linux-kernel - Re: [PATCH v5 05/16] swiotlb: Add restricted DMA pool initialization

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Message-ID: <64137d13-cfa2-5f72-94c1-19b367489c78@arm.com>
Date:   Wed, 28 Apr 2021 10:50:24 +0100
From:   Steven Price <steven.price@....com>
To:     Claire Chang <tientzu@...omium.org>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
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Subject: Re: [PATCH v5 05/16] swiotlb: Add restricted DMA pool initialization

On 26/04/2021 17:37, Claire Chang wrote:
> On Fri, Apr 23, 2021 at 7:34 PM Steven Price <steven.price@....com> wrote:
[...]
>>
>> But even then if it's not and we have the situation where debugfs==NULL
>> then the debugfs_create_dir() here will cause a subsequent attempt in
>> swiotlb_create_debugfs() to fail (directory already exists) leading to
>> mem->debugfs being assigned an error value. I suspect the creation of
>> the debugfs directory needs to be separated from io_tlb_default_mem
>> being set.
> 
> debugfs creation should move into the if (!mem) {...} above to avoid
> duplication.
> I think having a separated struct dentry pointer for the default
> debugfs should be enough?
> 
> if (!debugfs)
>      debugfs = debugfs_create_dir("swiotlb", NULL);
> swiotlb_create_debugfs(mem, rmem->name, debugfs);

Yes that looks like a good solution to me. Although I'd name the 
variable something a bit more descriptive than just "debugfs" e.g. 
"debugfs_dir" or "debugfs_root".

Thanks,

Steve