Merge tag 'io_uring-5.11-2021-01-16' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / net / rds / recv.c

/*
 * Copyright (c) 2006, 2019 Oracle and/or its affiliates. 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/kernel.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/in.h>
#include <linux/export.h>
#include <linux/time.h>
#include <linux/rds.h>

#include "rds.h"

void rds_inc_init(struct rds_incoming *inc, struct rds_connection *conn,
                 struct in6_addr *saddr)
{
        refcount_set(&inc->i_refcount, 1);
        INIT_LIST_HEAD(&inc->i_item);
        inc->i_conn = conn;
        inc->i_saddr = *saddr;
        inc->i_usercopy.rdma_cookie = 0;
        inc->i_usercopy.rx_tstamp = ktime_set(0, 0);

        memset(inc->i_rx_lat_trace, 0, sizeof(inc->i_rx_lat_trace));
}
EXPORT_SYMBOL_GPL(rds_inc_init);

void rds_inc_path_init(struct rds_incoming *inc, struct rds_conn_path *cp,
                       struct in6_addr  *saddr)
{
        refcount_set(&inc->i_refcount, 1);
        INIT_LIST_HEAD(&inc->i_item);
        inc->i_conn = cp->cp_conn;
        inc->i_conn_path = cp;
        inc->i_saddr = *saddr;
        inc->i_usercopy.rdma_cookie = 0;
        inc->i_usercopy.rx_tstamp = ktime_set(0, 0);
}
EXPORT_SYMBOL_GPL(rds_inc_path_init);

static void rds_inc_addref(struct rds_incoming *inc)
{
        rdsdebug("addref inc %p ref %d\n", inc, refcount_read(&inc->i_refcount));
        refcount_inc(&inc->i_refcount);
}

void rds_inc_put(struct rds_incoming *inc)
{
        rdsdebug("put inc %p ref %d\n", inc, refcount_read(&inc->i_refcount));
        if (refcount_dec_and_test(&inc->i_refcount)) {
                BUG_ON(!list_empty(&inc->i_item));

                inc->i_conn->c_trans->inc_free(inc);
        }
}
EXPORT_SYMBOL_GPL(rds_inc_put);

static void rds_recv_rcvbuf_delta(struct rds_sock *rs, struct sock *sk,
                                  struct rds_cong_map *map,
                                  int delta, __be16 port)
{
        int now_congested;

        if (delta == 0)
                return;

        rs->rs_rcv_bytes += delta;
        if (delta > 0)
                rds_stats_add(s_recv_bytes_added_to_socket, delta);
        else
                rds_stats_add(s_recv_bytes_removed_from_socket, -delta);

        /* loop transport doesn't send/recv congestion updates */
        if (rs->rs_transport->t_type == RDS_TRANS_LOOP)
                return;

        now_congested = rs->rs_rcv_bytes > rds_sk_rcvbuf(rs);

        rdsdebug("rs %p (%pI6c:%u) recv bytes %d buf %d "
          "now_cong %d delta %d\n",
          rs, &rs->rs_bound_addr,
          ntohs(rs->rs_bound_port), rs->rs_rcv_bytes,
          rds_sk_rcvbuf(rs), now_congested, delta);

        /* wasn't -> am congested */
        if (!rs->rs_congested && now_congested) {
                rs->rs_congested = 1;
                rds_cong_set_bit(map, port);
                rds_cong_queue_updates(map);
        }
        /* was -> aren't congested */
        /* Require more free space before reporting uncongested to prevent
           bouncing cong/uncong state too often */
        else if (rs->rs_congested && (rs->rs_rcv_bytes < (rds_sk_rcvbuf(rs)/2))) {
                rs->rs_congested = 0;
                rds_cong_clear_bit(map, port);
                rds_cong_queue_updates(map);
        }

        /* do nothing if no change in cong state */
}

static void rds_conn_peer_gen_update(struct rds_connection *conn,
                                     u32 peer_gen_num)
{
        int i;
        struct rds_message *rm, *tmp;
        unsigned long flags;

        WARN_ON(conn->c_trans->t_type != RDS_TRANS_TCP);
        if (peer_gen_num != 0) {
                if (conn->c_peer_gen_num != 0 &&
                    peer_gen_num != conn->c_peer_gen_num) {
                        for (i = 0; i < RDS_MPATH_WORKERS; i++) {
                                struct rds_conn_path *cp;

