netdev - Re: [Bugme-new] [Bug 16083] New: swapper: Page allocation failure

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Message-ID: <1275601036.2533.63.camel@edumazet-laptop>
Date:	Thu, 03 Jun 2010 23:37:16 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [Bugme-new] [Bug 16083] New: swapper: Page allocation failure

Le jeudi 03 juin 2010 à 23:13 +0200, Eric Dumazet a écrit :

> MTU=9000 on a system with 4K pages... Oh well...
> 
> maybe net/ipv6/mcast.c should cap dev->mtu to PAGE_SIZE-128 or
> something, so that order-0 allocations are done.
> 
> 

Something like this patch (completely untested) :

[PATCH] ipv6: avoid high order allocations

With mtu=9000, mld_newpack() use order-2 GFP_ATOMIC allocations, that
are very unreliable, on machines where PAGE_SIZE=4K

Limit allocated skbs to be at most one page. (order-0 allocations)

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/ipv6/mcast.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 59f1881..3484794 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1356,7 +1356,10 @@ static struct sk_buff *mld_newpack(struct net_device *dev, int size)
 		     IPV6_TLV_PADN, 0 };
 
 	/* we assume size > sizeof(ra) here */
-	skb = sock_alloc_send_skb(sk, size + LL_ALLOCATED_SPACE(dev), 1, &err);
+	size += LL_ALLOCATED_SPACE(dev);
+	/* limit our allocations to order-0 page */
+	size = min(size, SKB_MAX_ORDER(0, 0));
+	skb = sock_alloc_send_skb(sk, size, 1, &err);
 
 	if (!skb)
 		return NULL;


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