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 /*
  * Copyright (c) 2006, 2018 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/moduleparam.h>
 #include <linux/gfp.h>
 #include <net/sock.h>
 #include <linux/in.h>
 #include <linux/list.h>
 #include <linux/ratelimit.h>
 #include <linux/export.h>
 #include <linux/sizes.h>
 
 #include "rds.h"
 
 /* When transmitting messages in rds_send_xmit, we need to emerge from
  * time to time and briefly release the CPU. Otherwise the softlock watchdog
  * will kick our shin.
  * Also, it seems fairer to not let one busy connection stall all the
  * others.
  *
  * send_batch_count is the number of times we'll loop in send_xmit. Setting
  * it to 0 will restore the old behavior (where we looped until we had
  * drained the queue).
  */
 static int send_batch_count = SZ_1K;
 module_param(send_batch_count, int, 0444);
 MODULE_PARM_DESC(send_batch_count, " batch factor when working the send queue");
 
 static void rds_send_remove_from_sock(struct list_head *messages, int status);
 
 /*
  * Reset the send state.  Callers must ensure that this doesn't race with
  * rds_send_xmit().
  */
 void rds_send_path_reset(struct rds_conn_path *cp)
 {
     struct rds_message *rm, *tmp;
     unsigned long flags;
 
     if (cp->cp_xmit_rm) {
         rm = cp->cp_xmit_rm;
         cp->cp_xmit_rm = NULL;
         /* Tell the user the RDMA op is no longer mapped by the
          * transport. This isn't entirely true (it's flushed out
          * independently) but as the connection is down, there's
          * no ongoing RDMA to/from that memory */
         rds_message_unmapped(rm);
         rds_message_put(rm);
     }
 
     cp->cp_xmit_sg = 0;
     cp->cp_xmit_hdr_off = 0;
     cp->cp_xmit_data_off = 0;
     cp->cp_xmit_atomic_sent = 0;
     cp->cp_xmit_rdma_sent = 0;
     cp->cp_xmit_data_sent = 0;
 
     cp->cp_conn->c_map_queued = 0;
 
     cp->cp_unacked_packets = rds_sysctl_max_unacked_packets;
     cp->cp_unacked_bytes = rds_sysctl_max_unacked_bytes;
 
     /* Mark messages as retransmissions, and move them to the send q */
     spin_lock_irqsave(&cp->cp_lock, flags);
     list_for_each_entry_safe(rm, tmp, &cp->cp_retrans, m_conn_item) {
         set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
         set_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags);
     }
     list_splice_init(&cp->cp_retrans, &cp->cp_send_queue);
     spin_unlock_irqrestore(&cp->cp_lock, flags);
 }
 EXPORT_SYMBOL_GPL(rds_send_path_reset);
 
 static int acquire_in_xmit(struct rds_conn_path *cp)
 {
     return test_and_set_bit(RDS_IN_XMIT, &cp->cp_flags) == 0;
 }
 
 static void release_in_xmit(struct rds_conn_path *cp)
 {
     clear_bit(RDS_IN_XMIT, &cp->cp_flags);
     smp_mb__after_atomic();
     /*
      * We don't use wait_on_bit()/wake_up_bit() because our waking is in a
      * hot path and finding waiters is very rare.  We don't want to walk
      * the system-wide hashed waitqueue buckets in the fast path only to
      * almost never find waiters.
      */
     if (waitqueue_active(&cp->cp_waitq))
         wake_up_all(&cp->cp_waitq);
 }
 
 /*
  * We're making the conscious trade-off here to only send one message
  * down the connection at a time.
  *   Pro:
  *      - tx queueing is a simple fifo list
  *      - reassembly is optional and easily done by transports per conn
  *      - no per flow rx lookup at all, straight to the socket
  *      - less per-frag memory and wire overhead
  *   Con:
  *      - queued acks can be delayed behind large messages
  *   Depends:
  *      - small message latency is higher behind queued large messages
  *      - large message latency isn't starved by intervening small sends
  */
 int rds_send_xmit(struct rds_conn_path *cp)
 {
     struct rds_connection *conn = cp->cp_conn;
     struct rds_message *rm;
     unsigned long flags;
     unsigned int tmp;
     struct scatterlist *sg;
     int ret = 0;
     LIST_HEAD(to_be_dropped);
     int batch_count;
     unsigned long send_gen = 0;
     int same_rm = 0;
 
 restart:
     batch_count = 0;
 
     /*
      * sendmsg calls here after having queued its message on the send
      * queue.  We only have one task feeding the connection at a time.  If
      * another thread is already feeding the queue then we back off.  This
      * avoids blocking the caller and trading per-connection data between
      * caches per message.
      */
     if (!acquire_in_xmit(cp)) {
         rds_stats_inc(s_send_lock_contention);
         ret = -ENOMEM;
         goto out;
     }
 
     if (rds_destroy_pending(cp->cp_conn)) {
         release_in_xmit(cp);
         ret = -ENETUNREACH; /* dont requeue send work */
         goto out;
     }
 
     /*
      * we record the send generation after doing the xmit acquire.
      * if someone else manages to jump in and do some work, we'll use
      * this to avoid a goto restart farther down.
      *
      * The acquire_in_xmit() check above ensures that only one
      * caller can increment c_send_gen at any time.
      */
     send_gen = READ_ONCE(cp->cp_send_gen) + 1;
     WRITE_ONCE(cp->cp_send_gen, send_gen);
 
     /*
      * rds_conn_shutdown() sets the conn state and then tests RDS_IN_XMIT,
      * we do the opposite to avoid races.
      */
     if (!rds_conn_path_up(cp)) {
         release_in_xmit(cp);
         ret = 0;
         goto out;
     }
 
     if (conn->c_trans->xmit_path_prepare)
         conn->c_trans->xmit_path_prepare(cp);
 
     /*
      * spin trying to push headers and data down the connection until
      * the connection doesn't make forward progress.
      */
     while (1) {
 
         rm = cp->cp_xmit_rm;
 
         if (!rm) {
             same_rm = 0;
         } else {
             same_rm++;
             if (same_rm >= 4096) {
                 rds_stats_inc(s_send_stuck_rm);
                 ret = -EAGAIN;
                 break;
             }
         }
 
