WIP FPC-III support

[linux/fpc-iii.git] / fs / afs / rxrpc.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Maintain an RxRPC server socket to do AFS communications through
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <linux/sched/signal.h>

#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "internal.h"
#include "afs_cm.h"
#include "protocol_yfs.h"

struct workqueue_struct *afs_async_calls;

static void afs_wake_up_call_waiter(struct sock *, struct rxrpc_call *, unsigned long);
static void afs_wake_up_async_call(struct sock *, struct rxrpc_call *, unsigned long);
static void afs_process_async_call(struct work_struct *);
static void afs_rx_new_call(struct sock *, struct rxrpc_call *, unsigned long);
static void afs_rx_discard_new_call(struct rxrpc_call *, unsigned long);
static int afs_deliver_cm_op_id(struct afs_call *);

/* asynchronous incoming call initial processing */
static const struct afs_call_type afs_RXCMxxxx = {
        .name           = "CB.xxxx",
        .deliver        = afs_deliver_cm_op_id,
};

/*
 * open an RxRPC socket and bind it to be a server for callback notifications
 * - the socket is left in blocking mode and non-blocking ops use MSG_DONTWAIT
 */
int afs_open_socket(struct afs_net *net)
{
        struct sockaddr_rxrpc srx;
        struct socket *socket;
        int ret;

        _enter("");

        ret = sock_create_kern(net->net, AF_RXRPC, SOCK_DGRAM, PF_INET6, &socket);
        if (ret < 0)
                goto error_1;

        socket->sk->sk_allocation = GFP_NOFS;

        /* bind the callback manager's address to make this a server socket */
        memset(&srx, 0, sizeof(srx));
        srx.srx_family                  = AF_RXRPC;
        srx.srx_service                 = CM_SERVICE;
        srx.transport_type              = SOCK_DGRAM;
        srx.transport_len               = sizeof(srx.transport.sin6);
        srx.transport.sin6.sin6_family  = AF_INET6;
        srx.transport.sin6.sin6_port    = htons(AFS_CM_PORT);

        ret = rxrpc_sock_set_min_security_level(socket->sk,
                                                RXRPC_SECURITY_ENCRYPT);
        if (ret < 0)
                goto error_2;

        ret = kernel_bind(socket, (struct sockaddr *) &srx, sizeof(srx));
        if (ret == -EADDRINUSE) {
                srx.transport.sin6.sin6_port = 0;
                ret = kernel_bind(socket, (struct sockaddr *) &srx, sizeof(srx));
        }
        if (ret < 0)
                goto error_2;

        srx.srx_service = YFS_CM_SERVICE;
        ret = kernel_bind(socket, (struct sockaddr *) &srx, sizeof(srx));
        if (ret < 0)
                goto error_2;

        /* Ideally, we'd turn on service upgrade here, but we can't because
         * OpenAFS is buggy and leaks the userStatus field from packet to
         * packet and between FS packets and CB packets - so if we try to do an
         * upgrade on an FS packet, OpenAFS will leak that into the CB packet
         * it sends back to us.
         */

        rxrpc_kernel_new_call_notification(socket, afs_rx_new_call,
                                           afs_rx_discard_new_call);

        ret = kernel_listen(socket, INT_MAX);
        if (ret < 0)
                goto error_2;

        net->socket = socket;
        afs_charge_preallocation(&net->charge_preallocation_work);
        _leave(" = 0");
        return 0;

error_2:
        sock_release(socket);
error_1:
        _leave(" = %d", ret);
        return ret;
}

/*
 * close the RxRPC socket AFS was using
 */
void afs_close_socket(struct afs_net *net)
{
        _enter("");

        kernel_listen(net->socket, 0);
        flush_workqueue(afs_async_calls);

        if (net->spare_incoming_call) {
                afs_put_call(net->spare_incoming_call);
                net->spare_incoming_call = NULL;
        }

        _debug("outstanding %u", atomic_read(&net->nr_outstanding_calls));
        wait_var_event(&net->nr_outstanding_calls,
                       !atomic_read(&net->nr_outstanding_calls));
        _debug("no outstanding calls");

        kernel_sock_shutdown(net->socket, SHUT_RDWR);
        flush_workqueue(afs_async_calls);
        sock_release(net->socket);