                                cp = &conn->c_path[i];
                                spin_lock_irqsave(&cp->cp_lock, flags);
                                cp->cp_next_tx_seq = 1;
                                cp->cp_next_rx_seq = 0;
                                list_for_each_entry_safe(rm, tmp,
                                                         &cp->cp_retrans,
                                                         m_conn_item) {
                                        set_bit(RDS_MSG_FLUSH, &rm->m_flags);
                                }
                                spin_unlock_irqrestore(&cp->cp_lock, flags);
                        }
                }
                conn->c_peer_gen_num = peer_gen_num;
        }
}

/*
 * Process all extension headers that come with this message.
 */
static void rds_recv_incoming_exthdrs(struct rds_incoming *inc, struct rds_sock *rs)
{
        struct rds_header *hdr = &inc->i_hdr;
        unsigned int pos = 0, type, len;
        union {
                struct rds_ext_header_version version;
                struct rds_ext_header_rdma rdma;
                struct rds_ext_header_rdma_dest rdma_dest;
        } buffer;

        while (1) {
                len = sizeof(buffer);
                type = rds_message_next_extension(hdr, &pos, &buffer, &len);
                if (type == RDS_EXTHDR_NONE)
                        break;
                /* Process extension header here */
                switch (type) {
                case RDS_EXTHDR_RDMA:
                        rds_rdma_unuse(rs, be32_to_cpu(buffer.rdma.h_rdma_rkey), 0);
                        break;

                case RDS_EXTHDR_RDMA_DEST:
                        /* We ignore the size for now. We could stash it
                         * somewhere and use it for error checking. */
                        inc->i_usercopy.rdma_cookie = rds_rdma_make_cookie(
                                        be32_to_cpu(buffer.rdma_dest.h_rdma_rkey),
                                        be32_to_cpu(buffer.rdma_dest.h_rdma_offset));

                        break;
                }
        }
}

static void rds_recv_hs_exthdrs(struct rds_header *hdr,
                                struct rds_connection *conn)
{
        unsigned int pos = 0, type, len;
        union {
                struct rds_ext_header_version version;
                u16 rds_npaths;
                u32 rds_gen_num;
        } buffer;
        u32 new_peer_gen_num = 0;

        while (1) {
                len = sizeof(buffer);
                type = rds_message_next_extension(hdr, &pos, &buffer, &len);
                if (type == RDS_EXTHDR_NONE)
                        break;
                /* Process extension header here */
                switch (type) {
                case RDS_EXTHDR_NPATHS:
                        conn->c_npaths = min_t(int, RDS_MPATH_WORKERS,
                                               be16_to_cpu(buffer.rds_npaths));
                        break;
                case RDS_EXTHDR_GEN_NUM:
                        new_peer_gen_num = be32_to_cpu(buffer.rds_gen_num);
                        break;
                default:
                        pr_warn_ratelimited("ignoring unknown exthdr type "
                                             "0x%x\n", type);
                }
        }
        /* if RDS_EXTHDR_NPATHS was not found, default to a single-path */
        conn->c_npaths = max_t(int, conn->c_npaths, 1);
        conn->c_ping_triggered = 0;
        rds_conn_peer_gen_update(conn, new_peer_gen_num);
}

/* rds_start_mprds() will synchronously start multiple paths when appropriate.
 * The scheme is based on the following rules:
 *
 * 1. rds_sendmsg on first connect attempt sends the probe ping, with the
 *    sender's npaths (s_npaths)
 * 2. rcvr of probe-ping knows the mprds_paths = min(s_npaths, r_npaths). It
 *    sends back a probe-pong with r_npaths. After that, if rcvr is the
 *    smaller ip addr, it starts rds_conn_path_connect_if_down on all
 *    mprds_paths.
 * 3. sender gets woken up, and can move to rds_conn_path_connect_if_down.
 *    If it is the smaller ipaddr, rds_conn_path_connect_if_down can be
 *    called after reception of the probe-pong on all mprds_paths.
 *    Otherwise (sender of probe-ping is not the smaller ip addr): just call
 *    rds_conn_path_connect_if_down on the hashed path. (see rule 4)
 * 4. rds_connect_worker must only trigger a connection if laddr < faddr.
 * 5. sender may end up queuing the packet on the cp. will get sent out later.
 *    when connection is completed.
 */
static void rds_start_mprds(struct rds_connection *conn)
{
        int i;
        struct rds_conn_path *cp;

        if (conn->c_npaths > 1 &&
            rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) < 0) {
                for (i = 0; i < conn->c_npaths; i++) {
                        cp = &conn->c_path[i];
                        rds_conn_path_connect_if_down(cp);
                }
        }
}

