netdev - [PATCH net] niu: remove unnecessary atomic operation

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Message-ID: <1412875428.18196.3.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 09 Oct 2014 10:23:48 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH net] niu: remove unnecessary atomic operation

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

We allocate single page, compound_head() is not needed.

We own the page, we can simply set page->_count to the
needed value instead of doing a locked addition.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 drivers/net/ethernet/sun/niu.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/sun/niu.c b/drivers/net/ethernet/sun/niu.c
index 904fd1ab5f6e..ec2cd8a6d5bc 100644
--- a/drivers/net/ethernet/sun/niu.c
+++ b/drivers/net/ethernet/sun/niu.c
@@ -3340,9 +3340,8 @@ static int niu_rbr_add_page(struct niu *np, struct rx_ring_info *rp,
 	}
 
 	niu_hash_page(rp, page, addr);
-	if (rp->rbr_blocks_per_page > 1)
-		atomic_add(rp->rbr_blocks_per_page - 1,
-			   &compound_head(page)->_count);
+
+	atomic_set(&page->_count, rp->rbr_blocks_per_page);
 
 	for (i = 0; i < rp->rbr_blocks_per_page; i++) {
 		__le32 *rbr = &rp->rbr[start_index + i];


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