Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1131 insertions, 0 deletions

diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c
new file mode 100644
index 000000000..bdb335cb2
--- /dev/null
+++ b/net/rxrpc/conn_client.c
@@ -0,0 +1,1131 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Client connection-specific management code.
+ *
+ * Copyright (C) 2016, 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * Client connections need to be cached for a little while after they've made a
+ * call so as to handle retransmitted DATA packets in case the server didn't
+ * receive the final ACK or terminating ABORT we sent it.
+ *
+ * There are flags of relevance to the cache:
+ *
+ *  (2) DONT_REUSE - The connection should be discarded as soon as possible and
+ *      should not be reused.  This is set when an exclusive connection is used
+ *      or a call ID counter overflows.
+ *
+ * The caching state may only be changed if the cache lock is held.
+ *
+ * There are two idle client connection expiry durations.  If the total number
+ * of connections is below the reap threshold, we use the normal duration; if
+ * it's above, we use the fast duration.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/idr.h>
+#include <linux/timer.h>
+#include <linux/sched/signal.h>
+
+#include "ar-internal.h"
+
+__read_mostly unsigned int rxrpc_reap_client_connections = 900;
+__read_mostly unsigned long rxrpc_conn_idle_client_expiry = 2 * 60 * HZ;
+__read_mostly unsigned long rxrpc_conn_idle_client_fast_expiry = 2 * HZ;
+
+/*
+ * We use machine-unique IDs for our client connections.
+ */
+DEFINE_IDR(rxrpc_client_conn_ids);
+static DEFINE_SPINLOCK(rxrpc_conn_id_lock);
+
+static void rxrpc_deactivate_bundle(struct rxrpc_bundle *bundle);
+
+/*
+ * Get a connection ID and epoch for a client connection from the global pool.
+ * The connection struct pointer is then recorded in the idr radix tree.  The
+ * epoch doesn't change until the client is rebooted (or, at least, unless the
+ * module is unloaded).
+ */
+static int rxrpc_get_client_connection_id(struct rxrpc_connection *conn,
+					  gfp_t gfp)
+{
+	struct rxrpc_net *rxnet = conn->params.local->rxnet;
+	int id;
+
+	_enter("");
+
+	idr_preload(gfp);
+	spin_lock(&rxrpc_conn_id_lock);
+
+	id = idr_alloc_cyclic(&rxrpc_client_conn_ids, conn,
+			      1, 0x40000000, GFP_NOWAIT);
+	if (id < 0)
+		goto error;
+
+	spin_unlock(&rxrpc_conn_id_lock);
+	idr_preload_end();
+
+	conn->proto.epoch = rxnet->epoch;
+	conn->proto.cid = id << RXRPC_CIDSHIFT;
+	set_bit(RXRPC_CONN_HAS_IDR, &conn->flags);
+	_leave(" [CID %x]", conn->proto.cid);
+	return 0;
+
+error:
+	spin_unlock(&rxrpc_conn_id_lock);
+	idr_preload_end();
+	_leave(" = %d", id);
+	return id;
+}
+
+/*
+ * Release a connection ID for a client connection from the global pool.
+ */
+static void rxrpc_put_client_connection_id(struct rxrpc_connection *conn)
+{
+	if (test_bit(RXRPC_CONN_HAS_IDR, &conn->flags)) {
+		spin_lock(&rxrpc_conn_id_lock);
+		idr_remove(&rxrpc_client_conn_ids,
+			   conn->proto.cid >> RXRPC_CIDSHIFT);
+		spin_unlock(&rxrpc_conn_id_lock);
+	}
+}
+
+/*
+ * Destroy the client connection ID tree.
+ */
+void rxrpc_destroy_client_conn_ids(void)
+{
+	struct rxrpc_connection *conn;
+	int id;
+
+	if (!idr_is_empty(&rxrpc_client_conn_ids)) {
+		idr_for_each_entry(&rxrpc_client_conn_ids, conn, id) {
+			pr_err("AF_RXRPC: Leaked client conn %p {%d}\n",
+			       conn, refcount_read(&conn->ref));
+		}
+		BUG();
+	}
+
+	idr_destroy(&rxrpc_client_conn_ids);
+}
+
+/*
+ * Allocate a connection bundle.
+ */
+static struct rxrpc_bundle *rxrpc_alloc_bundle(struct rxrpc_conn_parameters *cp,
+					       gfp_t gfp)
+{
+	struct rxrpc_bundle *bundle;
+
+	bundle = kzalloc(sizeof(*bundle), gfp);
+	if (bundle) {
+		bundle->params = *cp;
+		rxrpc_get_peer(bundle->params.peer);
+		refcount_set(&bundle->ref, 1);
+		atomic_set(&bundle->active, 1);
+		spin_lock_init(&bundle->channel_lock);
+		INIT_LIST_HEAD(&bundle->waiting_calls);
+	}
+	return bundle;
+}
+
+struct rxrpc_bundle *rxrpc_get_bundle(struct rxrpc_bundle *bundle)
+{
+	refcount_inc(&bundle->ref);
+	return bundle;
+}
+
+static void rxrpc_free_bundle(struct rxrpc_bundle *bundle)
+{
+	rxrpc_put_peer(bundle->params.peer);
+	kfree(bundle);
+}
+
+void rxrpc_put_bundle(struct rxrpc_bundle *bundle)
+{
+	unsigned int d = bundle->debug_id;
+	bool dead;
+	int r;
+
+	dead = __refcount_dec_and_test(&bundle->ref, &r);
+
+	_debug("PUT B=%x %d", d, r - 1);
+	if (dead)
+		rxrpc_free_bundle(bundle);
+}
+
+/*
+ * Allocate a client connection.