        _debug("dework");
        _leave("");
}

/*
 * Allocate a call.
 */
static struct afs_call *afs_alloc_call(struct afs_net *net,
                                       const struct afs_call_type *type,
                                       gfp_t gfp)
{
        struct afs_call *call;
        int o;

        call = kzalloc(sizeof(*call), gfp);
        if (!call)
                return NULL;

        call->type = type;
        call->net = net;
        call->debug_id = atomic_inc_return(&rxrpc_debug_id);
        atomic_set(&call->usage, 1);
        INIT_WORK(&call->async_work, afs_process_async_call);
        init_waitqueue_head(&call->waitq);
        spin_lock_init(&call->state_lock);
        call->iter = &call->def_iter;

        o = atomic_inc_return(&net->nr_outstanding_calls);
        trace_afs_call(call, afs_call_trace_alloc, 1, o,
                       __builtin_return_address(0));
        return call;
}

/*
 * Dispose of a reference on a call.
 */
void afs_put_call(struct afs_call *call)
{
        struct afs_net *net = call->net;
        int n = atomic_dec_return(&call->usage);
        int o = atomic_read(&net->nr_outstanding_calls);

        trace_afs_call(call, afs_call_trace_put, n, o,
                       __builtin_return_address(0));

        ASSERTCMP(n, >=, 0);
        if (n == 0) {
                ASSERT(!work_pending(&call->async_work));
                ASSERT(call->type->name != NULL);

                if (call->rxcall) {
                        rxrpc_kernel_end_call(net->socket, call->rxcall);
                        call->rxcall = NULL;
                }
                if (call->type->destructor)
                        call->type->destructor(call);

                afs_unuse_server_notime(call->net, call->server, afs_server_trace_put_call);
                afs_put_addrlist(call->alist);
                kfree(call->request);

                trace_afs_call(call, afs_call_trace_free, 0, o,
                               __builtin_return_address(0));
                kfree(call);

                o = atomic_dec_return(&net->nr_outstanding_calls);
                if (o == 0)
                        wake_up_var(&net->nr_outstanding_calls);
        }
}

static struct afs_call *afs_get_call(struct afs_call *call,
                                     enum afs_call_trace why)
{
        int u = atomic_inc_return(&call->usage);

        trace_afs_call(call, why, u,
                       atomic_read(&call->net->nr_outstanding_calls),
                       __builtin_return_address(0));
        return call;
}

/*
 * Queue the call for actual work.
 */
static void afs_queue_call_work(struct afs_call *call)
{
        if (call->type->work) {
                INIT_WORK(&call->work, call->type->work);

                afs_get_call(call, afs_call_trace_work);
                if (!queue_work(afs_wq, &call->work))
                        afs_put_call(call);
        }
}

/*
 * allocate a call with flat request and reply buffers
 */
struct afs_call *afs_alloc_flat_call(struct afs_net *net,
                                     const struct afs_call_type *type,
                                     size_t request_size, size_t reply_max)
{
        struct afs_call *call;

        call = afs_alloc_call(net, type, GFP_NOFS);
        if (!call)
                goto nomem_call;

        if (request_size) {
                call->request_size = request_size;
                call->request = kmalloc(request_size, GFP_NOFS);
                if (!call->request)
                        goto nomem_free;
        }

        if (reply_max) {
                call->reply_max = reply_max;
                call->buffer = kmalloc(reply_max, GFP_NOFS);
                if (!call->buffer)
                        goto nomem_free;
        }

        afs_extract_to_buf(call, call->reply_max);
        call->operation_ID = type->op;
        init_waitqueue_head(&call->waitq);
        return call;

nomem_free:
        afs_put_call(call);
nomem_call:
        return NULL;
}

/*
 * clean up a call with flat buffer
 */
void afs_flat_call_destructor(struct afs_call *call)
{
        _enter("");

        kfree(call->request);
        call->request = NULL;
        kfree(call->buffer);
        call->buffer = NULL;
}

