linux-kernel - Re: [BUG] mm: bdi: export BDI attributes in sysfs

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Date:	Thu, 15 May 2008 16:20:13 -0700
From:	Greg KH <greg@...ah.com>
To:	Arthur Jones <ajones@...erbed.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Miklos Szeredi <miklos@...redi.hu>,
	Arthur Jones <Arthur.Jones@...erbed.com>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"mszeredi@...e.cz" <mszeredi@...e.cz>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kay.sievers@...y.org" <kay.sievers@...y.org>,
	"trond.myklebust@....uio.no" <trond.myklebust@....uio.no>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] mm: bdi: export BDI attributes in sysfs

On Thu, May 15, 2008 at 03:05:10PM -0700, Arthur Jones wrote:
> Hi Greg, ...
> 
> On Thu, May 15, 2008 at 02:02:54PM -0700, Greg KH wrote:
> > On Thu, May 15, 2008 at 12:54:57PM -0700, Linus Torvalds wrote:
> > >
> > >
> > > On Thu, 15 May 2008, Miklos Szeredi wrote:
> > > >
> > > > Actually nothing should need protection.  The only problem AFAICS is
> > > > that the device_create()/dev_set_drvdata() interface is racy: somebody
> > > > can come in after the device has been created but before drvdata has
> > > > been set, and then we are in trouble.
> > >
> > > Well, I'm not sure that the locking should be at that level. Maybe the
> > > locking *should* be in the driver that does this. It may need to do other
> > > setup too, after all.
> > >
> > > Of course, doing a device_create_drvdata() thing might be the right
> > > solution, at least part of the time. Greg?
> > 
> > Here's a patch that is build tested only.
> > 
> > Can someone who can reproduce this let me know if it solves the problem?
> 
> Yes, this patch survives many power cycles
> without hitting the BUG...
> 
> Thanks for looking into this...

Great!

Thanks for testing this, I'll clean it up a bit more and send it to
Linus later this evening.  Gotta go take the kids to swimming lessons...

thanks,

greg k-h
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