net/rxrpc/call_accept.c - kernel/msm-4.9 - Gitiles

 /* incoming call handling
  *
  * 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.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/net.h>
 #include <linux/skbuff.h>
 #include <linux/errqueue.h>
 #include <linux/udp.h>
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <linux/icmp.h>
 #include <linux/gfp.h>
 #include <linux/circ_buf.h>
 #include <net/sock.h>
 #include <net/af_rxrpc.h>
 #include <net/ip.h>
 #include "ar-internal.h"

 /*
  * Preallocate a single service call, connection and peer and, if possible,
  * give them a user ID and attach the user's side of the ID to them.
  */
 static int rxrpc_service_prealloc_one(struct rxrpc_sock *rx,
 				      struct rxrpc_backlog *b,
 				      rxrpc_notify_rx_t notify_rx,
 				      rxrpc_user_attach_call_t user_attach_call,
 				      unsigned long user_call_ID, gfp_t gfp)
 {
 	const void *here = __builtin_return_address(0);
 	struct rxrpc_call *call;
 	int max, tmp;
 	unsigned int size = RXRPC_BACKLOG_MAX;
 	unsigned int head, tail, call_head, call_tail;

 	max = rx->sk.sk_max_ack_backlog;
 	tmp = rx->sk.sk_ack_backlog;
 	if (tmp >= max) {
 		_leave(" = -ENOBUFS [full %u]", max);
 		return -ENOBUFS;
 	}
 	max -= tmp;

 	/* We don't need more conns and peers than we have calls, but on the
 	 * other hand, we shouldn't ever use more peers than conns or conns
 	 * than calls.
 	 */
 	call_head = b->call_backlog_head;
 	call_tail = READ_ONCE(b->call_backlog_tail);
 	tmp = CIRC_CNT(call_head, call_tail, size);
 	if (tmp >= max) {
 		_leave(" = -ENOBUFS [enough %u]", tmp);
 		return -ENOBUFS;
 	}
 	max = tmp + 1;

 	head = b->peer_backlog_head;
 	tail = READ_ONCE(b->peer_backlog_tail);
 	if (CIRC_CNT(head, tail, size) < max) {
 		struct rxrpc_peer *peer = rxrpc_alloc_peer(rx->local, gfp);
 		if (!peer)
 			return -ENOMEM;
 		b->peer_backlog[head] = peer;
 		smp_store_release(&b->peer_backlog_head,
 				  (head + 1) & (size - 1));
 	}

 	head = b->conn_backlog_head;
 	tail = READ_ONCE(b->conn_backlog_tail);
 	if (CIRC_CNT(head, tail, size) < max) {
 		struct rxrpc_connection *conn;

 		conn = rxrpc_prealloc_service_connection(gfp);
 		if (!conn)
 			return -ENOMEM;
 		b->conn_backlog[head] = conn;
 		smp_store_release(&b->conn_backlog_head,
 				  (head + 1) & (size - 1));

 		trace_rxrpc_conn(conn, rxrpc_conn_new_service,
 				 atomic_read(&conn->usage), here);
 	}

 	/* Now it gets complicated, because calls get registered with the
 	 * socket here, particularly if a user ID is preassigned by the user.
 	 */
 	call = rxrpc_alloc_call(gfp);
 	if (!call)
 		return -ENOMEM;
 	call->flags |= (1 << RXRPC_CALL_IS_SERVICE);
 	call->state = RXRPC_CALL_SERVER_PREALLOC;

 	trace_rxrpc_call(call, rxrpc_call_new_service,
 			 atomic_read(&call->usage),
 			 here, (const void *)user_call_ID);

 	write_lock(&rx->call_lock);
 	if (user_attach_call) {
 		struct rxrpc_call *xcall;
 		struct rb_node *parent, **pp;

 		/* Check the user ID isn't already in use */
 		pp = &rx->calls.rb_node;
 		parent = NULL;
 		while (*pp) {
 			parent = *pp;
 			xcall = rb_entry(parent, struct rxrpc_call, sock_node);
 			if (user_call_ID < call->user_call_ID)
 				pp = &(*pp)->rb_left;
 			else if (user_call_ID > call->user_call_ID)
 				pp = &(*pp)->rb_right;
 			else
 				goto id_in_use;
 		}

 		call->user_call_ID = user_call_ID;
 		call->notify_rx = notify_rx;
 		rxrpc_get_call(call, rxrpc_call_got_kernel);
 		user_attach_call(call, user_call_ID);
 		rxrpc_get_call(call, rxrpc_call_got_userid);
 		rb_link_node(&call->sock_node, parent, pp);
 		rb_insert_color(&call->sock_node, &rx->calls);
 		set_bit(RXRPC_CALL_HAS_USERID, &call->flags);
 	}

 	list_add(&call->sock_link, &rx->sock_calls);

 	write_unlock(&rx->call_lock);

 	write_lock(&rxrpc_call_lock);
 	list_add_tail(&call->link, &rxrpc_calls);
 	write_unlock(&rxrpc_call_lock);

 	b->call_backlog[call_head] = call;
 	smp_store_release(&b->call_backlog_head, (call_head + 1) & (size - 1));
 	_leave(" = 0 [%d -> %lx]", call->debug_id, user_call_ID);
 	return 0;

 id_in_use:
 	write_unlock(&rx->call_lock);
 	rxrpc_cleanup_call(call);
 	_leave(" = -EBADSLT");
 	return -EBADSLT;
 }

