aoe: add module parameter for users who need more outstanding I/O

An AoE target provides an estimate of the number of outstanding commands that
the AoE initiator can send before getting a response.  The aoe_maxout
parameter provides a way to set an even lower limit.  It will not allow a user
to use more outstanding commands than the target permits.  If a user discovers
a problem with a large setting, this parameter provides a way for us to work
with them to debug the problem.  We expect to improve the dynamic window
sizing algorithm and drop this parameter.  For the time being, it is a
debugging aid.
Signed-off-by: Ed L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/aoe/aoecmd.c

@@ -18,6 +18,11 @@ static int aoe_deadsecs = 60 * 3;
 module_param(aoe_deadsecs, int, 0644);
 MODULE_PARM_DESC(aoe_deadsecs, "After aoe_deadsecs seconds, give up and fail dev.");
 
+static int aoe_maxout = 16;
+module_param(aoe_maxout, int, 0644);
+MODULE_PARM_DESC(aoe_maxout,
+	"Only aoe_maxout outstanding packets for every MAC on eX.Y.");
+
 static struct sk_buff *
 new_skb(ulong len)
 {
@@ -984,7 +989,6 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
 	struct aoeif *ifp;
 	ulong flags, sysminor, aoemajor;
 	struct sk_buff *sl;
-	enum { MAXFRAMES = 16 };
 	u16 n;
 
 	h = (struct aoe_hdr *) skb_mac_header(skb);
@@ -1009,8 +1013,8 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
 	}
 
 	n = be16_to_cpu(ch->bufcnt);
-	if (n > MAXFRAMES)	/* keep it reasonable */
-		n = MAXFRAMES;
+	if (n > aoe_maxout)	/* keep it reasonable */
+		n = aoe_maxout;
 
 	d = aoedev_by_sysminor_m(sysminor);
 	if (d == NULL) {