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Message-Id: <1537806178-10944-7-git-send-email-vladbu@mellanox.com>
Date: Mon, 24 Sep 2018 19:22:54 +0300
From: Vlad Buslov <vladbu@...lanox.com>
To: netdev@...r.kernel.org
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
davem@...emloft.net, stephen@...workplumber.org,
ktkhai@...tuozzo.com, nicolas.dichtel@...nd.com,
gregkh@...uxfoundation.org, mark.rutland@....com, leon@...nel.org,
paulmck@...ux.vnet.ibm.com, fw@...len.de, dsahern@...il.com,
christian@...uner.io, lucien.xin@...il.com,
jakub.kicinski@...ronome.com, jbenc@...hat.com,
Vlad Buslov <vladbu@...lanox.com>
Subject: [PATCH net-next v3 06/10] 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@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
---
include/net/sch_generic.h | 2 +-
net/sched/cls_api.c | 59 ++++++++++++++++++++++++++++-------------------
2 files changed, 36 insertions(+), 25 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 43b17f82d8ee..4a86f4d33f07 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -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;
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index c33636e7b431..90843b6a8fa9 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 (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 (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.
*/
- list_for_each_entry(chain, &block->chain_list, list)
- tcf_chain_hold(chain);
+ bool free_block = list_empty(&block->chain_list);
- list_for_each_entry(chain, &block->chain_list, list)
- tcf_chain_flush(chain);
- }
+ if (tcf_block_shared(block))
+ tcf_block_remove(block, block->net);
- tcf_block_offload_unbind(block, q, ei);
+ 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);
- 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);
--
2.7.5
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