/*
* Copyright (c) 2007 Oracle. All rights reserved.
*
* This software is available to you under a choice of one of two
* licenses. You may choose to be licensed under the terms of the GNU
* General Public License (GPL) Version 2, available from the file
* COPYING in the main directory of this source tree, or the
* OpenIB.org BSD license below:
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*/
#include <linux/types.h>
#include <linux/rbtree.h>
#include "rds.h"
/*
* This file implements the receive side of the unconventional congestion
* management in RDS.
*
* Messages waiting in the receive queue on the receiving socket are accounted
* against the sockets SO_RCVBUF option value. Only the payload bytes in the
* message are accounted for. If the number of bytes queued equals or exceeds
* rcvbuf then the socket is congested. All sends attempted to this socket's
* address should return block or return -EWOULDBLOCK.
*
* Applications are expected to be reasonably tuned such that this situation
* very rarely occurs. An application encountering this "back-pressure" is
* considered a bug.
*
* This is implemented by having each node maintain bitmaps which indicate
* which ports on bound addresses are congested. As the bitmap changes it is
* sent through all the connections which terminate in the local address of the
* bitmap which changed.
*
* The bitmaps are allocated as connections are brought up. This avoids
* allocation in the interrupt handling path which queues messages on sockets.
* The dense bitmaps let transports send the entire bitmap on any bitmap change
* reasonably efficiently. This is much easier to implement than some
* finer-grained communication of per-port congestion. The sender does a very
* inexpensive bit test to test if the port it's about to send to is congested
* or not.
*/
/*
* Interaction with poll is a tad tricky. We want all processes stuck in
* poll to wake up and check whether a congested destination became uncongested.
* The really sad thing is we have no idea which destinations the application
* wants to send to - we don't even know which rds_connections are involved.
* So until we implement a more flexible rds poll interface, we have to make
* do with this:
* We maintain a global counter that is incremented each time a congestion map
* update is received. Each rds socket tracks this value, and if rds_poll
* finds that the saved generation number is smaller than the global generation
* number, it wakes up the process.
*/
static atomic_t rds_cong_generation = ATOMIC_INIT(0);
/*
* Congestion monitoring
*/
static LIST_HEAD(rds_cong_monitor);
static DEFINE_RWLOCK(rds_cong_monitor_lock);
/*
* Yes, a global lock. It's used so infrequently that it's worth keeping it
* global to simplify the locking. It's only used in the following
* circumstances:
*
* - on connection buildup to associate a conn with its maps
* - on map changes to inform conns of a new map to send
*
* It's sadly ordered under the socket callback lock and the connection lock.
* Receive paths can mark ports congested from interrupt context so the
* lock masks interrupts.
*/
static DEFINE_SPINLOCK(rds_cong_lock);
static struct rb_root rds_cong_tree = RB_ROOT;
static struct rds_cong_map *rds_cong_tree_walk(__be32 addr,
struct rds_cong_map *insert)
{
struct rb_node **p = &rds_cong_tree.rb_node;
struct rb_node *parent = NULL;
struct rds_cong_map *map;
while (*p) {
parent = *p;
map = rb_entry(parent, struct rds_cong_map, m_rb_node);
if (addr < map->m_addr)
p = &(*p)->rb_left;
else if (addr > map->m_addr)
p = &(*p)->rb_right;
else
return map;
}
if (insert) {
rb_link_node(&insert->m_rb_node, parent, p);
rb_insert_color(&insert->m_rb_node, &rds_cong_tree);
}
return NULL;
}
/*
* There is only ever one bitmap for any address. Connections try and allocate
* these bitmaps in the process getting pointers to them. The bitmaps are only
* ever freed as the module is removed after all connections have been freed.
