Re: [PATCH 4/5] gtp: remove unnecessary rcu_read_lock

[Pablo Neira Ayuso]

On Tue, Jan 24, 2017 at 06:24:01PM +0100, Andreas Schultz wrote:
> The rcu read lock is hold by default in the ip input path. There
> is no need to hold it twice in the socket recv decapsulate code path.

I think this is net-next material since it is not essencial.

[PATCH 4/5] gtp: remove unnecessary rcu_read_lock

[Andreas Schultz]

The rcu read lock is hold by default in the ip input path. There
is no need to hold it twice in the socket recv decapsulate code path.

Signed-off-by: Andreas Schultz 
---
 drivers/net/gtp.c | 24 
 1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 72dd1ba..912721e 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -183,7 +183,6 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct 
sk_buff *skb,
  sizeof(struct gtp0_header);
struct gtp0_header *gtp0;
struct pdp_ctx *pctx;
-   int ret = 0;
 
if (!pskb_may_pull(skb, hdrlen))
return -1;
@@ -196,26 +195,19 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, 
struct sk_buff *skb,
if (gtp0->type != GTP_TPDU)
return 1;
 
-   rcu_read_lock();
pctx = gtp0_pdp_find(gtp, be64_to_cpu(gtp0->tid));
if (!pctx) {
netdev_dbg(gtp->dev, "No PDP ctx to decap skb=%p\n", skb);
-   ret = -1;
-   goto out_rcu;
+   return -1;
}
 
if (!gtp_check_src_ms(skb, pctx, hdrlen)) {
netdev_dbg(gtp->dev, "No PDP ctx for this MS\n");
-   ret = -1;
-   goto out_rcu;
+   return -1;
}
-   rcu_read_unlock();
 
/* Get rid of the GTP + UDP headers. */
return iptunnel_pull_header(skb, hdrlen, skb->protocol, xnet);
-out_rcu:
-   rcu_read_unlock();
-   return ret;
 }
 
 static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb,
@@ -225,7 +217,6 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct 
sk_buff *skb,
  sizeof(struct gtp1_header);
struct gtp1_header *gtp1;
struct pdp_ctx *pctx;
-   int ret = 0;
 
if (!pskb_may_pull(skb, hdrlen))
return -1;
@@ -253,26 +244,19 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, 
struct sk_buff *skb,
 
gtp1 = (struct gtp1_header *)(skb->data + sizeof(struct udphdr));
 
-   rcu_read_lock();
pctx = gtp1_pdp_find(gtp, ntohl(gtp1->tid));
if (!pctx) {
netdev_dbg(gtp->dev, "No PDP ctx to decap skb=%p\n", skb);
-   ret = -1;
-   goto out_rcu;
+   return -1;
}
 
if (!gtp_check_src_ms(skb, pctx, hdrlen)) {
netdev_dbg(gtp->dev, "No PDP ctx for this MS\n");
-   ret = -1;
-   goto out_rcu;
+   return -1;
}
-   rcu_read_unlock();
 
/* Get rid of the GTP + UDP headers. */
return iptunnel_pull_header(skb, hdrlen, skb->protocol, xnet);
-out_rcu:
-   rcu_read_unlock();
-   return ret;
 }
 
 static void gtp_encap_disable(struct gtp_dev *gtp)
-- 
2.10.2