/*
 * The transport must make sure that this is serialized against other
 * rx and conn reset on this specific conn.
 *
 * We currently assert that only one fragmented message will be sent
 * down a connection at a time.  This lets us reassemble in the conn
 * instead of per-flow which means that we don't have to go digging through
 * flows to tear down partial reassembly progress on conn failure and
 * we save flow lookup and locking for each frag arrival.  It does mean
 * that small messages will wait behind large ones.  Fragmenting at all
 * is only to reduce the memory consumption of pre-posted buffers.
 *
 * The caller passes in saddr and daddr instead of us getting it from the
 * conn.  This lets loopback, who only has one conn for both directions,
 * tell us which roles the addrs in the conn are playing for this message.
 */
void rds_recv_incoming(struct rds_connection *conn, struct in6_addr *saddr,
                       struct in6_addr *daddr,
                       struct rds_incoming *inc, gfp_t gfp)
{
        struct rds_sock *rs = NULL;
        struct sock *sk;
        unsigned long flags;
        struct rds_conn_path *cp;

        inc->i_conn = conn;
        inc->i_rx_jiffies = jiffies;
        if (conn->c_trans->t_mp_capable)
                cp = inc->i_conn_path;
        else
                cp = &conn->c_path[0];

        rdsdebug("conn %p next %llu inc %p seq %llu len %u sport %u dport %u "
                 "flags 0x%x rx_jiffies %lu\n", conn,
                 (unsigned long long)cp->cp_next_rx_seq,
                 inc,
                 (unsigned long long)be64_to_cpu(inc->i_hdr.h_sequence),
                 be32_to_cpu(inc->i_hdr.h_len),
                 be16_to_cpu(inc->i_hdr.h_sport),
                 be16_to_cpu(inc->i_hdr.h_dport),
                 inc->i_hdr.h_flags,
                 inc->i_rx_jiffies);

        /*
         * Sequence numbers should only increase.  Messages get their
         * sequence number as they're queued in a sending conn.  They
         * can be dropped, though, if the sending socket is closed before
         * they hit the wire.  So sequence numbers can skip forward
         * under normal operation.  They can also drop back in the conn
         * failover case as previously sent messages are resent down the
         * new instance of a conn.  We drop those, otherwise we have
         * to assume that the next valid seq does not come after a
         * hole in the fragment stream.
         *
         * The headers don't give us a way to realize if fragments of
         * a message have been dropped.  We assume that frags that arrive
         * to a flow are part of the current message on the flow that is
         * being reassembled.  This means that senders can't drop messages
         * from the sending conn until all their frags are sent.
         *
         * XXX we could spend more on the wire to get more robust failure
         * detection, arguably worth it to avoid data corruption.
         */
        if (be64_to_cpu(inc->i_hdr.h_sequence) < cp->cp_next_rx_seq &&
            (inc->i_hdr.h_flags & RDS_FLAG_RETRANSMITTED)) {
                rds_stats_inc(s_recv_drop_old_seq);
                goto out;
        }
        cp->cp_next_rx_seq = be64_to_cpu(inc->i_hdr.h_sequence) + 1;

        if (rds_sysctl_ping_enable && inc->i_hdr.h_dport == 0) {
                if (inc->i_hdr.h_sport == 0) {
                        rdsdebug("ignore ping with 0 sport from %pI6c\n",
                                 saddr);
                        goto out;
                }
                rds_stats_inc(s_recv_ping);
                rds_send_pong(cp, inc->i_hdr.h_sport);
                /* if this is a handshake ping, start multipath if necessary */
                if (RDS_HS_PROBE(be16_to_cpu(inc->i_hdr.h_sport),
                                 be16_to_cpu(inc->i_hdr.h_dport))) {
                        rds_recv_hs_exthdrs(&inc->i_hdr, cp->cp_conn);
                        rds_start_mprds(cp->cp_conn);
                }
                goto out;
        }