*/
static struct rds_cong_map *rds_cong_from_addr(__be32 addr)
{
struct rds_cong_map *map;
struct rds_cong_map *ret = NULL;
unsigned long zp;
unsigned long i;
unsigned long flags;
map = kzalloc(sizeof(struct rds_cong_map), GFP_KERNEL);
if (map == NULL)
return NULL;
map->m_addr = addr;
init_waitqueue_head(&map->m_waitq);
INIT_LIST_HEAD(&map->m_conn_list);
for (i = 0; i < RDS_CONG_MAP_PAGES; i++) {
zp = get_zeroed_page(GFP_KERNEL);
if (zp == 0)
goto out;
map->m_page_addrs[i] = zp;
}
spin_lock_irqsave(&rds_cong_lock, flags);
ret = rds_cong_tree_walk(addr, map);
spin_unlock_irqrestore(&rds_cong_lock, flags);
if (ret == NULL) {
ret = map;
map = NULL;
}
out:
if (map) {
for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
free_page(map->m_page_addrs[i]);
kfree(map);
}
rdsdebug("map %p for addr %x\n", ret, be32_to_cpu(addr));
return ret;
}
/*
* Put the conn on its local map's list. This is called when the conn is
* really added to the hash. It's nested under the rds_conn_lock, sadly.
*/
void rds_cong_add_conn(struct rds_connection *conn)
{
unsigned long flags;
rdsdebug("conn %p now on map %p\n", conn, conn->c_lcong);
spin_lock_irqsave(&rds_cong_lock, flags);
list_add_tail(&conn->c_map_item, &conn->c_lcong->m_conn_list);
spin_unlock_irqrestore(&rds_cong_lock, flags);
}
void rds_cong_remove_conn(struct rds_connection *conn)
{
unsigned long flags;
rdsdebug("removing conn %p from map %p\n", conn, conn->c_lcong);
spin_lock_irqsave(&rds_cong_lock, flags);
list_del_init(&conn->c_map_item);
spin_unlock_irqrestore(&rds_cong_lock, flags);
}
int rds_cong_get_maps(struct rds_connection *conn)
{
conn->c_lcong = rds_cong_from_addr(conn->c_laddr);
conn->c_fcong = rds_cong_from_addr(conn->c_faddr);
if (conn->c_lcong == NULL || conn->c_fcong == NULL)
return -ENOMEM;
return 0;
}
void rds_cong_queue_updates(struct rds_cong_map *map)
{
struct rds_connection *conn;
unsigned long flags;
spin_lock_irqsave(&rds_cong_lock, flags);
list_for_each_entry(conn, &map->m_conn_list, c_map_item) {
if (!test_and_set_bit(0, &conn->c_map_queued)) {
rds_stats_inc(s_cong_update_queued);
queue_delayed_work(rds_wq, &conn->c_send_w, 0);
}
}
spin_unlock_irqrestore(&rds_cong_lock, flags);
}
void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask)
{
rdsdebug("waking map %p for %pI4\n",
map, &map->m_addr);
rds_stats_inc(s_cong_update_received);
atomic_inc(&rds_cong_generation);
if (waitqueue_active(&map->m_waitq))
wake_up(&map->m_waitq);
if (waitqueue_active(&rds_poll_waitq))
wake_up_all(&rds_poll_waitq);
if (portmask && !list_empty(&rds_cong_monitor)) {
unsigned long flags;
struct rds_sock *rs;
read_lock_irqsave(&rds_cong_monitor_lock, flags);
list_for_each_entry(rs, &rds_cong_monitor, rs_cong_list) {
spin_lock(&rs->rs_lock);
rs->rs_cong_notify |= (rs->rs_cong_mask & portmask);
rs->rs_cong_mask &= ~portmask;
spin_unlock(&rs->rs_lock);
if (rs->rs_cong_notify)
rds_wake_sk_sleep(rs);
}
read_unlock_irqrestore(&rds_cong_monitor_lock, flags);
}
}
int rds_cong_updated_since(unsigned long *recent)
{
unsigned long gen = atomic_read(&rds_cong_generation);
if (likely(*recent == gen))
return 0;
*recent = gen;
return 1;
}
/*
* We're called under the locking that protects the sockets receive buffer
* consumption. This makes it a lot easier for the caller to only call us
* when it knows that an existing set bit needs to be cleared, and vice versa.