         /*
          * If between sending messages, we can send a pending congestion
          * map update.
          */
         if (!rm && test_and_clear_bit(0, &conn->c_map_queued)) {
             rm = rds_cong_update_alloc(conn);
             if (IS_ERR(rm)) {
                 ret = PTR_ERR(rm);
                 break;
             }
             rm->data.op_active = 1;
             rm->m_inc.i_conn_path = cp;
             rm->m_inc.i_conn = cp->cp_conn;
 
             cp->cp_xmit_rm = rm;
         }
 
         /*
          * If not already working on one, grab the next message.
          *
          * cp_xmit_rm holds a ref while we're sending this message down
          * the connction.  We can use this ref while holding the
          * send_sem.. rds_send_reset() is serialized with it.
          */
         if (!rm) {
             unsigned int len;
 
             batch_count++;
 
             /* we want to process as big a batch as we can, but
              * we also want to avoid softlockups.  If we've been
              * through a lot of messages, lets back off and see
              * if anyone else jumps in
              */
             if (batch_count >= send_batch_count)
                 goto over_batch;
 
             spin_lock_irqsave(&cp->cp_lock, flags);
 
             if (!list_empty(&cp->cp_send_queue)) {
                 rm = list_entry(cp->cp_send_queue.next,
                         struct rds_message,
                         m_conn_item);
                 rds_message_addref(rm);
 
                 /*
                  * Move the message from the send queue to the retransmit
                  * list right away.
                  */
                 list_move_tail(&rm->m_conn_item,
                            &cp->cp_retrans);
             }
 
             spin_unlock_irqrestore(&cp->cp_lock, flags);
 
             if (!rm)
                 break;
 
             /* Unfortunately, the way Infiniband deals with
              * RDMA to a bad MR key is by moving the entire
              * queue pair to error state. We could possibly
              * recover from that, but right now we drop the
              * connection.
              * Therefore, we never retransmit messages with RDMA ops.
              */
             if (test_bit(RDS_MSG_FLUSH, &rm->m_flags) ||
                 (rm->rdma.op_active &&
                 test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))) {
                 spin_lock_irqsave(&cp->cp_lock, flags);
                 if (test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags))
                     list_move(&rm->m_conn_item, &to_be_dropped);
                 spin_unlock_irqrestore(&cp->cp_lock, flags);
                 continue;
             }
 
             /* Require an ACK every once in a while */
             len = ntohl(rm->m_inc.i_hdr.h_len);
             if (cp->cp_unacked_packets == 0 ||
                 cp->cp_unacked_bytes < len) {
                 set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
 
                 cp->cp_unacked_packets =
                     rds_sysctl_max_unacked_packets;
                 cp->cp_unacked_bytes =
                     rds_sysctl_max_unacked_bytes;
                 rds_stats_inc(s_send_ack_required);
             } else {
                 cp->cp_unacked_bytes -= len;
                 cp->cp_unacked_packets--;
             }
 
             cp->cp_xmit_rm = rm;
         }
 
         /* The transport either sends the whole rdma or none of it */
         if (rm->rdma.op_active && !cp->cp_xmit_rdma_sent) {
             rm->m_final_op = &rm->rdma;
             /* The transport owns the mapped memory for now.
              * You can't unmap it while it's on the send queue
              */
             set_bit(RDS_MSG_MAPPED, &rm->m_flags);
             ret = conn->c_trans->xmit_rdma(conn, &rm->rdma);
             if (ret) {
                 clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
                 wake_up_interruptible(&rm->m_flush_wait);
                 break;
             }
             cp->cp_xmit_rdma_sent = 1;
 
         }
 
         if (rm->atomic.op_active && !cp->cp_xmit_atomic_sent) {
             rm->m_final_op = &rm->atomic;
             /* The transport owns the mapped memory for now.
              * You can't unmap it while it's on the send queue
              */
             set_bit(RDS_MSG_MAPPED, &rm->m_flags);
             ret = conn->c_trans->xmit_atomic(conn, &rm->atomic);
             if (ret) {
                 clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
                 wake_up_interruptible(&rm->m_flush_wait);
                 break;
             }
             cp->cp_xmit_atomic_sent = 1;
 
         }
 
         /*
          * A number of cases require an RDS header to be sent
          * even if there is no data.
          * We permit 0-byte sends; rds-ping depends on this.
          * However, if there are exclusively attached silent ops,
          * we skip the hdr/data send, to enable silent operation.
          */
         if (rm->data.op_nents == 0) {
             int ops_present;
             int all_ops_are_silent = 1;
 
             ops_present = (rm->atomic.op_active || rm->rdma.op_active);
             if (rm->atomic.op_active && !rm->atomic.op_silent)
                 all_ops_are_silent = 0;
             if (rm->rdma.op_active && !rm->rdma.op_silent)
                 all_ops_are_silent = 0;
 
             if (ops_present && all_ops_are_silent
                 && !rm->m_rdma_cookie)
                 rm->data.op_active = 0;
         }
 
         if (rm->data.op_active && !cp->cp_xmit_data_sent) {
             rm->m_final_op = &rm->data;
 
             ret = conn->c_trans->xmit(conn, rm,
                           cp->cp_xmit_hdr_off,
                           cp->cp_xmit_sg,
                           cp->cp_xmit_data_off);
             if (ret <= 0)
                 break;
 
             if (cp->cp_xmit_hdr_off < sizeof(struct rds_header)) {
                 tmp = min_t(int, ret,
                         sizeof(struct rds_header) -
                         cp->cp_xmit_hdr_off);
                 cp->cp_xmit_hdr_off += tmp;
                 ret -= tmp;
             }
 
             sg = &rm->data.op_sg[cp->cp_xmit_sg];
             while (ret) {
                 tmp = min_t(int, ret, sg->length -
                               cp->cp_xmit_data_off);
                 cp->cp_xmit_data_off += tmp;
                 ret -= tmp;
                 if (cp->cp_xmit_data_off == sg->length) {
                     cp->cp_xmit_data_off = 0;
                     sg++;
                     cp->cp_xmit_sg++;
                     BUG_ON(ret != 0 && cp->cp_xmit_sg ==
                            rm->data.op_nents);
                 }
             }
 
             if (cp->cp_xmit_hdr_off == sizeof(struct rds_header) &&
                 (cp->cp_xmit_sg == rm->data.op_nents))
                 cp->cp_xmit_data_sent = 1;
         }
 
