Re: kernel 3.2.27 on arm: WARNING: at mm/page_alloc.c:2109 __alloc_pages_nodemask+0x1d4/0x68c()

Eric Dumazet
2012-10-05T13:02:53Z

On Fri, 2012-10-05 at 14:51 +0200, Maxime Bizon wrote:

> > New convention would be : pass number of needed bytes after current
> > tail, not after current end.
>
> Fully agree on this
>

Here is the proposal :

Change all occurrences of :

pskb_expand_head(skb, 0, 0, gfp)

to

pskb_realloc_head(skb, gfp)
[ an inline calling a common function ]

And few other pskb_expand_head() calls a new function

pskb_may_expand_head(skb, nhead, ntail, gfp)
[ an inline calling same common function ]

nhead : number of needed bytes before [data,tail] portion
(might be already < skb_headroom(skb))

ntail : number of needed bytes after [data,tail] portion
(might be already > skb_tailroom(skb))

For example, net/xfrm/xfrm_output.c would be like the following :

(Note how all the various ugly tests will be centralized in the common
function)

And the common function would now know the caller intent.

diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index 95a338c..15760df 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -24,18 +24,10 @@ static int xfrm_output2(struct sk_buff *skb);
static int xfrm_skb_check_space(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
- int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev)
- - skb_headroom(skb);
- int ntail = dst->dev->needed_tailroom - skb_tailroom(skb);
-
- if (nhead <= 0) {
- if (ntail <= 0)
- return 0;
- nhead = 0;
- } else if (ntail < 0)
- ntail = 0;
-
- return pskb_expand_head(skb, nhead, ntail, GFP_ATOMIC);
+ int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev);
+ int ntail = dst->dev->needed_tailroom;
+
+ return pskb_may_expand_head(skb, nhead, ntail, GFP_ATOMIC);
}

static int xfrm_output_one(struct sk_buff *skb, int err)