linux-kernel - Re: [PATCH v3] swiotlb: fix implicit debugfs_create

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Message-ID: <0ed2f689-2593-5387-dccb-96a82243910f@arm.com>
Date:   Wed, 30 Jun 2021 14:49:54 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Claire Chang <tientzu@...omium.org>, konrad.wilk@...cle.com,
        hch@....de, m.szyprowski@...sung.com,
        Will Deacon <will@...nel.org>, sstabellini@...nel.org
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org, Nicolas Boichat <drinkcat@...omium.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3] swiotlb: fix implicit debugfs_create_dir declaration

On 2021-06-30 05:06, Claire Chang wrote:
> Factor out the debugfs bits from rmem_swiotlb_device_init() into a separate
> rmem_swiotlb_debugfs_init().
> 
> Fixes: 461021875c50 ("swiotlb: Add restricted DMA pool initialization")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Claire Chang <tientzu@...omium.org>
> ---
>   kernel/dma/swiotlb.c | 17 ++++++++++++-----
>   1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 0ffbaae9fba2..355dc98d381c 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -709,6 +709,16 @@ static int __init swiotlb_create_default_debugfs(void)
>   
>   late_initcall(swiotlb_create_default_debugfs);
>   
> +static void rmem_swiotlb_debugfs_init(const char *name, struct io_tlb_mem *mem)

Nit: maybe just pass in the reserved_mem, then dereference rmem->name 
and rmem->priv inside here?

> +{
> +	mem->debugfs = debugfs_create_dir(name, debugfs_dir);
> +	swiotlb_create_debugfs_files(mem);
> +}
> +#else
> +__maybe_unused static void rmem_swiotlb_debugfs_init(const char *name,
> +						     struct io_tlb_mem *mem)
> +{
> +}
>   #endif
>   
>   #ifdef CONFIG_DMA_RESTRICTED_POOL
> @@ -766,11 +776,8 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
>   
>   		rmem->priv = mem;
>   
> -		if (IS_ENABLED(CONFIG_DEBUG_FS)) {
> -			mem->debugfs =
> -				debugfs_create_dir(rmem->name, debugfs_dir);
> -			swiotlb_create_debugfs_files(mem);
> -		}
> +		if (IS_ENABLED(CONFIG_DEBUG_FS))
> +			rmem_swiotlb_debugfs_init(rmem->name, mem);

Just make the call unconditional (and drop the __maybe_unused annotation 
above) - the stub already does nothing for the DEBUG_FS=n case, so the 
IS_ENABLED() is pointless.

Robin.

>   	}
>   
>   	dev->dma_io_tlb_mem = mem;
>