+ */
+static struct rxrpc_connection *
+rxrpc_alloc_client_connection(struct rxrpc_bundle *bundle, gfp_t gfp)
+{
+	struct rxrpc_connection *conn;
+	struct rxrpc_net *rxnet = bundle->params.local->rxnet;
+	int ret;
+
+	_enter("");
+
+	conn = rxrpc_alloc_connection(gfp);
+	if (!conn) {
+		_leave(" = -ENOMEM");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	refcount_set(&conn->ref, 1);
+	conn->bundle		= bundle;
+	conn->params		= bundle->params;
+	conn->out_clientflag	= RXRPC_CLIENT_INITIATED;
+	conn->state		= RXRPC_CONN_CLIENT;
+	conn->service_id	= conn->params.service_id;
+
+	ret = rxrpc_get_client_connection_id(conn, gfp);
+	if (ret < 0)
+		goto error_0;
+
+	ret = rxrpc_init_client_conn_security(conn);
+	if (ret < 0)
+		goto error_1;
+
+	atomic_inc(&rxnet->nr_conns);
+	write_lock(&rxnet->conn_lock);
+	list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
+	write_unlock(&rxnet->conn_lock);
+
+	rxrpc_get_bundle(bundle);
+	rxrpc_get_peer(conn->params.peer);
+	rxrpc_get_local(conn->params.local);
+	key_get(conn->params.key);
+
+	trace_rxrpc_conn(conn->debug_id, rxrpc_conn_new_client,
+			 refcount_read(&conn->ref),
+			 __builtin_return_address(0));
+
+	atomic_inc(&rxnet->nr_client_conns);
+	trace_rxrpc_client(conn, -1, rxrpc_client_alloc);
+	_leave(" = %p", conn);
+	return conn;
+
+error_1:
+	rxrpc_put_client_connection_id(conn);
+error_0:
+	kfree(conn);
+	_leave(" = %d", ret);
+	return ERR_PTR(ret);
+}
+
+/*
+ * Determine if a connection may be reused.
+ */
+static bool rxrpc_may_reuse_conn(struct rxrpc_connection *conn)
+{
+	struct rxrpc_net *rxnet;
+	int id_cursor, id, distance, limit;
+
+	if (!conn)
+		goto dont_reuse;
+
+	rxnet = conn->params.local->rxnet;
+	if (test_bit(RXRPC_CONN_DONT_REUSE, &conn->flags))
+		goto dont_reuse;
+
+	if (conn->state != RXRPC_CONN_CLIENT ||
+	    conn->proto.epoch != rxnet->epoch)
+		goto mark_dont_reuse;
+
+	/* The IDR tree gets very expensive on memory if the connection IDs are
+	 * widely scattered throughout the number space, so we shall want to
+	 * kill off connections that, say, have an ID more than about four
+	 * times the maximum number of client conns away from the current
+	 * allocation point to try and keep the IDs concentrated.
+	 */
+	id_cursor = idr_get_cursor(&rxrpc_client_conn_ids);
+	id = conn->proto.cid >> RXRPC_CIDSHIFT;
+	distance = id - id_cursor;
+	if (distance < 0)
+		distance = -distance;
+	limit = max_t(unsigned long, atomic_read(&rxnet->nr_conns) * 4, 1024);
+	if (distance > limit)
+		goto mark_dont_reuse;
+
+	return true;
+
+mark_dont_reuse:
+	set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
+dont_reuse:
+	return false;
+}
+
+/*
+ * Look up the conn bundle that matches the connection parameters, adding it if
+ * it doesn't yet exist.