* We can't block and we need to deal with concurrent sockets working against
* the same per-address map.
*/
void rds_cong_set_bit(struct rds_cong_map *map, __be16 port)
{
unsigned long i;
unsigned long off;
rdsdebug("setting congestion for %pI4:%u in map %p\n",
&map->m_addr, ntohs(port), map);
i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
generic___set_le_bit(off, (void *)map->m_page_addrs[i]);
}
void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
{
unsigned long i;
unsigned long off;
rdsdebug("clearing congestion for %pI4:%u in map %p\n",
&map->m_addr, ntohs(port), map);
i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
generic___clear_le_bit(off, (void *)map->m_page_addrs[i]);
}
static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port)
{
unsigned long i;
unsigned long off;
i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
return generic_test_le_bit(off, (void *)map->m_page_addrs[i]);
}
void rds_cong_add_socket(struct rds_sock *rs)
{
unsigned long flags;
write_lock_irqsave(&rds_cong_monitor_lock, flags);
if (list_empty(&rs->rs_cong_list))
list_add(&rs->rs_cong_list, &rds_cong_monitor);
write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
}
void rds_cong_remove_socket(struct rds_sock *rs)
{
unsigned long flags;
struct rds_cong_map *map;
write_lock_irqsave(&rds_cong_monitor_lock, flags);
list_del_init(&rs->rs_cong_list);
write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
/* update congestion map for now-closed port */
spin_lock_irqsave(&rds_cong_lock, flags);
map = rds_cong_tree_walk(rs->rs_bound_addr, NULL);
spin_unlock_irqrestore(&rds_cong_lock, flags);
if (map && rds_cong_test_bit(map, rs->rs_bound_port)) {
rds_cong_clear_bit(map, rs->rs_bound_port);
rds_cong_queue_updates(map);
}
}
int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock,
struct rds_sock *rs)
{
if (!rds_cong_test_bit(map, port))
return 0;
if (nonblock) {
if (rs && rs->rs_cong_monitor) {
unsigned long flags;
/* It would have been nice to have an atomic set_bit on
* a uint64_t. */
spin_lock_irqsave(&rs->rs_lock, flags);
rs->rs_cong_mask |= RDS_CONG_MONITOR_MASK(ntohs(port));
spin_unlock_irqrestore(&rs->rs_lock, flags);
/* Test again - a congestion update may have arrived in
* the meantime. */
if (!rds_cong_test_bit(map, port))
return 0;
}
rds_stats_inc(s_cong_send_error);
return -ENOBUFS;
}
rds_stats_inc(s_cong_send_blocked);
rdsdebug("waiting on map %p for port %u\n", map, be16_to_cpu(port));
return wait_event_interruptible(map->m_waitq,
!rds_cong_test_bit(map, port));
}
void rds_cong_exit(void)
{
struct rb_node *node;
struct rds_cong_map *map;
unsigned long i;
while ((node = rb_first(&rds_cong_tree))) {
map = rb_entry(node, struct rds_cong_map, m_rb_node);
rdsdebug("freeing map %p\n", map);
rb_erase(&map->m_rb_node, &rds_cong_tree);
for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
free_page(map->m_page_addrs[i]);
kfree(map);
}
}
/*
* Allocate a RDS message containing a congestion update.
*/
struct rds_message *rds_cong_update_alloc(struct rds_connection *conn)
{
struct rds_cong_map *map = conn->c_lcong;
struct rds_message *rm;
rm = rds_message_map_pages(map->m_page_addrs, RDS_CONG_MAP_BYTES);
if (!IS_ERR(rm))
rm->m_inc.i_hdr.h_flags = RDS_FLAG_CONG_BITMAP;
return rm;
}
