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rtnetlink: Add per-netns RTNL.

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The goal is to break RTNL down into per-netns mutex.

This patch adds per-netns mutex and its helper functions, rtnl_net_lock()
and rtnl_net_unlock().

rtnl_net_lock() acquires the global RTNL and per-netns RTNL mutex, and
rtnl_net_unlock() releases them.

We will replace 800+ rtnl_lock() with rtnl_net_lock() and finally removes
rtnl_lock() in rtnl_net_lock().

When we need to nest per-netns RTNL mutex, we will use __rtnl_net_lock(),
and its locking order is defined by rtnl_net_lock_cmp_fn() as follows:

  1. init_net is first
  2. netns address ascending order

Note that the conversion will be done under CONFIG_DEBUG_NET_SMALL_RTNL
with LOCKDEP so that we can carefully add the extra mutex without slowing
down RTNL operations during conversion.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima
2024-10-04 15:10:29 -07:00
committed by Paolo Abeni
parent ec763c234d
commit 76aed95319
5 changed files with 104 additions and 0 deletions
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15
net/Kconfig.debug
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@@ -24,3 +24,18 @@ config DEBUG_NET
help
Enable extra sanity checks in networking.
This is mostly used by fuzzers, but is safe to select.
config DEBUG_NET_SMALL_RTNL
bool "Add extra per-netns mutex inside RTNL"
depends on DEBUG_KERNEL && NET && LOCK_DEBUGGING_SUPPORT
select PROVE_LOCKING
default n
help
rtnl_lock() is being replaced with rtnl_net_lock() that
acquires the global RTNL and a small per-netns RTNL mutex.
During the conversion, rtnl_net_lock() just adds an extra
mutex in every RTNL scope and slows down the operations.
Once the conversion completes, rtnl_lock() will be removed
and rtnetlink will gain per-netns scalability.