         /*
          * A rm will only take multiple times through this loop
          * if there is a data op. Thus, if the data is sent (or there was
          * none), then we're done with the rm.
          */
         if (!rm->data.op_active || cp->cp_xmit_data_sent) {
             cp->cp_xmit_rm = NULL;
             cp->cp_xmit_sg = 0;
             cp->cp_xmit_hdr_off = 0;
             cp->cp_xmit_data_off = 0;
             cp->cp_xmit_rdma_sent = 0;
             cp->cp_xmit_atomic_sent = 0;
             cp->cp_xmit_data_sent = 0;
 
             rds_message_put(rm);
         }
     }
 
 over_batch:
     if (conn->c_trans->xmit_path_complete)
         conn->c_trans->xmit_path_complete(cp);
     release_in_xmit(cp);
 
     /* Nuke any messages we decided not to retransmit. */
     if (!list_empty(&to_be_dropped)) {
         /* irqs on here, so we can put(), unlike above */
         list_for_each_entry(rm, &to_be_dropped, m_conn_item)
             rds_message_put(rm);
         rds_send_remove_from_sock(&to_be_dropped, RDS_RDMA_DROPPED);
     }
 
     /*
      * Other senders can queue a message after we last test the send queue
      * but before we clear RDS_IN_XMIT.  In that case they'd back off and
      * not try and send their newly queued message.  We need to check the
      * send queue after having cleared RDS_IN_XMIT so that their message
      * doesn't get stuck on the send queue.
      *
      * If the transport cannot continue (i.e ret != 0), then it must
      * call us when more room is available, such as from the tx
      * completion handler.
      *
      * We have an extra generation check here so that if someone manages
      * to jump in after our release_in_xmit, we'll see that they have done
      * some work and we will skip our goto
      */
     if (ret == 0) {
         bool raced;
 
         smp_mb();
         raced = send_gen != READ_ONCE(cp->cp_send_gen);
 
         if ((test_bit(0, &conn->c_map_queued) ||
             !list_empty(&cp->cp_send_queue)) && !raced) {
             if (batch_count < send_batch_count)
                 goto restart;
             rcu_read_lock();
             if (rds_destroy_pending(cp->cp_conn))
                 ret = -ENETUNREACH;
             else
                 queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
             rcu_read_unlock();
         } else if (raced) {
             rds_stats_inc(s_send_lock_queue_raced);
         }
     }
 out:
     return ret;
 }
 EXPORT_SYMBOL_GPL(rds_send_xmit);
 
 static void rds_send_sndbuf_remove(struct rds_sock *rs, struct rds_message *rm)
 {
     u32 len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
 
     assert_spin_locked(&rs->rs_lock);
 
     BUG_ON(rs->rs_snd_bytes < len);
     rs->rs_snd_bytes -= len;
 
     if (rs->rs_snd_bytes == 0)
         rds_stats_inc(s_send_queue_empty);
 }
 
 static inline int rds_send_is_acked(struct rds_message *rm, u64 ack,
                     is_acked_func is_acked)
 {
     if (is_acked)
         return is_acked(rm, ack);
     return be64_to_cpu(rm->m_inc.i_hdr.h_sequence) <= ack;
 }
 
 /*
  * This is pretty similar to what happens below in the ACK
  * handling code - except that we call here as soon as we get
  * the IB send completion on the RDMA op and the accompanying
  * message.
  */
 void rds_rdma_send_complete(struct rds_message *rm, int status)
 {
     struct rds_sock *rs = NULL;
     struct rm_rdma_op *ro;
     struct rds_notifier *notifier;
     unsigned long flags;
 
     spin_lock_irqsave(&rm->m_rs_lock, flags);
 
     ro = &rm->rdma;
     if (test_bit(RDS_MSG_ON_SOCK, &rm->m_flags) &&
         ro->op_active && ro->op_notify && ro->op_notifier) {
         notifier = ro->op_notifier;
         rs = rm->m_rs;
         sock_hold(rds_rs_to_sk(rs));
 
         notifier->n_status = status;
         spin_lock(&rs->rs_lock);
         list_add_tail(&notifier->n_list, &rs->rs_notify_queue);
         spin_unlock(&rs->rs_lock);
 
         ro->op_notifier = NULL;
     }
 
     spin_unlock_irqrestore(&rm->m_rs_lock, flags);
 
     if (rs) {
         rds_wake_sk_sleep(rs);
         sock_put(rds_rs_to_sk(rs));
     }
 }
 EXPORT_SYMBOL_GPL(rds_rdma_send_complete);
 
 /*
  * Just like above, except looks at atomic op
  */
 void rds_atomic_send_complete(struct rds_message *rm, int status)
 {
     struct rds_sock *rs = NULL;
     struct rm_atomic_op *ao;
     struct rds_notifier *notifier;
     unsigned long flags;
 
     spin_lock_irqsave(&rm->m_rs_lock, flags);
 
     ao = &rm->atomic;
     if (test_bit(RDS_MSG_ON_SOCK, &rm->m_flags)
         && ao->op_active && ao->op_notify && ao->op_notifier) {
         notifier = ao->op_notifier;
         rs = rm->m_rs;
         sock_hold(rds_rs_to_sk(rs));
 
         notifier->n_status = status;
         spin_lock(&rs->rs_lock);
         list_add_tail(&notifier->n_list, &rs->rs_notify_queue);
         spin_unlock(&rs->rs_lock);
 
         ao->op_notifier = NULL;
     }
 
     spin_unlock_irqrestore(&rm->m_rs_lock, flags);
 
     if (rs) {
         rds_wake_sk_sleep(rs);
         sock_put(rds_rs_to_sk(rs));
     }
 }
 EXPORT_SYMBOL_GPL(rds_atomic_send_complete);
 
 /*
  * This is the same as rds_rdma_send_complete except we
  * don't do any locking - we have all the ingredients (message,
  * socket, socket lock) and can just move the notifier.
  */
 static inline void
 __rds_send_complete(struct rds_sock *rs, struct rds_message *rm, int status)
 {
     struct rm_rdma_op *ro;
     struct rm_atomic_op *ao;
 
     ro = &rm->rdma;
     if (ro->op_active && ro->op_notify && ro->op_notifier) {
         ro->op_notifier->n_status = status;
         list_add_tail(&ro->op_notifier->n_list, &rs->rs_notify_queue);
         ro->op_notifier = NULL;
     }
 
     ao = &rm->atomic;
     if (ao->op_active && ao->op_notify && ao->op_notifier) {
         ao->op_notifier->n_status = status;
         list_add_tail(&ao->op_notifier->n_list, &rs->rs_notify_queue);
         ao->op_notifier = NULL;
     }
 
