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net: allow pskb_expand_head() to get maximum tailroom

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Marc Merlin reported many order-1 allocations failures in TX path on its
wireless setup, that dont make any sense with MTU=1500 network, and non
SG capable hardware.

Turns out part of the problem comes from pskb_expand_head() not using
ksize() to get exact head size given by kmalloc(). Doing the same thing
than __alloc_skb() allows more tailroom in skb and can prevent future
reallocations.

As a bonus, struct skb_shared_info becomes cache line aligned.

Reported-by: Marc MERLIN <marc@merlins.org>
Tested-by: Marc MERLIN <marc@merlins.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-04-10 20:08:39 +00:00 • committed by David S. Miller
commit 87151b8689
1 changed files with 3 additions and 1 deletions
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4
net/core/skbuff.c
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@ -952,9 +952,11 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
goto adjust_others; goto adjust_others;
} }
data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask); data = kmalloc(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
gfp_mask);
if (!data) if (!data)
goto nodata; goto nodata;
size = SKB_WITH_OVERHEAD(ksize(data));
/* Copy only real data... and, alas, header. This should be /* Copy only real data... and, alas, header. This should be
* optimized for the cases when header is void. * optimized for the cases when header is void.