linux-kernel - Re: [RFC PATCH 0/1] Initialize debugfs/ksysfs earlier?

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Date:   Fri, 04 Jun 2021 19:06:58 +0300
From:   Adrian Ratiu <adrian.ratiu@...labora.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kernel@...labora.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/1] Initialize debugfs/ksysfs earlier?

On Fri, 04 Jun 2021, Greg Kroah-Hartman 
<gregkh@...uxfoundation.org> wrote:
> On Thu, Jun 03, 2021 at 11:00:00PM +0300, Adrian Ratiu wrote: 
>> Hi and thank you for the quick response!   On Thu, 03 Jun 2021, 
>> Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote: 
>> > On Thu, Jun 03, 2021 at 03:55:33PM +0300, Adrian Ratiu wrote: 
>> > > Hi Greg & all,  I would like to add a new debugfs file like 
>> > > in the next patch but I'm having a problem with commit 
>> > > 56348560d495 ("debugfs: do not attempt to create a new file 
>> > > before the filesystem is initalized"). 
>> >  You should have had a problem before that commit happened as 
>> > well, right?  
>>  Actually no, it works without problems before commit 
>> 56348560d495 and also works if I revert that commit or move the 
>> debugfs_init() and its dependency ksysfs_init() before the 
>> driver core init. 
> 
> And the file shows up properly?  How can that be?  Is it ok to 
> create a file before the superblock is created in the system? 
> For some reason I thought these were just silently failing and 
> no one noticed.  Maybe we should revisit that commit... 

Yes the file shows up and works properly, but I do not know 
why. My tests run after the system boots to an interactive shell 
and by that time everything is initialized and working.

I thought maybe there were some specific corner-cases you wanted 
to guard against by adding that initialization -ENOENT check, but 
honestly since we're not adding a file earlier in the driver core 
anymore, I'd just leave it as is because the check makes sense in 
general.

Thanks again,
Adrian

>
> thanks,
>
> greg k-h