     /* No need to wake the app - caller does this */
 }
 
 /*
  * This removes messages from the socket's list if they're on it.  The list
  * argument must be private to the caller, we must be able to modify it
  * without locks.  The messages must have a reference held for their
  * position on the list.  This function will drop that reference after
  * removing the messages from the 'messages' list regardless of if it found
  * the messages on the socket list or not.
  */
 static void rds_send_remove_from_sock(struct list_head *messages, int status)
 {
     unsigned long flags;
     struct rds_sock *rs = NULL;
     struct rds_message *rm;
 
     while (!list_empty(messages)) {
         int was_on_sock = 0;
 
         rm = list_entry(messages->next, struct rds_message,
                 m_conn_item);
         list_del_init(&rm->m_conn_item);
 
         /*
          * If we see this flag cleared then we're *sure* that someone
          * else beat us to removing it from the sock.  If we race
          * with their flag update we'll get the lock and then really
          * see that the flag has been cleared.
          *
          * The message spinlock makes sure nobody clears rm->m_rs
          * while we're messing with it. It does not prevent the
          * message from being removed from the socket, though.
          */
         spin_lock_irqsave(&rm->m_rs_lock, flags);
         if (!test_bit(RDS_MSG_ON_SOCK, &rm->m_flags))
             goto unlock_and_drop;
 
         if (rs != rm->m_rs) {
             if (rs) {
                 rds_wake_sk_sleep(rs);
                 sock_put(rds_rs_to_sk(rs));
             }
             rs = rm->m_rs;
             if (rs)
                 sock_hold(rds_rs_to_sk(rs));
         }
         if (!rs)
             goto unlock_and_drop;
         spin_lock(&rs->rs_lock);
 
         if (test_and_clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags)) {
             struct rm_rdma_op *ro = &rm->rdma;
             struct rds_notifier *notifier;
 
             list_del_init(&rm->m_sock_item);
             rds_send_sndbuf_remove(rs, rm);
 
             if (ro->op_active && ro->op_notifier &&
                    (ro->op_notify || (ro->op_recverr && status))) {
                 notifier = ro->op_notifier;
                 list_add_tail(&notifier->n_list,
                         &rs->rs_notify_queue);
                 if (!notifier->n_status)
                     notifier->n_status = status;
                 rm->rdma.op_notifier = NULL;
             }
             was_on_sock = 1;
         }
         spin_unlock(&rs->rs_lock);
 
 unlock_and_drop:
         spin_unlock_irqrestore(&rm->m_rs_lock, flags);
         rds_message_put(rm);
         if (was_on_sock)
             rds_message_put(rm);
     }
 
     if (rs) {
         rds_wake_sk_sleep(rs);
         sock_put(rds_rs_to_sk(rs));
     }
 }
 
 /*
  * Transports call here when they've determined that the receiver queued
  * messages up to, and including, the given sequence number.  Messages are
  * moved to the retrans queue when rds_send_xmit picks them off the send
  * queue. This means that in the TCP case, the message may not have been
  * assigned the m_ack_seq yet - but that's fine as long as tcp_is_acked
  * checks the RDS_MSG_HAS_ACK_SEQ bit.
  */
 void rds_send_path_drop_acked(struct rds_conn_path *cp, u64 ack,
                   is_acked_func is_acked)
 {
     struct rds_message *rm, *tmp;
     unsigned long flags;
     LIST_HEAD(list);
 
     spin_lock_irqsave(&cp->cp_lock, flags);
 
     list_for_each_entry_safe(rm, tmp, &cp->cp_retrans, m_conn_item) {
         if (!rds_send_is_acked(rm, ack, is_acked))
             break;
 
         list_move(&rm->m_conn_item, &list);
         clear_bit(RDS_MSG_ON_CONN, &rm->m_flags);
     }
 
     /* order flag updates with spin locks */
     if (!list_empty(&list))
         smp_mb__after_atomic();
 
     spin_unlock_irqrestore(&cp->cp_lock, flags);
 
     /* now remove the messages from the sock list as needed */
     rds_send_remove_from_sock(&list, RDS_RDMA_SUCCESS);
 }
 EXPORT_SYMBOL_GPL(rds_send_path_drop_acked);
 
 void rds_send_drop_acked(struct rds_connection *conn, u64 ack,
              is_acked_func is_acked)
 {
     WARN_ON(conn->c_trans->t_mp_capable);
     rds_send_path_drop_acked(&conn->c_path[0], ack, is_acked);
 }
 EXPORT_SYMBOL_GPL(rds_send_drop_acked);
 
 void rds_send_drop_to(struct rds_sock *rs, struct sockaddr_in6 *dest)
 {
     struct rds_message *rm, *tmp;
     struct rds_connection *conn;
     struct rds_conn_path *cp;
     unsigned long flags;
     LIST_HEAD(list);
 
     /* get all the messages we're dropping under the rs lock */
     spin_lock_irqsave(&rs->rs_lock, flags);
 
     list_for_each_entry_safe(rm, tmp, &rs->rs_send_queue, m_sock_item) {
         if (dest &&
             (!ipv6_addr_equal(&dest->sin6_addr, &rm->m_daddr) ||
              dest->sin6_port != rm->m_inc.i_hdr.h_dport))
             continue;
 
         list_move(&rm->m_sock_item, &list);
         rds_send_sndbuf_remove(rs, rm);
         clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
     }
 
     /* order flag updates with the rs lock */
     smp_mb__after_atomic();
 
     spin_unlock_irqrestore(&rs->rs_lock, flags);
 
     if (list_empty(&list))
         return;
 
     /* Remove the messages from the conn */
     list_for_each_entry(rm, &list, m_sock_item) {
 
         conn = rm->m_inc.i_conn;
         if (conn->c_trans->t_mp_capable)
             cp = rm->m_inc.i_conn_path;
         else
             cp = &conn->c_path[0];
 
         spin_lock_irqsave(&cp->cp_lock, flags);
         /*
          * Maybe someone else beat us to removing rm from the conn.
          * If we race with their flag update we'll get the lock and
          * then really see that the flag has been cleared.
          */
         if (!test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags)) {
             spin_unlock_irqrestore(&cp->cp_lock, flags);
             continue;
         }
         list_del_init(&rm->m_conn_item);
         spin_unlock_irqrestore(&cp->cp_lock, flags);
 