 /*
  * Preallocate sufficient service connections, calls and peers to cover the
  * entire backlog of a socket.  When a new call comes in, if we don't have
  * sufficient of each available, the call gets rejected as busy or ignored.
  *
  * The backlog is replenished when a connection is accepted or rejected.
  */
 int rxrpc_service_prealloc(struct rxrpc_sock *rx, gfp_t gfp)
 {
 	struct rxrpc_backlog *b = rx->backlog;

 	if (!b) {
 		b = kzalloc(sizeof(struct rxrpc_backlog), gfp);
 		if (!b)
 			return -ENOMEM;
 		rx->backlog = b;
 	}

 	if (rx->discard_new_call)
 		return 0;

 	while (rxrpc_service_prealloc_one(rx, b, NULL, NULL, 0, gfp) == 0)
 		;

 	return 0;
 }

 /*
  * Discard the preallocation on a service.
  */
 void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
 {
 	struct rxrpc_backlog *b = rx->backlog;
 	unsigned int size = RXRPC_BACKLOG_MAX, head, tail;

 	if (!b)
 		return;
 	rx->backlog = NULL;

 	/* Make sure that there aren't any incoming calls in progress before we
 	 * clear the preallocation buffers.
 	 */
 	spin_lock_bh(&rx->incoming_lock);
 	spin_unlock_bh(&rx->incoming_lock);

 	head = b->peer_backlog_head;
 	tail = b->peer_backlog_tail;
 	while (CIRC_CNT(head, tail, size) > 0) {
 		struct rxrpc_peer *peer = b->peer_backlog[tail];
 		kfree(peer);
 		tail = (tail + 1) & (size - 1);
 	}

 	head = b->conn_backlog_head;
 	tail = b->conn_backlog_tail;
 	while (CIRC_CNT(head, tail, size) > 0) {
 		struct rxrpc_connection *conn = b->conn_backlog[tail];
 		write_lock(&rxrpc_connection_lock);
 		list_del(&conn->link);
 		list_del(&conn->proc_link);
 		write_unlock(&rxrpc_connection_lock);
 		kfree(conn);
 		tail = (tail + 1) & (size - 1);
 	}

 	head = b->call_backlog_head;
 	tail = b->call_backlog_tail;
 	while (CIRC_CNT(head, tail, size) > 0) {
 		struct rxrpc_call *call = b->call_backlog[tail];
 		if (rx->discard_new_call) {
 			_debug("discard %lx", call->user_call_ID);
 			rx->discard_new_call(call, call->user_call_ID);
 			rxrpc_put_call(call, rxrpc_call_put_kernel);
 		}
 		rxrpc_call_completed(call);
 		rxrpc_release_call(rx, call);
 		rxrpc_put_call(call, rxrpc_call_put);
 		tail = (tail + 1) & (size - 1);
 	}

 	kfree(b);
 }

 /*
  * Allocate a new incoming call from the prealloc pool, along with a connection
  * and a peer as necessary.
  */
 static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
 						    struct rxrpc_local *local,
 						    struct rxrpc_connection *conn,
 						    struct sk_buff *skb)
 {
 	struct rxrpc_backlog *b = rx->backlog;
 	struct rxrpc_peer *peer, *xpeer;
 	struct rxrpc_call *call;
 	unsigned short call_head, conn_head, peer_head;
 	unsigned short call_tail, conn_tail, peer_tail;
 	unsigned short call_count, conn_count;

 	/* #calls >= #conns >= #peers must hold true. */
 	call_head = smp_load_acquire(&b->call_backlog_head);
 	call_tail = b->call_backlog_tail;
 	call_count = CIRC_CNT(call_head, call_tail, RXRPC_BACKLOG_MAX);
 	conn_head = smp_load_acquire(&b->conn_backlog_head);
 	conn_tail = b->conn_backlog_tail;
 	conn_count = CIRC_CNT(conn_head, conn_tail, RXRPC_BACKLOG_MAX);
 	ASSERTCMP(conn_count, >=, call_count);
 	peer_head = smp_load_acquire(&b->peer_backlog_head);
 	peer_tail = b->peer_backlog_tail;
 	ASSERTCMP(CIRC_CNT(peer_head, peer_tail, RXRPC_BACKLOG_MAX), >=,
 		  conn_count);

 	if (call_count == 0)
 		return NULL;

 	if (!conn) {
 		/* No connection.  We're going to need a peer to start off
 		 * with.  If one doesn't yet exist, use a spare from the
 		 * preallocation set.  We dump the address into the spare in
 		 * anticipation - and to save on stack space.
 		 */
 		xpeer = b->peer_backlog[peer_tail];
 		if (rxrpc_extract_addr_from_skb(&xpeer->srx, skb) < 0)
 			return NULL;

 		peer = rxrpc_lookup_incoming_peer(local, xpeer);
 		if (peer == xpeer) {
 			b->peer_backlog[peer_tail] = NULL;
 			smp_store_release(&b->peer_backlog_tail,
 					  (peer_tail + 1) &
 					  (RXRPC_BACKLOG_MAX - 1));
 		}

