[SK_BUFF]: Convert skb->tail to sk_buff_data_t

So that it is also an offset from skb->head, reduces its size from 8 to 4 bytes
on 64bit architectures, allowing us to combine the 4 bytes hole left by the
layer headers conversion, reducing struct sk_buff size to 256 bytes, i.e. 4
64byte cachelines, and since the sk_buff slab cache is SLAB_HWCACHE_ALIGN...
:-)

Many calculations that previously required that skb->{transport,network,
mac}_header be first converted to a pointer now can be done directly, being
meaningful as offsets or pointers.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 10 insertions, 10 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 1ff47b1..18b97ee 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -612,7 +612,7 @@ int sctp_rcv_ootb(struct sk_buff *skb)
 			break;
 
 		ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
-		if (ch_end > skb->tail)
+		if (ch_end > skb_tail_pointer(skb))
 			break;
 
 		/* RFC 8.4, 2) If the OOTB packet contains an ABORT chunk, the
@@ -644,7 +644,7 @@ int sctp_rcv_ootb(struct sk_buff *skb)
 		}
 
 		ch = (sctp_chunkhdr_t *) ch_end;
-	} while (ch_end < skb->tail);
+	} while (ch_end < skb_tail_pointer(skb));
 
 	return 0;
 
diff --git a/net/sctp/inqueue.c b/net/sctp/inqueue.c
index c30629e..88aa224 100644
--- a/net/sctp/inqueue.c
+++ b/net/sctp/inqueue.c
@@ -159,16 +159,16 @@ struct sctp_chunk *sctp_inq_pop(struct sctp_inq *queue)
 	 * the skb->tail.
 	 */
 	if (unlikely(skb_is_nonlinear(chunk->skb))) {
-		if (chunk->chunk_end > chunk->skb->tail)
-			chunk->chunk_end = chunk->skb->tail;
+		if (chunk->chunk_end > skb_tail_pointer(chunk->skb))
+			chunk->chunk_end = skb_tail_pointer(chunk->skb);
 	}
 	skb_pull(chunk->skb, sizeof(sctp_chunkhdr_t));
 	chunk->subh.v = NULL; /* Subheader is no longer valid.  */
 
-	if (chunk->chunk_end < chunk->skb->tail) {
+	if (chunk->chunk_end < skb_tail_pointer(chunk->skb)) {
 		/* This is not a singleton */
 		chunk->singleton = 0;
-	} else if (chunk->chunk_end > chunk->skb->tail) {
+	} else if (chunk->chunk_end > skb_tail_pointer(chunk->skb)) {
 		/* RFC 2960, Section 6.10  Bundling
 		 *
 		 * Partial chunks MUST NOT be placed in an SCTP packet.
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 60c5b59..759ea3d 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1143,7 +1143,7 @@ void *sctp_addto_chunk(struct sctp_chunk *chunk, int len, const void *data)
 
 	/* Adjust the chunk length field.  */
 	chunk->chunk_hdr->length = htons(chunklen + padlen + len);
-	chunk->chunk_end = chunk->skb->tail;
+	chunk->chunk_end = skb_tail_pointer(chunk->skb);
 
 	return target;
 }
@@ -1168,7 +1168,7 @@ int sctp_user_addto_chunk(struct sctp_chunk *chunk, int off, int len,
 	/* Adjust the chunk length field.  */
 	chunk->chunk_hdr->length =
 		htons(ntohs(chunk->chunk_hdr->length) + len);
-	chunk->chunk_end = chunk->skb->tail;
+	chunk->chunk_end = skb_tail_pointer(chunk->skb);
 
 out:
 	return err;
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index bf502c4..438e5dc 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -3115,7 +3115,7 @@ sctp_disposition_t sctp_sf_ootb(const struct sctp_endpoint *ep,
 			break;
 
 		ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
-		if (ch_end > skb->tail)
+		if (ch_end > skb_tail_pointer(skb))
 			break;
 
 		if (SCTP_CID_SHUTDOWN_ACK == ch->type)
@@ -3130,7 +3130,7 @@ sctp_disposition_t sctp_sf_ootb(const struct sctp_endpoint *ep,
 			return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
 
 		ch = (sctp_chunkhdr_t *) ch_end;
-	} while (ch_end < skb->tail);
+	} while (ch_end < skb_tail_pointer(skb));
 
 	if (ootb_shut_ack)
 		sctp_sf_shut_8_4_5(ep, asoc, type, arg, commands);