+ */
+static struct rxrpc_bundle *rxrpc_look_up_bundle(struct rxrpc_conn_parameters *cp,
+						 gfp_t gfp)
+{
+	static atomic_t rxrpc_bundle_id;
+	struct rxrpc_bundle *bundle, *candidate;
+	struct rxrpc_local *local = cp->local;
+	struct rb_node *p, **pp, *parent;
+	long diff;
+
+	_enter("{%px,%x,%u,%u}",
+	       cp->peer, key_serial(cp->key), cp->security_level, cp->upgrade);
+
+	if (cp->exclusive)
+		return rxrpc_alloc_bundle(cp, gfp);
+
+	/* First, see if the bundle is already there. */
+	_debug("search 1");
+	spin_lock(&local->client_bundles_lock);
+	p = local->client_bundles.rb_node;
+	while (p) {
+		bundle = rb_entry(p, struct rxrpc_bundle, local_node);
+
+#define cmp(X) ((long)bundle->params.X - (long)cp->X)
+		diff = (cmp(peer) ?:
+			cmp(key) ?:
+			cmp(security_level) ?:
+			cmp(upgrade));
+#undef cmp
+		if (diff < 0)
+			p = p->rb_left;
+		else if (diff > 0)
+			p = p->rb_right;
+		else
+			goto found_bundle;
+	}
+	spin_unlock(&local->client_bundles_lock);
+	_debug("not found");
+
+	/* It wasn't.  We need to add one. */
+	candidate = rxrpc_alloc_bundle(cp, gfp);
+	if (!candidate)
+		return NULL;
+
+	_debug("search 2");
+	spin_lock(&local->client_bundles_lock);
+	pp = &local->client_bundles.rb_node;
+	parent = NULL;
+	while (*pp) {
+		parent = *pp;
+		bundle = rb_entry(parent, struct rxrpc_bundle, local_node);
+
+#define cmp(X) ((long)bundle->params.X - (long)cp->X)
+		diff = (cmp(peer) ?:
+			cmp(key) ?:
+			cmp(security_level) ?:
+			cmp(upgrade));
+#undef cmp
+		if (diff < 0)
+			pp = &(*pp)->rb_left;
+		else if (diff > 0)
+			pp = &(*pp)->rb_right;
+		else
+			goto found_bundle_free;
+	}
+
+	_debug("new bundle");
+	candidate->debug_id = atomic_inc_return(&rxrpc_bundle_id);
+	rb_link_node(&candidate->local_node, parent, pp);
+	rb_insert_color(&candidate->local_node, &local->client_bundles);
+	rxrpc_get_bundle(candidate);
+	spin_unlock(&local->client_bundles_lock);
+	_leave(" = %u [new]", candidate->debug_id);
+	return candidate;
+
+found_bundle_free:
+	rxrpc_free_bundle(candidate);
+found_bundle:
+	rxrpc_get_bundle(bundle);
+	atomic_inc(&bundle->active);
+	spin_unlock(&local->client_bundles_lock);
+	_leave(" = %u [found]", bundle->debug_id);
+	return bundle;
+}
+
+/*
+ * Create or find a client bundle to use for a call.
+ *
+ * If we return with a connection, the call will be on its waiting list.  It's
+ * left to the caller to assign a channel and wake up the call.
+ */
+static struct rxrpc_bundle *rxrpc_prep_call(struct rxrpc_sock *rx,
+					    struct rxrpc_call *call,
+					    struct rxrpc_conn_parameters *cp,
+					    struct sockaddr_rxrpc *srx,
+					    gfp_t gfp)
+{
+	struct rxrpc_bundle *bundle;
+
+	_enter("{%d,%lx},", call->debug_id, call->user_call_ID);
+
+	cp->peer = rxrpc_lookup_peer(rx, cp->local, srx, gfp);
+	if (!cp->peer)
+		goto error;
+
+	call->cong_cwnd = cp->peer->cong_cwnd;
+	if (call->cong_cwnd >= call->cong_ssthresh)
+		call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
+	else
+		call->cong_mode = RXRPC_CALL_SLOW_START;
+	if (cp->upgrade)
+		__set_bit(RXRPC_CALL_UPGRADE, &call->flags);
+
+	/* Find the client connection bundle. */
+	bundle = rxrpc_look_up_bundle(cp, gfp);
+	if (!bundle)
+		goto error;
+
+	/* Get this call queued.  Someone else may activate it whilst we're
+	 * lining up a new connection, but that's fine.
+	 */
+	spin_lock(&bundle->channel_lock);
+	list_add_tail(&call->chan_wait_link, &bundle->waiting_calls);
+	spin_unlock(&bundle->channel_lock);
+
+	_leave(" = [B=%x]", bundle->debug_id);
+	return bundle;
+
+error:
+	_leave(" = -ENOMEM");
+	return ERR_PTR(-ENOMEM);
+}
+
+/*
+ * Allocate a new connection and add it into a bundle.
