netdev - Re: [PATCH/RESEND] drivers/net/ethernet: dev_alloc_skb to netdev_alloc

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Message-Id: <20120123.165329.738852681807240808.davem@davemloft.net>
Date:	Mon, 23 Jan 2012 16:53:29 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	netdev@...deepdalvi.com
Cc:	joe@...ches.com, netdev@...r.kernel.org, hch@....de,
	linux-kernel@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH/RESEND] drivers/net/ethernet: dev_alloc_skb to
 netdev_alloc_skb

From: "Pradeep A. Dalvi" <netdev@...deepdalvi.com>
Date: Tue, 24 Jan 2012 02:11:43 +0530

> On Tue, Jan 24, 2012 at 1:26 AM, Joe Perches <joe@...ches.com> wrote:
>> On Tue, 2012-01-24 at 00:49 +0530, Pradeep A. Dalvi wrote:
>>> On Tue, Jan 24, 2012 at 12:10 AM, Joe Perches <joe@...ches.com> wrote:
>>> > On Mon, 2012-01-23 at 23:58 +0530, Pradeep A. Dalvi wrote:
>>> >> Replaced deprecating dev_alloc_skb with netdev_alloc_skb in drivers/net/ethernet
>>> >>   - Removed extra skb->dev = dev after netdev_alloc_skb
>>> > []
>>> >> diff --git a/drivers/net/ethernet/amd/lance.c b/drivers/net/ethernet/amd/lance.c
>>> > []
>>> >> @@ -871,13 +871,12 @@ lance_init_ring(struct net_device *dev, gfp_t gfp)
>>> >>               struct sk_buff *skb;
>>> >>               void *rx_buff;
>>> >>
>>> >> -             skb = alloc_skb(PKT_BUF_SZ, GFP_DMA | gfp);
>>> >> +             skb = netdev_alloc_skb(dev, PKT_BUF_SZ);
>>> >
>>> > This change seems suspect.
>>> Not really sure what made you suspect something in here. If you could
>>> help me understand possibly broken scenarios, would essentially be
>>> helpful. Thanks in advance!
>>
>> Where did the GFP_DMA go?
> 
> Aah! Is that really needed? Cause from my understanding, priority GFP
> flag __GFP_DMA is anyway negated in __alloc_skb, in a way from all
> sources i.e. netdev_alloc_skb or dev_alloc_skb or even alloc_skb. Am I
> missing something here?

GFP_DATA is negated for the SKB metadata allocation, but preserved for
the actual packet data allocation.

Could you please back off a bit and take your time on these changes?

Your transformations are adding bugs, and you make it clear that you
don't even understand how the allocation functions work semantically.

I don't really think you are knowledgable enough to make these
transformations safely at this time, and this is needlessly wasting
patch reviewer resources.
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