the fileserver is probably
     	 indicating that the volume couldn't be attached and needs
     	 salvaging.

     (e) If statfs() sees one of these aborts, it does not sleep, but
     	 rather returns an error, so as not to block the umount program.

 (5) The fileserver iteration functions in vnode.c are now merged into
     their callers and more heavily macroised around the cursor.  vnode.c
     is removed.

 (6) Operations on a particular vnode are serialised on that vnode because
     the server will lock that vnode whilst it operates on it, so a second
     op sent will just have to wait.

 (7) Fileservers are probed with FS.GetCapabilities before being used.
     This is where service upgrade will be done.

 (8) A callback interest on a fileserver is set up before an FS operation
     is performed and passed through to afs_make_call() so that it can be
     set on the vnode if the operation returns a callback.  The callback
     interest is passed through to afs_iget() also so that it can be set
     there too.

In general, record updating is done on an as-needed basis when we try to
access servers, volumes or vnodes rather than offloading it to work items
and special threads.

Notes:

 (1) Pre AFS-3.4 servers are no longer supported, though this can be added
     back if necessary (AFS-3.4 was released in 1998).

 (2) VBUSY is retried forever for the moment at intervals of 1s.

 (3) /proc/fs/afs/<cell>/servers no longer exists.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Add an RCU replaceable address list structure to hold a list of server
addresses.  The list also holds the

To this end:

 (1) A cell's VL server address list can be loaded directly via insmod or
     echo to /proc/fs/afs/cells or dynamically from a DNS query for AFSDB
     or SRV records.

 (2) Anyone wanting to use a cell's VL server address must wait until the
     cell record comes online and has tried to obtain some addresses.

 (3) An FS server's address list, for the moment, has a single entry that
     is the key to the server list.  This will change in the future when a
     server is instead keyed on its UUID and the VL.GetAddrsU operation is
     used.

 (4) An 'address cursor' concept is introduced to handle iteration through
     the address list.  This is passed to the afs_make_call() as, in the
     future, stuff (such as abort code) that doesn't outlast the call will
     be returned in it.

In the future, we might want to annotate the list with information about
how each address fares.  We might then want to propagate such annotations
over address list replacement.

Whilst we're at it, we allow IPv6 addresses to be specified in
colon-delimited lists by enclosing them in square brackets.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Rename the server member of struct afs_call to cm_server as we're only
going to be using it for incoming calls for the Cache Manager service.
This makes it easier to differentiate from the pointer to the target server
for the client, which will point to a different structure to allow for
callback handling.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

If call->ret_reply0 is set, return call->reply[0] on success.  Change the
return type of afs_make_call() to long so that this can be passed back
without bit loss and then cast to a pointer if required.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Condense struct afs_call's reply anchor members - reply{,2,3,4} - into an
array.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

The AFS abort code space is shared across all services, so there's no need
for separate abort_to_error translators for each service.

Consolidate them into a single function and remove the function pointers
for them.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Allow VL server specifications to be given IPv6 addresses as well as IPv4
addresses, for example as:

	echo add foo.org 1111:2222:3333:0:4444:5555:6666:7777 >/proc/fs/afs/cells

Note that ':' is the expected separator for separating IPv4 addresses, but
if a ',' is detected or no '.' is detected in the string, the delimiter is
switched to ','.

This also works with DNS AFSDB or SRV record strings fetched by upcall from
userspace.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Keep and pass sockaddr_rxrpc addresses around rather than keeping and
passing in_addr addresses to allow for the use of IPv6 and non-standard
port numbers in future.

This also allows the port and service_id fields to be removed from the
afs_call struct.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Lay the groundwork for supporting network namespaces (netns) to the AFS
filesystem by moving various global features to a network-namespace struct
(afs_net) and providing an instance of this as a temporary global variable
that everything uses via accessor functions for the moment.

The following changes have been made:

 (1) Store the netns in the superblock info.  This will be obtained from
     the mounter's nsproxy on a manual mount and inherited from the parent
     superblock on an automount.

 (2) The cell list is made per-netns.  It can be viewed through
     /proc/net/afs/cells and also be modified by writing commands to that
     file.

 (3) The local workstation cell is set per-ns in /proc/net/afs/rootcell.
     This is unset by default.

 (4) The 'rootcell' module parameter, which sets a cell and VL server list
     modifies the init net namespace, thereby allowing an AFS root fs to be
     theoretically used.

 (5) The volume location lists and the file lock manager are made
     per-netns.

