[PATCH net-next 04/17] net: sched: protect block->chain0 with block->lock

[Vlad Buslov]

In order to remove dependency on rtnl lock, use block->lock to protect
chain0 struct from concurrent modification. Rearrange code in chain0
callback add and del functions to only access chain0 when block->lock is
held.

Signed-off-by: Vlad Buslov <vla...@mellanox.com>
Acked-by: Jiri Pirko <j...@mellanox.com>
---
 net/sched/cls_api.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 146a02094905..beffcc2ab1fa 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -260,8 +260,11 @@ static void tcf_chain0_head_change(struct tcf_chain *chain,
 
        if (chain->index)
                return;
+
+       spin_lock(&block->lock);
        list_for_each_entry(item, &block->chain0.filter_chain_list, list)
                tcf_chain_head_change_item(item, tp_head);
+       spin_unlock(&block->lock);
 }
 
 /* Returns true if block can be safely freed. */
@@ -519,8 +522,8 @@ tcf_chain0_head_change_cb_add(struct tcf_block *block,
                              struct tcf_block_ext_info *ei,
                              struct netlink_ext_ack *extack)
 {
-       struct tcf_chain *chain0 = block->chain0.chain;
        struct tcf_filter_chain_list_item *item;
+       struct tcf_chain *chain0;
 
        item = kmalloc(sizeof(*item), GFP_KERNEL);
        if (!item) {
@@ -529,9 +532,14 @@ tcf_chain0_head_change_cb_add(struct tcf_block *block,
        }
        item->chain_head_change = ei->chain_head_change;
        item->chain_head_change_priv = ei->chain_head_change_priv;
+
+       spin_lock(&block->lock);
+       chain0 = block->chain0.chain;
        if (chain0 && chain0->filter_chain)
                tcf_chain_head_change_item(item, chain0->filter_chain);
        list_add(&item->list, &block->chain0.filter_chain_list);
+       spin_unlock(&block->lock);
+
        return 0;
 }
 
@@ -539,20 +547,23 @@ static void
 tcf_chain0_head_change_cb_del(struct tcf_block *block,
                              struct tcf_block_ext_info *ei)
 {
-       struct tcf_chain *chain0 = block->chain0.chain;
        struct tcf_filter_chain_list_item *item;
 
+       spin_lock(&block->lock);
        list_for_each_entry(item, &block->chain0.filter_chain_list, list) {
                if ((!ei->chain_head_change && !ei->chain_head_change_priv) ||
                    (item->chain_head_change == ei->chain_head_change &&
                     item->chain_head_change_priv == 
ei->chain_head_change_priv)) {
-                       if (chain0)
+                       if (block->chain0.chain)
                                tcf_chain_head_change_item(item, NULL);
                        list_del(&item->list);
+                       spin_unlock(&block->lock);
+
                        kfree(item);
                        return;
                }
        }
+       spin_unlock(&block->lock);
        WARN_ON(1);
 }
 
-- 
2.7.5