net: sched: flower: handle concurrent filter insertion in fl_change

Check if user specified a handle and another filter with the same handle
was inserted concurrently. Return EAGAIN to retry filter processing (in
case it is an overwrite request).

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index db47828..70b357f 100644 (file)
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1542,6 +1542,15 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
                        /* user specifies a handle and it doesn't exist */
                        err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
                                            handle, GFP_ATOMIC);
+
+                       /* Filter with specified handle was concurrently
+                        * inserted after initial check in cls_api. This is not
+                        * necessarily an error if NLM_F_EXCL is not set in
+                        * message flags. Returning EAGAIN will cause cls_api to
+                        * try to update concurrently inserted rule.
+                        */
+                       if (err == -ENOSPC)
+                               err = -EAGAIN;
                } else {
                        handle = 1;
                        err = idr_alloc_u32(&head->handle_idr, fnew, &handle,