         /*
          * Couldn't grab m_rs_lock in top loop (lock ordering),
          * but we can now.
          */
         spin_lock_irqsave(&rm->m_rs_lock, flags);
 
         spin_lock(&rs->rs_lock);
         __rds_send_complete(rs, rm, RDS_RDMA_CANCELED);
         spin_unlock(&rs->rs_lock);
 
         spin_unlock_irqrestore(&rm->m_rs_lock, flags);
 
         rds_message_put(rm);
     }
 
     rds_wake_sk_sleep(rs);
 
     while (!list_empty(&list)) {
         rm = list_entry(list.next, struct rds_message, m_sock_item);
         list_del_init(&rm->m_sock_item);
         rds_message_wait(rm);
 
         /* just in case the code above skipped this message
          * because RDS_MSG_ON_CONN wasn't set, run it again here
          * taking m_rs_lock is the only thing that keeps us
          * from racing with ack processing.
          */
         spin_lock_irqsave(&rm->m_rs_lock, flags);
 
         spin_lock(&rs->rs_lock);
         __rds_send_complete(rs, rm, RDS_RDMA_CANCELED);
         spin_unlock(&rs->rs_lock);
 
         spin_unlock_irqrestore(&rm->m_rs_lock, flags);
 
         rds_message_put(rm);
     }
 }
 
 /*
  * we only want this to fire once so we use the callers 'queued'.  It's
  * possible that another thread can race with us and remove the
  * message from the flow with RDS_CANCEL_SENT_TO.
  */
 static int rds_send_queue_rm(struct rds_sock *rs, struct rds_connection *conn,
                  struct rds_conn_path *cp,
                  struct rds_message *rm, __be16 sport,
                  __be16 dport, int *queued)
 {
     unsigned long flags;
     u32 len;
 
     if (*queued)
         goto out;
 
     len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
 
     /* this is the only place which holds both the socket's rs_lock
      * and the connection's c_lock */
     spin_lock_irqsave(&rs->rs_lock, flags);
 
     /*
      * If there is a little space in sndbuf, we don't queue anything,
      * and userspace gets -EAGAIN. But poll() indicates there's send
      * room. This can lead to bad behavior (spinning) if snd_bytes isn't
      * freed up by incoming acks. So we check the *old* value of
      * rs_snd_bytes here to allow the last msg to exceed the buffer,
      * and poll() now knows no more data can be sent.
      */
     if (rs->rs_snd_bytes < rds_sk_sndbuf(rs)) {
         rs->rs_snd_bytes += len;
 
         /* let recv side know we are close to send space exhaustion.
          * This is probably not the optimal way to do it, as this
          * means we set the flag on *all* messages as soon as our
          * throughput hits a certain threshold.
          */
         if (rs->rs_snd_bytes >= rds_sk_sndbuf(rs) / 2)
             set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
 
         list_add_tail(&rm->m_sock_item, &rs->rs_send_queue);
         set_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
         rds_message_addref(rm);
         sock_hold(rds_rs_to_sk(rs));
         rm->m_rs = rs;
 
         /* The code ordering is a little weird, but we're
            trying to minimize the time we hold c_lock */
         rds_message_populate_header(&rm->m_inc.i_hdr, sport, dport, 0);
         rm->m_inc.i_conn = conn;
         rm->m_inc.i_conn_path = cp;
         rds_message_addref(rm);
 
         spin_lock(&cp->cp_lock);
         rm->m_inc.i_hdr.h_sequence = cpu_to_be64(cp->cp_next_tx_seq++);
         list_add_tail(&rm->m_conn_item, &cp->cp_send_queue);
         set_bit(RDS_MSG_ON_CONN, &rm->m_flags);
         spin_unlock(&cp->cp_lock);
 
         rdsdebug("queued msg %p len %d, rs %p bytes %d seq %llu\n",
              rm, len, rs, rs->rs_snd_bytes,
              (unsigned long long)be64_to_cpu(rm->m_inc.i_hdr.h_sequence));
 
         *queued = 1;
     }
 
     spin_unlock_irqrestore(&rs->rs_lock, flags);
 out:
     return *queued;
 }
 
 /*
  * rds_message is getting to be quite complicated, and we'd like to allocate
  * it all in one go. This figures out how big it needs to be up front.
  */
 static int rds_rm_size(struct msghdr *msg, int num_sgs,
                struct rds_iov_vector_arr *vct)
 {
     struct cmsghdr *cmsg;
     int size = 0;
     int cmsg_groups = 0;
     int retval;
     bool zcopy_cookie = false;
     struct rds_iov_vector *iov, *tmp_iov;
 
     if (num_sgs < 0)
         return -EINVAL;
 
     for_each_cmsghdr(cmsg, msg) {
         if (!CMSG_OK(msg, cmsg))
             return -EINVAL;
 
         if (cmsg->cmsg_level != SOL_RDS)
             continue;
 
         switch (cmsg->cmsg_type) {
         case RDS_CMSG_RDMA_ARGS:
             if (vct->indx >= vct->len) {
                 vct->len += vct->incr;
                 tmp_iov =
                     krealloc(vct->vec,
                          vct->len *
                          sizeof(struct rds_iov_vector),
                          GFP_KERNEL);
                 if (!tmp_iov) {
                     vct->len -= vct->incr;
                     return -ENOMEM;
                 }
                 vct->vec = tmp_iov;
             }
             iov = &vct->vec[vct->indx];
             memset(iov, 0, sizeof(struct rds_iov_vector));
             vct->indx++;
             cmsg_groups |= 1;
             retval = rds_rdma_extra_size(CMSG_DATA(cmsg), iov);
             if (retval < 0)
                 return retval;
             size += retval;
 
             break;
 
         case RDS_CMSG_ZCOPY_COOKIE:
             zcopy_cookie = true;
             fallthrough;
 
         case RDS_CMSG_RDMA_DEST:
         case RDS_CMSG_RDMA_MAP:
             cmsg_groups |= 2;
             /* these are valid but do no add any size */
             break;
 
         case RDS_CMSG_ATOMIC_CSWP:
         case RDS_CMSG_ATOMIC_FADD:
         case RDS_CMSG_MASKED_ATOMIC_CSWP:
         case RDS_CMSG_MASKED_ATOMIC_FADD:
             cmsg_groups |= 1;
             size += sizeof(struct scatterlist);
             break;
 
         default:
             return -EINVAL;
         }
 
     }
 
     if ((msg->msg_flags & MSG_ZEROCOPY) && !zcopy_cookie)
         return -EINVAL;
 
     size += num_sgs * sizeof(struct scatterlist);
 