#define AFS_BVEC_MAX 8

/*
 * Load the given bvec with the next few pages.
 */
static void afs_load_bvec(struct afs_call *call, struct msghdr *msg,
                          struct bio_vec *bv, pgoff_t first, pgoff_t last,
                          unsigned offset)
{
        struct afs_operation *op = call->op;
        struct page *pages[AFS_BVEC_MAX];
        unsigned int nr, n, i, to, bytes = 0;

        nr = min_t(pgoff_t, last - first + 1, AFS_BVEC_MAX);
        n = find_get_pages_contig(op->store.mapping, first, nr, pages);
        ASSERTCMP(n, ==, nr);

        msg->msg_flags |= MSG_MORE;
        for (i = 0; i < nr; i++) {
                to = PAGE_SIZE;
                if (first + i >= last) {
                        to = op->store.last_to;
                        msg->msg_flags &= ~MSG_MORE;
                }
                bv[i].bv_page = pages[i];
                bv[i].bv_len = to - offset;
                bv[i].bv_offset = offset;
                bytes += to - offset;
                offset = 0;
        }

        iov_iter_bvec(&msg->msg_iter, WRITE, bv, nr, bytes);
}

/*
 * Advance the AFS call state when the RxRPC call ends the transmit phase.
 */
static void afs_notify_end_request_tx(struct sock *sock,
                                      struct rxrpc_call *rxcall,
                                      unsigned long call_user_ID)
{
        struct afs_call *call = (struct afs_call *)call_user_ID;

        afs_set_call_state(call, AFS_CALL_CL_REQUESTING, AFS_CALL_CL_AWAIT_REPLY);
}

/*
 * attach the data from a bunch of pages on an inode to a call
 */
static int afs_send_pages(struct afs_call *call, struct msghdr *msg)
{
        struct afs_operation *op = call->op;
        struct bio_vec bv[AFS_BVEC_MAX];
        unsigned int bytes, nr, loop, offset;
        pgoff_t first = op->store.first, last = op->store.last;
        int ret;

        offset = op->store.first_offset;
        op->store.first_offset = 0;

        do {
                afs_load_bvec(call, msg, bv, first, last, offset);
                trace_afs_send_pages(call, msg, first, last, offset);

                offset = 0;
                bytes = msg->msg_iter.count;
                nr = msg->msg_iter.nr_segs;

                ret = rxrpc_kernel_send_data(op->net->socket, call->rxcall, msg,
                                             bytes, afs_notify_end_request_tx);
                for (loop = 0; loop < nr; loop++)
                        put_page(bv[loop].bv_page);
                if (ret < 0)
                        break;

                first += nr;
        } while (first <= last);

        trace_afs_sent_pages(call, op->store.first, last, first, ret);
        return ret;
}

/*
 * Initiate a call and synchronously queue up the parameters for dispatch.  Any
 * error is stored into the call struct, which the caller must check for.
 */
void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
{
        struct sockaddr_rxrpc *srx = &ac->alist->addrs[ac->index];
        struct rxrpc_call *rxcall;
        struct msghdr msg;
        struct kvec iov[1];
        s64 tx_total_len;
        int ret;

        _enter(",{%pISp},", &srx->transport);

        ASSERT(call->type != NULL);
        ASSERT(call->type->name != NULL);

        _debug("____MAKE %p{%s,%x} [%d]____",
               call, call->type->name, key_serial(call->key),
               atomic_read(&call->net->nr_outstanding_calls));

        call->addr_ix = ac->index;
        call->alist = afs_get_addrlist(ac->alist);

        /* Work out the length we're going to transmit.  This is awkward for
         * calls such as FS.StoreData where there's an extra injection of data
         * after the initial fixed part.
         */
        tx_total_len = call->request_size;
        if (call->send_pages) {
                struct afs_operation *op = call->op;

                if (op->store.last == op->store.first) {
                        tx_total_len += op->store.last_to - op->store.first_offset;
                } else {
                        /* It looks mathematically like you should be able to
                         * combine the following lines with the ones above, but
                         * unsigned arithmetic is fun when it wraps...
                         */
                        tx_total_len += PAGE_SIZE - op->store.first_offset;
                        tx_total_len += op->store.last_to;
                        tx_total_len += (op->store.last - op->store.first - 1) * PAGE_SIZE;
                }
        }