+ */
+static void rxrpc_add_conn_to_bundle(struct rxrpc_bundle *bundle, gfp_t gfp)
+	__releases(bundle->channel_lock)
+{
+	struct rxrpc_connection *candidate = NULL, *old = NULL;
+	bool conflict;
+	int i;
+
+	_enter("");
+
+	conflict = bundle->alloc_conn;
+	if (!conflict)
+		bundle->alloc_conn = true;
+	spin_unlock(&bundle->channel_lock);
+	if (conflict) {
+		_leave(" [conf]");
+		return;
+	}
+
+	candidate = rxrpc_alloc_client_connection(bundle, gfp);
+
+	spin_lock(&bundle->channel_lock);
+	bundle->alloc_conn = false;
+
+	if (IS_ERR(candidate)) {
+		bundle->alloc_error = PTR_ERR(candidate);
+		spin_unlock(&bundle->channel_lock);
+		_leave(" [err %ld]", PTR_ERR(candidate));
+		return;
+	}
+
+	bundle->alloc_error = 0;
+
+	for (i = 0; i < ARRAY_SIZE(bundle->conns); i++) {
+		unsigned int shift = i * RXRPC_MAXCALLS;
+		int j;
+
+		old = bundle->conns[i];
+		if (!rxrpc_may_reuse_conn(old)) {
+			if (old)
+				trace_rxrpc_client(old, -1, rxrpc_client_replace);
+			candidate->bundle_shift = shift;
+			atomic_inc(&bundle->active);
+			bundle->conns[i] = candidate;
+			for (j = 0; j < RXRPC_MAXCALLS; j++)
+				set_bit(shift + j, &bundle->avail_chans);
+			candidate = NULL;
+			break;
+		}
+
+		old = NULL;
+	}
+
+	spin_unlock(&bundle->channel_lock);
+
+	if (candidate) {
+		_debug("discard C=%x", candidate->debug_id);
+		trace_rxrpc_client(candidate, -1, rxrpc_client_duplicate);
+		rxrpc_put_connection(candidate);
+	}
+
+	rxrpc_put_connection(old);
+	_leave("");
+}
+
+/*
+ * Add a connection to a bundle if there are no usable connections or we have
+ * connections waiting for extra capacity.
+ */
+static void rxrpc_maybe_add_conn(struct rxrpc_bundle *bundle, gfp_t gfp)
+{
+	struct rxrpc_call *call;
+	int i, usable;
+
+	_enter("");
+
+	spin_lock(&bundle->channel_lock);
+
+	/* See if there are any usable connections. */
+	usable = 0;
+	for (i = 0; i < ARRAY_SIZE(bundle->conns); i++)
+		if (rxrpc_may_reuse_conn(bundle->conns[i]))
+			usable++;
+
+	if (!usable && !list_empty(&bundle->waiting_calls)) {
+		call = list_first_entry(&bundle->waiting_calls,
+					struct rxrpc_call, chan_wait_link);
+		if (test_bit(RXRPC_CALL_UPGRADE, &call->flags))
+			bundle->try_upgrade = true;
+	}
+
+	if (!usable)
+		goto alloc_conn;
+
+	if (!bundle->avail_chans &&
+	    !bundle->try_upgrade &&
+	    !list_empty(&bundle->waiting_calls) &&
+	    usable < ARRAY_SIZE(bundle->conns))
+		goto alloc_conn;
+
+	spin_unlock(&bundle->channel_lock);
+	_leave("");
+	return;
+
+alloc_conn:
+	return rxrpc_add_conn_to_bundle(bundle, gfp);
+}
+
+/*
+ * Assign a channel to the call at the front of the queue and wake the call up.
+ * We don't increment the callNumber counter until this number has been exposed
+ * to the world.
+ */
+static void rxrpc_activate_one_channel(struct rxrpc_connection *conn,
+				       unsigned int channel)
+{
+	struct rxrpc_channel *chan = &conn->channels[channel];
+	struct rxrpc_bundle *bundle = conn->bundle;
+	struct rxrpc_call *call = list_entry(bundle->waiting_calls.next,
+					     struct rxrpc_call, chan_wait_link);
+	u32 call_id = chan->call_counter + 1;
+
+	_enter("C=%x,%u", conn->debug_id, channel);
+
+	trace_rxrpc_client(conn, channel, rxrpc_client_chan_activate);
+
+	/* Cancel the final ACK on the previous call if it hasn't been sent yet
+	 * as the DATA packet will implicitly ACK it.
+	 */
+	clear_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags);
+	clear_bit(conn->bundle_shift + channel, &bundle->avail_chans);
+
+	rxrpc_see_call(call);
+	list_del_init(&call->chan_wait_link);
+	call->peer	= rxrpc_get_peer(conn->params.peer);
+	call->conn	= rxrpc_get_connection(conn);
+	call->cid	= conn->proto.cid | channel;
+	call->call_id	= call_id;
+	call->security	= conn->security;
+	call->security_ix = conn->security_ix;
+	call->service_id = conn->service_id;
+
+	trace_rxrpc_connect_call(call);
+	_net("CONNECT call %08x:%08x as call %d on conn %d",
+	     call->cid, call->call_id, call->debug_id, conn->debug_id);
+
+	write_lock_bh(&call->state_lock);
+	call->state = RXRPC_CALL_CLIENT_SEND_REQUEST;
+	write_unlock_bh(&call->state_lock);
+
+	/* Paired with the read barrier in rxrpc_connect_call().  This orders
+	 * cid and epoch in the connection wrt to call_id without the need to
+	 * take the channel_lock.
+	 *
+	 * We provisionally assign a callNumber at this point, but we don't
+	 * confirm it until the call is about to be exposed.
+	 *
+	 * TODO: Pair with a barrier in the data_ready handler when that looks
+	 * at the call ID through a connection channel.
