[PATCH] fix aoe without scatter-gather [Bug 7662]

Fix a bug that only appears when AoE goes over a network card that does not
support scatter-gather.  The headers in the linear part of the skb appeared
to be larger than they really were, resulting in data that was offset by 24
bytes.

This patch eliminates the offset data on cards that don't support
scatter-gather or have had scatter-gather turned off.  There remains an
unrelated issue that I'll address in a separate email.

Fixes bugzilla #7662

Signed-off-by: "Ed L. Cashin" <ecashin@coraid.com>
Cc: <stable@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: <boddingt@optusnet.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/block/aoe/aoecmd.c

@@ -30,8 +30,6 @@ new_skb(ulong len)
 		skb->nh.raw = skb->mac.raw = skb->data;
 		skb->protocol = __constant_htons(ETH_P_AOE);
 		skb->priority = 0;
-		skb_put(skb, len);
-		memset(skb->head, 0, len);
 		skb->next = skb->prev = NULL;
 
 		/* tell the network layer not to perform IP checksums
@@ -122,8 +120,8 @@ aoecmd_ata_rw(struct aoedev *d, struct frame *f)
 	skb = f->skb;
 	h = (struct aoe_hdr *) skb->mac.raw;
 	ah = (struct aoe_atahdr *) (h+1);
-	skb->len = sizeof *h + sizeof *ah;
-	memset(h, 0, ETH_ZLEN);
+	skb_put(skb, sizeof *h + sizeof *ah);
+	memset(h, 0, skb->len);
 	f->tag = aoehdr_atainit(d, h);
 	f->waited = 0;
 	f->buf = buf;
@@ -149,7 +147,6 @@ aoecmd_ata_rw(struct aoedev *d, struct frame *f)
 		skb->len += bcnt;
 		skb->data_len = bcnt;
 	} else {
-		skb->len = ETH_ZLEN;
 		writebit = 0;
 	}
 
@@ -206,6 +203,7 @@ aoecmd_cfg_pkts(ushort aoemajor, unsigned char aoeminor, struct sk_buff **tail)
 			printk(KERN_INFO "aoe: skb alloc failure\n");
 			continue;
 		}
+		skb_put(skb, sizeof *h + sizeof *ch);
 		skb->dev = ifp;
 		if (sl_tail == NULL)
 			sl_tail = skb;
@@ -243,6 +241,7 @@ freeframe(struct aoedev *d)
 			continue;
 		if (atomic_read(&skb_shinfo(f->skb)->dataref) == 1) {
 			skb_shinfo(f->skb)->nr_frags = f->skb->data_len = 0;
+			skb_trim(f->skb, 0);
 			return f;
 		}
 		n++;
@@ -698,8 +697,8 @@ aoecmd_ata_id(struct aoedev *d)
 	skb = f->skb;
 	h = (struct aoe_hdr *) skb->mac.raw;
 	ah = (struct aoe_atahdr *) (h+1);
-	skb->len = ETH_ZLEN;
-	memset(h, 0, ETH_ZLEN);
+	skb_put(skb, sizeof *h + sizeof *ah);
+	memset(h, 0, skb->len);
 	f->tag = aoehdr_atainit(d, h);
 	f->waited = 0;