        /* If the call is going to be asynchronous, we need an extra ref for
         * the call to hold itself so the caller need not hang on to its ref.
         */
        if (call->async) {
                afs_get_call(call, afs_call_trace_get);
                call->drop_ref = true;
        }

        /* create a call */
        rxcall = rxrpc_kernel_begin_call(call->net->socket, srx, call->key,
                                         (unsigned long)call,
                                         tx_total_len, gfp,
                                         (call->async ?
                                          afs_wake_up_async_call :
                                          afs_wake_up_call_waiter),
                                         call->upgrade,
                                         (call->intr ? RXRPC_PREINTERRUPTIBLE :
                                          RXRPC_UNINTERRUPTIBLE),
                                         call->debug_id);
        if (IS_ERR(rxcall)) {
                ret = PTR_ERR(rxcall);
                call->error = ret;
                goto error_kill_call;
        }

        call->rxcall = rxcall;

        if (call->max_lifespan)
                rxrpc_kernel_set_max_life(call->net->socket, rxcall,
                                          call->max_lifespan);

        /* send the request */
        iov[0].iov_base = call->request;
        iov[0].iov_len  = call->request_size;

        msg.msg_name            = NULL;
        msg.msg_namelen         = 0;
        iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, call->request_size);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = MSG_WAITALL | (call->send_pages ? MSG_MORE : 0);

        ret = rxrpc_kernel_send_data(call->net->socket, rxcall,
                                     &msg, call->request_size,
                                     afs_notify_end_request_tx);
        if (ret < 0)
                goto error_do_abort;

        if (call->send_pages) {
                ret = afs_send_pages(call, &msg);
                if (ret < 0)
                        goto error_do_abort;
        }

        /* Note that at this point, we may have received the reply or an abort
         * - and an asynchronous call may already have completed.
         *
         * afs_wait_for_call_to_complete(call, ac)
         * must be called to synchronously clean up.
         */
        return;

error_do_abort:
        if (ret != -ECONNABORTED) {
                rxrpc_kernel_abort_call(call->net->socket, rxcall,
                                        RX_USER_ABORT, ret, "KSD");
        } else {
                iov_iter_kvec(&msg.msg_iter, READ, NULL, 0, 0);
                rxrpc_kernel_recv_data(call->net->socket, rxcall,
                                       &msg.msg_iter, false,
                                       &call->abort_code, &call->service_id);
                ac->abort_code = call->abort_code;
                ac->responded = true;
        }
        call->error = ret;
        trace_afs_call_done(call);
error_kill_call:
        if (call->type->done)
                call->type->done(call);

        /* We need to dispose of the extra ref we grabbed for an async call.
         * The call, however, might be queued on afs_async_calls and we need to
         * make sure we don't get any more notifications that might requeue it.
         */
        if (call->rxcall) {
                rxrpc_kernel_end_call(call->net->socket, call->rxcall);
                call->rxcall = NULL;
        }
        if (call->async) {
                if (cancel_work_sync(&call->async_work))
                        afs_put_call(call);
                afs_put_call(call);
        }

        ac->error = ret;
        call->state = AFS_CALL_COMPLETE;
        _leave(" = %d", ret);
}

/*
 * deliver messages to a call
 */
static void afs_deliver_to_call(struct afs_call *call)
{
        enum afs_call_state state;
        u32 abort_code, remote_abort = 0;
        int ret;

        _enter("%s", call->type->name);

        while (state = READ_ONCE(call->state),
               state == AFS_CALL_CL_AWAIT_REPLY ||
               state == AFS_CALL_SV_AWAIT_OP_ID ||
               state == AFS_CALL_SV_AWAIT_REQUEST ||
               state == AFS_CALL_SV_AWAIT_ACK
               ) {
                if (state == AFS_CALL_SV_AWAIT_ACK) {
                        iov_iter_kvec(&call->def_iter, READ, NULL, 0, 0);
                        ret = rxrpc_kernel_recv_data(call->net->socket,
                                                     call->rxcall, &call->def_iter,
                                                     false, &remote_abort,
                                                     &call->service_id);
                        trace_afs_receive_data(call, &call->def_iter, false, ret);

