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Subject: Re: [PATCH 1/1] dma-mapping: to avoid exception when cpu_addr is NULL
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
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CC: Andrew Morton <akpm@linux-foundation.org>,
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        Hanjun Guo <guohanjun@huawei.com>
From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
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Date: Mon, 7 Mar 2016 20:22:00 +0800
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On 2016/3/7 19:41, One Thousand Gnomes wrote:
> On Mon, 7 Mar 2016 17:21:25 +0800
> Zhen Lei <thunder.leizhen@huawei.com> wrote:
> 
>> Do this to keep consistent with kfree, which tolerate ptr is NULL.
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> 
> This is inlined code so you are adding extra logic to every single
> instance of a call to the function. What is it's total effect on kernel
> size ?

This a simple if statement, I think it will only generates two instructions.
Maybe I need move it into function dma_free_attrs, as below:
if (!ops->free || !cpu_addr)
	return;

So that, it only generates one instruction. And dma_free_noncoherent can also be impacted.

Or I changed it to BUG_ON(!cpu_addr)?

Otherwise, I move it into ops->free, but that maybe more ARCHs.

> 
> Alan
> 
> .
>