     /* Ensure (DEST, MAP) are never used with (ARGS, ATOMIC) */
     if (cmsg_groups == 3)
         return -EINVAL;
 
     return size;
 }
 
 static int rds_cmsg_zcopy(struct rds_sock *rs, struct rds_message *rm,
               struct cmsghdr *cmsg)
 {
     u32 *cookie;
 
     if (cmsg->cmsg_len < CMSG_LEN(sizeof(*cookie)) ||
         !rm->data.op_mmp_znotifier)
         return -EINVAL;
     cookie = CMSG_DATA(cmsg);
     rm->data.op_mmp_znotifier->z_cookie = *cookie;
     return 0;
 }
 
 static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
              struct msghdr *msg, int *allocated_mr,
              struct rds_iov_vector_arr *vct)
 {
     struct cmsghdr *cmsg;
     int ret = 0, ind = 0;
 
     for_each_cmsghdr(cmsg, msg) {
         if (!CMSG_OK(msg, cmsg))
             return -EINVAL;
 
         if (cmsg->cmsg_level != SOL_RDS)
             continue;
 
         /* As a side effect, RDMA_DEST and RDMA_MAP will set
          * rm->rdma.m_rdma_cookie and rm->rdma.m_rdma_mr.
          */
         switch (cmsg->cmsg_type) {
         case RDS_CMSG_RDMA_ARGS:
             if (ind >= vct->indx)
                 return -ENOMEM;
             ret = rds_cmsg_rdma_args(rs, rm, cmsg, &vct->vec[ind]);
             ind++;
             break;
 
         case RDS_CMSG_RDMA_DEST:
             ret = rds_cmsg_rdma_dest(rs, rm, cmsg);
             break;
 
         case RDS_CMSG_RDMA_MAP:
             ret = rds_cmsg_rdma_map(rs, rm, cmsg);
             if (!ret)
                 *allocated_mr = 1;
             else if (ret == -ENODEV)
                 /* Accommodate the get_mr() case which can fail
                  * if connection isn't established yet.
                  */
                 ret = -EAGAIN;
             break;
         case RDS_CMSG_ATOMIC_CSWP:
         case RDS_CMSG_ATOMIC_FADD:
         case RDS_CMSG_MASKED_ATOMIC_CSWP:
         case RDS_CMSG_MASKED_ATOMIC_FADD:
             ret = rds_cmsg_atomic(rs, rm, cmsg);
             break;
 
         case RDS_CMSG_ZCOPY_COOKIE:
             ret = rds_cmsg_zcopy(rs, rm, cmsg);
             break;
 
         default:
             return -EINVAL;
         }
 
         if (ret)
             break;
     }
 
     return ret;
 }
 
 static int rds_send_mprds_hash(struct rds_sock *rs,
                    struct rds_connection *conn, int nonblock)
 {
     int hash;
 
     if (conn->c_npaths == 0)
         hash = RDS_MPATH_HASH(rs, RDS_MPATH_WORKERS);
     else
         hash = RDS_MPATH_HASH(rs, conn->c_npaths);
     if (conn->c_npaths == 0 && hash != 0) {
         rds_send_ping(conn, 0);
 
         /* The underlying connection is not up yet.  Need to wait
          * until it is up to be sure that the non-zero c_path can be
          * used.  But if we are interrupted, we have to use the zero
          * c_path in case the connection ends up being non-MP capable.
          */
         if (conn->c_npaths == 0) {
             /* Cannot wait for the connection be made, so just use
              * the base c_path.
              */
             if (nonblock)
                 return 0;
             if (wait_event_interruptible(conn->c_hs_waitq,
                              conn->c_npaths != 0))
                 hash = 0;
         }
         if (conn->c_npaths == 1)
             hash = 0;
     }
     return hash;
 }
 
 static int rds_rdma_bytes(struct msghdr *msg, size_t *rdma_bytes)
 {
     struct rds_rdma_args *args;
     struct cmsghdr *cmsg;
 
     for_each_cmsghdr(cmsg, msg) {
         if (!CMSG_OK(msg, cmsg))
             return -EINVAL;
 
         if (cmsg->cmsg_level != SOL_RDS)
             continue;
 
         if (cmsg->cmsg_type == RDS_CMSG_RDMA_ARGS) {
             if (cmsg->cmsg_len <
                 CMSG_LEN(sizeof(struct rds_rdma_args)))
                 return -EINVAL;
             args = CMSG_DATA(cmsg);
             *rdma_bytes += args->remote_vec.bytes;
         }
     }
     return 0;
 }
 
 int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 {
     struct sock *sk = sock->sk;
     struct rds_sock *rs = rds_sk_to_rs(sk);
     DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
     DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
     __be16 dport;
     struct rds_message *rm = NULL;
     struct rds_connection *conn;
     int ret = 0;
     int queued = 0, allocated_mr = 0;
     int nonblock = msg->msg_flags & MSG_DONTWAIT;
     long timeo = sock_sndtimeo(sk, nonblock);
     struct rds_conn_path *cpath;
     struct in6_addr daddr;
     __u32 scope_id = 0;
     size_t total_payload_len = payload_len, rdma_payload_len = 0;
     bool zcopy = ((msg->msg_flags & MSG_ZEROCOPY) &&
               sock_flag(rds_rs_to_sk(rs), SOCK_ZEROCOPY));
     int num_sgs = DIV_ROUND_UP(payload_len, PAGE_SIZE);
     int namelen;
     struct rds_iov_vector_arr vct;
     int ind;
 
     memset(&vct, 0, sizeof(vct));
 
     /* expect 1 RDMA CMSG per rds_sendmsg. can still grow if more needed. */
     vct.incr = 1;
 
