linux-kernel - Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3

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Date:	Thu, 28 May 2009 11:56:25 -0500
From:	Russ Anderson <rja@....com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Nick Piggin <npiggin@...e.de>, hugh@...itas.com, riel@...hat.com,
	akpm@...ux-foundation.org, chris.mason@...cle.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	fengguang.wu@...el.com, rja@....com
Subject: Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3

On Thu, May 28, 2009 at 03:45:20PM +0200, Andi Kleen wrote:
> On Thu, May 28, 2009 at 02:08:54PM +0200, Nick Piggin wrote:
> > > > > +			printk(KERN_ERR "MCE: Out of memory while machine check handling\n");
> > > > > +			return;
> > > > > +		}
> > > > > +	}
> > > > > +	tk->addr = page_address_in_vma(p, vma);
> > > > > +	if (tk->addr == -EFAULT) {
> > > > > +		printk(KERN_INFO "MCE: Failed to get address in VMA\n");
> > > > 
> > > > I don't know if this is very helpful message. I could legitimately happen and
> > > > nothing anybody can do about it...
> > > 
> > > Can you suggest a better message?
> > 
> > Well, for userspace, nothing? At the very least ratelimited, and preferably
> > telling a more high level of what the problem and consequences are.
> 
> I changed it to 
> 
>  "MCE: Unable to determine user space address during error handling\n")
> 
> Still not perfect, but hopefully better.

Is it even worth having a message at all?  Does the fact that page_address_in_vma()
failed change the behavior in any way?  (Does tk->addr == 0 matter?)  From
a quick scan of the code I do not believe it does.

If the message is for developers/debugging, it would be nice to have more
information, such as why did page_address_in_vma() return -EFAULT.  If
that is important, page_address_in_vma() sould return a different failure 
status for each of the three failing conditions.  But that would only
be needed if the code (potentially) was going to do some additional handling.


Thanks,
-- 
Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          rja@....com
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