Re: [PATCH] mm, page_alloc: warn about empty nodemask

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 07 Sep 2016 08:41:26 +0800 Li Zhong <zhong@linux.vnet.ibm.com> wrote:

> Warn about allocating with an empty nodemask, it would be easier to
> understand than oom messages. The check is added in the slow path.
> 
> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
> --- 
> mm/page_alloc.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a2214c6..d624ff3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3448,6 +3448,12 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	if (page)
>  		goto got_pg;
>  
> +	if (ac->nodemask && nodes_empty(*ac->nodemask)) {
> +		pr_warn("nodemask is empty\n");
> +		gfp_mask &= ~__GFP_NOWARN;
> +		goto nopage;
> +	}
> +

Wouldn't it be better to do

	if (WARN_ON(ac->nodemask && nodes_empty(*ac->nodemask)) {
		...

so we can identify the misbehaving call site?

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