+	 */
+	smp_wmb();
+
+	chan->call_id		= call_id;
+	chan->call_debug_id	= call->debug_id;
+	rcu_assign_pointer(chan->call, call);
+	wake_up(&call->waitq);
+}
+
+/*
+ * Remove a connection from the idle list if it's on it.
+ */
+static void rxrpc_unidle_conn(struct rxrpc_bundle *bundle, struct rxrpc_connection *conn)
+{
+	struct rxrpc_net *rxnet = bundle->params.local->rxnet;
+	bool drop_ref;
+
+	if (!list_empty(&conn->cache_link)) {
+		drop_ref = false;
+		spin_lock(&rxnet->client_conn_cache_lock);
+		if (!list_empty(&conn->cache_link)) {
+			list_del_init(&conn->cache_link);
+			drop_ref = true;
+		}
+		spin_unlock(&rxnet->client_conn_cache_lock);
+		if (drop_ref)
+			rxrpc_put_connection(conn);
+	}
+}
+
+/*
+ * Assign channels and callNumbers to waiting calls with channel_lock
+ * held by caller.
+ */
+static void rxrpc_activate_channels_locked(struct rxrpc_bundle *bundle)
+{
+	struct rxrpc_connection *conn;
+	unsigned long avail, mask;
+	unsigned int channel, slot;
+
+	if (bundle->try_upgrade)
+		mask = 1;
+	else
+		mask = ULONG_MAX;
+
+	while (!list_empty(&bundle->waiting_calls)) {
+		avail = bundle->avail_chans & mask;
+		if (!avail)
+			break;
+		channel = __ffs(avail);
+		clear_bit(channel, &bundle->avail_chans);
+
+		slot = channel / RXRPC_MAXCALLS;
+		conn = bundle->conns[slot];
+		if (!conn)
+			break;
+
+		if (bundle->try_upgrade)
+			set_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags);
+		rxrpc_unidle_conn(bundle, conn);
+
+		channel &= (RXRPC_MAXCALLS - 1);
+		conn->act_chans	|= 1 << channel;
+		rxrpc_activate_one_channel(conn, channel);
+	}
+}
+
+/*
+ * Assign channels and callNumbers to waiting calls.
+ */
+static void rxrpc_activate_channels(struct rxrpc_bundle *bundle)
+{
+	_enter("B=%x", bundle->debug_id);
+
+	trace_rxrpc_client(NULL, -1, rxrpc_client_activate_chans);
+
+	if (!bundle->avail_chans)
+		return;
+
+	spin_lock(&bundle->channel_lock);
+	rxrpc_activate_channels_locked(bundle);
+	spin_unlock(&bundle->channel_lock);
+	_leave("");
+}
+
+/*
+ * Wait for a callNumber and a channel to be granted to a call.
+ */
+static int rxrpc_wait_for_channel(struct rxrpc_bundle *bundle,
+				  struct rxrpc_call *call, gfp_t gfp)
+{
+	DECLARE_WAITQUEUE(myself, current);
+	int ret = 0;
+
+	_enter("%d", call->debug_id);
+
+	if (!gfpflags_allow_blocking(gfp)) {
+		rxrpc_maybe_add_conn(bundle, gfp);
+		rxrpc_activate_channels(bundle);
+		ret = bundle->alloc_error ?: -EAGAIN;
+		goto out;
+	}
+
+	add_wait_queue_exclusive(&call->waitq, &myself);
+	for (;;) {
+		rxrpc_maybe_add_conn(bundle, gfp);
+		rxrpc_activate_channels(bundle);
+		ret = bundle->alloc_error;
+		if (ret < 0)
+			break;
+
+		switch (call->interruptibility) {
+		case RXRPC_INTERRUPTIBLE:
+		case RXRPC_PREINTERRUPTIBLE:
+			set_current_state(TASK_INTERRUPTIBLE);
+			break;
+		case RXRPC_UNINTERRUPTIBLE:
+		default:
+			set_current_state(TASK_UNINTERRUPTIBLE);
+			break;
+		}
+		if (READ_ONCE(call->state) != RXRPC_CALL_CLIENT_AWAIT_CONN)
+			break;
+		if ((call->interruptibility == RXRPC_INTERRUPTIBLE ||
+		     call->interruptibility == RXRPC_PREINTERRUPTIBLE) &&
+		    signal_pending(current)) {
+			ret = -ERESTARTSYS;
+			break;
+		}
+		schedule();
+	}
+	remove_wait_queue(&call->waitq, &myself);
+	__set_current_state(TASK_RUNNING);
+
+out:
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * find a connection for a call
+ * - called in process context with IRQs enabled
+ */
+int rxrpc_connect_call(struct rxrpc_sock *rx,
+		       struct rxrpc_call *call,
+		       struct rxrpc_conn_parameters *cp,
+		       struct sockaddr_rxrpc *srx,
+		       gfp_t gfp)
+{
+	struct rxrpc_bundle *bundle;