        if (be16_to_cpu(inc->i_hdr.h_dport) ==  RDS_FLAG_PROBE_PORT &&
            inc->i_hdr.h_sport == 0) {
                rds_recv_hs_exthdrs(&inc->i_hdr, cp->cp_conn);
                /* if this is a handshake pong, start multipath if necessary */
                rds_start_mprds(cp->cp_conn);
                wake_up(&cp->cp_conn->c_hs_waitq);
                goto out;
        }

        rs = rds_find_bound(daddr, inc->i_hdr.h_dport, conn->c_bound_if);
        if (!rs) {
                rds_stats_inc(s_recv_drop_no_sock);
                goto out;
        }

        /* Process extension headers */
        rds_recv_incoming_exthdrs(inc, rs);

        /* We can be racing with rds_release() which marks the socket dead. */
        sk = rds_rs_to_sk(rs);

        /* serialize with rds_release -> sock_orphan */
        write_lock_irqsave(&rs->rs_recv_lock, flags);
        if (!sock_flag(sk, SOCK_DEAD)) {
                rdsdebug("adding inc %p to rs %p's recv queue\n", inc, rs);
                rds_stats_inc(s_recv_queued);
                rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
                                      be32_to_cpu(inc->i_hdr.h_len),
                                      inc->i_hdr.h_dport);
                if (sock_flag(sk, SOCK_RCVTSTAMP))
                        inc->i_usercopy.rx_tstamp = ktime_get_real();
                rds_inc_addref(inc);
                inc->i_rx_lat_trace[RDS_MSG_RX_END] = local_clock();
                list_add_tail(&inc->i_item, &rs->rs_recv_queue);
                __rds_wake_sk_sleep(sk);
        } else {
                rds_stats_inc(s_recv_drop_dead_sock);
        }
        write_unlock_irqrestore(&rs->rs_recv_lock, flags);

out:
        if (rs)
                rds_sock_put(rs);
}
EXPORT_SYMBOL_GPL(rds_recv_incoming);

/*
 * be very careful here.  This is being called as the condition in
 * wait_event_*() needs to cope with being called many times.
 */
static int rds_next_incoming(struct rds_sock *rs, struct rds_incoming **inc)
{
        unsigned long flags;

        if (!*inc) {
                read_lock_irqsave(&rs->rs_recv_lock, flags);
                if (!list_empty(&rs->rs_recv_queue)) {
                        *inc = list_entry(rs->rs_recv_queue.next,
                                          struct rds_incoming,
                                          i_item);
                        rds_inc_addref(*inc);
                }
                read_unlock_irqrestore(&rs->rs_recv_lock, flags);
        }

        return *inc != NULL;
}

static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc,
                            int drop)
{
        struct sock *sk = rds_rs_to_sk(rs);
        int ret = 0;
        unsigned long flags;

        write_lock_irqsave(&rs->rs_recv_lock, flags);
        if (!list_empty(&inc->i_item)) {
                ret = 1;
                if (drop) {
                        /* XXX make sure this i_conn is reliable */
                        rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
                                              -be32_to_cpu(inc->i_hdr.h_len),
                                              inc->i_hdr.h_dport);
                        list_del_init(&inc->i_item);
                        rds_inc_put(inc);
                }
        }
        write_unlock_irqrestore(&rs->rs_recv_lock, flags);

        rdsdebug("inc %p rs %p still %d dropped %d\n", inc, rs, ret, drop);
        return ret;
}

