linux-kernel - Re: [PATCH] locking/lock_events: no need to check return value of debugfs

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Date:   Mon, 9 Nov 2020 11:04:09 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH] locking/lock_events: no need to check return value of
 debugfs_create functions

On Mon, Nov 09, 2020 at 05:51:56PM +0800, Tiezhu Yang wrote:
> On 11/09/2020 04:32 PM, Peter Zijlstra wrote:
> > On Sat, Nov 07, 2020 at 05:19:13PM +0800, Tiezhu Yang wrote:
> > > When calling debugfs functions, there is no need to ever check the
> > > return value.  The function can work or not, but the code logic should
> > > never do something different based on this.
> > I strongly disagree and have told this to Greg before. Having half a
> > debug interface is weird at best, so upon failure we remove the whole
> > thing, which is consistent.
> 
> Hi Peter,
> 
> Thanks for your reply.
> 
> I find the early discussion and see the following opinion by Greg:
> 
> https://lore.kernel.org/patchwork/patch/1290162/
> 
> [ For debugfs, this isn't an issue, what can a user do with something like
> "debugfs isn't working?  What does that mean???"
> 
> And if we _really_ want warnings like this, it should go into the
> debugfs core, not require this to be done for every debugfs user, right?

The debugfs core does spit out a warning when this happens, so no need
to duplicate it in your code as well.

And for subsystems that _really_ want to check this, that's fine, it's
the minority for the whole tree, but please, document it well with a
comment on the check so that it doesn't get "cleanup" patches sent for
it in the future.

thanks,

greg k-h