This patch backports the following two upstream commits and
add a new symbol HAVE_NET_RWSEM in acinclude.m4 to determine
whether to use new introduced rw_semaphore, net_rwsem.
Upstream commit:
commit f0b07bb151b098d291fd1fd71ef7a2df56fb124a
Author: Kirill Tkhai <[email protected]>
Date: Thu Mar 29 19:20:32 2018 +0300
net: Introduce net_rwsem to protect net_namespace_list
rtnl_lock() is used everywhere, and contention is very high.
When someone wants to iterate over alive net namespaces,
he/she has no a possibility to do that without exclusive lock.
But the exclusive rtnl_lock() in such places is overkill,
and it just increases the contention. Yes, there is already
for_each_net_rcu() in kernel, but it requires rcu_read_lock(),
and this can't be sleepable. Also, sometimes it may be need
really prevent net_namespace_list growth, so for_each_net_rcu()
is not fit there.
This patch introduces new rw_semaphore, which will be used
instead of rtnl_mutex to protect net_namespace_list. It is
sleepable and allows not-exclusive iterations over net
namespaces list. It allows to stop using rtnl_lock()
in several places (what is made in next patches) and makes
less the time, we keep rtnl_mutex. Here we just add new lock,
while the explanation of we can remove rtnl_lock() there are
in next patches.
Fine grained locks generally are better, then one big lock,
so let's do that with net_namespace_list, while the situation
allows that.
Signed-off-by: Kirill Tkhai <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Upstream commit:
commit ec9c780925c57588637e1dbd8650d294107311c0
Author: Kirill Tkhai <[email protected]>
Date: Thu Mar 29 19:21:09 2018 +0300
ovs: Remove rtnl_lock() from ovs_exit_net()
Here we iterate for_each_net() and removes
vport from alive net to the exiting net.
ovs_net::dps are protected by ovs_mutex(),
and the others, who change it (ovs_dp_cmd_new(),
__dp_destroy()) also take it.
The same with datapath::ports list.
So, we remove rtnl_lock() here.
Signed-off-by: Kirill Tkhai <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Yi-Hung Wei <[email protected]>
---
acinclude.m4 | 1 +
datapath/datapath.c | 8 ++++++++
2 files changed, 9 insertions(+)
diff --git a/acinclude.m4 b/acinclude.m4
index 991a6275b978..ae8e66fc4967 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -634,6 +634,7 @@ AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
[OVS_GREP_IFELSE([$KSRC/include/linux/rtnetlink.h],
[rcu_read_lock_held])])
OVS_GREP_IFELSE([$KSRC/include/linux/rtnetlink.h], [lockdep_rtnl_is_held])
+ OVS_GREP_IFELSE([$KSRC/include/linux/rtnetlink.h], [net_rwsem])
# Check for the proto_data_valid member in struct sk_buff. The [^@]
# is necessary because some versions of this header remove the
diff --git a/datapath/datapath.c b/datapath/datapath.c
index 43f0d7432593..72b5e8b5c29c 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -2385,10 +2385,18 @@ static void __net_exit ovs_exit_net(struct net *dnet)
list_for_each_entry_safe(dp, dp_next, &ovs_net->dps, list_node)
__dp_destroy(dp);
+#ifdef HAVE_NET_RWSEM
+ down_read(&net_rwsem);
+#else
rtnl_lock();
+#endif
for_each_net(net)
list_vports_from_net(net, dnet, &head);
+#ifdef HAVE_NET_RWSEM
+ up_read(&net_rwsem);
+#else
rtnl_unlock();
+#endif
/* Detach all vports from given namespace. */
list_for_each_entry_safe(vport, vport_next, &head, detach_list) {
--
2.7.4
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