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[3.16.y-ckt,stable] Patch "net: do not deplete pfmemalloc reserve" has been added to staging queue

Message ID 1430905748-24199-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques May 6, 2015, 9:49 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    net: do not deplete pfmemalloc reserve

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt11.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From dff9eb052112ca49c872f48d38a0aec7e6b2f3ed Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 22 Apr 2015 07:33:36 -0700
Subject: net: do not deplete pfmemalloc reserve

commit 79930f5892e134c6da1254389577fffb8bd72c66 upstream.

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>
[ luis: backported to 3.16: used davem's backport to 3.14 ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 net/core/skbuff.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
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Patch

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index fe07faaed256..0f27eae2ccc1 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -309,7 +309,11 @@  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;
@@ -352,7 +356,8 @@  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;