net: sched: change tcf block reference counter type to refcount_t
As a preparation for removing rtnl lock dependency from rules update path,
change tcf block reference counter type to refcount_t to allow modification
by concurrent users.
In block put function perform decrement and check reference counter once to
accommodate concurrent modification by unlocked users. After this change
tcf_chain_put at the end of block put function is called with
block->refcnt==0 and will deallocate block after the last chain is
released, so there is no need to manually deallocate block in this case.
However, if block reference counter reached 0 and there are no chains to
release, block must still be deallocated manually.
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index c33636e..90843b6a 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -240,7 +240,7 @@ static void tcf_chain_destroy(struct tcf_chain *chain)
if (!chain->index)
block->chain0.chain = NULL;
kfree(chain);
- if (list_empty(&block->chain_list) && block->refcnt == 0)
+ if (list_empty(&block->chain_list) && !refcount_read(&block->refcnt))
kfree(block);
}
@@ -510,7 +510,7 @@ static struct tcf_block *tcf_block_create(struct net *net, struct Qdisc *q,
INIT_LIST_HEAD(&block->owner_list);
INIT_LIST_HEAD(&block->chain0.filter_chain_list);
- block->refcnt = 1;
+ refcount_set(&block->refcnt, 1);
block->net = net;
block->index = block_index;
@@ -710,7 +710,7 @@ int tcf_block_get_ext(struct tcf_block **p_block, struct Qdisc *q,
/* block_index not 0 means the shared block is requested */
block = tcf_block_lookup(net, ei->block_index);
if (block)
- block->refcnt++;
+ refcount_inc(&block->refcnt);
}
if (!block) {
@@ -753,7 +753,7 @@ int tcf_block_get_ext(struct tcf_block **p_block, struct Qdisc *q,
err_block_insert:
kfree(block);
} else {
- block->refcnt--;
+ refcount_dec(&block->refcnt);
}
return err;
}
@@ -793,34 +793,45 @@ void tcf_block_put_ext(struct tcf_block *block, struct Qdisc *q,
tcf_chain0_head_change_cb_del(block, ei);
tcf_block_owner_del(block, q, ei->binder_type);
- if (block->refcnt == 1) {
+ if (refcount_dec_and_test(&block->refcnt)) {
+ /* Flushing/putting all chains will cause the block to be
+ * deallocated when last chain is freed. However, if chain_list
+ * is empty, block has to be manually deallocated. After block
+ * reference counter reached 0, it is no longer possible to
+ * increment it or add new chains to block.
+ */
+ bool free_block = list_empty(&block->chain_list);
+
if (tcf_block_shared(block))
tcf_block_remove(block, block->net);
- /* Hold a refcnt for all chains, so that they don't disappear
- * while we are iterating.
- */
- list_for_each_entry(chain, &block->chain_list, list)
- tcf_chain_hold(chain);
+ if (!free_block) {
+ /* Hold a refcnt for all chains, so that they don't
+ * disappear while we are iterating.
+ */
+ list_for_each_entry(chain, &block->chain_list, list)
+ tcf_chain_hold(chain);
- list_for_each_entry(chain, &block->chain_list, list)
- tcf_chain_flush(chain);
- }
-
- tcf_block_offload_unbind(block, q, ei);
-
- if (block->refcnt == 1) {
- /* At this point, all the chains should have refcnt >= 1. */
- list_for_each_entry_safe(chain, tmp, &block->chain_list, list) {
- tcf_chain_put_explicitly_created(chain);
- tcf_chain_put(chain);
+ list_for_each_entry(chain, &block->chain_list, list)
+ tcf_chain_flush(chain);
}
- block->refcnt--;
- if (list_empty(&block->chain_list))
+ tcf_block_offload_unbind(block, q, ei);
+
+ if (free_block) {
kfree(block);
+ } else {
+ /* At this point, all the chains should have
+ * refcnt >= 1.
+ */
+ list_for_each_entry_safe(chain, tmp, &block->chain_list,
+ list) {
+ tcf_chain_put_explicitly_created(chain);
+ tcf_chain_put(chain);
+ }
+ }
} else {
- block->refcnt--;
+ tcf_block_offload_unbind(block, q, ei);
}
}
EXPORT_SYMBOL(tcf_block_put_ext);