[Xen-devel] [PATCH 01/10] net: add and use SKB_ALLOCSIZE

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

This gives the allocation size required for an skb containing X bytes of data

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 drivers/net/ethernet/broadcom/bnx2.c        |    7 +++----
 drivers/net/ethernet/broadcom/bnx2x/bnx2x.h |    3 +--
 drivers/net/ethernet/broadcom/tg3.c         |    3 +--
 include/linux/skbuff.h                      |   12 ++++++++++++
 net/core/skbuff.c                           |    8 +-------
 5 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2.c 
b/drivers/net/ethernet/broadcom/bnx2.c
index 8297e28..dede71f 100644
--- a/drivers/net/ethernet/broadcom/bnx2.c
+++ b/drivers/net/ethernet/broadcom/bnx2.c
@@ -5321,8 +5321,7 @@ bnx2_set_rx_ring_size(struct bnx2 *bp, u32 size)
        /* 8 for CRC and VLAN */
        rx_size = bp->dev->mtu + ETH_HLEN + BNX2_RX_OFFSET + 8;
 
-       rx_space = SKB_DATA_ALIGN(rx_size + BNX2_RX_ALIGN) + NET_SKB_PAD +
-               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+       rx_space = SKB_ALLOCSIZE(rx_size + BNX2_RX_ALIGN) + NET_SKB_PAD;
 
        bp->rx_copy_thresh = BNX2_RX_COPY_THRESH;
        bp->rx_pg_ring_size = 0;
@@ -5345,8 +5344,8 @@ bnx2_set_rx_ring_size(struct bnx2 *bp, u32 size)
 
        bp->rx_buf_use_size = rx_size;
        /* hw alignment + build_skb() overhead*/
-       bp->rx_buf_size = SKB_DATA_ALIGN(bp->rx_buf_use_size + BNX2_RX_ALIGN) +
-               NET_SKB_PAD + SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+       bp->rx_buf_size = SKB_ALLOCSIZE(bp->rx_buf_use_size + BNX2_RX_ALIGN) +
+               NET_SKB_PAD;
        bp->rx_jumbo_thresh = rx_size - BNX2_RX_OFFSET;
        bp->rx_ring_size = size;
        bp->rx_max_ring = bnx2_find_max_ring(size, MAX_RX_RINGS);
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h 
b/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
index e37161f..12f2ceb 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
@@ -1229,8 +1229,7 @@ struct bnx2x {
 #define BNX2X_FW_RX_ALIGN_START        (1UL << BNX2X_RX_ALIGN_SHIFT)
 
 #define BNX2X_FW_RX_ALIGN_END                                  \
-       max(1UL << BNX2X_RX_ALIGN_SHIFT,                        \
-           SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+       max(1UL << BNX2X_RX_ALIGN_SHIFT, SKB_ALLOCSIZE(0))
 
 #define BNX2X_PXP_DRAM_ALIGN           (BNX2X_RX_ALIGN_SHIFT - 5)
 
diff --git a/drivers/net/ethernet/broadcom/tg3.c 
b/drivers/net/ethernet/broadcom/tg3.c
index 7b71387..4d4b063 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -5672,8 +5672,7 @@ static int tg3_alloc_rx_data(struct tg3 *tp, struct 
tg3_rx_prodring_set *tpr,
         * Callers depend upon this behavior and assume that
         * we leave everything unchanged if we fail.
         */
-       skb_size = SKB_DATA_ALIGN(data_size + TG3_RX_OFFSET(tp)) +
-                  SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+       skb_size = SKB_ALLOCSIZE(data_size + TG3_RX_OFFSET(tp));
        data = kmalloc(skb_size, GFP_ATOMIC);
        if (!data)
                return -ENOMEM;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 192250b..fbc92b2 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -41,8 +41,20 @@
 
 #define SKB_DATA_ALIGN(X)      (((X) + (SMP_CACHE_BYTES - 1)) & \
                                 ~(SMP_CACHE_BYTES - 1))
+/* maximum data size which can fit into an allocation of X bytes */
 #define SKB_WITH_OVERHEAD(X)   \
        ((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+/*
+ * minimum allocation size required for an skb containing X bytes of data
+ *
+ * We do our best to align skb_shared_info on a separate cache
+ * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives
+ * aligned memory blocks, unless SLUB/SLAB debug is enabled.  Both
+ * skb->head and skb_shared_info are cache line aligned.
+ */
+#define SKB_ALLOCSIZE(X)       \
+       (SKB_DATA_ALIGN((X)) + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
 #define SKB_MAX_ORDER(X, ORDER) \
        SKB_WITH_OVERHEAD((PAGE_SIZE << (ORDER)) - (X))
 #define SKB_MAX_HEAD(X)                (SKB_MAX_ORDER((X), 0))
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a690cae..59a1ecb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -184,13 +184,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t 
gfp_mask,
                goto out;
        prefetchw(skb);
 
-       /* We do our best to align skb_shared_info on a separate cache
-        * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives
-        * aligned memory blocks, unless SLUB/SLAB debug is enabled.
-        * Both skb->head and skb_shared_info are cache line aligned.
-        */
-       size = SKB_DATA_ALIGN(size);
-       size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+       size = SKB_ALLOCSIZE(size);
        data = kmalloc_node_track_caller(size, gfp_mask, node);
        if (!data)
                goto nodata;
-- 
1.7.2.5


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