Subject: Re: [PATCH net] bpf: cpumap: use GFP_KERNEL instead of GFP_ATOMIC in __cpu_map_entry_alloc()

From: Jesper Dangaard Brouer <[email-masked]>
Date: Wed, 14 Feb 2018 15:20:20 +0100

On Wed, 14 Feb 2018 22:17:34 +0800
Jason Wang <[email-masked]> wrote:

> There're several implications after commit 0bf7800f1799 ("ptr_ring:
> try vmalloc() when kmalloc() fails") with the using of vmalloc() since
> can't allow GFP_ATOMIC but mandate GFP_KERNEL. This will lead a WARN
> since cpumap try to call with GFP_ATOMIC. Fortunately, entry
> allocation of cpumap can only be done through syscall path which means
> GFP_ATOMIC is not necessary, so fixing this by replacing GFP_ATOMIC
> with GFP_KERNEL.
> 
> Reported-by: [email-masked]
> Fixes: 0bf7800f1799 ("ptr_ring: try vmalloc() when kmalloc() fails")
> Cc: Michal Hocko <[email-masked]>
> Cc: Daniel Borkmann <[email-masked]>
> Cc: Matthew Wilcox <[email-masked]>
> Cc: Jesper Dangaard Brouer <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]
> Cc: [email-masked]
> Signed-off-by: Jason Wang <[email-masked]>
> ---
>  kernel/bpf/cpumap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Acked-by: Jesper Dangaard Brouer <[email-masked]>

> diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
> index fbfdada6..a4bb0b3 100644
> --- a/kernel/bpf/cpumap.c
> +++ b/kernel/bpf/cpumap.c
> @@ -334,7 +334,7 @@ static int cpu_map_kthread_run(void *data)
>  static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu,
>  						       int map_id)
>  {
> -	gfp_t gfp = GFP_ATOMIC|__GFP_NOWARN;
> +	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
>  	struct bpf_cpu_map_entry *rcpu;
>  	int numa, err;
>  

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer