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428 lines
13 KiB
428 lines
13 KiB
/* |
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* Copyright (c) 2007, 2017 Oracle and/or its affiliates. All rights reserved. |
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* |
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* This software is available to you under a choice of one of two |
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* licenses. You may choose to be licensed under the terms of the GNU |
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* General Public License (GPL) Version 2, available from the file |
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* COPYING in the main directory of this source tree, or the |
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* OpenIB.org BSD license below: |
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* |
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* Redistribution and use in source and binary forms, with or |
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* without modification, are permitted provided that the following |
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* conditions are met: |
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* |
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* - Redistributions of source code must retain the above |
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* copyright notice, this list of conditions and the following |
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* disclaimer. |
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* |
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* - Redistributions in binary form must reproduce the above |
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* copyright notice, this list of conditions and the following |
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* disclaimer in the documentation and/or other materials |
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* provided with the distribution. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS |
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN |
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN |
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
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* SOFTWARE. |
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* |
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*/ |
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#include <linux/slab.h> |
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#include <linux/types.h> |
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#include <linux/rbtree.h> |
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#include <linux/bitops.h> |
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#include <linux/export.h> |
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#include "rds.h" |
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/* |
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* This file implements the receive side of the unconventional congestion |
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* management in RDS. |
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* |
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* Messages waiting in the receive queue on the receiving socket are accounted |
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* against the sockets SO_RCVBUF option value. Only the payload bytes in the |
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* message are accounted for. If the number of bytes queued equals or exceeds |
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* rcvbuf then the socket is congested. All sends attempted to this socket's |
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* address should return block or return -EWOULDBLOCK. |
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* |
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* Applications are expected to be reasonably tuned such that this situation |
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* very rarely occurs. An application encountering this "back-pressure" is |
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* considered a bug. |
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* |
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* This is implemented by having each node maintain bitmaps which indicate |
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* which ports on bound addresses are congested. As the bitmap changes it is |
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* sent through all the connections which terminate in the local address of the |
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* bitmap which changed. |
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* |
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* The bitmaps are allocated as connections are brought up. This avoids |
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* allocation in the interrupt handling path which queues messages on sockets. |
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* The dense bitmaps let transports send the entire bitmap on any bitmap change |
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* reasonably efficiently. This is much easier to implement than some |
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* finer-grained communication of per-port congestion. The sender does a very |
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* inexpensive bit test to test if the port it's about to send to is congested |
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* or not. |
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*/ |
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/* |
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* Interaction with poll is a tad tricky. We want all processes stuck in |
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* poll to wake up and check whether a congested destination became uncongested. |
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* The really sad thing is we have no idea which destinations the application |
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* wants to send to - we don't even know which rds_connections are involved. |
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* So until we implement a more flexible rds poll interface, we have to make |
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* do with this: |
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* We maintain a global counter that is incremented each time a congestion map |
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* update is received. Each rds socket tracks this value, and if rds_poll |
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* finds that the saved generation number is smaller than the global generation |
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* number, it wakes up the process. |
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*/ |
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static atomic_t rds_cong_generation = ATOMIC_INIT(0); |
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/* |
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* Congestion monitoring |
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*/ |
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static LIST_HEAD(rds_cong_monitor); |
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static DEFINE_RWLOCK(rds_cong_monitor_lock); |
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/* |
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* Yes, a global lock. It's used so infrequently that it's worth keeping it |
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* global to simplify the locking. It's only used in the following |
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* circumstances: |
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* |
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* - on connection buildup to associate a conn with its maps |
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* - on map changes to inform conns of a new map to send |
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* |
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* It's sadly ordered under the socket callback lock and the connection lock. |
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* Receive paths can mark ports congested from interrupt context so the |
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* lock masks interrupts. |
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*/ |
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static DEFINE_SPINLOCK(rds_cong_lock); |
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static struct rb_root rds_cong_tree = RB_ROOT; |
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static struct rds_cong_map *rds_cong_tree_walk(const struct in6_addr *addr, |
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struct rds_cong_map *insert) |
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{ |
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struct rb_node **p = &rds_cong_tree.rb_node; |
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struct rb_node *parent = NULL; |
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struct rds_cong_map *map; |
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while (*p) { |
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int diff; |
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parent = *p; |
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map = rb_entry(parent, struct rds_cong_map, m_rb_node); |
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diff = rds_addr_cmp(addr, &map->m_addr); |
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if (diff < 0) |
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p = &(*p)->rb_left; |
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else if (diff > 0) |
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p = &(*p)->rb_right; |
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else |
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return map; |
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} |
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if (insert) { |
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rb_link_node(&insert->m_rb_node, parent, p); |
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rb_insert_color(&insert->m_rb_node, &rds_cong_tree); |
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} |