+	struct rxrpc_net *rxnet = cp->local->rxnet;
+	int ret = 0;
+
+	_enter("{%d,%lx},", call->debug_id, call->user_call_ID);
+
+	rxrpc_discard_expired_client_conns(&rxnet->client_conn_reaper);
+
+	bundle = rxrpc_prep_call(rx, call, cp, srx, gfp);
+	if (IS_ERR(bundle)) {
+		ret = PTR_ERR(bundle);
+		goto out;
+	}
+
+	if (call->state == RXRPC_CALL_CLIENT_AWAIT_CONN) {
+		ret = rxrpc_wait_for_channel(bundle, call, gfp);
+		if (ret < 0)
+			goto wait_failed;
+	}
+
+granted_channel:
+	/* Paired with the write barrier in rxrpc_activate_one_channel(). */
+	smp_rmb();
+
+out_put_bundle:
+	rxrpc_deactivate_bundle(bundle);
+	rxrpc_put_bundle(bundle);
+out:
+	_leave(" = %d", ret);
+	return ret;
+
+wait_failed:
+	spin_lock(&bundle->channel_lock);
+	list_del_init(&call->chan_wait_link);
+	spin_unlock(&bundle->channel_lock);
+
+	if (call->state != RXRPC_CALL_CLIENT_AWAIT_CONN) {
+		ret = 0;
+		goto granted_channel;
+	}
+
+	trace_rxrpc_client(call->conn, ret, rxrpc_client_chan_wait_failed);
+	rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR, 0, ret);
+	rxrpc_disconnect_client_call(bundle, call);
+	goto out_put_bundle;
+}
+
+/*
+ * Note that a call, and thus a connection, is about to be exposed to the
+ * world.
+ */
+void rxrpc_expose_client_call(struct rxrpc_call *call)
+{
+	unsigned int channel = call->cid & RXRPC_CHANNELMASK;
+	struct rxrpc_connection *conn = call->conn;
+	struct rxrpc_channel *chan = &conn->channels[channel];
+
+	if (!test_and_set_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
+		/* Mark the call ID as being used.  If the callNumber counter
+		 * exceeds ~2 billion, we kill the connection after its
+		 * outstanding calls have finished so that the counter doesn't
+		 * wrap.
+		 */
+		chan->call_counter++;
+		if (chan->call_counter >= INT_MAX)
+			set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
+		trace_rxrpc_client(conn, channel, rxrpc_client_exposed);
+	}
+}
+
+/*
+ * Set the reap timer.
+ */
+static void rxrpc_set_client_reap_timer(struct rxrpc_net *rxnet)
+{
+	if (!rxnet->kill_all_client_conns) {
+		unsigned long now = jiffies;
+		unsigned long reap_at = now + rxrpc_conn_idle_client_expiry;
+
+		if (rxnet->live)
+			timer_reduce(&rxnet->client_conn_reap_timer, reap_at);
+	}
+}
+
+/*
+ * Disconnect a client call.
+ */
+void rxrpc_disconnect_client_call(struct rxrpc_bundle *bundle, struct rxrpc_call *call)
+{
+	struct rxrpc_connection *conn;
+	struct rxrpc_channel *chan = NULL;
+	struct rxrpc_net *rxnet = bundle->params.local->rxnet;
+	unsigned int channel;
+	bool may_reuse;
+	u32 cid;
+
+	_enter("c=%x", call->debug_id);
+
+	spin_lock(&bundle->channel_lock);
+	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
+
+	/* Calls that have never actually been assigned a channel can simply be
+	 * discarded.
+	 */
+	conn = call->conn;
+	if (!conn) {
+		_debug("call is waiting");
+		ASSERTCMP(call->call_id, ==, 0);
+		ASSERT(!test_bit(RXRPC_CALL_EXPOSED, &call->flags));
+		list_del_init(&call->chan_wait_link);
+		goto out;
+	}
+
+	cid = call->cid;
+	channel = cid & RXRPC_CHANNELMASK;
+	chan = &conn->channels[channel];
+	trace_rxrpc_client(conn, channel, rxrpc_client_chan_disconnect);
+
+	if (rcu_access_pointer(chan->call) != call) {
+		spin_unlock(&bundle->channel_lock);
+		BUG();
+	}
+
+	may_reuse = rxrpc_may_reuse_conn(conn);
+
+	/* If a client call was exposed to the world, we save the result for
+	 * retransmission.
+	 *
+	 * We use a barrier here so that the call number and abort code can be
+	 * read without needing to take a lock.
+	 *
+	 * TODO: Make the incoming packet handler check this and handle
+	 * terminal retransmission without requiring access to the call.
