Re: [PATCH RFC] solos-pci: Fix BUG() with shared skb

[David Woodhouse <dwmw2@infradead.org>]

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On Wed, 2013-09-04 at 14:30 -0400, David Miller wrote:
> skb_realloc_headroom() should do everything you need.

Great, thanks! Something like this then... ? 

Do I really need the truesize check? And if so, is there a better way to
handle the ATM accounting? It just *happens* to be the case that the the
br2684_pop() and pppoatm_pop() functions don't mind being bypassed in
this fashion, and we should probably get away with tweaking the core ATM
accounting directly like this. Doesn't make me happy though...

diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c
index 32784d1..4492c0f 100644
--- a/drivers/atm/solos-pci.c
+++ b/drivers/atm/solos-pci.c
@@ -1145,19 +1145,19 @@ static int psend(struct atm_vcc *vcc, struct sk_buff *skb)
 		return 0;
 	}
 
-	if (!skb_clone_writable(skb, sizeof(*header))) {
-		int expand_by = 0;
-		int ret;
-
-		if (skb_headroom(skb) < sizeof(*header))
-			expand_by = sizeof(*header) - skb_headroom(skb);
-
-		ret = pskb_expand_head(skb, expand_by, 0, GFP_ATOMIC);
-		if (ret) {
-			dev_warn(&card->dev->dev, "pskb_expand_head failed.\n");
-			solos_pop(vcc, skb);
-			return ret;
-		}
+	if (skb_headroom(skb) < sizeof(*header)) {
+		struct sk_buff *nskb;
+
+		nskb = skb_realloc_headroom(skb, sizeof(*header));
+		if (!nskb) {
+			solos_pop(vcc, skb);
+			return -ENOMEM;
+		}
+		if (skb->truesize != nskb->truesize)
+			atm_force_charge(vcc, nskb->truesize - skb->truesize);
+ 
+		dev_kfree_skb_any(skb);
+		skb = nskb;
 	}
 
 	header = (void *)skb_push(skb, sizeof(*header));


-- 
dwmw2


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