 		/* Now allocate and set up the connection */
 		conn = b->conn_backlog[conn_tail];
 		b->conn_backlog[conn_tail] = NULL;
 		smp_store_release(&b->conn_backlog_tail,
 				  (conn_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
 		rxrpc_get_local(local);
 		conn->params.local = local;
 		conn->params.peer = peer;
 		rxrpc_see_connection(conn);
 		rxrpc_new_incoming_connection(conn, skb);
 	} else {
 		rxrpc_get_connection(conn);
 	}

 	/* And now we can allocate and set up a new call */
 	call = b->call_backlog[call_tail];
 	b->call_backlog[call_tail] = NULL;
 	smp_store_release(&b->call_backlog_tail,
 			  (call_tail + 1) & (RXRPC_BACKLOG_MAX - 1));

 	rxrpc_see_call(call);
 	call->conn = conn;
 	call->peer = rxrpc_get_peer(conn->params.peer);
 	return call;
 }

 /*
  * Set up a new incoming call.  Called in BH context with the RCU read lock
  * held.
  *
  * If this is for a kernel service, when we allocate the call, it will have
  * three refs on it: (1) the kernel service, (2) the user_call_ID tree, (3) the
  * retainer ref obtained from the backlog buffer.  Prealloc calls for userspace
  * services only have the ref from the backlog buffer.  We want to pass this
  * ref to non-BH context to dispose of.
  *
  * If we want to report an error, we mark the skb with the packet type and
  * abort code and return NULL.
  */
 struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 					   struct rxrpc_connection *conn,
 					   struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct rxrpc_sock *rx;
 	struct rxrpc_call *call;

 	_enter("");

 	/* Get the socket providing the service */
 	hlist_for_each_entry_rcu_bh(rx, &local->services, listen_link) {
 		if (rx->srx.srx_service == sp->hdr.serviceId)
 			goto found_service;
 	}

 	trace_rxrpc_abort("INV", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
 			  RX_INVALID_OPERATION, EOPNOTSUPP);
 	skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
 	skb->priority = RX_INVALID_OPERATION;
 	_leave(" = NULL [service]");
 	return NULL;

 found_service:
 	spin_lock(&rx->incoming_lock);
 	if (rx->sk.sk_state == RXRPC_CLOSE) {
 		trace_rxrpc_abort("CLS", sp->hdr.cid, sp->hdr.callNumber,
 				  sp->hdr.seq, RX_INVALID_OPERATION, ESHUTDOWN);
 		skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
 		skb->priority = RX_INVALID_OPERATION;
 		_leave(" = NULL [close]");
 		call = NULL;
 		goto out;
 	}

 	call = rxrpc_alloc_incoming_call(rx, local, conn, skb);
 	if (!call) {
 		skb->mark = RXRPC_SKB_MARK_BUSY;
 		_leave(" = NULL [busy]");
 		call = NULL;
 		goto out;
 	}

 	/* Make the call live. */
 	rxrpc_incoming_call(rx, call, skb);
 	conn = call->conn;

 	if (rx->notify_new_call)
 		rx->notify_new_call(&rx->sk, call, call->user_call_ID);
 	else
 		sk_acceptq_added(&rx->sk);

 	spin_lock(&conn->state_lock);
 	switch (conn->state) {
 	case RXRPC_CONN_SERVICE_UNSECURED:
 		conn->state = RXRPC_CONN_SERVICE_CHALLENGING;
 		set_bit(RXRPC_CONN_EV_CHALLENGE, &call->conn->events);
 		rxrpc_queue_conn(call->conn);
 		break;

 	case RXRPC_CONN_SERVICE:
 		write_lock(&call->state_lock);
 		if (rx->discard_new_call)
 			call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
 		else
 			call->state = RXRPC_CALL_SERVER_ACCEPTING;
 		write_unlock(&call->state_lock);
 		break;

 	case RXRPC_CONN_REMOTELY_ABORTED:
 		rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
 					  conn->remote_abort, ECONNABORTED);
 		break;
 	case RXRPC_CONN_LOCALLY_ABORTED:
 		rxrpc_abort_call("CON", call, sp->hdr.seq,
 				 conn->local_abort, ECONNABORTED);
 		break;
 	default:
 		BUG();
 	}
 	spin_unlock(&conn->state_lock);

 	if (call->state == RXRPC_CALL_SERVER_ACCEPTING)
 		rxrpc_notify_socket(call);

 	/* We have to discard the prealloc queue's ref here and rely on a
 	 * combination of the RCU read lock and refs held either by the socket
 	 * (recvmsg queue, to-be-accepted queue or user ID tree) or the kernel
 	 * service to prevent the call from being deallocated too early.
 	 */
 	rxrpc_put_call(call, rxrpc_call_put);

 	_leave(" = %p{%d}", call, call->debug_id);
 out:
 	spin_unlock(&rx->incoming_lock);
 	return call;
 }

 /*
  * handle acceptance of a call by userspace
  * - assign the user call ID to the call at the front of the queue
  */
 struct rxrpc_call *rxrpc_accept_call(struct rxrpc_sock *rx,
 				     unsigned long user_call_ID,
 				     rxrpc_notify_rx_t notify_rx)
 {
 	struct rxrpc_call *call;
 	struct rb_node *parent, **pp;
 	int ret;