+	 */
+	if (test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
+		_debug("exposed %u,%u", call->call_id, call->abort_code);
+		__rxrpc_disconnect_call(conn, call);
+
+		if (test_and_clear_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags)) {
+			trace_rxrpc_client(conn, channel, rxrpc_client_to_active);
+			bundle->try_upgrade = false;
+			if (may_reuse)
+				rxrpc_activate_channels_locked(bundle);
+		}
+
+	}
+
+	/* See if we can pass the channel directly to another call. */
+	if (may_reuse && !list_empty(&bundle->waiting_calls)) {
+		trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
+		rxrpc_activate_one_channel(conn, channel);
+		goto out;
+	}
+
+	/* Schedule the final ACK to be transmitted in a short while so that it
+	 * can be skipped if we find a follow-on call.  The first DATA packet
+	 * of the follow on call will implicitly ACK this call.
+	 */
+	if (call->completion == RXRPC_CALL_SUCCEEDED &&
+	    test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
+		unsigned long final_ack_at = jiffies + 2;
+
+		WRITE_ONCE(chan->final_ack_at, final_ack_at);
+		smp_wmb(); /* vs rxrpc_process_delayed_final_acks() */
+		set_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags);
+		rxrpc_reduce_conn_timer(conn, final_ack_at);
+	}
+
+	/* Deactivate the channel. */
+	rcu_assign_pointer(chan->call, NULL);
+	set_bit(conn->bundle_shift + channel, &conn->bundle->avail_chans);
+	conn->act_chans	&= ~(1 << channel);
+
+	/* If no channels remain active, then put the connection on the idle
+	 * list for a short while.  Give it a ref to stop it going away if it
+	 * becomes unbundled.
+	 */
+	if (!conn->act_chans) {
+		trace_rxrpc_client(conn, channel, rxrpc_client_to_idle);
+		conn->idle_timestamp = jiffies;
+
+		rxrpc_get_connection(conn);
+		spin_lock(&rxnet->client_conn_cache_lock);
+		list_move_tail(&conn->cache_link, &rxnet->idle_client_conns);
+		spin_unlock(&rxnet->client_conn_cache_lock);
+
+		rxrpc_set_client_reap_timer(rxnet);
+	}
+
+out:
+	spin_unlock(&bundle->channel_lock);
+	_leave("");
+	return;
+}
+
+/*
+ * Remove a connection from a bundle.
+ */
+static void rxrpc_unbundle_conn(struct rxrpc_connection *conn)
+{
+	struct rxrpc_bundle *bundle = conn->bundle;
+	unsigned int bindex;
+	bool need_drop = false;
+	int i;
+
+	_enter("C=%x", conn->debug_id);
+
+	if (conn->flags & RXRPC_CONN_FINAL_ACK_MASK)
+		rxrpc_process_delayed_final_acks(conn, true);
+
+	spin_lock(&bundle->channel_lock);
+	bindex = conn->bundle_shift / RXRPC_MAXCALLS;
+	if (bundle->conns[bindex] == conn) {
+		_debug("clear slot %u", bindex);
+		bundle->conns[bindex] = NULL;
+		for (i = 0; i < RXRPC_MAXCALLS; i++)
+			clear_bit(conn->bundle_shift + i, &bundle->avail_chans);
+		need_drop = true;
+	}
+	spin_unlock(&bundle->channel_lock);
+
+	if (need_drop) {
+		rxrpc_deactivate_bundle(bundle);
+		rxrpc_put_connection(conn);
+	}
+}
+
+/*
+ * Drop the active count on a bundle.
+ */
+static void rxrpc_deactivate_bundle(struct rxrpc_bundle *bundle)
+{
+	struct rxrpc_local *local = bundle->params.local;
+	bool need_put = false;
+
+	if (atomic_dec_and_lock(&bundle->active, &local->client_bundles_lock)) {
+		if (!bundle->params.exclusive) {
+			_debug("erase bundle");
+			rb_erase(&bundle->local_node, &local->client_bundles);
+			need_put = true;
+		}
+
+		spin_unlock(&local->client_bundles_lock);
+		if (need_put)
+			rxrpc_put_bundle(bundle);
+	}
+}
+
+/*
+ * Clean up a dead client connection.
+ */
+static void rxrpc_kill_client_conn(struct rxrpc_connection *conn)
+{
+	struct rxrpc_local *local = conn->params.local;
+	struct rxrpc_net *rxnet = local->rxnet;
+
+	_enter("C=%x", conn->debug_id);
+
+	trace_rxrpc_client(conn, -1, rxrpc_client_cleanup);
+	atomic_dec(&rxnet->nr_client_conns);
+
+	rxrpc_put_client_connection_id(conn);
+	rxrpc_kill_connection(conn);
+}
+
+/*
+ * Clean up a dead client connections.
+ */
+void rxrpc_put_client_conn(struct rxrpc_connection *conn)
+{
+	const void *here = __builtin_return_address(0);
+	unsigned int debug_id = conn->debug_id;
+	bool dead;
+	int r;
+
+	dead = __refcount_dec_and_test(&conn->ref, &r);
+	trace_rxrpc_conn(debug_id, rxrpc_conn_put_client, r - 1, here);
+	if (dead)
+		rxrpc_kill_client_conn(conn);
+}
+
+/*
+ * Discard expired client connections from the idle list.  Each conn in the
+ * idle list has been exposed and holds an extra ref because of that.
