From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Date: Mon, 20 Jul 2020 17:55:20 +0200
Subject: netfilter: conntrack: Use sequence counter with associated spinlock
Patch-mainline: v5.9-rc1
Git-commit: 8201d923f492703a7d6c980cff3034759a452b86
References: bsc#1176564 bsc#1162702

A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-15-a.darwish@linutronix.de
Acked-by: Daniel Wagner <dwagner@suse.de>
---
 include/net/netfilter/nf_conntrack.h |    2 +-
 net/netfilter/nf_conntrack_core.c    |    5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -291,7 +291,7 @@ int nf_conntrack_hash_resize(unsigned in
 
 extern struct hlist_nulls_head *nf_conntrack_hash;
 extern unsigned int nf_conntrack_htable_size;
-extern seqcount_t nf_conntrack_generation;
+extern seqcount_spinlock_t nf_conntrack_generation;
 extern unsigned int nf_conntrack_max;
 
 /* must be called with rcu read lock held */
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -178,7 +178,7 @@ EXPORT_SYMBOL_GPL(nf_conntrack_htable_si
 
 unsigned int nf_conntrack_max __read_mostly;
 EXPORT_SYMBOL_GPL(nf_conntrack_max);
-seqcount_t nf_conntrack_generation __read_mostly;
+seqcount_spinlock_t nf_conntrack_generation __read_mostly;
 static unsigned int nf_conntrack_hash_rnd __read_mostly;
 
 static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple,
@@ -2377,7 +2377,8 @@ int nf_conntrack_init_start(void)
 	/* struct nf_ct_ext uses u8 to store offsets/size */
 	BUILD_BUG_ON(total_extension_size() > 255u);
 
-	seqcount_init(&nf_conntrack_generation);
+	seqcount_spinlock_init(&nf_conntrack_generation,
+			       &nf_conntrack_locks_all_lock);
 
 	for (i = 0; i < CONNTRACK_LOCKS; i++)
 		spin_lock_init(&nf_conntrack_locks[i]);