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return NULL; |
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} |
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/* |
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* There is only ever one bitmap for any address. Connections try and allocate |
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* these bitmaps in the process getting pointers to them. The bitmaps are only |
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* ever freed as the module is removed after all connections have been freed. |
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*/ |
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static struct rds_cong_map *rds_cong_from_addr(const struct in6_addr *addr) |
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{ |
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struct rds_cong_map *map; |
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struct rds_cong_map *ret = NULL; |
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unsigned long zp; |
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unsigned long i; |
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unsigned long flags; |
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map = kzalloc(sizeof(struct rds_cong_map), GFP_KERNEL); |
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if (!map) |
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return NULL; |
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map->m_addr = *addr; |
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init_waitqueue_head(&map->m_waitq); |
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INIT_LIST_HEAD(&map->m_conn_list); |
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for (i = 0; i < RDS_CONG_MAP_PAGES; i++) { |
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zp = get_zeroed_page(GFP_KERNEL); |
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if (zp == 0) |
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goto out; |
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map->m_page_addrs[i] = zp; |
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} |
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spin_lock_irqsave(&rds_cong_lock, flags); |
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ret = rds_cong_tree_walk(addr, map); |
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spin_unlock_irqrestore(&rds_cong_lock, flags); |
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if (!ret) { |
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ret = map; |
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map = NULL; |
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} |
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out: |
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if (map) { |
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for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++) |
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free_page(map->m_page_addrs[i]); |
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kfree(map); |
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} |
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rdsdebug("map %p for addr %pI6c\n", ret, addr); |
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return ret; |
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} |
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/* |
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* Put the conn on its local map's list. This is called when the conn is |
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* really added to the hash. It's nested under the rds_conn_lock, sadly. |
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*/ |
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void rds_cong_add_conn(struct rds_connection *conn) |
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{ |
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unsigned long flags; |
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rdsdebug("conn %p now on map %p\n", conn, conn->c_lcong); |
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spin_lock_irqsave(&rds_cong_lock, flags); |
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list_add_tail(&conn->c_map_item, &conn->c_lcong->m_conn_list); |
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spin_unlock_irqrestore(&rds_cong_lock, flags); |
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} |
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void rds_cong_remove_conn(struct rds_connection *conn) |
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{ |
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unsigned long flags; |
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rdsdebug("removing conn %p from map %p\n", conn, conn->c_lcong); |
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spin_lock_irqsave(&rds_cong_lock, flags); |
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list_del_init(&conn->c_map_item); |
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spin_unlock_irqrestore(&rds_cong_lock, flags); |
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} |
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int rds_cong_get_maps(struct rds_connection *conn) |
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{ |
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conn->c_lcong = rds_cong_from_addr(&conn->c_laddr); |
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conn->c_fcong = rds_cong_from_addr(&conn->c_faddr); |
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if (!(conn->c_lcong && conn->c_fcong)) |
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return -ENOMEM; |
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return 0; |
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} |
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void rds_cong_queue_updates(struct rds_cong_map *map) |
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{ |
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struct rds_connection *conn; |
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unsigned long flags; |
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spin_lock_irqsave(&rds_cong_lock, flags); |
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list_for_each_entry(conn, &map->m_conn_list, c_map_item) { |
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struct rds_conn_path *cp = &conn->c_path[0]; |
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rcu_read_lock(); |
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if (!test_and_set_bit(0, &conn->c_map_queued) && |
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!rds_destroy_pending(cp->cp_conn)) { |
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rds_stats_inc(s_cong_update_queued); |
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/* We cannot inline the call to rds_send_xmit() here |
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* for two reasons (both pertaining to a TCP transport): |
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* 1. When we get here from the receive path, we |
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* are already holding the sock_lock (held by |
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* tcp_v4_rcv()). So inlining calls to |
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* tcp_setsockopt and/or tcp_sendmsg will deadlock |
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* when it tries to get the sock_lock()) |
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* 2. Interrupts are masked so that we can mark the |
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* port congested from both send and recv paths. |
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* (See comment around declaration of rdc_cong_lock). |
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* An attempt to get the sock_lock() here will |
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* therefore trigger warnings. |
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* Defer the xmit to rds_send_worker() instead. |
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*/ |
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queue_delayed_work(rds_wq, &cp->cp_send_w, 0); |
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} |
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rcu_read_unlock(); |
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} |
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spin_unlock_irqrestore(&rds_cong_lock, flags); |
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} |
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void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask) |
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{ |
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rdsdebug("waking map %p for %pI4\n", |
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map, &map->m_addr); |
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rds_stats_inc(s_cong_update_received); |
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atomic_inc(&rds_cong_generation); |
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if (waitqueue_active(&map->m_waitq)) |
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wake_up(&map->m_waitq); |
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if (waitqueue_active(&rds_poll_waitq)) |
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wake_up_all(&rds_poll_waitq); |
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if (portmask && !list_empty(&rds_cong_monitor)) { |
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unsigned long flags; |
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struct rds_sock *rs; |
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read_lock_irqsave(&rds_cong_monitor_lock, flags); |
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list_for_each_entry(rs, &rds_cong_monitor, rs_cong_list) { |
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spin_lock(&rs->rs_lock); |
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rs->rs_cong_notify |= (rs->rs_cong_mask & portmask); |
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rs->rs_cong_mask &= ~portmask; |
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spin_unlock(&rs->rs_lock); |
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if (rs->rs_cong_notify) |
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rds_wake_sk_sleep(rs); |
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} |