+ *
+ * This may be called from conn setup or from a work item so cannot be
+ * considered non-reentrant.
+ */
+void rxrpc_discard_expired_client_conns(struct work_struct *work)
+{
+	struct rxrpc_connection *conn;
+	struct rxrpc_net *rxnet =
+		container_of(work, struct rxrpc_net, client_conn_reaper);
+	unsigned long expiry, conn_expires_at, now;
+	unsigned int nr_conns;
+
+	_enter("");
+
+	if (list_empty(&rxnet->idle_client_conns)) {
+		_leave(" [empty]");
+		return;
+	}
+
+	/* Don't double up on the discarding */
+	if (!spin_trylock(&rxnet->client_conn_discard_lock)) {
+		_leave(" [already]");
+		return;
+	}
+
+	/* We keep an estimate of what the number of conns ought to be after
+	 * we've discarded some so that we don't overdo the discarding.
+	 */
+	nr_conns = atomic_read(&rxnet->nr_client_conns);
+
+next:
+	spin_lock(&rxnet->client_conn_cache_lock);
+
+	if (list_empty(&rxnet->idle_client_conns))
+		goto out;
+
+	conn = list_entry(rxnet->idle_client_conns.next,
+			  struct rxrpc_connection, cache_link);
+
+	if (!rxnet->kill_all_client_conns) {
+		/* If the number of connections is over the reap limit, we
+		 * expedite discard by reducing the expiry timeout.  We must,
+		 * however, have at least a short grace period to be able to do
+		 * final-ACK or ABORT retransmission.
+		 */
+		expiry = rxrpc_conn_idle_client_expiry;
+		if (nr_conns > rxrpc_reap_client_connections)
+			expiry = rxrpc_conn_idle_client_fast_expiry;
+		if (conn->params.local->service_closed)
+			expiry = rxrpc_closed_conn_expiry * HZ;
+
+		conn_expires_at = conn->idle_timestamp + expiry;
+
+		now = READ_ONCE(jiffies);
+		if (time_after(conn_expires_at, now))
+			goto not_yet_expired;
+	}
+
+	trace_rxrpc_client(conn, -1, rxrpc_client_discard);
+	list_del_init(&conn->cache_link);
+
+	spin_unlock(&rxnet->client_conn_cache_lock);
+
+	rxrpc_unbundle_conn(conn);
+	rxrpc_put_connection(conn); /* Drop the ->cache_link ref */
+
+	nr_conns--;
+	goto next;
+
+not_yet_expired:
+	/* The connection at the front of the queue hasn't yet expired, so
+	 * schedule the work item for that point if we discarded something.
+	 *
+	 * We don't worry if the work item is already scheduled - it can look
+	 * after rescheduling itself at a later time.  We could cancel it, but
+	 * then things get messier.
+	 */
+	_debug("not yet");
+	if (!rxnet->kill_all_client_conns)
+		timer_reduce(&rxnet->client_conn_reap_timer, conn_expires_at);
+
+out:
+	spin_unlock(&rxnet->client_conn_cache_lock);
+	spin_unlock(&rxnet->client_conn_discard_lock);
+	_leave("");
+}
+
+/*
+ * Preemptively destroy all the client connection records rather than waiting
+ * for them to time out
+ */
+void rxrpc_destroy_all_client_connections(struct rxrpc_net *rxnet)
+{
+	_enter("");
+
+	spin_lock(&rxnet->client_conn_cache_lock);
+	rxnet->kill_all_client_conns = true;
+	spin_unlock(&rxnet->client_conn_cache_lock);
+
+	del_timer_sync(&rxnet->client_conn_reap_timer);
+
+	if (!rxrpc_queue_work(&rxnet->client_conn_reaper))
+		_debug("destroy: queue failed");
+
+	_leave("");
+}
+
+/*
+ * Clean up the client connections on a local endpoint.
+ */
+void rxrpc_clean_up_local_conns(struct rxrpc_local *local)
+{
+	struct rxrpc_connection *conn, *tmp;
+	struct rxrpc_net *rxnet = local->rxnet;
+	LIST_HEAD(graveyard);
+
+	_enter("");
+
+	spin_lock(&rxnet->client_conn_cache_lock);
+
+	list_for_each_entry_safe(conn, tmp, &rxnet->idle_client_conns,
+				 cache_link) {
+		if (conn->params.local == local) {
+			trace_rxrpc_client(conn, -1, rxrpc_client_discard);
+			list_move(&conn->cache_link, &graveyard);
+		}
+	}
+
+	spin_unlock(&rxnet->client_conn_cache_lock);
+
+	while (!list_empty(&graveyard)) {
+		conn = list_entry(graveyard.next,
+				  struct rxrpc_connection, cache_link);
+		list_del_init(&conn->cache_link);
+		rxrpc_unbundle_conn(conn);
+		rxrpc_put_connection(conn);
+	}
+
+	_leave(" [culled]");
+}