/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * This file contains code imported from the OFED rds source file cong.c
 * Oracle elects to have and use the contents of cong.c under and governed
 * by the OpenIB.org BSD license (see below for full license text). However,
 * the following notice accompanied the original version of this file:
 */


/*
 * 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 <sys/rds.h>

#include <sys/ib/clients/rdsv3/rdsv3.h>
#include <sys/ib/clients/rdsv3/rdsv3_impl.h>
#include <sys/ib/clients/rdsv3/rdsv3_debug.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 rdsv3_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 rdsv3_poll
 * finds that the saved generation number is smaller than the global generation
 * number, it wakes up the process.
 */
static atomic_t         rdsv3_cong_generation = ATOMIC_INIT(0);

/*
 * Congestion monitoring
 */
static struct list rdsv3_cong_monitor;
static krwlock_t rdsv3_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 kmutex_t rdsv3_cong_lock;
static struct avl_tree rdsv3_cong_tree;

static struct rdsv3_cong_map *
rdsv3_cong_tree_walk(uint32_be_t addr, struct rdsv3_cong_map *insert)
{
        struct rdsv3_cong_map *map;
        avl_index_t where;

        if (insert) {
                map = avl_find(&rdsv3_cong_tree, insert, &where);
                if (map == NULL) {
                        avl_insert(&rdsv3_cong_tree, insert, where);
                        return (NULL);
                }
        } else {
                struct rdsv3_cong_map map1;
                map1.m_addr = addr;
                map = avl_find(&rdsv3_cong_tree, &map1, &where);
        }

        return (map);
}

/*
 * 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 rdsv3_cong_map *
rdsv3_cong_from_addr(uint32_be_t addr)
{
        struct rdsv3_cong_map *map;
        struct rdsv3_cong_map *ret = NULL;
        unsigned long zp;
        unsigned long i;

        RDSV3_DPRINTF4("rdsv3_cong_from_addr", "Enter(addr: %x)", ntohl(addr));

        map = kmem_zalloc(sizeof (struct rdsv3_cong_map), KM_NOSLEEP);
        if (!map)
                return (NULL);

        map->m_addr = addr;
        rdsv3_init_waitqueue(&map->m_waitq);
        list_create(&map->m_conn_list, sizeof (struct rdsv3_connection),
            offsetof(struct rdsv3_connection, c_map_item));

        for (i = 0; i < RDSV3_CONG_MAP_PAGES; i++) {
                zp = (unsigned long)kmem_zalloc(PAGE_SIZE, KM_NOSLEEP);
                if (zp == 0)
                        goto out;
                map->m_page_addrs[i] = zp;
        }

        mutex_enter(&rdsv3_cong_lock);
        ret = rdsv3_cong_tree_walk(addr, map);
        mutex_exit(&rdsv3_cong_lock);

        if (!ret) {
                ret = map;
                map = NULL;
        }

out:
        if (map) {
                for (i = 0; i < RDSV3_CONG_MAP_PAGES && map->m_page_addrs[i];
                    i++)
                        kmem_free((void *)map->m_page_addrs[i], PAGE_SIZE);
                kmem_free(map, sizeof (*map));
        }

        RDSV3_DPRINTF5("rdsv3_cong_from_addr", "map %p for addr %x",
            ret, ntohl(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 rdsv3_conn_lock, sadly.
 */
void
rdsv3_cong_add_conn(struct rdsv3_connection *conn)
{
        RDSV3_DPRINTF4("rdsv3_cong_add_conn", "Enter(conn: %p)", conn);

        RDSV3_DPRINTF5("rdsv3_cong_add_conn", "conn %p now on map %p",
            conn, conn->c_lcong);
        mutex_enter(&rdsv3_cong_lock);
        list_insert_tail(&conn->c_lcong->m_conn_list, conn);
        mutex_exit(&rdsv3_cong_lock);

        RDSV3_DPRINTF4("rdsv3_cong_add_conn", "Return(conn: %p)", conn);
}

void
rdsv3_cong_remove_conn(struct rdsv3_connection *conn)
{
        RDSV3_DPRINTF4("rdsv3_cong_remove_conn", "Enter(conn: %p)", conn);

        RDSV3_DPRINTF5("rdsv3_cong_remove_conn", "removing conn %p from map %p",
            conn, conn->c_lcong);
        mutex_enter(&rdsv3_cong_lock);
        list_remove_node(&conn->c_map_item);
        mutex_exit(&rdsv3_cong_lock);

        RDSV3_DPRINTF4("rdsv3_cong_remove_conn", "Return(conn: %p)", conn);
}

int
rdsv3_cong_get_maps(struct rdsv3_connection *conn)
{
        conn->c_lcong = rdsv3_cong_from_addr(conn->c_laddr);
        conn->c_fcong = rdsv3_cong_from_addr(conn->c_faddr);

        if (!(conn->c_lcong && conn->c_fcong))
                return (-ENOMEM);

        return (0);
}

void
rdsv3_cong_queue_updates(struct rdsv3_cong_map *map)
{
        struct rdsv3_connection *conn;