                        if (ret == -EINPROGRESS || ret == -EAGAIN)
                                return;
                        if (ret < 0 || ret == 1) {
                                if (ret == 1)
                                        ret = 0;
                                goto call_complete;
                        }
                        return;
                }

                if (!call->have_reply_time &&
                    rxrpc_kernel_get_reply_time(call->net->socket,
                                                call->rxcall,
                                                &call->reply_time))
                        call->have_reply_time = true;

                ret = call->type->deliver(call);
                state = READ_ONCE(call->state);
                if (ret == 0 && call->unmarshalling_error)
                        ret = -EBADMSG;
                switch (ret) {
                case 0:
                        afs_queue_call_work(call);
                        if (state == AFS_CALL_CL_PROC_REPLY) {
                                if (call->op)
                                        set_bit(AFS_SERVER_FL_MAY_HAVE_CB,
                                                &call->op->server->flags);
                                goto call_complete;
                        }
                        ASSERTCMP(state, >, AFS_CALL_CL_PROC_REPLY);
                        goto done;
                case -EINPROGRESS:
                case -EAGAIN:
                        goto out;
                case -ECONNABORTED:
                        ASSERTCMP(state, ==, AFS_CALL_COMPLETE);
                        goto done;
                case -ENOTSUPP:
                        abort_code = RXGEN_OPCODE;
                        rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
                                                abort_code, ret, "KIV");
                        goto local_abort;
                case -EIO:
                        pr_err("kAFS: Call %u in bad state %u\n",
                               call->debug_id, state);
                        fallthrough;
                case -ENODATA:
                case -EBADMSG:
                case -EMSGSIZE:
                        abort_code = RXGEN_CC_UNMARSHAL;
                        if (state != AFS_CALL_CL_AWAIT_REPLY)
                                abort_code = RXGEN_SS_UNMARSHAL;
                        rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
                                                abort_code, ret, "KUM");
                        goto local_abort;
                default:
                        abort_code = RX_USER_ABORT;
                        rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
                                                abort_code, ret, "KER");
                        goto local_abort;
                }
        }

done:
        if (call->type->done)
                call->type->done(call);
out:
        _leave("");
        return;

local_abort:
        abort_code = 0;
call_complete:
        afs_set_call_complete(call, ret, remote_abort);
        state = AFS_CALL_COMPLETE;
        goto done;
}

/*
 * Wait synchronously for a call to complete and clean up the call struct.
 */
long afs_wait_for_call_to_complete(struct afs_call *call,
                                   struct afs_addr_cursor *ac)
{
        long ret;
        bool rxrpc_complete = false;

        DECLARE_WAITQUEUE(myself, current);

        _enter("");

        ret = call->error;
        if (ret < 0)
                goto out;

        add_wait_queue(&call->waitq, &myself);
        for (;;) {
                set_current_state(TASK_UNINTERRUPTIBLE);

                /* deliver any messages that are in the queue */
                if (!afs_check_call_state(call, AFS_CALL_COMPLETE) &&
                    call->need_attention) {
                        call->need_attention = false;
                        __set_current_state(TASK_RUNNING);
                        afs_deliver_to_call(call);
                        continue;
                }

                if (afs_check_call_state(call, AFS_CALL_COMPLETE))
                        break;

                if (!rxrpc_kernel_check_life(call->net->socket, call->rxcall)) {
                        /* rxrpc terminated the call. */
                        rxrpc_complete = true;
                        break;
                }

                schedule();
        }

        remove_wait_queue(&call->waitq, &myself);
        __set_current_state(TASK_RUNNING);

        if (!afs_check_call_state(call, AFS_CALL_COMPLETE)) {
                if (rxrpc_complete) {
                        afs_set_call_complete(call, call->error, call->abort_code);
                } else {
                        /* Kill off the call if it's still live. */
                        _debug("call interrupted");
                        if (rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
                                                    RX_USER_ABORT, -EINTR, "KWI"))
                                afs_set_call_complete(call, -EINTR, 0);
                }
        }

        spin_lock_bh(&call->state_lock);
        ac->abort_code = call->abort_code;
        ac->error = call->error;
        spin_unlock_bh(&call->state_lock);

        ret = ac->error;
        switch (ret) {
        case 0:
                ret = call->ret0;
                call->ret0 = 0;

                fallthrough;
        case -ECONNABORTED:
                ac->responded = true;
                break;
        }

out:
        _debug("call complete");
        afs_put_call(call);
        _leave(" = %p", (void *)ret);
        return ret;
}