 	_enter(",%lx", user_call_ID);

 	ASSERT(!irqs_disabled());

 	write_lock(&rx->call_lock);

 	if (list_empty(&rx->to_be_accepted)) {
 		write_unlock(&rx->call_lock);
 		kleave(" = -ENODATA [empty]");
 		return ERR_PTR(-ENODATA);
 	}

 	/* check the user ID isn't already in use */
 	pp = &rx->calls.rb_node;
 	parent = NULL;
 	while (*pp) {
 		parent = *pp;
 		call = rb_entry(parent, struct rxrpc_call, sock_node);

 		if (user_call_ID < call->user_call_ID)
 			pp = &(*pp)->rb_left;
 		else if (user_call_ID > call->user_call_ID)
 			pp = &(*pp)->rb_right;
 		else
 			goto id_in_use;
 	}

 	/* Dequeue the first call and check it's still valid.  We gain
 	 * responsibility for the queue's reference.
 	 */
 	call = list_entry(rx->to_be_accepted.next,
 			  struct rxrpc_call, accept_link);
 	list_del_init(&call->accept_link);
 	sk_acceptq_removed(&rx->sk);
 	rxrpc_see_call(call);

 	write_lock_bh(&call->state_lock);
 	switch (call->state) {
 	case RXRPC_CALL_SERVER_ACCEPTING:
 		call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
 		break;
 	case RXRPC_CALL_COMPLETE:
 		ret = call->error;
 		goto out_release;
 	default:
 		BUG();
 	}

 	/* formalise the acceptance */
 	call->notify_rx = notify_rx;
 	call->user_call_ID = user_call_ID;
 	rxrpc_get_call(call, rxrpc_call_got_userid);
 	rb_link_node(&call->sock_node, parent, pp);
 	rb_insert_color(&call->sock_node, &rx->calls);
 	if (test_and_set_bit(RXRPC_CALL_HAS_USERID, &call->flags))
 		BUG();

 	write_unlock_bh(&call->state_lock);
 	write_unlock(&rx->call_lock);
 	rxrpc_notify_socket(call);
 	rxrpc_service_prealloc(rx, GFP_KERNEL);
 	_leave(" = %p{%d}", call, call->debug_id);
 	return call;

 out_release:
 	_debug("release %p", call);
 	write_unlock_bh(&call->state_lock);
 	write_unlock(&rx->call_lock);
 	rxrpc_release_call(rx, call);
 	rxrpc_put_call(call, rxrpc_call_put);
 	goto out;

 id_in_use:
 	ret = -EBADSLT;
 	write_unlock(&rx->call_lock);
 out:
 	rxrpc_service_prealloc(rx, GFP_KERNEL);
 	_leave(" = %d", ret);
 	return ERR_PTR(ret);
 }

 /*
  * Handle rejection of a call by userspace
  * - reject the call at the front of the queue
  */
 int rxrpc_reject_call(struct rxrpc_sock *rx)
 {
 	struct rxrpc_call *call;
 	bool abort = false;
 	int ret;

 	_enter("");

 	ASSERT(!irqs_disabled());

 	write_lock(&rx->call_lock);

 	if (list_empty(&rx->to_be_accepted)) {
 		write_unlock(&rx->call_lock);
 		return -ENODATA;
 	}

 	/* Dequeue the first call and check it's still valid.  We gain
 	 * responsibility for the queue's reference.
 	 */
 	call = list_entry(rx->to_be_accepted.next,
 			  struct rxrpc_call, accept_link);
 	list_del_init(&call->accept_link);
 	sk_acceptq_removed(&rx->sk);
 	rxrpc_see_call(call);

 	write_lock_bh(&call->state_lock);
 	switch (call->state) {
 	case RXRPC_CALL_SERVER_ACCEPTING:
 		__rxrpc_abort_call("REJ", call, 1, RX_USER_ABORT, ECONNABORTED);
 		abort = true;
 		/* fall through */
 	case RXRPC_CALL_COMPLETE:
 		ret = call->error;
 		goto out_discard;
 	default:
 		BUG();
 	}

 out_discard:
 	write_unlock_bh(&call->state_lock);
 	write_unlock(&rx->call_lock);
 	if (abort) {
 		rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ABORT);
 		rxrpc_release_call(rx, call);
 		rxrpc_put_call(call, rxrpc_call_put);
 	}
 	rxrpc_service_prealloc(rx, GFP_KERNEL);
 	_leave(" = %d", ret);
 	return ret;
 }

 /*
  * rxrpc_kernel_charge_accept - Charge up socket with preallocated calls
  * @sock: The socket on which to preallocate
  * @notify_rx: Event notification function for the call
  * @user_attach_call: Func to attach call to user_call_ID
  * @user_call_ID: The tag to attach to the preallocated call
  * @gfp: The allocation conditions.
  *
  * Charge up the socket with preallocated calls, each with a user ID.  A
  * function should be provided to effect the attachment from the user's side.
  * The user is given a ref to hold on the call.
  *
  * Note that the call may be come connected before this function returns.
  */
 int rxrpc_kernel_charge_accept(struct socket *sock,
 			       rxrpc_notify_rx_t notify_rx,
 			       rxrpc_user_attach_call_t user_attach_call,
 			       unsigned long user_call_ID, gfp_t gfp)
 {
 	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
 	struct rxrpc_backlog *b = rx->backlog;