 (6) The AF_RXRPC socket and associated I/O bits are made per-ns.

The various workqueues remain global for the moment.

Changes still to be made:

 (1) /proc/fs/afs/ should be moved to /proc/net/afs/ and a symlink emplaced
     from the old name.

 (2) A per-netns subsys needs to be registered for AFS into which it can
     store its per-netns data.

 (3) Rather than the AF_RXRPC socket being opened on module init, it needs
     to be opened on the creation of a superblock in that netns.

 (4) The socket needs to be closed when the last superblock using it is
     destroyed and all outstanding client calls on it have been completed.
     This prevents a reference loop on the namespace.

 (5) It is possible that several namespaces will want to use AFS, in which
     case each one will need its own UDP port.  These can either be set
     through /proc/net/afs/cm_port or the kernel can pick one at random.
     The init_ns gets 7001 by default.

Other issues that need resolving:

 (1) The DNS keyring needs net-namespacing.

 (2) Where do upcalls go (eg. DNS request-key upcall)?

 (3) Need something like open_socket_in_file_ns() syscall so that AFS
     command line tools attempting to operate on an AFS file/volume have
     their RPC calls go to the right place.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Make wait_on_atomic_t() pass the TASK_* mode onto its action function as an
extra argument and make it 'unsigned int throughout.

Also, consolidate a bunch of identical action functions into a default
function that can do the appropriate thing for the mode.

Also, change the argument name in the bit_wait*() function declarations to
reflect the fact that it's the mode and not the bit number.

[Peter Z gives this a grudging ACK, but thinks that the whole atomic_t wait
should be done differently, though he's not immediately sure as to how]
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
cc: Ingo Molnar <mingo@kernel.org>

Make AF_RXRPC accept MSG_WAITALL as a flag to sendmsg() to tell it to
ignore signals whilst loading up the message queue, provided progress is
being made in emptying the queue at the other side.

Progress is defined as the base of the transmit window having being
advanced within 2 RTT periods.  If the period is exceeded with no progress,
sendmsg() will return anyway, indicating how much data has been copied, if
any.

Once the supplied buffer is entirely decanted, the sendmsg() will return.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Provide support for a kernel service to make use of the service upgrade
facility.  This involves:

 (1) Pass an upgrade request flag to rxrpc_kernel_begin_call().

 (2) Make rxrpc_kernel_recv_data() return the call's current service ID so
     that the caller can detect service upgrade and see what the service
     was upgraded to.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Add a callback to rxrpc_kernel_send_data() so that a kernel service can get
a notification that the AF_RXRPC call has transitioned out the Tx phase and
is now waiting for a reply or a final ACK.

This is called from AF_RXRPC with the call state lock held so the
notification is guaranteed to come before any reply is passed back.

Further, modify the AFS filesystem to make use of this so that we don't have
to change the afs_call state before sending the last bit of data.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Move the protocol description header file into net/rxrpc/ and rename it to
protocol.h.  It's no longer necessary to expose it as packets are no longer
exposed to kernel services (such as AFS) that use the facility.

The abort codes are transferred to the UAPI header instead as we pass these
back to userspace and also to kernel services.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Provide a control message that can be specified on the first sendmsg() of a
client call or the first sendmsg() of a service response to indicate the
total length of the data to be transmitted for that call.

Currently, because the length of the payload of an encrypted DATA packet is
encrypted in front of the data, the packet cannot be encrypted until we
know how much data it will hold.

By specifying the length at the beginning of the transmit phase, each DATA
packet length can be set before we start loading data from userspace (where
several sendmsg() calls may contribute to a particular packet).

An error will be returned if too little or too much data is presented in
the Tx phase.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Use negative error codes in struct rxrpc_call::error because that's what
the kernel normally deals with and to make the code consistent.  We only
turn them positive when transcribing into a cmsg for userspace recvmsg.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Fix the way in which a call that's in progress and being waited for is
aborted in the case that EINTR is detected.  We should be sending
RX_USER_ABORT rather than RX_CALL_DEAD as the abort code.

Note that since the only two ways out of the loop are if the call completes
or if a signal happens, the kill-the-call clause after the loop has
finished can only happen in the case of EINTR.  This means that we only
have one abort case to deal with, not two, and the "KWC" case can never
happen and so can be deleted.

