Commit 5f2f8920 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

inetpeer: do not use zero refcnt for freed entries 



Followup of commit aa1039e7 (inetpeer: RCU conversion)

Unused inet_peer entries have a null refcnt.

Using atomic_inc_not_zero() in rcu lookups is not going to work for
them, and slow path is taken.

Fix this using -1 marker instead of 0 for deleted entries.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d5f31fbf

net/ipv4/inetpeer.c

+8 −2
Original line number Diff line number Diff line
@@ -187,7 +187,12 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr) 


	while (u != peer_avl_empty) {

		if (daddr == u->v4daddr) {

			if (unlikely(!atomic_inc_not_zero(&u->refcnt)))

			/* Before taking a reference, check if this entry was

			 * deleted, unlink_from_pool() sets refcnt=-1 to make

			 * distinction between an unused entry (refcnt=0) and

			 * a freed one.

			 */

			if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1)))

				u = NULL;

			return u;

		}
@@ -322,8 +327,9 @@ static void unlink_from_pool(struct inet_peer *p) 
	 * in cleanup() function to prevent sudden disappearing.  If we can

	 * atomically (because of lockless readers) take this last reference,

	 * it's safe to remove the node and free it later.

	 * We use refcnt=-1 to alert lockless readers this entry is deleted.

	 */

	if (atomic_cmpxchg(&p->refcnt, 1, 0) == 1) {

	if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {

		struct inet_peer **stack[PEER_MAXDEPTH];

		struct inet_peer ***stackptr, ***delp;

		if (lookup(p->v4daddr, stack) != p)

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