inet: frag: use seqlock for hash rebuild
rehash is rare operation, don't force readers to take
the read-side rwlock.
Instead, we only have to detect the (rare) case where
the secret was altered while we are trying to insert
a new inetfrag queue into the table.
If it was changed, drop the bucket lock and recompute
the hash to get the 'new' chain bucket that we have to
insert into.
Joint work with Nikolay Aleksandrov.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index d9cc5bb..6f4930a 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -53,11 +53,6 @@
struct inet_frags {
struct inet_frag_bucket hash[INETFRAGS_HASHSZ];
- /* This rwlock is a global lock (seperate per IPv4, IPv6 and
- * netfilter). Important to keep this on a seperate cacheline.
- * Its primarily a rebuild protection rwlock.
- */
- rwlock_t lock ____cacheline_aligned_in_smp;
struct work_struct frags_work;
unsigned int next_bucket;
@@ -66,8 +61,12 @@
/* The first call to hashfn is responsible to initialize
* rnd. This is best done with net_get_random_once.
+ *
+ * rnd_seqlock is used to let hash insertion detect
+ * when it needs to re-lookup the hash chain to use.
*/
u32 rnd;
+ seqlock_t rnd_seqlock;
int qsize;
unsigned int (*hashfn)(const struct inet_frag_queue *);
@@ -89,8 +88,8 @@
void inet_frag_kill(struct inet_frag_queue *q, struct inet_frags *f);
void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f);
struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
- struct inet_frags *f, void *key, unsigned int hash)
- __releases(&f->lock);
+ struct inet_frags *f, void *key, unsigned int hash);
+
void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
const char *prefix);