linux-kernel - Re: [PATCH] slab: prevent warnings when allocating with __GFP

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Message-ID: <CAOJsxLGDH2iwznRkP-iwiMZw7Ee3mirhjLvhShrWLHR0qguRxA@mail.gmail.com>
Date:	Mon, 10 Jun 2013 22:31:15 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slab: prevent warnings when allocating with __GFP_NOWARN

Hello Sasha,

On Mon, Jun 10, 2013 at 10:18 PM, Sasha Levin <sasha.levin@...cle.com> wrote:
> slab would still spew a warning when a big allocation happens with the
> __GFP_NOWARN fleg is set. Prevent that to conform to __GFP_NOWARN.
>
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  mm/slab_common.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index ff3218a..2d41450 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -373,8 +373,10 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
>  {
>         int index;
>
> -       if (WARN_ON_ONCE(size > KMALLOC_MAX_SIZE))
> +       if (size > KMALLOC_MAX_SIZE) {
> +               WARN_ON_ONCE(!(flags & __GFP_NOWARN));
>                 return NULL;
> +       }

Does this fix a real problem you're seeing? __GFP_NOWARN is about not
warning if a memory allocation fails but this particular WARN_ON
suggests a kernel bug.

                         Pekka
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