[SCSI] libfc: fcoe_transport_create fails in single-CPU environment

Starting fcoe fails at fcoe_transport_create when attempting to allocate a
pool of 4K exchanges on a 64-bit single-CPU environment because the call to
__alloc_percpu() is greater than the max of 32K.  This patch reduces the
number of exchanges to fit within the maximum allowed space.

[ Whitespace problems fixed by Robert Love to satisfy chechpatch.pl ]
Signed-off-by: Steven Clark <sclark@crossbeam.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/libfc/fc_exch.c

@@ -2263,7 +2263,18 @@ struct fc_exch_mgr *fc_exch_mgr_alloc(struct fc_lport *lport,
 	mp->class = class;
 	/* adjust em exch xid range for offload */
 	mp->min_xid = min_xid;
-	mp->max_xid = max_xid;
+
+       /* reduce range so per cpu pool fits into PCPU_MIN_UNIT_SIZE pool */
+	pool_exch_range = (PCPU_MIN_UNIT_SIZE - sizeof(*pool)) /
+		sizeof(struct fc_exch *);
+	if ((max_xid - min_xid + 1) / (fc_cpu_mask + 1) > pool_exch_range) {
+		mp->max_xid = pool_exch_range * (fc_cpu_mask + 1) +
+			min_xid - 1;
+	} else {
+		mp->max_xid = max_xid;
+		pool_exch_range = (mp->max_xid - mp->min_xid + 1) /
+			(fc_cpu_mask + 1);
+	}
 
 	mp->ep_pool = mempool_create_slab_pool(2, fc_em_cachep);
 	if (!mp->ep_pool)
@@ -2274,7 +2285,6 @@ struct fc_exch_mgr *fc_exch_mgr_alloc(struct fc_lport *lport,
 	 * divided across all cpus. The exch pointers array memory is
 	 * allocated for exch range per pool.
 	 */
-	pool_exch_range = (mp->max_xid - mp->min_xid + 1) / (fc_cpu_mask + 1);
 	mp->pool_max_index = pool_exch_range - 1;
 
 	/*