     /* Mirror Linux UDP mirror of BSD error message compatibility */
     /* XXX: Perhaps MSG_MORE someday */
     if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_CMSG_COMPAT | MSG_ZEROCOPY)) {
         ret = -EOPNOTSUPP;
         goto out;
     }
 
     namelen = msg->msg_namelen;
     if (namelen != 0) {
         if (namelen < sizeof(*usin)) {
             ret = -EINVAL;
             goto out;
         }
         switch (usin->sin_family) {
         case AF_INET:
             if (usin->sin_addr.s_addr == htonl(INADDR_ANY) ||
                 usin->sin_addr.s_addr == htonl(INADDR_BROADCAST) ||
                 ipv4_is_multicast(usin->sin_addr.s_addr)) {
                 ret = -EINVAL;
                 goto out;
             }
             ipv6_addr_set_v4mapped(usin->sin_addr.s_addr, &daddr);
             dport = usin->sin_port;
             break;
 
 #if IS_ENABLED(CONFIG_IPV6)
         case AF_INET6: {
             int addr_type;
 
             if (namelen < sizeof(*sin6)) {
                 ret = -EINVAL;
                 goto out;
             }
             addr_type = ipv6_addr_type(&sin6->sin6_addr);
             if (!(addr_type & IPV6_ADDR_UNICAST)) {
                 __be32 addr4;
 
                 if (!(addr_type & IPV6_ADDR_MAPPED)) {
                     ret = -EINVAL;
                     goto out;
                 }
 
                 /* It is a mapped address.  Need to do some
                  * sanity checks.
                  */
                 addr4 = sin6->sin6_addr.s6_addr32[3];
                 if (addr4 == htonl(INADDR_ANY) ||
                     addr4 == htonl(INADDR_BROADCAST) ||
                     ipv4_is_multicast(addr4)) {
                     ret = -EINVAL;
                     goto out;
                 }
             }
             if (addr_type & IPV6_ADDR_LINKLOCAL) {
                 if (sin6->sin6_scope_id == 0) {
                     ret = -EINVAL;
                     goto out;
                 }
                 scope_id = sin6->sin6_scope_id;
             }
 
             daddr = sin6->sin6_addr;
             dport = sin6->sin6_port;
             break;
         }
 #endif
 
         default:
             ret = -EINVAL;
             goto out;
         }
     } else {
         /* We only care about consistency with ->connect() */
         lock_sock(sk);
         daddr = rs->rs_conn_addr;
         dport = rs->rs_conn_port;
         scope_id = rs->rs_bound_scope_id;
         release_sock(sk);
     }
 
     lock_sock(sk);
     if (ipv6_addr_any(&rs->rs_bound_addr) || ipv6_addr_any(&daddr)) {
         release_sock(sk);
         ret = -ENOTCONN;
         goto out;
     } else if (namelen != 0) {
         /* Cannot send to an IPv4 address using an IPv6 source
          * address and cannot send to an IPv6 address using an
          * IPv4 source address.
          */
         if (ipv6_addr_v4mapped(&daddr) ^
             ipv6_addr_v4mapped(&rs->rs_bound_addr)) {
             release_sock(sk);
             ret = -EOPNOTSUPP;
             goto out;
         }
         /* If the socket is already bound to a link local address,
          * it can only send to peers on the same link.  But allow
          * communicating between link local and non-link local address.
          */
         if (scope_id != rs->rs_bound_scope_id) {
             if (!scope_id) {
                 scope_id = rs->rs_bound_scope_id;
             } else if (rs->rs_bound_scope_id) {
                 release_sock(sk);
                 ret = -EINVAL;
                 goto out;
             }
         }
     }
     release_sock(sk);
 
     ret = rds_rdma_bytes(msg, &rdma_payload_len);
     if (ret)
         goto out;
 
     total_payload_len += rdma_payload_len;
     if (max_t(size_t, payload_len, rdma_payload_len) > RDS_MAX_MSG_SIZE) {
         ret = -EMSGSIZE;
         goto out;
     }
 
     if (payload_len > rds_sk_sndbuf(rs)) {
         ret = -EMSGSIZE;
         goto out;
     }
 
     if (zcopy) {
         if (rs->rs_transport->t_type != RDS_TRANS_TCP) {
             ret = -EOPNOTSUPP;
             goto out;
         }
         num_sgs = iov_iter_npages(&msg->msg_iter, INT_MAX);
     }
     /* size of rm including all sgs */
     ret = rds_rm_size(msg, num_sgs, &vct);
     if (ret < 0)
         goto out;
 
     rm = rds_message_alloc(ret, GFP_KERNEL);
     if (!rm) {
         ret = -ENOMEM;
         goto out;
     }
 
     /* Attach data to the rm */
     if (payload_len) {
         rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
         if (IS_ERR(rm->data.op_sg)) {
             ret = PTR_ERR(rm->data.op_sg);
             goto out;
         }
         ret = rds_message_copy_from_user(rm, &msg->msg_iter, zcopy);
         if (ret)
             goto out;
     }
     rm->data.op_active = 1;
 
     rm->m_daddr = daddr;
 
     /* rds_conn_create has a spinlock that runs with IRQ off.
      * Caching the conn in the socket helps a lot. */
     if (rs->rs_conn && ipv6_addr_equal(&rs->rs_conn->c_faddr, &daddr) &&
         rs->rs_tos == rs->rs_conn->c_tos) {
         conn = rs->rs_conn;
     } else {
         conn = rds_conn_create_outgoing(sock_net(sock->sk),
                         &rs->rs_bound_addr, &daddr,
                         rs->rs_transport, rs->rs_tos,
                         sock->sk->sk_allocation,
                         scope_id);
         if (IS_ERR(conn)) {
             ret = PTR_ERR(conn);
             goto out;
         }
         rs->rs_conn = conn;
     }
 
     if (conn->c_trans->t_mp_capable)
         cpath = &conn->c_path[rds_send_mprds_hash(rs, conn, nonblock)];
     else
         cpath = &conn->c_path[0];
 
     rm->m_conn_path = cpath;
 
