linux-kernel - Re: [PATCH] driver core: remove CONFIG_SYSFS

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Date:	Wed, 14 Jul 2010 21:29:53 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Greg KH <gregkh@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, alsa-devel@...a-project.org,
	Jens Axboe <axboe@...nel.dk>,
	Stephen Hemminger <shemminger@...tta.com>,
	Kay Sievers <kay.sievers@...y.org>,
	Alan Stern <stern@...land.harvard.edu>,
	"James E.J. Bottomley" <James.Bottomley@...e.de>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Tejun Heo <tj@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	David Howells <dhowells@...hat.com>,
	Dave Airlie <airlied@...il.com>
Subject: Re: [PATCH] driver core: remove CONFIG_SYSFS_DEPRECATED

Greg KH <gregkh@...e.de> writes:

> On Wed, Jul 14, 2010 at 05:40:27PM -0700, Eric W. Biederman wrote:
>> Andrew Morton <akpm@...ux-foundation.org> writes:
>> 
>> > On Fri, 9 Jul 2010 11:54:50 -0700
>> > Greg Kroah-Hartman <gregkh@...e.de> wrote:
>> >
>> >> This is no longer needed by any userspace tools, so it's safe to
>> >> remove.
>> >
>> > Makes my FC6 test box not boot - can't find /dev/root.  Then when I go
>> > back to plain old mainline (2.6.35-rc5) and run `make oldconfig', the
>> > .config change sticks:
>> >
>> > @@ -106,8 +106,7 @@
>> >  CONFIG_LOG_BUF_SHIFT=17
>> >  CONFIG_HAVE_UNSTABLE_SCHED_CLOCK=y
>> >  # CONFIG_CGROUPS is not set
>> > -CONFIG_SYSFS_DEPRECATED=y
>> > -CONFIG_SYSFS_DEPRECATED_V2=y
>> > +# CONFIG_SYSFS_DEPRECATED_V2 is not set
>> >  CONFIG_RELAY=y
>> >  CONFIG_NAMESPACES=y
>> >  # CONFIG_UTS_NS is not set
>> >
>> > and the box still won't boot.
>> 
>> The reason FC6 doesn't boot is there is a userspace tool
>> I believe in the initrd that cares about symlinks when it should
>> not.
>
> Anyone happen to know which tool it is?  I remember we had had issues
> with FC3 around this area, but I thought we resolved them, so it's
> supprising to me that FC6 has issues.

It was something in the initrd, that didn't like the symlinks.  It
has been a year or more since I looked at it.  At that point I just
enabled SYSFS_DEPRECATED and moved on.

>> What is more interesting is that currently there is a bug in
>> 2.6.35-rc5 where rmmod <netdriver> modprobe <netdriver> will in fact
>> fail.  There was an inadvertent regression and no one has noticed or
>> complained.  I spotted it by code review just a little bit ago and I
>> haven't had a chance to write and test the fix yet.
>> 
>> If the code is going to start bitrotting and no one is going to
>> notice or care simply removing the code instead of subjecting users
>> to weird unexpected breakage seems like a responsible thing to do.
>
> Yeah, that's what prompted this removal.  After the s390 guys said that
> they were all good to go, I figured no one else would have problems with
> it :)
>
> If it turns out there still are issues with older userspaces like FC6
> that we can't resolve, I have no problem dropping this patch and then we
> will have to fix up the regression.

I still have to test it but it looks like a one liner.  Actually two lines
now that I have to fix the error in symlink creation as well.

Eric
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