netfilter: conntrack: Use sequence counter with associated spinlock
authorAhmed S. Darwish <a.darwish@linutronix.de>
Mon, 20 Jul 2020 15:55:20 +0000 (17:55 +0200)
committerPeter Zijlstra <peterz@infradead.org>
Wed, 29 Jul 2020 14:14:26 +0000 (16:14 +0200)
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
include/net/netfilter/nf_conntrack.h
net/netfilter/nf_conntrack_core.c

index 90690e37a56f0ebf33b2cd8961d89ed5e55f66b2..ea4e2010b2465bd58511904dfdf63717df64de64 100644 (file)
@@ -286,7 +286,7 @@ int nf_conntrack_hash_resize(unsigned int hashsize);
 
 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 */
index f33d72c5b06e123dd97c11933467b3197877d1d5..b597b5b16ba1919785468ddf84b96c316fa00d58 100644 (file)
@@ -180,7 +180,7 @@ EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);
 
 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,
@@ -2600,7 +2600,8 @@ 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]);