     /* Parse any control messages the user may have included. */
     ret = rds_cmsg_send(rs, rm, msg, &allocated_mr, &vct);
     if (ret) {
         /* Trigger connection so that its ready for the next retry */
         if (ret ==  -EAGAIN)
             rds_conn_connect_if_down(conn);
         goto out;
     }
 
     if (rm->rdma.op_active && !conn->c_trans->xmit_rdma) {
         printk_ratelimited(KERN_NOTICE "rdma_op %p conn xmit_rdma %p\n",
                    &rm->rdma, conn->c_trans->xmit_rdma);
         ret = -EOPNOTSUPP;
         goto out;
     }
 
     if (rm->atomic.op_active && !conn->c_trans->xmit_atomic) {
         printk_ratelimited(KERN_NOTICE "atomic_op %p conn xmit_atomic %p\n",
                    &rm->atomic, conn->c_trans->xmit_atomic);
         ret = -EOPNOTSUPP;
         goto out;
     }
 
     if (rds_destroy_pending(conn)) {
         ret = -EAGAIN;
         goto out;
     }
 
     if (rds_conn_path_down(cpath))
         rds_check_all_paths(conn);
 
     ret = rds_cong_wait(conn->c_fcong, dport, nonblock, rs);
     if (ret) {
         rs->rs_seen_congestion = 1;
         goto out;
     }
     while (!rds_send_queue_rm(rs, conn, cpath, rm, rs->rs_bound_port,
                   dport, &queued)) {
         rds_stats_inc(s_send_queue_full);
 
         if (nonblock) {
             ret = -EAGAIN;
             goto out;
         }
 
         timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
                     rds_send_queue_rm(rs, conn, cpath, rm,
                               rs->rs_bound_port,
                               dport,
                               &queued),
                     timeo);
         rdsdebug("sendmsg woke queued %d timeo %ld\n", queued, timeo);
         if (timeo > 0 || timeo == MAX_SCHEDULE_TIMEOUT)
             continue;
 
         ret = timeo;
         if (ret == 0)
             ret = -ETIMEDOUT;
         goto out;
     }
 
     /*
      * By now we've committed to the send.  We reuse rds_send_worker()
      * to retry sends in the rds thread if the transport asks us to.
      */
     rds_stats_inc(s_send_queued);
 
     ret = rds_send_xmit(cpath);
     if (ret == -ENOMEM || ret == -EAGAIN) {
         ret = 0;
         rcu_read_lock();
         if (rds_destroy_pending(cpath->cp_conn))
             ret = -ENETUNREACH;
         else
             queue_delayed_work(rds_wq, &cpath->cp_send_w, 1);
         rcu_read_unlock();
     }
     if (ret)
         goto out;
     rds_message_put(rm);
 
     for (ind = 0; ind < vct.indx; ind++)
         kfree(vct.vec[ind].iov);
     kfree(vct.vec);
 
     return payload_len;
 
 out:
     for (ind = 0; ind < vct.indx; ind++)
         kfree(vct.vec[ind].iov);
     kfree(vct.vec);
 
     /* If the user included a RDMA_MAP cmsg, we allocated a MR on the fly.
      * If the sendmsg goes through, we keep the MR. If it fails with EAGAIN
      * or in any other way, we need to destroy the MR again */
     if (allocated_mr)
         rds_rdma_unuse(rs, rds_rdma_cookie_key(rm->m_rdma_cookie), 1);
 
     if (rm)
         rds_message_put(rm);
     return ret;
 }
 
 /*
  * send out a probe. Can be shared by rds_send_ping,
  * rds_send_pong, rds_send_hb.
  * rds_send_hb should use h_flags
  *   RDS_FLAG_HB_PING|RDS_FLAG_ACK_REQUIRED
  * or
  *   RDS_FLAG_HB_PONG|RDS_FLAG_ACK_REQUIRED
  */
 static int
 rds_send_probe(struct rds_conn_path *cp, __be16 sport,
            __be16 dport, u8 h_flags)
 {
     struct rds_message *rm;
     unsigned long flags;
     int ret = 0;
 
     rm = rds_message_alloc(0, GFP_ATOMIC);
     if (!rm) {
         ret = -ENOMEM;
         goto out;
     }
 
     rm->m_daddr = cp->cp_conn->c_faddr;
     rm->data.op_active = 1;
 
     rds_conn_path_connect_if_down(cp);
 
     ret = rds_cong_wait(cp->cp_conn->c_fcong, dport, 1, NULL);
     if (ret)
         goto out;
 
     spin_lock_irqsave(&cp->cp_lock, flags);
     list_add_tail(&rm->m_conn_item, &cp->cp_send_queue);
     set_bit(RDS_MSG_ON_CONN, &rm->m_flags);
     rds_message_addref(rm);
     rm->m_inc.i_conn = cp->cp_conn;
     rm->m_inc.i_conn_path = cp;
 
     rds_message_populate_header(&rm->m_inc.i_hdr, sport, dport,
                     cp->cp_next_tx_seq);
     rm->m_inc.i_hdr.h_flags |= h_flags;
     cp->cp_next_tx_seq++;
 
     if (RDS_HS_PROBE(be16_to_cpu(sport), be16_to_cpu(dport)) &&
         cp->cp_conn->c_trans->t_mp_capable) {
         u16 npaths = cpu_to_be16(RDS_MPATH_WORKERS);
         u32 my_gen_num = cpu_to_be32(cp->cp_conn->c_my_gen_num);
 
         rds_message_add_extension(&rm->m_inc.i_hdr,
                       RDS_EXTHDR_NPATHS, &npaths,
                       sizeof(npaths));
         rds_message_add_extension(&rm->m_inc.i_hdr,
                       RDS_EXTHDR_GEN_NUM,
                       &my_gen_num,
                       sizeof(u32));
     }
     spin_unlock_irqrestore(&cp->cp_lock, flags);
 
     rds_stats_inc(s_send_queued);
     rds_stats_inc(s_send_pong);
 
     /* schedule the send work on rds_wq */
     rcu_read_lock();
     if (!rds_destroy_pending(cp->cp_conn))
         queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
     rcu_read_unlock();
 
     rds_message_put(rm);
     return 0;
 
 out:
     if (rm)
         rds_message_put(rm);
     return ret;
 }
 
 int
 rds_send_pong(struct rds_conn_path *cp, __be16 dport)
 {
     return rds_send_probe(cp, 0, dport, 0);
 }
 
 void
 rds_send_ping(struct rds_connection *conn, int cp_index)
 {
     unsigned long flags;
     struct rds_conn_path *cp = &conn->c_path[cp_index];
 
     spin_lock_irqsave(&cp->cp_lock, flags);
     if (conn->c_ping_triggered) {
         spin_unlock_irqrestore(&cp->cp_lock, flags);
         return;
     }
     conn->c_ping_triggered = 1;
     spin_unlock_irqrestore(&cp->cp_lock, flags);
     rds_send_probe(cp, cpu_to_be16(RDS_FLAG_PROBE_PORT), 0, 0);
 }
 EXPORT_SYMBOL_GPL(rds_send_ping);

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