        RDSV3_DPRINTF4("rdsv3_cong_queue_updates", "Enter(map: %p)", map);

        mutex_enter(&rdsv3_cong_lock);

        RDSV3_FOR_EACH_LIST_NODE(conn, &map->m_conn_list, c_map_item) {
                if (!test_and_set_bit(0, &conn->c_map_queued)) {
                        rdsv3_stats_inc(s_cong_update_queued);
                        (void) rdsv3_send_xmit(conn);
                }
        }

        mutex_exit(&rdsv3_cong_lock);

        RDSV3_DPRINTF4("rdsv3_cong_queue_updates", "Return(map: %p)", map);
}

void
rdsv3_cong_map_updated(struct rdsv3_cong_map *map, uint64_t portmask)
{
        RDSV3_DPRINTF4("rdsv3_cong_map_updated",
            "waking map %p for %u.%u.%u.%u",
            map, NIPQUAD(map->m_addr));

        rdsv3_stats_inc(s_cong_update_received);
        atomic_inc_32(&rdsv3_cong_generation);
#if 0
XXX
        if (waitqueue_active(&map->m_waitq))
#endif
                rdsv3_wake_up(&map->m_waitq);

        if (portmask && !list_is_empty(&rdsv3_cong_monitor)) {
                struct rdsv3_sock *rs;

                rw_enter(&rdsv3_cong_monitor_lock, RW_READER);
                RDSV3_FOR_EACH_LIST_NODE(rs, &rdsv3_cong_monitor,
                    rs_cong_list) {
                        mutex_enter(&rs->rs_lock);
                        rs->rs_cong_notify |= (rs->rs_cong_mask & portmask);
                        rs->rs_cong_mask &= ~portmask;
                        mutex_exit(&rs->rs_lock);
                        if (rs->rs_cong_notify)
                                rdsv3_wake_sk_sleep(rs);
                }
                rw_exit(&rdsv3_cong_monitor_lock);
        }

        RDSV3_DPRINTF4("rdsv3_cong_map_updated", "Return(map: %p)", map);
}

int
rdsv3_cong_updated_since(unsigned long *recent)
{
        unsigned long gen = atomic_get(&rdsv3_cong_generation);

        if (*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
rdsv3_cong_set_bit(struct rdsv3_cong_map *map, uint16_be_t port)
{
        unsigned long i;
        unsigned long off;

        RDSV3_DPRINTF4("rdsv3_cong_set_bit",
            "setting congestion for %u.%u.%u.%u:%u in map %p",
            NIPQUAD(map->m_addr), ntohs(port), map);

        i = ntohs(port) / RDSV3_CONG_MAP_PAGE_BITS;
        off = ntohs(port) % RDSV3_CONG_MAP_PAGE_BITS;
        set_le_bit(off, (void *)map->m_page_addrs[i]);
}

void
rdsv3_cong_clear_bit(struct rdsv3_cong_map *map, uint16_be_t port)
{
        unsigned long i;
        unsigned long off;

        RDSV3_DPRINTF4("rdsv3_cong_clear_bit",
            "clearing congestion for %u.%u.%u.%u:%u in map %p\n",
            NIPQUAD(map->m_addr), ntohs(port), map);

        i = ntohs(port) / RDSV3_CONG_MAP_PAGE_BITS;
        off = ntohs(port) % RDSV3_CONG_MAP_PAGE_BITS;
        clear_le_bit(off, (void *)map->m_page_addrs[i]);
}

static int
rdsv3_cong_test_bit(struct rdsv3_cong_map *map, uint16_be_t port)
{
        unsigned long i;
        unsigned long off;

        i = ntohs(port) / RDSV3_CONG_MAP_PAGE_BITS;
        off = ntohs(port) % RDSV3_CONG_MAP_PAGE_BITS;

        RDSV3_DPRINTF5("rdsv3_cong_test_bit", "port: 0x%x i = %lx off = %lx",
            ntohs(port), i, off);

        return (test_le_bit(off, (void *)map->m_page_addrs[i]));
}

void
rdsv3_cong_add_socket(struct rdsv3_sock *rs)
{
        RDSV3_DPRINTF4("rdsv3_cong_add_socket", "Enter(rs: %p)", rs);

        rw_enter(&rdsv3_cong_monitor_lock, RW_WRITER);
        if (!list_link_active(&rs->rs_cong_list))
                list_insert_head(&rdsv3_cong_monitor, rs);
        rw_exit(&rdsv3_cong_monitor_lock);
}

void
rdsv3_cong_remove_socket(struct rdsv3_sock *rs)
{
        struct rdsv3_cong_map *map;

