Re: [PATCH 08/13] netvm: Allow skb allocation to use PFMEMALLOCreserves

[NeilBrown]

On Wed, 27 Apr 2011 17:08:06 +0100 Mel Gorman <mgorman@xxxxxxx> wrote:


> @@ -1578,7 +1589,7 @@ static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
>   */
>  static inline struct page *__netdev_alloc_page(struct net_device *dev, gfp_t gfp_mask)
>  {
> -	return alloc_pages_node(NUMA_NO_NODE, gfp_mask, 0);
> +	return alloc_pages_node(NUMA_NO_NODE, gfp_mask | __GFP_MEMALLOC, 0);
>  }
>  

I'm puzzling a bit over this change.
__netdev_alloc_page appears to be used to get pages to put in ring buffer
for a network card to DMA received packets into.  So it is OK to use
__GFP_MEMALLOC for these allocations providing we mark the resulting skb as
'pfmemalloc' if a reserved page was used.

However I don't see where that marking is done.
I think it should be in skb_fill_page_desc, something like:

  if (page->pfmemalloc)
	skb->pfmemalloc = true;

Is this covered somewhere else that I am missing?

Thanks,
NeilBrown

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