/* 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)
 *
 * 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.
 */

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

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

struct socket *afs_socket; /* my RxRPC socket */
static struct workqueue_struct *afs_async_calls;
static struct afs_call *afs_spare_incoming_call;
atomic_t afs_outstanding_calls;

static void afs_wake_up_call_waiter(struct sock *, struct rxrpc_call *, unsigned long);
static int afs_wait_for_call_to_complete(struct afs_call *);
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,
        .abort_to_error = afs_abort_to_error,
};

static void afs_charge_preallocation(struct work_struct *);

static DECLARE_WORK(afs_charge_preallocation_work, afs_charge_preallocation);

static int afs_wait_atomic_t(atomic_t *p)
{
        schedule();
        return 0;
}

/*
 * 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(void)
{
        struct sockaddr_rxrpc srx;
        struct socket *socket;
        int ret;

        _enter("");

        ret = -ENOMEM;
        afs_async_calls = alloc_workqueue("kafsd", WQ_MEM_RECLAIM, 0);
        if (!afs_async_calls)
                goto error_0;

        ret = sock_create_kern(&init_net, AF_RXRPC, SOCK_DGRAM, PF_INET, &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 */
        srx.srx_family                  = AF_RXRPC;
        srx.srx_service                 = CM_SERVICE;
        srx.transport_type              = SOCK_DGRAM;
        srx.transport_len               = sizeof(srx.transport.sin);
        srx.transport.sin.sin_family    = AF_INET;
        srx.transport.sin.sin_port      = htons(AFS_CM_PORT);
        memset(&srx.transport.sin.sin_addr, 0,
               sizeof(srx.transport.sin.sin_addr));

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

        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;

        afs_socket = socket;
        afs_charge_preallocation(NULL);
        _leave(" = 0");
        return 0;

error_2:
        sock_release(socket);
error_1:
        destroy_workqueue(afs_async_calls);
error_0:
        _leave(" = %d", ret);
        return ret;
}

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

        kernel_listen(afs_socket, 0);
        flush_workqueue(afs_async_calls);

        if (afs_spare_incoming_call) {
                afs_put_call(afs_spare_incoming_call);
                afs_spare_incoming_call = NULL;
        }

        _debug("outstanding %u", atomic_read(&afs_outstanding_calls));
        wait_on_atomic_t(&afs_outstanding_calls, afs_wait_atomic_t,
                         TASK_UNINTERRUPTIBLE);
        _debug("no outstanding calls");

        kernel_sock_shutdown(afs_socket, SHUT_RDWR);
        flush_workqueue(afs_async_calls);
        sock_release(afs_socket);

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

/*
 * Allocate a call.
 */
static struct afs_call *afs_alloc_call(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;
        atomic_set(&call->usage, 1);
        INIT_WORK(&call->async_work, afs_process_async_call);
        init_waitqueue_head(&call->waitq);

        o = atomic_inc_return(&afs_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)
{
        int n = atomic_dec_return(&call->usage);
        int o = atomic_read(&afs_outstanding_calls);

        trace_afs_call(call, afs_call_trace_put, n + 1, 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(afs_socket, call->rxcall);
                        call->rxcall = NULL;
                }
                if (call->type->destructor)
                        call->type->destructor(call);

                kfree(call->request);
                kfree(call);

                o = atomic_dec_return(&afs_outstanding_calls);
                trace_afs_call(call, afs_call_trace_free, 0, o,
                               __builtin_return_address(0));
                if (o == 0)
                        wake_up_atomic_t(&afs_outstanding_calls);
        }
}

/*
 * Queue the call for actual work.  Returns 0 unconditionally for convenience.
 */
int afs_queue_call_work(struct afs_call *call)
{
        int u = atomic_inc_return(&call->usage);

        trace_afs_call(call, afs_call_trace_work, u,
                       atomic_read(&afs_outstanding_calls),
                       __builtin_return_address(0));

        INIT_WORK(&call->work, call->type->work);

        if (!queue_work(afs_wq, &call->work))
                afs_put_call(call);
        return 0;
}

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

        call = afs_alloc_call(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;
        }

        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 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(call->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 = call->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 | ITER_BVEC, bv, nr, bytes);
}

/*
 * 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 bio_vec bv[AFS_BVEC_MAX];
        unsigned int bytes, nr, loop, offset;
        pgoff_t first = call->first, last = call->last;
        int ret;

        offset = call->first_offset;
        call->first_offset = 0;

        do {
                afs_load_bvec(call, msg, bv, first, last, offset);
                offset = 0;
                bytes = msg->msg_iter.count;
                nr = msg->msg_iter.nr_segs;

                /* Have to change the state *before* sending the last
                 * packet as RxRPC might give us the reply before it
                 * returns from sending the request.
                 */
                if (first + nr - 1 >= last)
                        call->state = AFS_CALL_AWAIT_REPLY;
                ret = rxrpc_kernel_send_data(afs_socket, call->rxcall,
                                             msg, bytes);
                for (loop = 0; loop < nr; loop++)
                        put_page(bv[loop].bv_page);
                if (ret < 0)
                        break;

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

        return ret;
}

/*
 * initiate a call
 */
int afs_make_call(struct in_addr *addr, struct afs_call *call, gfp_t gfp,
                  bool async)
{
        struct sockaddr_rxrpc srx;
        struct rxrpc_call *rxcall;
        struct msghdr msg;
        struct kvec iov[1];
        size_t offset;
        u32 abort_code;
        int ret;

        _enter("%x,{%d},", addr->s_addr, ntohs(call->port));

        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(&afs_outstanding_calls));

        call->async = async;

        memset(&srx, 0, sizeof(srx));
        srx.srx_family = AF_RXRPC;
        srx.srx_service = call->service_id;
        srx.transport_type = SOCK_DGRAM;
        srx.transport_len = sizeof(srx.transport.sin);
        srx.transport.sin.sin_family = AF_INET;
        srx.transport.sin.sin_port = call->port;
        memcpy(&srx.transport.sin.sin_addr, addr, 4);

        /* create a call */
        rxcall = rxrpc_kernel_begin_call(afs_socket, &srx, call->key,
                                         (unsigned long) call, gfp,
                                         (async ?
                                          afs_wake_up_async_call :
                                          afs_wake_up_call_waiter));
        call->key = NULL;
        if (IS_ERR(rxcall)) {
                ret = PTR_ERR(rxcall);
                goto error_kill_call;
        }

        call->rxcall = rxcall;

        /* 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 | ITER_KVEC, iov, 1,
                      call->request_size);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = (call->send_pages ? MSG_MORE : 0);

        /* We have to change the state *before* sending the last packet as
         * rxrpc might give us the reply before it returns from sending the
         * request.  Further, if the send fails, we may already have been given
         * a notification and may have collected it.
         */
        if (!call->send_pages)
                call->state = AFS_CALL_AWAIT_REPLY;
        ret = rxrpc_kernel_send_data(afs_socket, rxcall,
                                     &msg, call->request_size);
        if (ret < 0)
                goto error_do_abort;

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

        /* at this point, an async call may no longer exist as it may have
         * already completed */
        if (call->async)
                return -EINPROGRESS;

        return afs_wait_for_call_to_complete(call);

error_do_abort:
        call->state = AFS_CALL_COMPLETE;
        if (ret != -ECONNABORTED) {
                rxrpc_kernel_abort_call(afs_socket, rxcall, RX_USER_ABORT,
                                        ret, "KSD");
        } else {
                abort_code = 0;
                offset = 0;
                rxrpc_kernel_recv_data(afs_socket, rxcall, NULL, 0, &offset,
                                       false, &abort_code);
                ret = call->type->abort_to_error(abort_code);
        }
error_kill_call:
        afs_put_call(call);
        _leave(" = %d", ret);
        return ret;
}

/*
 * deliver messages to a call
 */
static void afs_deliver_to_call(struct afs_call *call)
{
        u32 abort_code;
        int ret;

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

        while (call->state == AFS_CALL_AWAIT_REPLY ||
               call->state == AFS_CALL_AWAIT_OP_ID ||
               call->state == AFS_CALL_AWAIT_REQUEST ||
               call->state == AFS_CALL_AWAIT_ACK
               ) {
                if (call->state == AFS_CALL_AWAIT_ACK) {
                        size_t offset = 0;
                        ret = rxrpc_kernel_recv_data(afs_socket, call->rxcall,
                                                     NULL, 0, &offset, false,
                                                     &call->abort_code);
                        trace_afs_recv_data(call, 0, offset, false, ret);

                        if (ret == -EINPROGRESS || ret == -EAGAIN)
                                return;
                        if (ret == 1 || ret < 0) {
                                call->state = AFS_CALL_COMPLETE;
                                goto done;
                        }
                        return;
                }

                ret = call->type->deliver(call);
                switch (ret) {
                case 0:
                        if (call->state == AFS_CALL_AWAIT_REPLY)
                                call->state = AFS_CALL_COMPLETE;
                        goto done;
                case -EINPROGRESS:
                case -EAGAIN:
                        goto out;
                case -ECONNABORTED:
                        goto call_complete;
                case -ENOTCONN:
                        abort_code = RX_CALL_DEAD;
                        rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                                abort_code, ret, "KNC");
                        goto save_error;
                case -ENOTSUPP:
                        abort_code = RXGEN_OPCODE;
                        rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                                abort_code, ret, "KIV");
                        goto save_error;
                case -ENODATA:
                case -EBADMSG:
                case -EMSGSIZE:
                default:
                        abort_code = RXGEN_CC_UNMARSHAL;
                        if (call->state != AFS_CALL_AWAIT_REPLY)
                                abort_code = RXGEN_SS_UNMARSHAL;
                        rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                                abort_code, -EBADMSG, "KUM");
                        goto save_error;
                }
        }

done:
        if (call->state == AFS_CALL_COMPLETE && call->incoming)
                afs_put_call(call);
out:
        _leave("");
        return;

save_error:
        call->error = ret;
call_complete:
        call->state = AFS_CALL_COMPLETE;
        goto done;
}

