netdev - [PATCH net-next] netlink: do not enter direct reclaim from netlink

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Date:   Fri, 13 Jan 2017 09:11:22 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] netlink: do not enter direct reclaim from
 netlink_trim()

From: Eric Dumazet <edumazet@...gle.com>

In commit d35c99ff77ecb ("netlink: do not enter direct reclaim from
netlink_dump()") we made sure to not trigger expensive memory reclaim.

Problem is that a bit later, netlink_trim() might be called and
trigger memory reclaim.

netlink_trim() should be best effort, and really as fast as possible.
Under memory pressure, it is fine to not trim this skb.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/netlink/af_netlink.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 161b628ab2b08bf4321dbe617022c4c50486534d..edcc1e19ad532641f51f6809b8c90d1e377081ff 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1210,7 +1210,9 @@ static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
 		skb = nskb;
 	}
 
-	if (!pskb_expand_head(skb, 0, -delta, allocation))
+	if (!pskb_expand_head(skb, 0, -delta,
+			      (allocation & ~__GFP_DIRECT_RECLAIM) |
+			      __GFP_NOWARN | __GFP_NORETRY))
 		skb->truesize -= delta;
 
 	return skb;