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read_unlock_irqrestore(&rds_cong_monitor_lock, flags); |
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} |
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} |
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EXPORT_SYMBOL_GPL(rds_cong_map_updated); |
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int rds_cong_updated_since(unsigned long *recent) |
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{ |
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unsigned long gen = atomic_read(&rds_cong_generation); |
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if (likely(*recent == gen)) |
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return 0; |
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*recent = gen; |
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return 1; |
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} |
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/* |
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* We're called under the locking that protects the sockets receive buffer |
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* consumption. This makes it a lot easier for the caller to only call us |
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* when it knows that an existing set bit needs to be cleared, and vice versa. |
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* We can't block and we need to deal with concurrent sockets working against |
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* the same per-address map. |
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*/ |
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void rds_cong_set_bit(struct rds_cong_map *map, __be16 port) |
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{ |
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unsigned long i; |
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unsigned long off; |
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rdsdebug("setting congestion for %pI4:%u in map %p\n", |
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&map->m_addr, ntohs(port), map); |
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i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS; |
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off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS; |
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set_bit_le(off, (void *)map->m_page_addrs[i]); |
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} |
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void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port) |
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{ |
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unsigned long i; |
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unsigned long off; |
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rdsdebug("clearing congestion for %pI4:%u in map %p\n", |
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&map->m_addr, ntohs(port), map); |
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i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS; |
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off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS; |
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clear_bit_le(off, (void *)map->m_page_addrs[i]); |
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} |
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static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port) |
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{ |
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unsigned long i; |
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unsigned long off; |
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i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS; |
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off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS; |
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return test_bit_le(off, (void *)map->m_page_addrs[i]); |
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} |
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void rds_cong_add_socket(struct rds_sock *rs) |
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{ |
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unsigned long flags; |
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write_lock_irqsave(&rds_cong_monitor_lock, flags); |
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if (list_empty(&rs->rs_cong_list)) |
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list_add(&rs->rs_cong_list, &rds_cong_monitor); |
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write_unlock_irqrestore(&rds_cong_monitor_lock, flags); |
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} |
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void rds_cong_remove_socket(struct rds_sock *rs) |
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{ |
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unsigned long flags; |
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struct rds_cong_map *map; |
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write_lock_irqsave(&rds_cong_monitor_lock, flags); |
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list_del_init(&rs->rs_cong_list); |
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write_unlock_irqrestore(&rds_cong_monitor_lock, flags); |
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/* update congestion map for now-closed port */ |
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spin_lock_irqsave(&rds_cong_lock, flags); |
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map = rds_cong_tree_walk(&rs->rs_bound_addr, NULL); |
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spin_unlock_irqrestore(&rds_cong_lock, flags); |
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if (map && rds_cong_test_bit(map, rs->rs_bound_port)) { |
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rds_cong_clear_bit(map, rs->rs_bound_port); |
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rds_cong_queue_updates(map); |
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} |
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} |
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int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock, |
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struct rds_sock *rs) |
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{ |
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if (!rds_cong_test_bit(map, port)) |
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return 0; |
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if (nonblock) { |
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if (rs && rs->rs_cong_monitor) { |
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unsigned long flags; |
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/* It would have been nice to have an atomic set_bit on |
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* a uint64_t. */ |
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spin_lock_irqsave(&rs->rs_lock, flags); |
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rs->rs_cong_mask |= RDS_CONG_MONITOR_MASK(ntohs(port)); |
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spin_unlock_irqrestore(&rs->rs_lock, flags); |
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/* Test again - a congestion update may have arrived in |
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* the meantime. */ |
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if (!rds_cong_test_bit(map, port)) |
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return 0; |
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} |
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rds_stats_inc(s_cong_send_error); |
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return -ENOBUFS; |
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} |
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rds_stats_inc(s_cong_send_blocked); |
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rdsdebug("waiting on map %p for port %u\n", map, be16_to_cpu(port)); |
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return wait_event_interruptible(map->m_waitq, |
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!rds_cong_test_bit(map, port)); |
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} |
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void rds_cong_exit(void) |
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{ |
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struct rb_node *node; |
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struct rds_cong_map *map; |
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unsigned long i; |
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while ((node = rb_first(&rds_cong_tree))) { |
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map = rb_entry(node, struct rds_cong_map, m_rb_node); |
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rdsdebug("freeing map %p\n", map); |
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rb_erase(&map->m_rb_node, &rds_cong_tree); |
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for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++) |
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free_page(map->m_page_addrs[i]); |
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kfree(map); |
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} |
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} |
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/* |
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* Allocate a RDS message containing a congestion update. |
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*/ |
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struct rds_message *rds_cong_update_alloc(struct rds_connection *conn) |
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{ |
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struct rds_cong_map *map = conn->c_lcong; |
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struct rds_message *rm; |
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rm = rds_message_map_pages(map->m_page_addrs, RDS_CONG_MAP_BYTES); |
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if (!IS_ERR(rm)) |
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rm->m_inc.i_hdr.h_flags = RDS_FLAG_CONG_BITMAP; |
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return rm; |
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}
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