/*
 * wake up a waiting call
 */
static void afs_wake_up_call_waiter(struct sock *sk, struct rxrpc_call *rxcall,
                                    unsigned long call_user_ID)
{
        struct afs_call *call = (struct afs_call *)call_user_ID;

        call->need_attention = true;
        wake_up(&call->waitq);
}

/*
 * wake up an asynchronous call
 */
static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall,
                                   unsigned long call_user_ID)
{
        struct afs_call *call = (struct afs_call *)call_user_ID;
        int u;

        trace_afs_notify_call(rxcall, call);
        call->need_attention = true;

        u = atomic_fetch_add_unless(&call->usage, 1, 0);
        if (u != 0) {
                trace_afs_call(call, afs_call_trace_wake, u + 1,
                               atomic_read(&call->net->nr_outstanding_calls),
                               __builtin_return_address(0));

                if (!queue_work(afs_async_calls, &call->async_work))
                        afs_put_call(call);
        }
}

/*
 * Perform I/O processing on an asynchronous call.  The work item carries a ref
 * to the call struct that we either need to release or to pass on.
 */
static void afs_process_async_call(struct work_struct *work)
{
        struct afs_call *call = container_of(work, struct afs_call, async_work);

        _enter("");

        if (call->state < AFS_CALL_COMPLETE && call->need_attention) {
                call->need_attention = false;
                afs_deliver_to_call(call);
        }

        afs_put_call(call);
        _leave("");
}

static void afs_rx_attach(struct rxrpc_call *rxcall, unsigned long user_call_ID)
{
        struct afs_call *call = (struct afs_call *)user_call_ID;

        call->rxcall = rxcall;
}

/*
 * Charge the incoming call preallocation.
 */
void afs_charge_preallocation(struct work_struct *work)
{
        struct afs_net *net =
                container_of(work, struct afs_net, charge_preallocation_work);
        struct afs_call *call = net->spare_incoming_call;

        for (;;) {
                if (!call) {
                        call = afs_alloc_call(net, &afs_RXCMxxxx, GFP_KERNEL);
                        if (!call)
                                break;

                        call->drop_ref = true;
                        call->async = true;
                        call->state = AFS_CALL_SV_AWAIT_OP_ID;
                        init_waitqueue_head(&call->waitq);
                        afs_extract_to_tmp(call);
                }

                if (rxrpc_kernel_charge_accept(net->socket,
                                               afs_wake_up_async_call,
                                               afs_rx_attach,
                                               (unsigned long)call,
                                               GFP_KERNEL,
                                               call->debug_id) < 0)
                        break;
                call = NULL;
        }
        net->spare_incoming_call = call;
}

/*
 * Discard a preallocated call when a socket is shut down.
 */
static void afs_rx_discard_new_call(struct rxrpc_call *rxcall,
                                    unsigned long user_call_ID)
{
        struct afs_call *call = (struct afs_call *)user_call_ID;

        call->rxcall = NULL;
        afs_put_call(call);
}

/*
 * Notification of an incoming call.
 */
static void afs_rx_new_call(struct sock *sk, struct rxrpc_call *rxcall,
                            unsigned long user_call_ID)
{
        struct afs_net *net = afs_sock2net(sk);

        queue_work(afs_wq, &net->charge_preallocation_work);
}

/*
 * Grab the operation ID from an incoming cache manager call.  The socket
 * buffer is discarded on error or if we don't yet have sufficient data.
 */
static int afs_deliver_cm_op_id(struct afs_call *call)
{
        int ret;

        _enter("{%zu}", iov_iter_count(call->iter));

        /* the operation ID forms the first four bytes of the request data */
        ret = afs_extract_data(call, true);
        if (ret < 0)
                return ret;

        call->operation_ID = ntohl(call->tmp);
        afs_set_call_state(call, AFS_CALL_SV_AWAIT_OP_ID, AFS_CALL_SV_AWAIT_REQUEST);