 	if (sock->sk->sk_state == RXRPC_CLOSE)
 		return -ESHUTDOWN;

 	return rxrpc_service_prealloc_one(rx, b, notify_rx,
 					  user_attach_call, user_call_ID,
 					  gfp);
 }
 EXPORT_SYMBOL(rxrpc_kernel_charge_accept);
	/* incoming call handling
	*
	* 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.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/net.h>
	#include <linux/skbuff.h>
	#include <linux/errqueue.h>
	#include <linux/udp.h>
	#include <linux/in.h>
	#include <linux/in6.h>
	#include <linux/icmp.h>
	#include <linux/gfp.h>
	#include <linux/circ_buf.h>
	#include <net/sock.h>
	#include <net/af_rxrpc.h>
	#include <net/ip.h>
	#include "ar-internal.h"

	/*
	* Preallocate a single service call, connection and peer and, if possible,
	* give them a user ID and attach the user's side of the ID to them.
	*/
	static int rxrpc_service_prealloc_one(struct rxrpc_sock *rx,
	struct rxrpc_backlog *b,
	rxrpc_notify_rx_t notify_rx,
	rxrpc_user_attach_call_t user_attach_call,
	unsigned long user_call_ID, gfp_t gfp)
	{
	const void *here = __builtin_return_address(0);
	struct rxrpc_call *call;
	int max, tmp;
	unsigned int size = RXRPC_BACKLOG_MAX;
	unsigned int head, tail, call_head, call_tail;

	max = rx->sk.sk_max_ack_backlog;
	tmp = rx->sk.sk_ack_backlog;
	if (tmp >= max) {
	_leave(" = -ENOBUFS [full %u]", max);
	return -ENOBUFS;
	}
	max -= tmp;

	/* We don't need more conns and peers than we have calls, but on the
	* other hand, we shouldn't ever use more peers than conns or conns
	* than calls.
	*/
	call_head = b->call_backlog_head;
	call_tail = READ_ONCE(b->call_backlog_tail);
	tmp = CIRC_CNT(call_head, call_tail, size);
	if (tmp >= max) {
	_leave(" = -ENOBUFS [enough %u]", tmp);
	return -ENOBUFS;
	}
	max = tmp + 1;

	head = b->peer_backlog_head;
	tail = READ_ONCE(b->peer_backlog_tail);
	if (CIRC_CNT(head, tail, size) < max) {
	struct rxrpc_peer *peer = rxrpc_alloc_peer(rx->local, gfp);
	if (!peer)
	return -ENOMEM;
	b->peer_backlog[head] = peer;
	smp_store_release(&b->peer_backlog_head,
	(head + 1) & (size - 1));
	}

	head = b->conn_backlog_head;
	tail = READ_ONCE(b->conn_backlog_tail);
	if (CIRC_CNT(head, tail, size) < max) {
	struct rxrpc_connection *conn;

	conn = rxrpc_prealloc_service_connection(gfp);
	if (!conn)
	return -ENOMEM;
	b->conn_backlog[head] = conn;
	smp_store_release(&b->conn_backlog_head,
	(head + 1) & (size - 1));

	trace_rxrpc_conn(conn, rxrpc_conn_new_service,
	atomic_read(&conn->usage), here);
	}

	/* Now it gets complicated, because calls get registered with the
	* socket here, particularly if a user ID is preassigned by the user.
	*/
	call = rxrpc_alloc_call(gfp);
	if (!call)
	return -ENOMEM;
	call->flags \|= (1 << RXRPC_CALL_IS_SERVICE);
	call->state = RXRPC_CALL_SERVER_PREALLOC;

	trace_rxrpc_call(call, rxrpc_call_new_service,
	atomic_read(&call->usage),
	here, (const void *)user_call_ID);

	write_lock(&rx->call_lock);
	if (user_attach_call) {
	struct rxrpc_call *xcall;
	struct rb_node parent, *pp;

	/* Check the user ID isn't already in use */
	pp = &rx->calls.rb_node;
	parent = NULL;
	while (*pp) {
	parent = *pp;
	xcall = rb_entry(parent, struct rxrpc_call, sock_node);
	if (user_call_ID < call->user_call_ID)
	pp = &(*pp)->rb_left;
	else if (user_call_ID > call->user_call_ID)
	pp = &(*pp)->rb_right;
	else
	goto id_in_use;
	}

	call->user_call_ID = user_call_ID;
	call->notify_rx = notify_rx;
	rxrpc_get_call(call, rxrpc_call_got_kernel);
	user_attach_call(call, user_call_ID);
	rxrpc_get_call(call, rxrpc_call_got_userid);
	rb_link_node(&call->sock_node, parent, pp);
	rb_insert_color(&call->sock_node, &rx->calls);
	set_bit(RXRPC_CALL_HAS_USERID, &call->flags);
	}

	list_add(&call->sock_link, &rx->sock_calls);

	write_unlock(&rx->call_lock);

	write_lock(&rxrpc_call_lock);
	list_add_tail(&call->link, &rxrpc_calls);
	write_unlock(&rxrpc_call_lock);

	b->call_backlog[call_head] = call;
	smp_store_release(&b->call_backlog_head, (call_head + 1) & (size - 1));
	_leave(" = 0 [%d -> %lx]", call->debug_id, user_call_ID);
	return 0;

	id_in_use:
	write_unlock(&rx->call_lock);
	rxrpc_cleanup_call(call);
	_leave(" = -EBADSLT");
	return -EBADSLT;
	}