Note further that simply aborting the call isn't necessarily the best thing
here since at this point: the request has been entirely sent and it's
likely the server will do the operation anyway - whether we abort it or
not.  In future, we should punt the handling of the remainder of the call
off to a background thread.
Reported-by: NMarc Dionne <marc.c.dionne@auristor.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

afs_send_pages() should only put the call into the AFS_CALL_AWAIT_REPLY
state if it has sent all the pages - but the check it makes is incorrect
and sometimes it will finish the loop early.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

If we receive a network error, a remote abort or a protocol error whilst
we're still transmitting data, make sure we return an appropriate error to
the caller rather than ESHUTDOWN or ECONNABORTED.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

When we are given an invalid operation ID, we should abort that with
RXGEN_OPCODE rather than RX_INVALID_OPERATION.

Also map RXGEN_OPCODE to -ENOTSUPP.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Use a bvec rather than a kvec in afs_send_pages() as we don't then have to
call kmap() in advance.  This allows us to pass the array of contiguous
pages that we extracted through to rxrpc in one go rather than passing a
single page at a time.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

sched/headers: Prepare to move signal wakeup & sigpending methods from <linux/sched.h> into <linux/sched/signal.h>

Fix up affected files that include this signal functionality via sched.h.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

A static checker warning occurs in the AFS filesystem:

	fs/afs/cmservice.c:155 SRXAFSCB_CallBack()
	error: dereferencing freed memory 'call'

due to the reply being sent before we access the server it points to.  The
act of sending the reply causes the call to be freed if an error occurs
(but not if it doesn't).

On top of this, the lifetime handling of afs_call structs is fragile
because they get passed around through workqueues without any sort of
refcounting.

Deal with the issues by:

 (1) Fix the maybe/maybe not nature of the reply sending functions with
     regards to whether they release the call struct.

 (2) Refcount the afs_call struct and sort out places that need to get/put
     references.

 (3) Pass a ref through the work queue and release (or pass on) that ref in
     the work function.  Care has to be taken because a work queue may
     already own a ref to the call.

 (4) Do the cleaning up in the put function only.

 (5) Simplify module cleanup by always incrementing afs_outstanding_calls
     whenever a call is allocated.

 (6) Set the backlog to 0 with kernel_listen() at the beginning of the
     process of closing the socket to prevent new incoming calls from
     occurring and to remove the contribution of preallocated calls from
     afs_outstanding_calls before we wait on it.

A tracepoint is also added to monitor the afs_call refcount and lifetime.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Fixes: 08e0e7c8: "[AF_RXRPC]: Make the in-kernel AFS filesystem use AF_RXRPC."

The afs_wait_mode struct isn't really necessary.  Client calls only use one
of a choice of two (synchronous or the asynchronous) and incoming calls
don't use the wait at all.  Replace with a boolean parameter.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Add three tracepoints to the AFS filesystem:

 (1) The afs_recv_data tracepoint logs data segments that are extracted
     from the data received from the peer through afs_extract_data().

 (2) The afs_notify_call tracepoint logs notification from AF_RXRPC of data
     coming in to an asynchronous call.

 (3) The afs_cb_call tracepoint logs incoming calls that have had their
     operation ID extracted and mapped into a supported cache manager
     service call.

To make (3) work, the name strings in the afs_call_type struct objects have
to be annotated with __tracepoint_string.  This is done with the CM_NAME()
macro.

Further, the AFS call state enum needs a name so that it can be used to
declare parameter types.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

call->operation_ID is sometimes being used as __be32 sometimes is being
used as u32.  Be consistent and settle on using as u32.

Signed-off-by: David Howells <dhowells@redhat.com.

When it's in the waiting-for-ACK state, the AFS filesystem needs to check
the result of rxrpc_kernel_recv_data() any time it is notified to see if it
is indicating a fatal error.  If this is the case, it needs to mark the
call completed otherwise the call just sits there and never goes away.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Rewrite the data and ack handling code such that:

 (1) Parsing of received ACK and ABORT packets and the distribution and the
     filing of DATA packets happens entirely within the data_ready context
     called from the UDP socket.  This allows us to process and discard ACK
     and ABORT packets much more quickly (they're no longer stashed on a
     queue for a background thread to process).

 (2) We avoid calling skb_clone(), pskb_pull() and pskb_trim().  We instead
     keep track of the offset and length of the content of each packet in
     the sk_buff metadata.  This means we don't do any allocation in the
     receive path.

 (3) Jumbo DATA packet parsing is now done in data_ready context.  Rather
     than cloning the packet once for each subpacket and pulling/trimming
     it, we file the packet multiple times with an annotation for each
     indicating which subpacket is there.  From that we can directly
     calculate the offset and length.