        /* ask the cache manager to route the call (it'll change the call type
         * if successful) */
        if (!afs_cm_incoming_call(call))
                return -ENOTSUPP;

        trace_afs_cb_call(call);

        /* pass responsibility for the remainer of this message off to the
         * cache manager op */
        return call->type->deliver(call);
}

/*
 * Advance the AFS call state when an RxRPC service call ends the transmit
 * phase.
 */
static void afs_notify_end_reply_tx(struct sock *sock,
                                    struct rxrpc_call *rxcall,
                                    unsigned long call_user_ID)
{
        struct afs_call *call = (struct afs_call *)call_user_ID;

        afs_set_call_state(call, AFS_CALL_SV_REPLYING, AFS_CALL_SV_AWAIT_ACK);
}

/*
 * send an empty reply
 */
void afs_send_empty_reply(struct afs_call *call)
{
        struct afs_net *net = call->net;
        struct msghdr msg;

        _enter("");

        rxrpc_kernel_set_tx_length(net->socket, call->rxcall, 0);

        msg.msg_name            = NULL;
        msg.msg_namelen         = 0;
        iov_iter_kvec(&msg.msg_iter, WRITE, NULL, 0, 0);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = 0;

        switch (rxrpc_kernel_send_data(net->socket, call->rxcall, &msg, 0,
                                       afs_notify_end_reply_tx)) {
        case 0:
                _leave(" [replied]");
                return;

        case -ENOMEM:
                _debug("oom");
                rxrpc_kernel_abort_call(net->socket, call->rxcall,
                                        RX_USER_ABORT, -ENOMEM, "KOO");
                fallthrough;
        default:
                _leave(" [error]");
                return;
        }
}

/*
 * send a simple reply
 */
void afs_send_simple_reply(struct afs_call *call, const void *buf, size_t len)
{
        struct afs_net *net = call->net;
        struct msghdr msg;
        struct kvec iov[1];
        int n;

        _enter("");

        rxrpc_kernel_set_tx_length(net->socket, call->rxcall, len);

        iov[0].iov_base         = (void *) buf;
        iov[0].iov_len          = len;
        msg.msg_name            = NULL;
        msg.msg_namelen         = 0;
        iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, len);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = 0;

        n = rxrpc_kernel_send_data(net->socket, call->rxcall, &msg, len,
                                   afs_notify_end_reply_tx);
        if (n >= 0) {
                /* Success */
                _leave(" [replied]");
                return;
        }

        if (n == -ENOMEM) {
                _debug("oom");
                rxrpc_kernel_abort_call(net->socket, call->rxcall,
                                        RX_USER_ABORT, -ENOMEM, "KOO");
        }
        _leave(" [error]");
}

/*
 * Extract a piece of data from the received data socket buffers.
 */
int afs_extract_data(struct afs_call *call, bool want_more)
{
        struct afs_net *net = call->net;
        struct iov_iter *iter = call->iter;
        enum afs_call_state state;
        u32 remote_abort = 0;
        int ret;

        _enter("{%s,%zu},%d", call->type->name, iov_iter_count(iter), want_more);

        ret = rxrpc_kernel_recv_data(net->socket, call->rxcall, iter,
                                     want_more, &remote_abort,
                                     &call->service_id);
        if (ret == 0 || ret == -EAGAIN)
                return ret;

        state = READ_ONCE(call->state);
        if (ret == 1) {
                switch (state) {
                case AFS_CALL_CL_AWAIT_REPLY:
                        afs_set_call_state(call, state, AFS_CALL_CL_PROC_REPLY);
                        break;
                case AFS_CALL_SV_AWAIT_REQUEST:
                        afs_set_call_state(call, state, AFS_CALL_SV_REPLYING);
                        break;
                case AFS_CALL_COMPLETE:
                        kdebug("prem complete %d", call->error);
                        return afs_io_error(call, afs_io_error_extract);
                default:
                        break;
                }
                return 0;
        }

        afs_set_call_complete(call, ret, remote_abort);
        return ret;
}

/*
 * Log protocol error production.
 */
noinline int afs_protocol_error(struct afs_call *call,
                                enum afs_eproto_cause cause)
{
        trace_afs_protocol_error(call, cause);
        if (call)
                call->unmarshalling_error = true;
        return -EBADMSG;
}