linux-kernel - Re: [PATCH] kmemleak: Only use GFP_KERNEL|GFP

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Message-Id: <1245245448.5604.31.camel@penberg-laptop>
Date:	Wed, 17 Jun 2009 16:30:48 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Mel Gorman <mel@....ul.ie>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, fengguang.wu@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kmemleak: Only use GFP_KERNEL|GFP_ATOMIC for the
 internal  allocations

On Wed, 2009-06-17 at 14:23 +0100, Catalin Marinas wrote:
> On Wed, 2009-06-17 at 16:01 +0300, Pekka Enberg wrote:
> > On Wed, Jun 17, 2009 at 3:52 PM, Catalin Marinas<catalin.marinas@....com> wrote:
> > > Kmemleak allocates memory for pointer tracking and it tries to avoid
> > > using GFP_ATOMIC if the caller doesn't require it. However other gfp
> > > flags may be passed by the caller which aren't required by kmemleak.
> > > This patch filters the gfp flags so that only GFP_KERNEL | GFP_ATOMIC
> > > are used.
> > >
> > > Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> > 
> > Is this really safe? What if we're in a middle of a filesystem
> > operation that uses GFP_NOFAIL and all of a sudden kmemleak allocation
> > fails and causes a panic?
> 
> A kmemleak_panic() call only disables the kmemleak but doesn't stop the
> kernel. The __GFP_NOFAIL allocation had already happened and the pointer
> returned to the caller.

Ah, ok. I was confused by the name of kmemleak_panic() (which could use
renaming methinks).

Acked-by: Pekka Enberg <penberg@...helsinki.fi>

			Pekka

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