        RDSV3_DPRINTF4("rdsv3_cong_remove_socket", "Enter(rs: %p)", rs);

        rw_enter(&rdsv3_cong_monitor_lock, RW_WRITER);
        list_remove_node(&rs->rs_cong_list);
        rw_exit(&rdsv3_cong_monitor_lock);

        /* update congestion map for now-closed port */
        mutex_enter(&rdsv3_cong_lock);
        map = rdsv3_cong_tree_walk(rs->rs_bound_addr, NULL);
        mutex_exit(&rdsv3_cong_lock);

        if (map && rdsv3_cong_test_bit(map, rs->rs_bound_port)) {
                rdsv3_cong_clear_bit(map, rs->rs_bound_port);
                rdsv3_cong_queue_updates(map);
        }
}

int
rdsv3_cong_wait(struct rdsv3_cong_map *map, uint16_be_t port, int nonblock,
    struct rdsv3_sock *rs)
{
        int ret = 0;

        RDSV3_DPRINTF4("rdsv3_cong_wait", "Enter(rs: %p, mode: %d)",
            rs, nonblock);

        if (!rdsv3_cong_test_bit(map, port))
                return (0);
        if (nonblock) {
                if (rs && rs->rs_cong_monitor) {
                        /*
                         * It would have been nice to have an atomic set_bit on
                         * a uint64_t.
                         */
                        mutex_enter(&rs->rs_lock);
                        rs->rs_cong_mask |=
                            RDS_CONG_MONITOR_MASK(ntohs(port));
                        mutex_exit(&rs->rs_lock);

                        /*
                         * Test again - a congestion update may have arrived in
                         * the meantime.
                         */
                        if (!rdsv3_cong_test_bit(map, port))
                                return (0);
                }
                rdsv3_stats_inc(s_cong_send_error);
                return (-ENOBUFS);
        }

        rdsv3_stats_inc(s_cong_send_blocked);
        RDSV3_DPRINTF3("rdsv3_cong_wait", "waiting on map %p for port %u",
            map, ntohs(port));

#if 0
        ret = rdsv3_wait_sig(&map->m_waitq, !rdsv3_cong_test_bit(map, port));
        if (ret == 0)
                return (-ERESTART);
        return (0);
#else
        mutex_enter(&map->m_waitq.waitq_mutex);
        map->m_waitq.waitq_waiters++;
        while (rdsv3_cong_test_bit(map, port)) {
                ret = cv_wait_sig(&map->m_waitq.waitq_cv,
                    &map->m_waitq.waitq_mutex);
                if (ret == 0) {
                        ret = -EINTR;
                        break;
                }
        }
        map->m_waitq.waitq_waiters--;
        mutex_exit(&map->m_waitq.waitq_mutex);
        return (ret);
#endif
}

void
rdsv3_cong_exit(void)
{
        struct rdsv3_cong_map *map;
        unsigned long i;

        RDSV3_DPRINTF4("rdsv3_cong_exit", "Enter");

        while ((map = avl_first(&rdsv3_cong_tree))) {
                RDSV3_DPRINTF5("rdsv3_cong_exit", "freeing map %p\n", map);
                avl_remove(&rdsv3_cong_tree, map);
                for (i = 0; i < RDSV3_CONG_MAP_PAGES && map->m_page_addrs[i];
                    i++)
                        kmem_free((void *)map->m_page_addrs[i], PAGE_SIZE);
                kmem_free(map, sizeof (*map));
        }

        RDSV3_DPRINTF4("rdsv3_cong_exit", "Return");
}

/*
 * Allocate a RDS message containing a congestion update.
 */
struct rdsv3_message *
rdsv3_cong_update_alloc(struct rdsv3_connection *conn)
{
        struct rdsv3_cong_map *map = conn->c_lcong;
        struct rdsv3_message *rm;

        rm = rdsv3_message_map_pages(map->m_page_addrs, RDSV3_CONG_MAP_BYTES);
        if (!IS_ERR(rm))
                rm->m_inc.i_hdr.h_flags = RDSV3_FLAG_CONG_BITMAP;

        return (rm);
}

static int
rdsv3_cong_compare(const void *map1, const void *map2)
{
#define addr1   ((struct rdsv3_cong_map *)map1)->m_addr
#define addr2   ((struct rdsv3_cong_map *)map2)->m_addr

        if (addr1 < addr2)
                return (-1);
        if (addr1 > addr2)
                return (1);
        return (0);
}

void
rdsv3_cong_init(void)
{
        list_create(&rdsv3_cong_monitor, sizeof (struct rdsv3_sock),
            offsetof(struct rdsv3_sock, rs_cong_list));
        rw_init(&rdsv3_cong_monitor_lock, NULL, RW_DRIVER, NULL);
        mutex_init(&rdsv3_cong_lock, NULL, MUTEX_DRIVER, NULL);
        avl_create(&rdsv3_cong_tree, rdsv3_cong_compare,
            sizeof (struct rdsv3_cong_map), offsetof(struct rdsv3_cong_map,
            m_rb_node));
}