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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>
This commit is contained in:
Vlad Buslov 2018-09-24 19:22:54 +03:00 committed by David S. Miller
parent e368fdb61d
commit cfebd7e242
2 changed files with 36 additions and 25 deletions
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2
include/net/sch_generic.h
View File

@ -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;

59
net/sched/cls_api.c
View File

@ -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 @@ err_block_owner_add:
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);