/*
 * Pull errors off the error queue.
 * If msghdr is NULL, we will just purge the error queue.
 */
int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
{
        struct rds_notifier *notifier;
        struct rds_rdma_notify cmsg;
        unsigned int count = 0, max_messages = ~0U;
        unsigned long flags;
        LIST_HEAD(copy);
        int err = 0;

        memset(&cmsg, 0, sizeof(cmsg)); /* fill holes with zero */

        /* put_cmsg copies to user space and thus may sleep. We can't do this
         * with rs_lock held, so first grab as many notifications as we can stuff
         * in the user provided cmsg buffer. We don't try to copy more, to avoid
         * losing notifications - except when the buffer is so small that it wouldn't
         * even hold a single notification. Then we give him as much of this single
         * msg as we can squeeze in, and set MSG_CTRUNC.
         */
        if (msghdr) {
                max_messages = msghdr->msg_controllen / CMSG_SPACE(sizeof(cmsg));
                if (!max_messages)
                        max_messages = 1;
        }

        spin_lock_irqsave(&rs->rs_lock, flags);
        while (!list_empty(&rs->rs_notify_queue) && count < max_messages) {
                notifier = list_entry(rs->rs_notify_queue.next,
                                struct rds_notifier, n_list);
                list_move(&notifier->n_list, &copy);
                count++;
        }
        spin_unlock_irqrestore(&rs->rs_lock, flags);

        if (!count)
                return 0;

        while (!list_empty(&copy)) {
                notifier = list_entry(copy.next, struct rds_notifier, n_list);

                if (msghdr) {
                        cmsg.user_token = notifier->n_user_token;
                        cmsg.status = notifier->n_status;

                        err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_RDMA_STATUS,
                                       sizeof(cmsg), &cmsg);
                        if (err)
                                break;
                }

                list_del_init(&notifier->n_list);
                kfree(notifier);
        }

        /* If we bailed out because of an error in put_cmsg,
         * we may be left with one or more notifications that we
         * didn't process. Return them to the head of the list. */
        if (!list_empty(&copy)) {
                spin_lock_irqsave(&rs->rs_lock, flags);
                list_splice(&copy, &rs->rs_notify_queue);
                spin_unlock_irqrestore(&rs->rs_lock, flags);
        }

        return err;
}

/*
 * Queue a congestion notification
 */
static int rds_notify_cong(struct rds_sock *rs, struct msghdr *msghdr)
{
        uint64_t notify = rs->rs_cong_notify;
        unsigned long flags;
        int err;

        err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_CONG_UPDATE,
                        sizeof(notify), &notify);
        if (err)
                return err;

        spin_lock_irqsave(&rs->rs_lock, flags);
        rs->rs_cong_notify &= ~notify;
        spin_unlock_irqrestore(&rs->rs_lock, flags);

        return 0;
}

/*
 * Receive any control messages.
 */
static int rds_cmsg_recv(struct rds_incoming *inc, struct msghdr *msg,
                         struct rds_sock *rs)
{
        int ret = 0;

        if (inc->i_usercopy.rdma_cookie) {
                ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RDMA_DEST,
                                sizeof(inc->i_usercopy.rdma_cookie),
                                &inc->i_usercopy.rdma_cookie);
                if (ret)
                        goto out;
        }

        if ((inc->i_usercopy.rx_tstamp != 0) &&
            sock_flag(rds_rs_to_sk(rs), SOCK_RCVTSTAMP)) {
                struct __kernel_old_timeval tv =
                        ns_to_kernel_old_timeval(inc->i_usercopy.rx_tstamp);

                if (!sock_flag(rds_rs_to_sk(rs), SOCK_TSTAMP_NEW)) {
                        ret = put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_OLD,
                                       sizeof(tv), &tv);
                } else {
                        struct __kernel_sock_timeval sk_tv;

                        sk_tv.tv_sec = tv.tv_sec;
                        sk_tv.tv_usec = tv.tv_usec;

                        ret = put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_NEW,
                                       sizeof(sk_tv), &sk_tv);
                }

                if (ret)
                        goto out;
        }

        if (rs->rs_rx_traces) {
                struct rds_cmsg_rx_trace t;
                int i, j;

                memset(&t, 0, sizeof(t));
                inc->i_rx_lat_trace[RDS_MSG_RX_CMSG] = local_clock();
                t.rx_traces =  rs->rs_rx_traces;
                for (i = 0; i < rs->rs_rx_traces; i++) {
                        j = rs->rs_rx_trace[i];
                        t.rx_trace_pos[i] = j;
                        t.rx_trace[i] = inc->i_rx_lat_trace[j + 1] -
                                          inc->i_rx_lat_trace[j];
                }

                ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RXPATH_LATENCY,
                               sizeof(t), &t);
                if (ret)
                        goto out;
        }

out:
        return ret;
}

static bool rds_recvmsg_zcookie(struct rds_sock *rs, struct msghdr *msg)
{
        struct rds_msg_zcopy_queue *q = &rs->rs_zcookie_queue;
        struct rds_msg_zcopy_info *info = NULL;
        struct rds_zcopy_cookies *done;
        unsigned long flags;

        if (!msg->msg_control)
                return false;

        if (!sock_flag(rds_rs_to_sk(rs), SOCK_ZEROCOPY) ||
            msg->msg_controllen < CMSG_SPACE(sizeof(*done)))
                return false;

        spin_lock_irqsave(&q->lock, flags);
        if (!list_empty(&q->zcookie_head)) {
                info = list_entry(q->zcookie_head.next,
                                  struct rds_msg_zcopy_info, rs_zcookie_next);
                list_del(&info->rs_zcookie_next);
        }
        spin_unlock_irqrestore(&q->lock, flags);
        if (!info)
                return false;
        done = &info->zcookies;
        if (put_cmsg(msg, SOL_RDS, RDS_CMSG_ZCOPY_COMPLETION, sizeof(*done),
                     done)) {
                spin_lock_irqsave(&q->lock, flags);
                list_add(&info->rs_zcookie_next, &q->zcookie_head);
                spin_unlock_irqrestore(&q->lock, flags);
                return false;
        }
        kfree(info);
        return true;
}

int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
                int msg_flags)
{
        struct sock *sk = sock->sk;
        struct rds_sock *rs = rds_sk_to_rs(sk);
        long timeo;
        int ret = 0, nonblock = msg_flags & MSG_DONTWAIT;
        DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
        DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
        struct rds_incoming *inc = NULL;

        /* udp_recvmsg()->sock_recvtimeo() gets away without locking too.. */
        timeo = sock_rcvtimeo(sk, nonblock);

        rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);

        if (msg_flags & MSG_OOB)
                goto out;
        if (msg_flags & MSG_ERRQUEUE)
                return sock_recv_errqueue(sk, msg, size, SOL_IP, IP_RECVERR);

        while (1) {
                /* If there are pending notifications, do those - and nothing else */
                if (!list_empty(&rs->rs_notify_queue)) {
                        ret = rds_notify_queue_get(rs, msg);
                        break;
                }

                if (rs->rs_cong_notify) {
                        ret = rds_notify_cong(rs, msg);
                        break;
                }

                if (!rds_next_incoming(rs, &inc)) {
                        if (nonblock) {
                                bool reaped = rds_recvmsg_zcookie(rs, msg);

                                ret = reaped ?  0 : -EAGAIN;
                                break;
                        }

                        timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
                                        (!list_empty(&rs->rs_notify_queue) ||
                                         rs->rs_cong_notify ||
                                         rds_next_incoming(rs, &inc)), timeo);
                        rdsdebug("recvmsg woke inc %p timeo %ld\n", inc,
                                 timeo);
                        if (timeo > 0 || timeo == MAX_SCHEDULE_TIMEOUT)
                                continue;

                        ret = timeo;
                        if (ret == 0)
                                ret = -ETIMEDOUT;
                        break;
                }

                rdsdebug("copying inc %p from %pI6c:%u to user\n", inc,
                         &inc->i_conn->c_faddr,
                         ntohs(inc->i_hdr.h_sport));
                ret = inc->i_conn->c_trans->inc_copy_to_user(inc, &msg->msg_iter);
                if (ret < 0)
                        break;

                /*
                 * if the message we just copied isn't at the head of the
                 * recv queue then someone else raced us to return it, try
                 * to get the next message.
                 */
                if (!rds_still_queued(rs, inc, !(msg_flags & MSG_PEEK))) {
                        rds_inc_put(inc);
                        inc = NULL;
                        rds_stats_inc(s_recv_deliver_raced);
                        iov_iter_revert(&msg->msg_iter, ret);
                        continue;
                }

                if (ret < be32_to_cpu(inc->i_hdr.h_len)) {
                        if (msg_flags & MSG_TRUNC)
                                ret = be32_to_cpu(inc->i_hdr.h_len);
                        msg->msg_flags |= MSG_TRUNC;
                }

                if (rds_cmsg_recv(inc, msg, rs)) {
                        ret = -EFAULT;
                        goto out;
                }
                rds_recvmsg_zcookie(rs, msg);

                rds_stats_inc(s_recv_delivered);

                if (msg->msg_name) {
                        if (ipv6_addr_v4mapped(&inc->i_saddr)) {
                                sin = (struct sockaddr_in *)msg->msg_name;

