[PATCH 10/16] netvm: Propagate page->pfmemalloc to skb

From: Mel Gorman
Date: Mon Apr 16 2012 - 08:24:35 EST

The skb->pfmemalloc flag gets set to true iff during the slab
allocation of data in __alloc_skb that the the PFMEMALLOC reserves
were used. If the packet is fragmented, it is possible that pages
will be allocated from the PFMEMALLOC reserve without propagating
this information to the skb. This patch propagates page->pfmemalloc
from pages allocated for fragments to the skb.

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
include/linux/skbuff.h | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index e889594..b01a993 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1227,6 +1227,17 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];

+ /*
+ * Propagate page->pfmemalloc to the skb if we can. The problem is
+ * that not all callers have unique ownership of the page. If
+ * pfmemalloc is set, we check the mapping as a mapping implies
+ * page->index is set (index and pfmemalloc share space).
+ * If it's a valid mapping, we cannot use page->pfmemalloc but we
+ * do not lose pfmemalloc information as the pages would not be
+ * allocated using __GFP_MEMALLOC.
+ */
+ if (page->pfmemalloc && !page->mapping)
+ skb->pfmemalloc = true;
frag->page.p = page;
frag->page_offset = off;
skb_frag_size_set(frag, size);

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/