/*
 * wait synchronously for a call to complete
 */
static int afs_wait_for_call_to_complete(struct afs_call *call)
{
        int ret;

        DECLARE_WAITQUEUE(myself, current);

        _enter("");

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

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

                if (call->state == AFS_CALL_COMPLETE ||
                    signal_pending(current))
                        break;
                schedule();
        }

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

        /* Kill off the call if it's still live. */
        if (call->state < AFS_CALL_COMPLETE) {
                _debug("call interrupted");
                rxrpc_kernel_abort_call(afs_socket, call->rxcall,
                                        RX_USER_ABORT, -EINTR, "KWI");
        }

        ret = call->error;
        _debug("call complete");
        afs_put_call(call);
        _leave(" = %d", 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_add_unless(&call->usage, 1, 0);
        if (u != 0) {
                trace_afs_call(call, afs_call_trace_wake, u,
                               atomic_read(&afs_outstanding_calls),
                               __builtin_return_address(0));

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

/*
 * Delete an asynchronous call.  The work item carries a ref to the call struct
 * that we need to release.
 */
static void afs_delete_async_call(struct work_struct *work)
{
        struct afs_call *call = container_of(work, struct afs_call, async_work);

        _enter("");

        afs_put_call(call);

        _leave("");
}

/*
 * 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);
        }

        if (call->state == AFS_CALL_COMPLETE) {
                call->reply = NULL;

                /* We have two refs to release - one from the alloc and one
                 * queued with the work item - and we can't just deallocate the
                 * call because the work item may be queued again.
                 */
                call->async_work.func = afs_delete_async_call;
                if (!queue_work(afs_async_calls, &call->async_work))
                        afs_put_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.
 */
static void afs_charge_preallocation(struct work_struct *work)
{
        struct afs_call *call = afs_spare_incoming_call;

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

                        call->async = true;
                        call->state = AFS_CALL_AWAIT_OP_ID;
                        init_waitqueue_head(&call->waitq);
                }

                if (rxrpc_kernel_charge_accept(afs_socket,
                                               afs_wake_up_async_call,
                                               afs_rx_attach,
                                               (unsigned long)call,
                                               GFP_KERNEL) < 0)
                        break;
                call = NULL;
        }
        afs_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)
{
        queue_work(afs_wq, &afs_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}", call->offset);

        ASSERTCMP(call->offset, <, 4);

        /* the operation ID forms the first four bytes of the request data */
        ret = afs_extract_data(call, &call->tmp, 4, true);
        if (ret < 0)
                return ret;

        call->operation_ID = ntohl(call->tmp);
        call->state = AFS_CALL_AWAIT_REQUEST;
        call->offset = 0;

        /* 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);
}

/*
 * send an empty reply
 */
void afs_send_empty_reply(struct afs_call *call)
{
        struct msghdr msg;

        _enter("");

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

        call->state = AFS_CALL_AWAIT_ACK;
        switch (rxrpc_kernel_send_data(afs_socket, call->rxcall, &msg, 0)) {
        case 0:
                _leave(" [replied]");
                return;

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

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

        _enter("");

        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 | ITER_KVEC, iov, 1, len);
        msg.msg_control         = NULL;
        msg.msg_controllen      = 0;
        msg.msg_flags           = 0;

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

        if (n == -ENOMEM) {
                _debug("oom");
                rxrpc_kernel_abort_call(afs_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, void *buf, size_t count,
                     bool want_more)
{
        int ret;

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

        ASSERTCMP(call->offset, <=, count);

        ret = rxrpc_kernel_recv_data(afs_socket, call->rxcall,
                                     buf, count, &call->offset,
                                     want_more, &call->abort_code);
        trace_afs_recv_data(call, count, call->offset, want_more, ret);
        if (ret == 0 || ret == -EAGAIN)
                return ret;

        if (ret == 1) {
                switch (call->state) {
                case AFS_CALL_AWAIT_REPLY:
                        call->state = AFS_CALL_COMPLETE;
                        break;
                case AFS_CALL_AWAIT_REQUEST:
                        call->state = AFS_CALL_REPLYING;
                        break;
                default:
                        break;
                }
                return 0;
        }

        if (ret == -ECONNABORTED)
                call->error = call->type->abort_to_error(call->abort_code);
        else
                call->error = ret;
        call->state = AFS_CALL_COMPLETE;
        return ret;
}