linux-kernel - Re: [PATCH 2/3] mm, bootmem: panic in bootmem alloc functions even if slab is available

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Date:	Thu, 27 Dec 2012 14:25:12 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Sasha Levin <sasha.levin@...cle.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"David S. Miller" <davem@...emloft.net>, Tejun Heo <tj@...nel.org>,
	Joonsoo Kim <js1304@...il.com>,
	Yinghai Lu <yinghai@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm, bootmem: panic in bootmem alloc functions even
 if slab is available

On Sun, 23 Dec 2012, Sasha Levin wrote:

> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index 1324cd7..198a92f 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -763,9 +763,6 @@ void * __init ___alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
>  void * __init __alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
>  				   unsigned long align, unsigned long goal)
>  {
> -	if (WARN_ON_ONCE(slab_is_available()))
> -		return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
> -
>  	return  ___alloc_bootmem_node(pgdat, size, align, goal, 0);
>  }
>  

All you're doing is removing the fallback if this happens to be called 
with slab_is_available().  It's still possible that the slab allocator can 
successfully allocate the memory, though.  So it would be rather 
unfortunate to start panicking in a situation that used to only emit a 
warning.

Why can't you panic only kzalloc_node() returns NULL and otherwise just 
return the allocated memory?
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