netdev - [PATCH net-next v3 08/12] net: sched: flower: handle concurrent filter insertion in fl

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Message-Id: <20190321131744.19224-9-vladbu@mellanox.com>
Date:   Thu, 21 Mar 2019 15:17:40 +0200
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, sbrivio@...hat.com,
        Vlad Buslov <vladbu@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>
Subject: [PATCH net-next v3 08/12] 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@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
Reviewed-by: Stefano Brivio <sbrivio@...hat.com>
---
 net/sched/cls_flower.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index db47828ea5e2..70b357f23391 100644
--- 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,
-- 
2.21.0