 (4) A call's receive queue can be accessed without taking locks (memory
     barriers do have to be used, though).

 (5) Incoming calls are set up from preallocated resources and immediately
     made live.  They can than have packets queued upon them and ACKs
     generated.  If insufficient resources exist, DATA packet #1 is given a
     BUSY reply and other DATA packets are discarded).

 (6) sk_buffs no longer take a ref on their parent call.

To make this work, the following changes are made:

 (1) Each call's receive buffer is now a circular buffer of sk_buff
     pointers (rxtx_buffer) rather than a number of sk_buff_heads spread
     between the call and the socket.  This permits each sk_buff to be in
     the buffer multiple times.  The receive buffer is reused for the
     transmit buffer.

 (2) A circular buffer of annotations (rxtx_annotations) is kept parallel
     to the data buffer.  Transmission phase annotations indicate whether a
     buffered packet has been ACK'd or not and whether it needs
     retransmission.

     Receive phase annotations indicate whether a slot holds a whole packet
     or a jumbo subpacket and, if the latter, which subpacket.  They also
     note whether the packet has been decrypted in place.

 (3) DATA packet window tracking is much simplified.  Each phase has just
     two numbers representing the window (rx_hard_ack/rx_top and
     tx_hard_ack/tx_top).

     The hard_ack number is the sequence number before base of the window,
     representing the last packet the other side says it has consumed.
     hard_ack starts from 0 and the first packet is sequence number 1.

     The top number is the sequence number of the highest-numbered packet
     residing in the buffer.  Packets between hard_ack+1 and top are
     soft-ACK'd to indicate they've been received, but not yet consumed.

     Four macros, before(), before_eq(), after() and after_eq() are added
     to compare sequence numbers within the window.  This allows for the
     top of the window to wrap when the hard-ack sequence number gets close
     to the limit.

     Two flags, RXRPC_CALL_RX_LAST and RXRPC_CALL_TX_LAST, are added also
     to indicate when rx_top and tx_top point at the packets with the
     LAST_PACKET bit set, indicating the end of the phase.

 (4) Calls are queued on the socket 'receive queue' rather than packets.
     This means that we don't need have to invent dummy packets to queue to
     indicate abnormal/terminal states and we don't have to keep metadata
     packets (such as ABORTs) around

 (5) The offset and length of a (sub)packet's content are now passed to
     the verify_packet security op.  This is currently expected to decrypt
     the packet in place and validate it.

     However, there's now nowhere to store the revised offset and length of
     the actual data within the decrypted blob (there may be a header and
     padding to skip) because an sk_buff may represent multiple packets, so
     a locate_data security op is added to retrieve these details from the
     sk_buff content when needed.

 (6) recvmsg() now has to handle jumbo subpackets, where each subpacket is
     individually secured and needs to be individually decrypted.  The code
     to do this is broken out into rxrpc_recvmsg_data() and shared with the
     kernel API.  It now iterates over the call's receive buffer rather
     than walking the socket receive queue.

Additional changes:

 (1) The timers are condensed to a single timer that is set for the soonest
     of three timeouts (delayed ACK generation, DATA retransmission and
     call lifespan).

 (2) Transmission of ACK and ABORT packets is effected immediately from
     process-context socket ops/kernel API calls that cause them instead of
     them being punted off to a background work item.  The data_ready
     handler still has to defer to the background, though.

 (3) A shutdown op is added to the AF_RXRPC socket so that the AFS
     filesystem can shut down the socket and flush its own work items
     before closing the socket to deal with any in-progress service calls.

Future additional changes that will need to be considered:

 (1) Make sure that a call doesn't hog the front of the queue by receiving
     data from the network as fast as userspace is consuming it to the
     exclusion of other calls.

 (2) Transmit delayed ACKs from within recvmsg() when we've consumed
     sufficiently more packets to avoid the background work item needing to
     run.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Make it possible for the data_ready handler called from the UDP transport
socket to completely instantiate an rxrpc_call structure and make it
immediately live by preallocating all the memory it might need.  The idea
is to cut out the background thread usage as much as possible.

[Note that the preallocated structs are not actually used in this patch -
 that will be done in a future patch.]

If insufficient resources are available in the preallocation buffers, it
will be possible to discard the DATA packet in the data_ready handler or
schedule a BUSY packet without the need to schedule an attempt at
allocation in a background thread.