	/*
	* Preallocate sufficient service connections, calls and peers to cover the
	* entire backlog of a socket. When a new call comes in, if we don't have
	* sufficient of each available, the call gets rejected as busy or ignored.
	*
	* The backlog is replenished when a connection is accepted or rejected.
	*/
	int rxrpc_service_prealloc(struct rxrpc_sock *rx, gfp_t gfp)
	{
	struct rxrpc_backlog *b = rx->backlog;

	if (!b) {
	b = kzalloc(sizeof(struct rxrpc_backlog), gfp);
	if (!b)
	return -ENOMEM;
	rx->backlog = b;
	}

	if (rx->discard_new_call)
	return 0;

	while (rxrpc_service_prealloc_one(rx, b, NULL, NULL, 0, gfp) == 0)
	;

	return 0;
	}

	/*
	* Discard the preallocation on a service.
	*/
	void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
	{
	struct rxrpc_backlog *b = rx->backlog;
	unsigned int size = RXRPC_BACKLOG_MAX, head, tail;

	if (!b)
	return;
	rx->backlog = NULL;

	/* Make sure that there aren't any incoming calls in progress before we
	* clear the preallocation buffers.
	*/
	spin_lock_bh(&rx->incoming_lock);
	spin_unlock_bh(&rx->incoming_lock);

	head = b->peer_backlog_head;
	tail = b->peer_backlog_tail;
	while (CIRC_CNT(head, tail, size) > 0) {
	struct rxrpc_peer *peer = b->peer_backlog[tail];
	kfree(peer);
	tail = (tail + 1) & (size - 1);
	}

	head = b->conn_backlog_head;
	tail = b->conn_backlog_tail;
	while (CIRC_CNT(head, tail, size) > 0) {
	struct rxrpc_connection *conn = b->conn_backlog[tail];
	write_lock(&rxrpc_connection_lock);
	list_del(&conn->link);
	list_del(&conn->proc_link);
	write_unlock(&rxrpc_connection_lock);
	kfree(conn);
	tail = (tail + 1) & (size - 1);
	}

	head = b->call_backlog_head;
	tail = b->call_backlog_tail;
	while (CIRC_CNT(head, tail, size) > 0) {
	struct rxrpc_call *call = b->call_backlog[tail];
	if (rx->discard_new_call) {
	_debug("discard %lx", call->user_call_ID);
	rx->discard_new_call(call, call->user_call_ID);
	rxrpc_put_call(call, rxrpc_call_put_kernel);
	}
	rxrpc_call_completed(call);
	rxrpc_release_call(rx, call);
	rxrpc_put_call(call, rxrpc_call_put);
	tail = (tail + 1) & (size - 1);
	}

	kfree(b);
	}

	/*
	* Allocate a new incoming call from the prealloc pool, along with a connection
	* and a peer as necessary.
	*/
	static struct rxrpc_call rxrpc_alloc_incoming_call(struct rxrpc_sock rx,
	struct rxrpc_local *local,
	struct rxrpc_connection *conn,
	struct sk_buff *skb)
	{
	struct rxrpc_backlog *b = rx->backlog;
	struct rxrpc_peer peer, xpeer;
	struct rxrpc_call *call;
	unsigned short call_head, conn_head, peer_head;
	unsigned short call_tail, conn_tail, peer_tail;
	unsigned short call_count, conn_count;

	/* #calls >= #conns >= #peers must hold true. */
	call_head = smp_load_acquire(&b->call_backlog_head);
	call_tail = b->call_backlog_tail;
	call_count = CIRC_CNT(call_head, call_tail, RXRPC_BACKLOG_MAX);
	conn_head = smp_load_acquire(&b->conn_backlog_head);
	conn_tail = b->conn_backlog_tail;
	conn_count = CIRC_CNT(conn_head, conn_tail, RXRPC_BACKLOG_MAX);
	ASSERTCMP(conn_count, >=, call_count);
	peer_head = smp_load_acquire(&b->peer_backlog_head);
	peer_tail = b->peer_backlog_tail;
	ASSERTCMP(CIRC_CNT(peer_head, peer_tail, RXRPC_BACKLOG_MAX), >=,
	conn_count);

	if (call_count == 0)
	return NULL;

	if (!conn) {
	/* No connection. We're going to need a peer to start off
	* with. If one doesn't yet exist, use a spare from the
	* preallocation set. We dump the address into the spare in
	* anticipation - and to save on stack space.
	*/
	xpeer = b->peer_backlog[peer_tail];
	if (rxrpc_extract_addr_from_skb(&xpeer->srx, skb) < 0)
	return NULL;

	peer = rxrpc_lookup_incoming_peer(local, xpeer);
	if (peer == xpeer) {
	b->peer_backlog[peer_tail] = NULL;
	smp_store_release(&b->peer_backlog_tail,
	(peer_tail + 1) &
	(RXRPC_BACKLOG_MAX - 1));
	}

