linux-kernel - Re: [PATCH v2] b43: don't save dentries for debugfs

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Date:   Tue, 18 May 2021 15:00:44 -0700
From:   Jeff Johnson <jjohnson@...eaurora.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-wireless@...r.kernel.org, Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Chao Yu <chao@...nel.org>,
        Leon Romanovsky <leon@...nel.org>, b43-dev@...ts.infradead.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        jjohnson=codeaurora.org@...eaurora.org
Subject: Re: [PATCH v2] b43: don't save dentries for debugfs

On 2021-05-18 12:29, Jeff Johnson wrote:
> On 2021-05-18 09:33, Greg Kroah-Hartman wrote:
>> There is no need to keep around the dentry pointers for the debugfs
>> files as they will all be automatically removed when the subdir is
>> removed.  So save the space and logic involved in keeping them around 
>> by
>> just getting rid of them entirely.
>> 
>> By doing this change, we remove one of the last in-kernel user that 
>> was
>> storing the result of debugfs_create_bool(), so that api can be 
>> cleaned
>> up.
> 
> Question not about this specific change, but the general concept
> of keeping (or not keeping) dentry pointers. In the ath drivers,
> as well as in an out-of-tree driver for Android, we keep a
> debugfs dentry pointer to use as a param to relay_open().
> 
> Will we still be able to have a dentry pointer for this purpose?
> Or better, is there a recommended way to get a dentry pointer
> NOT associated with debugfs at all (which would be ideal for
> Android where debugfs is disabled).

Answering one of my questions: The dentry passed to relay_open() comes
from debugfs_create_dir() which is expected to return a dentry.

Would still like guidance on if there is a recommended way to get a
dentry not associated with debugfs.

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