To this end:

 (1) Preallocate rxrpc_peer, rxrpc_connection and rxrpc_call structs to a
     maximum number each of the listen backlog size.  The backlog size is
     limited to a maxmimum of 32.  Only this many of each can be in the
     preallocation buffer.

 (2) For userspace sockets, the preallocation is charged initially by
     listen() and will be recharged by accepting or rejecting pending
     new incoming calls.

 (3) For kernel services {,re,dis}charging of the preallocation buffers is
     handled manually.  Two notifier callbacks have to be provided before
     kernel_listen() is invoked:

     (a) An indication that a new call has been instantiated.  This can be
     	 used to trigger background recharging.

     (b) An indication that a call is being discarded.  This is used when
     	 the socket is being released.

     A function, rxrpc_kernel_charge_accept() is called by the kernel
     service to preallocate a single call.  It should be passed the user ID
     to be used for that call and a callback to associate the rxrpc call
     with the kernel service's side of the ID.

 (4) Discard the preallocation when the socket is closed.

 (5) Temporarily bump the refcount on the call allocated in
     rxrpc_incoming_call() so that rxrpc_release_call() can ditch the
     preallocation ref on service calls unconditionally.  This will no
     longer be necessary once the preallocation is used.

Note that this does not yet control the number of active service calls on a
client - that will come in a later patch.

A future development would be to provide a setsockopt() call that allows a
userspace server to manually charge the preallocation buffer.  This would
allow user call IDs to be provided in advance and the awkward manual accept
stage to be bypassed.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Add a tracepoint for working out where local aborts happen.  Each
tracepoint call is labelled with a 3-letter code so that they can be
distinguished - and the DATA sequence number is added too where available.

rxrpc_kernel_abort_call() also takes a 3-letter code so that AFS can
indicate the circumstances when it aborts a call.
Signed-off-by: NDavid Howells <dhowells@redhat.com>

The workqueue "afs_async_calls" queues work item
&call->async_work per afs_call. Since there could be multiple calls and since
these calls can be run concurrently, alloc_workqueue has been used to replace
the deprecated create_singlethread_workqueue instance.

The WQ_MEM_RECLAIM flag has been set to ensure forward progress under
memory pressure because the workqueue is being used on a memory reclaim
path.

Since there are fixed number of work items, explicit concurrency
limit is unnecessary here.
Signed-off-by: NBhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>

Don't expose skbs to in-kernel users, such as the AFS filesystem, but
instead provide a notification hook the indicates that a call needs
attention and another that indicates that there's a new call to be
collected.

This makes the following possibilities more achievable:

 (1) Call refcounting can be made simpler if skbs don't hold refs to calls.

 (2) skbs referring to non-data events will be able to be freed much sooner
     rather than being queued for AFS to pick up as rxrpc_kernel_recv_data
     will be able to consult the call state.

 (3) We can shortcut the receive phase when a call is remotely aborted
     because we don't have to go through all the packets to get to the one
     cancelling the operation.

 (4) It makes it easier to do encryption/decryption directly between AFS's
     buffers and sk_buffs.

 (5) Encryption/decryption can more easily be done in the AFS's thread
     contexts - usually that of the userspace process that issued a syscall
     - rather than in one of rxrpc's background threads on a workqueue.

 (6) AFS will be able to wait synchronously on a call inside AF_RXRPC.

To make this work, the following interface function has been added:

     int rxrpc_kernel_recv_data(
		struct socket *sock, struct rxrpc_call *call,
		void *buffer, size_t bufsize, size_t *_offset,
		bool want_more, u32 *_abort_code);

This is the recvmsg equivalent.  It allows the caller to find out about the
state of a specific call and to transfer received data into a buffer
piecemeal.

afs_extract_data() and rxrpc_kernel_recv_data() now do all the extraction
logic between them.  They don't wait synchronously yet because the socket
lock needs to be dealt with.

Five interface functions have been removed:

	rxrpc_kernel_is_data_last()
    	rxrpc_kernel_get_abort_code()
    	rxrpc_kernel_get_error_number()
    	rxrpc_kernel_free_skb()
    	rxrpc_kernel_data_consumed()

As a temporary hack, sk_buffs going to an in-kernel call are queued on the
rxrpc_call struct (->knlrecv_queue) rather than being handed over to the
in-kernel user.  To process the queue internally, a temporary function,
temp_deliver_data() has been added.  This will be replaced with common code
between the rxrpc_recvmsg() path and the kernel_rxrpc_recv_data() path in a
future patch.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>