linux-kernel - Re: sysfs regression: wrong link counts

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Message-ID: <20120130220611.GA26655@kroah.com>
Date:	Mon, 30 Jan 2012 14:06:11 -0800
From:	Greg KH <greg@...ah.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LKML <linux-kernel@...r.kernel.org>,
	systemd-devel@...ts.freedesktop.org
Subject: Re: sysfs regression: wrong link counts

On Mon, Jan 30, 2012 at 10:56:26PM +0100, Jiri Slaby wrote:
> Hi,
> 
> I cannot boot properly with this commit:
> commit 524b6c5b39b931311dfe5a2f5abae2f5c9731676
> Author: Eric W. Biederman <ebiederm@...ssion.com>
> Date:   Sun Dec 18 20:09:31 2011 -0800
> 
>     sysfs: Kill nlink counting.
> 
> 
> 1) network systemd rule doesn't start network
> 2) sensors complain:
>    sensors_init: Kernel interface error

Odd.

What in systemd is causing a reliance on this?

> ad 2) look at what it does:
> /* returns !0 if sysfs filesystem was found, 0 otherwise */
> int sensors_init_sysfs(void)
> {
>         struct stat statbuf;
> 
>         snprintf(sensors_sysfs_mount, NAME_MAX, "%s", "/sys");
>         if (stat(sensors_sysfs_mount, &statbuf) < 0
>          || statbuf.st_nlink <= 2)      /* Empty directory */
>                 return 0;
> 
>         return 1;
> }

Ah, a hack to see if the directory is empty.

Isn't there some other "proper" way of doing this in userspace, or is
this really the correct way?

> So this looks like it became a part of ABI we cannot break...
> 
> A revert of this commit on the top of today's -next fixes the problem.

Ick.

Eric, care to fix this up, or do you want me to revert it?

thanks,

greg k-h
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