[PATCH net-next] bnx2x: avoid two atomic ops per page on x86

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

Commit 4cace675d687 ("bnx2x: Alloc 4k fragment for each rx ring buffer
element") added extra put_page() and get_page() calls on arches where
PAGE_SIZE=4K like x86

Reorder things to avoid this overhead. 

Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Gabriel Krisman Bertazi <kris...@linux.vnet.ibm.com>
Cc: Yuval Mintz <yuval.mi...@cavium.com>
Cc: Ariel Elior <ariel.el...@cavium.com>
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c |   15 ++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c 
b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
index 
3e199d3e461ef5dd237e3176bcb666f878ac..c0dac0e5696d7d01457a42c2c13f1640c2e2 
100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
@@ -549,14 +549,7 @@ static int bnx2x_alloc_rx_sge(struct bnx2x *bp, struct 
bnx2x_fastpath *fp,
        struct bnx2x_alloc_pool *pool = &fp->page_pool;
        dma_addr_t mapping;
 
-       if (!pool->page || (PAGE_SIZE - pool->offset) < SGE_PAGE_SIZE) {
-
-               /* put page reference used by the memory pool, since we
-                * won't be using this page as the mempool anymore.
-                */
-               if (pool->page)
-                       put_page(pool->page);
-
+       if (!pool->page) {
                pool->page = alloc_pages(gfp_mask, PAGES_PER_SGE_SHIFT);
                if (unlikely(!pool->page))
                        return -ENOMEM;
@@ -571,7 +564,6 @@ static int bnx2x_alloc_rx_sge(struct bnx2x *bp, struct 
bnx2x_fastpath *fp,
                return -ENOMEM;
        }
 
-       get_page(pool->page);
        sw_buf->page = pool->page;
        sw_buf->offset = pool->offset;
 
@@ -581,7 +573,10 @@ static int bnx2x_alloc_rx_sge(struct bnx2x *bp, struct 
bnx2x_fastpath *fp,
        sge->addr_lo = cpu_to_le32(U64_LO(mapping));
 
        pool->offset += SGE_PAGE_SIZE;
-
+       if (PAGE_SIZE - pool->offset >= SGE_PAGE_SIZE)
+               get_page(pool->page);
+       else
+               pool->page = NULL;
        return 0;
 }