linux-kernel - Re: + mm-exec-rename-mm-exe_file-to-mm-exe

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Date:	Wed, 7 Mar 2012 23:34:33 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	adobriyan@...il.com, ebiederm@...ssion.com, keescook@...omium.org,
	kosaki.motohiro@...fujitsu.com, matthltc@...ibm.com, tj@...nel.org,
	xemul@...allels.com
Subject: Re: + mm-exec-rename-mm-exe_file-to-mm-exe_path.patch added to -mm
 tree

On Wed, Mar 07, 2012 at 06:41:13PM +0100, Oleg Nesterov wrote:
...
> 
> Of course I can be wrong, but currently I think that either this patch
> reveals another problem (unlikley), or (most likely) I did some stupid
> mistake.
> 
> Can you send me the reproducer just in case?
> 
> > [ 1961.066410] Code: 41 5c 41 5d c9 c3 55 48 89 e5 41 54 53 48 83 ec 30
> > 66 66 66 66 90 48 63 c2 89 55 cc 48 89 fb 48 8d 04 06 48 89 45 e8 48 8b
> > 7f 08 <48> 8b 87 a8 00 00 00 48 85 c0 74 0d 48 8b 40 38 48 85 c0 74 04
> 
> No sure I understand this asm... Looks like path->dentry is NULL, strange.
> 
> I do not think I really need it, but just in case... could you send me
> (privately) the result of "make fs/dcache.s" ?
> 

yes, just sent.

> I'll try to recheck the patch and think.
> 
> But if you can _explain_ why do you think that "struct path" can't work,
> please explain ;)

OK, the best way to prove myself that I was wrong is to try to
explain why it can't work. So I prepared a call trace to point
where we can get a reference to non-existing path and... found
that it's simply impossible. So then I tried to repeat oops
after the test machine got rebooted and found that I can't
repeat it. I'll continue testing but I think it was unrelated
OOPs. Sorry for false alarm, Oleg!

	Cyrill
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