	/* Now allocate and set up the connection */
	conn = b->conn_backlog[conn_tail];
	b->conn_backlog[conn_tail] = NULL;
	smp_store_release(&b->conn_backlog_tail,
	(conn_tail + 1) & (RXRPC_BACKLOG_MAX - 1));
	rxrpc_get_local(local);
	conn->params.local = local;
	conn->params.peer = peer;
	rxrpc_see_connection(conn);
	rxrpc_new_incoming_connection(conn, skb);
	} else {
	rxrpc_get_connection(conn);
	}

	/* And now we can allocate and set up a new call */
	call = b->call_backlog[call_tail];
	b->call_backlog[call_tail] = NULL;
	smp_store_release(&b->call_backlog_tail,
	(call_tail + 1) & (RXRPC_BACKLOG_MAX - 1));

	rxrpc_see_call(call);
	call->conn = conn;
	call->peer = rxrpc_get_peer(conn->params.peer);
	return call;
	}

	/*
	* Set up a new incoming call. Called in BH context with the RCU read lock
	* held.
	*
	* If this is for a kernel service, when we allocate the call, it will have
	* three refs on it: (1) the kernel service, (2) the user_call_ID tree, (3) the
	* retainer ref obtained from the backlog buffer. Prealloc calls for userspace
	* services only have the ref from the backlog buffer. We want to pass this
	* ref to non-BH context to dispose of.
	*
	* If we want to report an error, we mark the skb with the packet type and
	* abort code and return NULL.
	*/
	struct rxrpc_call rxrpc_new_incoming_call(struct rxrpc_local local,
	struct rxrpc_connection *conn,
	struct sk_buff *skb)
	{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct rxrpc_sock *rx;
	struct rxrpc_call *call;

	_enter("");

	/* Get the socket providing the service */
	hlist_for_each_entry_rcu_bh(rx, &local->services, listen_link) {
	if (rx->srx.srx_service == sp->hdr.serviceId)
	goto found_service;
	}

	trace_rxrpc_abort("INV", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
	RX_INVALID_OPERATION, EOPNOTSUPP);
	skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
	skb->priority = RX_INVALID_OPERATION;
	_leave(" = NULL [service]");
	return NULL;

	found_service:
	spin_lock(&rx->incoming_lock);
	if (rx->sk.sk_state == RXRPC_CLOSE) {
	trace_rxrpc_abort("CLS", sp->hdr.cid, sp->hdr.callNumber,
	sp->hdr.seq, RX_INVALID_OPERATION, ESHUTDOWN);
	skb->mark = RXRPC_SKB_MARK_LOCAL_ABORT;
	skb->priority = RX_INVALID_OPERATION;
	_leave(" = NULL [close]");
	call = NULL;
	goto out;
	}

	call = rxrpc_alloc_incoming_call(rx, local, conn, skb);
	if (!call) {
	skb->mark = RXRPC_SKB_MARK_BUSY;
	_leave(" = NULL [busy]");
	call = NULL;
	goto out;
	}

	/* Make the call live. */
	rxrpc_incoming_call(rx, call, skb);
	conn = call->conn;

	if (rx->notify_new_call)
	rx->notify_new_call(&rx->sk, call, call->user_call_ID);
	else
	sk_acceptq_added(&rx->sk);

	spin_lock(&conn->state_lock);
	switch (conn->state) {
	case RXRPC_CONN_SERVICE_UNSECURED:
	conn->state = RXRPC_CONN_SERVICE_CHALLENGING;
	set_bit(RXRPC_CONN_EV_CHALLENGE, &call->conn->events);
	rxrpc_queue_conn(call->conn);
	break;

	case RXRPC_CONN_SERVICE:
	write_lock(&call->state_lock);
	if (rx->discard_new_call)
	call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
	else
	call->state = RXRPC_CALL_SERVER_ACCEPTING;
	write_unlock(&call->state_lock);
	break;

	case RXRPC_CONN_REMOTELY_ABORTED:
	rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
	conn->remote_abort, ECONNABORTED);
	break;
	case RXRPC_CONN_LOCALLY_ABORTED:
	rxrpc_abort_call("CON", call, sp->hdr.seq,
	conn->local_abort, ECONNABORTED);
	break;
	default:
	BUG();
	}
	spin_unlock(&conn->state_lock);

	if (call->state == RXRPC_CALL_SERVER_ACCEPTING)
	rxrpc_notify_socket(call);

	/* We have to discard the prealloc queue's ref here and rely on a
	* combination of the RCU read lock and refs held either by the socket
	* (recvmsg queue, to-be-accepted queue or user ID tree) or the kernel
	* service to prevent the call from being deallocated too early.
	*/
	rxrpc_put_call(call, rxrpc_call_put);

	_leave(" = %p{%d}", call, call->debug_id);
	out:
	spin_unlock(&rx->incoming_lock);
	return call;
	}

	/*
	* handle acceptance of a call by userspace
	* - assign the user call ID to the call at the front of the queue
	*/
	struct rxrpc_call rxrpc_accept_call(struct rxrpc_sock rx,
	unsigned long user_call_ID,
	rxrpc_notify_rx_t notify_rx)
	{
	struct rxrpc_call *call;
	struct rb_node parent, *pp;
	int ret;

	_enter(",%lx", user_call_ID);

