linux-kernel - Re: [PATCH 3/3] dma-pool: limit DMA and DMA32 zone size pools

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Message-ID: <20220821104321.GB30530@lst.de>
Date:   Sun, 21 Aug 2022 12:43:21 +0200
From:   Christoph Hellwig <hch@....de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Christoph Hellwig <hch@....de>, iommu@...ts.linux.dev,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] dma-pool: limit DMA and DMA32 zone size pools

On Wed, Aug 17, 2022 at 01:50:09PM +0100, Robin Murphy wrote:
>>   +#if defined(CONFIG_ZONE_DMA) || defined(CONFIG_ZONE_DMA32)
>
> This #ifdeffery seems horribly clunky - I think it would be much nicer to 
> mark this __maybe_unused, and preserve the has_managed_dma/IS_ENABLED logic 
> below.

>>   static int __init dma_atomic_pool_init(void)
>>   {
>> +	unsigned long nr_zone_dma_pages, nr_zone_dma32_pages;
>
> ...otherwise, I expect the buildbots will be along shortly with unused 
> variable warnings for these :)

Amazingly they haven't complained yet, even if they should.  But
simple IS_ENABLED won't work either as the ZONE_DMA / ZONE_DMA32
constants are not defined unless the corresponding config options
are set.  I'll see what I can do here using helpers.