                                sin->sin_family = AF_INET;
                                sin->sin_port = inc->i_hdr.h_sport;
                                sin->sin_addr.s_addr =
                                    inc->i_saddr.s6_addr32[3];
                                memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
                                msg->msg_namelen = sizeof(*sin);
                        } else {
                                sin6 = (struct sockaddr_in6 *)msg->msg_name;

                                sin6->sin6_family = AF_INET6;
                                sin6->sin6_port = inc->i_hdr.h_sport;
                                sin6->sin6_addr = inc->i_saddr;
                                sin6->sin6_flowinfo = 0;
                                sin6->sin6_scope_id = rs->rs_bound_scope_id;
                                msg->msg_namelen = sizeof(*sin6);
                        }
                }
                break;
        }

        if (inc)
                rds_inc_put(inc);

out:
        return ret;
}

/*
 * The socket is being shut down and we're asked to drop messages that were
 * queued for recvmsg.  The caller has unbound the socket so the receive path
 * won't queue any more incoming fragments or messages on the socket.
 */
void rds_clear_recv_queue(struct rds_sock *rs)
{
        struct sock *sk = rds_rs_to_sk(rs);
        struct rds_incoming *inc, *tmp;
        unsigned long flags;

        write_lock_irqsave(&rs->rs_recv_lock, flags);
        list_for_each_entry_safe(inc, tmp, &rs->rs_recv_queue, i_item) {
                rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
                                      -be32_to_cpu(inc->i_hdr.h_len),
                                      inc->i_hdr.h_dport);
                list_del_init(&inc->i_item);
                rds_inc_put(inc);
        }
        write_unlock_irqrestore(&rs->rs_recv_lock, flags);
}

/*
 * inc->i_saddr isn't used here because it is only set in the receive
 * path.
 */
void rds_inc_info_copy(struct rds_incoming *inc,
                       struct rds_info_iterator *iter,
                       __be32 saddr, __be32 daddr, int flip)
{
        struct rds_info_message minfo;

        minfo.seq = be64_to_cpu(inc->i_hdr.h_sequence);
        minfo.len = be32_to_cpu(inc->i_hdr.h_len);
        minfo.tos = inc->i_conn->c_tos;

        if (flip) {
                minfo.laddr = daddr;
                minfo.faddr = saddr;
                minfo.lport = inc->i_hdr.h_dport;
                minfo.fport = inc->i_hdr.h_sport;
        } else {
                minfo.laddr = saddr;
                minfo.faddr = daddr;
                minfo.lport = inc->i_hdr.h_sport;
                minfo.fport = inc->i_hdr.h_dport;
        }

        minfo.flags = 0;

        rds_info_copy(iter, &minfo, sizeof(minfo));
}

#if IS_ENABLED(CONFIG_IPV6)
void rds6_inc_info_copy(struct rds_incoming *inc,
                        struct rds_info_iterator *iter,
                        struct in6_addr *saddr, struct in6_addr *daddr,
                        int flip)
{
        struct rds6_info_message minfo6;

        minfo6.seq = be64_to_cpu(inc->i_hdr.h_sequence);
        minfo6.len = be32_to_cpu(inc->i_hdr.h_len);
        minfo6.tos = inc->i_conn->c_tos;

        if (flip) {
                minfo6.laddr = *daddr;
                minfo6.faddr = *saddr;
                minfo6.lport = inc->i_hdr.h_dport;
                minfo6.fport = inc->i_hdr.h_sport;
        } else {
                minfo6.laddr = *saddr;
                minfo6.faddr = *daddr;
                minfo6.lport = inc->i_hdr.h_sport;
                minfo6.fport = inc->i_hdr.h_dport;
        }

        minfo6.flags = 0;

        rds_info_copy(iter, &minfo6, sizeof(minfo6));
}
#endif