	ASSERT(!irqs_disabled());

	write_lock(&rx->call_lock);

	if (list_empty(&rx->to_be_accepted)) {
	write_unlock(&rx->call_lock);
	kleave(" = -ENODATA [empty]");
	return ERR_PTR(-ENODATA);
	}

	/* check the user ID isn't already in use */
	pp = &rx->calls.rb_node;
	parent = NULL;
	while (*pp) {
	parent = *pp;
	call = rb_entry(parent, struct rxrpc_call, sock_node);

	if (user_call_ID < call->user_call_ID)
	pp = &(*pp)->rb_left;
	else if (user_call_ID > call->user_call_ID)
	pp = &(*pp)->rb_right;
	else
	goto id_in_use;
	}

	/* Dequeue the first call and check it's still valid. We gain
	* responsibility for the queue's reference.
	*/
	call = list_entry(rx->to_be_accepted.next,
	struct rxrpc_call, accept_link);
	list_del_init(&call->accept_link);
	sk_acceptq_removed(&rx->sk);
	rxrpc_see_call(call);

	write_lock_bh(&call->state_lock);
	switch (call->state) {
	case RXRPC_CALL_SERVER_ACCEPTING:
	call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
	break;
	case RXRPC_CALL_COMPLETE:
	ret = call->error;
	goto out_release;
	default:
	BUG();
	}

	/* formalise the acceptance */
	call->notify_rx = notify_rx;
	call->user_call_ID = user_call_ID;
	rxrpc_get_call(call, rxrpc_call_got_userid);
	rb_link_node(&call->sock_node, parent, pp);
	rb_insert_color(&call->sock_node, &rx->calls);
	if (test_and_set_bit(RXRPC_CALL_HAS_USERID, &call->flags))
	BUG();

	write_unlock_bh(&call->state_lock);
	write_unlock(&rx->call_lock);
	rxrpc_notify_socket(call);
	rxrpc_service_prealloc(rx, GFP_KERNEL);
	_leave(" = %p{%d}", call, call->debug_id);
	return call;

	out_release:
	_debug("release %p", call);
	write_unlock_bh(&call->state_lock);
	write_unlock(&rx->call_lock);
	rxrpc_release_call(rx, call);
	rxrpc_put_call(call, rxrpc_call_put);
	goto out;

	id_in_use:
	ret = -EBADSLT;
	write_unlock(&rx->call_lock);
	out:
	rxrpc_service_prealloc(rx, GFP_KERNEL);
	_leave(" = %d", ret);
	return ERR_PTR(ret);
	}

	/*
	* Handle rejection of a call by userspace
	* - reject the call at the front of the queue
	*/
	int rxrpc_reject_call(struct rxrpc_sock *rx)
	{
	struct rxrpc_call *call;
	bool abort = false;
	int ret;

	_enter("");

	ASSERT(!irqs_disabled());

	write_lock(&rx->call_lock);

	if (list_empty(&rx->to_be_accepted)) {
	write_unlock(&rx->call_lock);
	return -ENODATA;
	}

	/* Dequeue the first call and check it's still valid. We gain
	* responsibility for the queue's reference.
	*/
	call = list_entry(rx->to_be_accepted.next,
	struct rxrpc_call, accept_link);
	list_del_init(&call->accept_link);
	sk_acceptq_removed(&rx->sk);
	rxrpc_see_call(call);

	write_lock_bh(&call->state_lock);
	switch (call->state) {
	case RXRPC_CALL_SERVER_ACCEPTING:
	__rxrpc_abort_call("REJ", call, 1, RX_USER_ABORT, ECONNABORTED);
	abort = true;
	/* fall through */
	case RXRPC_CALL_COMPLETE:
	ret = call->error;
	goto out_discard;
	default:
	BUG();
	}

	out_discard:
	write_unlock_bh(&call->state_lock);
	write_unlock(&rx->call_lock);
	if (abort) {
	rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ABORT);
	rxrpc_release_call(rx, call);
	rxrpc_put_call(call, rxrpc_call_put);
	}
	rxrpc_service_prealloc(rx, GFP_KERNEL);
	_leave(" = %d", ret);
	return ret;
	}

	/*
	* rxrpc_kernel_charge_accept - Charge up socket with preallocated calls
	* @sock: The socket on which to preallocate
	* @notify_rx: Event notification function for the call
	* @user_attach_call: Func to attach call to user_call_ID
	* @user_call_ID: The tag to attach to the preallocated call
	* @gfp: The allocation conditions.
	*
	* Charge up the socket with preallocated calls, each with a user ID. A
	* function should be provided to effect the attachment from the user's side.
	* The user is given a ref to hold on the call.
	*
	* Note that the call may be come connected before this function returns.
	*/
	int rxrpc_kernel_charge_accept(struct socket *sock,
	rxrpc_notify_rx_t notify_rx,
	rxrpc_user_attach_call_t user_attach_call,
	unsigned long user_call_ID, gfp_t gfp)
	{
	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
	struct rxrpc_backlog *b = rx->backlog;

	if (sock->sk->sk_state == RXRPC_CLOSE)
	return -ESHUTDOWN;

	return rxrpc_service_prealloc_one(rx, b, notify_rx,
	user_attach_call, user_call_ID,
	gfp);
	}
	EXPORT_SYMBOL(rxrpc_kernel_charge_accept);