diff mbox

net: af_packet: Don't initialize vnet_hdr

Message ID 1305237348.6124.72.camel@Joe-Laptop
State Rejected, archived
Delegated to: David Miller
Headers show

Commit Message

Joe Perches May 12, 2011, 9:55 p.m. UTC 
Save an initialization because when this structure
is used it's completely filled by memcpy_fromiovec.

Add a new variable used for the 0 sized allocation
when this structure is not used.

Signed-off-by: Joe Perches <joe@perches.com>

---

On Thu, 2011-05-12 at 17:36 -0400, David Miller wrote:
> I would rather see the code rearranged such that this sort of
> hackish scheme isn't necessary.

 net/packet/af_packet.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)




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Comments

David Miller May 12, 2011, 9:59 p.m. UTC | #1 
From: Joe Perches <joe@perches.com>
Date: Thu, 12 May 2011 14:55:48 -0700

> Save an initialization because when this structure
> is used it's completely filled by memcpy_fromiovec.
> 
> Add a new variable used for the 0 sized allocation
> when this structure is not used.
> 
> Signed-off-by: Joe Perches <joe@perches.com>
> 
> ---
> 
> On Thu, 2011-05-12 at 17:36 -0400, David Miller wrote:
>> I would rather see the code rearranged such that this sort of
>> hackish scheme isn't necessary.

You misunderstood me.

It's this:

	struct virtio_net_hdr vnet_hdr;


	if (po->has_vnet_hdr) {
		initialize &vnet_hdr
	}

	...

	if (po->has_vnet_hdr) {
		use vnet_hdr
	}

which I'm talking about when I say "hackish scheme".

The compiler cannot conclusively see that the control flow always
goes to the code that initialized vnet_hdr every time it reaches
the code that uses it.

I want _that_ part rearranged, not what you decided to tackle
here.

For the third time, I'm not applying your patch.
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diff mbox

Patch

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 549527b..cc1e83d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1123,9 +1123,10 @@  static int packet_snd(struct socket *sock,
 	__be16 proto;
 	unsigned char *addr;
 	int ifindex, err, reserve = 0;
-	struct virtio_net_hdr vnet_hdr = { 0 };
+	struct virtio_net_hdr vnet_hdr;
 	int offset = 0;
 	int vnet_hdr_len;
+	size_t alloc_vnet_hdr_len;
 	struct packet_sock *po = pkt_sk(sk);
 	unsigned short gso_type = 0;
 
@@ -1206,7 +1207,10 @@  static int packet_snd(struct socket *sock,
 				goto out_unlock;
 
 		}
-	}
+		alloc_vnet_hdr_len = vnet_hdr.hdr_len;
+	} else
+		alloc_vnet_hdr_len = 0;
+
 
 	err = -EMSGSIZE;
 	if (!gso_type && (len > dev->mtu + reserve + VLAN_HLEN))
@@ -1214,7 +1218,7 @@  static int packet_snd(struct socket *sock,
 
 	err = -ENOBUFS;
 	skb = packet_alloc_skb(sk, LL_ALLOCATED_SPACE(dev),
-			       LL_RESERVED_SPACE(dev), len, vnet_hdr.hdr_len,
+			       LL_RESERVED_SPACE(dev), len, alloc_vnet_hdr_len,
 			       msg->msg_flags & MSG_DONTWAIT, &err);
 	if (skb == NULL)
 		goto out_unlock;