net: sched: atomically check-allocate action

Implement function that atomically checks if action exists and either takes
reference to it, or allocates idr slot for action index to prevent
concurrent allocations of actions with same index. Use EBUSY error pointer
to indicate that idr slot is reserved.

Implement cleanup helper function that removes temporary error pointer from
idr. (in case of error between idr allocation and insertion of newly
created action to specified index)

Refactor all action init functions to insert new action to idr using this
API.

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c
index 85e85dfba401..0dc787a57798 100644
--- a/net/sched/act_ipt.c
+++ b/net/sched/act_ipt.c
@@ -119,13 +119,18 @@ static int __tcf_ipt_init(struct net *net, unsigned int id, struct nlattr *nla,
 	if (tb[TCA_IPT_INDEX] != NULL)
 		index = nla_get_u32(tb[TCA_IPT_INDEX]);
 
-	exists = tcf_idr_check(tn, index, a, bind);
+	err = tcf_idr_check_alloc(tn, &index, a, bind);
+	if (err < 0)
+		return err;
+	exists = err;
 	if (exists && bind)
 		return 0;
 
 	if (tb[TCA_IPT_HOOK] == NULL || tb[TCA_IPT_TARG] == NULL) {
 		if (exists)
 			tcf_idr_release(*a, bind);
+		else
+			tcf_idr_cleanup(tn, index);
 		return -EINVAL;
 	}
 
@@ -133,14 +138,18 @@ static int __tcf_ipt_init(struct net *net, unsigned int id, struct nlattr *nla,
 	if (nla_len(tb[TCA_IPT_TARG]) < td->u.target_size) {
 		if (exists)
 			tcf_idr_release(*a, bind);
+		else
+			tcf_idr_cleanup(tn, index);
 		return -EINVAL;
 	}
 
 	if (!exists) {
 		ret = tcf_idr_create(tn, index, est, a, ops, bind,
 				     false);
-		if (ret)
+		if (ret) {
+			tcf_idr_cleanup(tn, index);
 			return ret;
+		}
 		ret = ACT_P_CREATED;
 	} else {
 		if (bind)/* dont override defaults */