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Commit cfebd7e2 authored by Vlad Buslov's avatar Vlad Buslov Committed by David S. Miller
Browse files

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: default avatarVlad Buslov <vladbu@mellanox.com>
Acked-by: default avatarJiri Pirko <jiri@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e368fdb6

include/net/sch_generic.h

+1 −1
Original line number Diff line number Diff line
@@ -345,7 +345,7 @@ struct tcf_chain { 
struct tcf_block {

	struct list_head chain_list;

	u32 index; /* block index for shared blocks */

	unsigned int refcnt;

	refcount_t refcnt;

	struct net *net;

	struct Qdisc *q;

	struct list_head cb_list;

net/sched/cls_api.c

+35 −24
Original line number Diff line number Diff line
@@ -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;

}
@@ -793,12 +793,21 @@ 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.

		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);
@@ -809,18 +818,20 @@ void tcf_block_put_ext(struct tcf_block *block, struct Qdisc *q, 


		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) {

		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);

			}



		block->refcnt--;

		if (list_empty(&block->chain_list))

			kfree(block);

		}

	} else {

		block->refcnt--;

		tcf_block_offload_unbind(block, q, ei);

	}

}

EXPORT_SYMBOL(tcf_block_put_ext);