From: zhong jiang <zhongjiang@huawei.com>
Date: Wed, 19 Sep 2018 19:32:12 +0800
Subject: net: core: Use FIELD_SIZEOF directly instead of reimplementing its
 function
Patch-mainline: v4.20-rc1
Git-commit: f195efb47d937bec8a2efb8e35a8ccf08dbbf777
References: bsc#1109837

FIELD_SIZEOF is defined as a macro to calculate the specified value. Therefore,
We prefer to use the macro rather than calculating its value.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/core/flow_dissector.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -380,8 +380,8 @@ __skb_flow_dissect_gre(const struct sk_b
 	offset += sizeof(struct gre_base_hdr);
 
 	if (hdr->flags & GRE_CSUM)
-		offset += sizeof(((struct gre_full_hdr *) 0)->csum) +
-			  sizeof(((struct gre_full_hdr *) 0)->reserved1);
+		offset += FIELD_SIZEOF(struct gre_full_hdr, csum) +
+			  FIELD_SIZEOF(struct gre_full_hdr, reserved1);
 
 	if (hdr->flags & GRE_KEY) {
 		const __be32 *keyid;
@@ -403,11 +403,11 @@ __skb_flow_dissect_gre(const struct sk_b
 			else
 				key_keyid->keyid = *keyid & GRE_PPTP_KEY_MASK;
 		}
-		offset += sizeof(((struct gre_full_hdr *) 0)->key);
+		offset += FIELD_SIZEOF(struct gre_full_hdr, key);
 	}
 
 	if (hdr->flags & GRE_SEQ)
-		offset += sizeof(((struct pptp_gre_header *) 0)->seq);
+		offset += FIELD_SIZEOF(struct pptp_gre_header, seq);
 
 	if (gre_ver == 0) {
 		if (*p_proto == htons(ETH_P_TEB)) {
@@ -434,7 +434,7 @@ __skb_flow_dissect_gre(const struct sk_b
 		u8 *ppp_hdr;
 
 		if (hdr->flags & GRE_ACK)
-			offset += sizeof(((struct pptp_gre_header *) 0)->ack);
+			offset += FIELD_SIZEOF(struct pptp_gre_header, ack);
 
 		ppp_hdr = __skb_header_pointer(skb, *p_nhoff + offset,
 					       sizeof(_ppp_hdr),