linux-kernel - Re: [PATCH 2.6.24-rc7 2/2] sysfs: fix bugs in sysfs_rename/move

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Message-ID: <20080117042216.GB27894@ZenIV.linux.org.uk>
Date:	Thu, 17 Jan 2008 04:22:16 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Tejun Heo <htejun@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Gabor Gombas <gombasg@...aki.hu>, Greg KH <greg@...ah.com>,
	Dave Young <hidave.darkstar@...il.com>,
	bluez-devel@...ts.sourceforge.net
Subject: Re: [PATCH 2.6.24-rc7 2/2] sysfs: fix bugs in sysfs_rename/move_dir()

On Wed, Jan 16, 2008 at 04:23:13PM +0900, Tejun Heo wrote:

> The two posted patches are bug fixes for apparent bugs which can be
> triggered by the current two users of the interface.  AFAICS, locking
> there is weird but correct for the current two users.  If you can find
> any problem there, please lemme know.

How about "what happens after that move-to-NULL if you have a cwd inside
the subtree", for starters?

>  We shouldn't hold this type of
> fixes for future clean ups.

No, but I'd rather see the rules for callers of sysfs/kobject primitives
spelled out - before cleanups or review become even possible.
 
> > As it is, I'm more than inclined
> > to propose ripping kobject_move() out, especially since it has only two
> > users - something s390-specific and rfcomm, with its shitloads of problems
> > beyond just sysfs interaction.
> 
> Can you please elaborate?  All sysfs problems discovered by the rfcomm
> are fixed by the posted patches.  Dave Young has a patch waiting for
> verification by the tester.

Umm...  IIRC, there'd been a lot of fun with tty and procfs sides of that;
will check.

> Furthermore, even if we rip out
> kobject_move() in the future, I don't think -rc7 is the right time to do it.

OK...  You do have a point, but at this stage I'm not convinced that this
thing is safe and usable.  I agree that patches do not make things worse,
but I suspect that the real problem with kobject_move() is that it's a
fundamentally broken interface.
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