net: do not deplete pfmemalloc reserve

[ Upstream commit 79930f5892e134c6da1254389577fffb8bd72c66 ]

build_skb() should look at the page pfmemalloc status.
If set, this means page allocator allocated this page in the
expectation it would help to free other pages. Networking
stack can do that only if skb->pfmemalloc is also set.

Also, we must refrain using high order pages from the pfmemalloc
reserve, so __page_frag_refill() must also use __GFP_NOMEMALLOC for
them. Under memory pressure, using order-0 pages is probably the best
strategy.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 17313d17a923568ec561a06d9f6200c92e54e05d..d354bb277539deaa29a5189b1ccddbd3a3a219a4 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -308,7 +308,11 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
 
        memset(skb, 0, offsetof(struct sk_buff, tail));
        skb->truesize = SKB_TRUESIZE(size);
-       skb->head_frag = frag_size != 0;
+       if (frag_size) {
+               skb->head_frag = 1;
+               if (virt_to_head_page(data)->pfmemalloc)
+                       skb->pfmemalloc = 1;
+       }
        atomic_set(&skb->users, 1);
        skb->head = data;
        skb->data = data;
@@ -351,7 +355,8 @@ refill:
                        gfp_t gfp = gfp_mask;
 
                        if (order)
-                               gfp |= __GFP_COMP | __GFP_NOWARN;
+                               gfp |= __GFP_COMP | __GFP_NOWARN |
+                                      __GFP_NOMEMALLOC;
                        nc->frag.page = alloc_pages(gfp, order);
                        if (likely(nc->frag.page))
                                break;