linux-kernel - Re: [PATCH] swiotlb: suppress warning when __GFP

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Date:   Thu, 4 Jan 2018 14:49:21 +0100
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     konrad.wilk@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] swiotlb: suppress warning when __GFP_NOWARN is set v5

Am 04.01.2018 um 14:29 schrieb Christoph Hellwig:
>> @@ -713,6 +713,7 @@ void *
>>   swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>>   		       dma_addr_t *dma_handle, gfp_t flags)
>>   {
>> +	bool warn = !(flags & __GFP_NOWARN);
> This is still wrong.  __GFP_NOWARN has no meaning for DMA coherent
> allocations, and if a driver expects it to do anything it's doing it
> wrong.  This needs to check for DMA_ATTR_NO_WARN, and thus get the attrs
> passed.

I perfectly agree on that, but this is for stable kernel backports. 
Because of this I want to keep the footprint as low as possible.

When your patchset to clean that up lands for 4.16 I have no problem 
changing that.

But till then I think we should just work on suppress the warning for now.

Regards,
Christian.