hpsa: clean up aborts

Do not send aborts to logical devices that do not support aborts

Instead of relying on what the Smart Array claims for supporting logical
drives, simply try an abort and see how it responds at device discovery
time.  This way devices that do support aborts (e.g. MSA2000) can work
and we do not waste time trying to send aborts to logical drives that do
not support them (important for high IOPS devices.)

While rescanning devices only test whether devices support aborts
the first time we encounter a device rather than every time.

Some Smart Arrays required aborts to be sent with tags in
the wrong endian byte order.  To avoid having to know about
this, we would send two aborts with tags with each endian order.
On high IOPS devices, this turns out to be not such a hot idea.
So we now have a list of the devices that got the tag backwards,
and we only send it one way.

If all available commands are outstanding and the abort handler
is invoked, the abort handler may not be able to allocate a command
and may busy-wait excessivly.  Reserve a small number of commands
for the abort handler and limit the number of concurrent abort
requests to the number of reserved commands.
Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Reviewed-by: Kevin Barnett <kevin.barnett@pmcs.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Reviewed-by: Hannes Reinecke <hare@Suse.de>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

drivers/scsi/hpsa.h

@@ -69,6 +69,7 @@ struct hpsa_scsi_dev_t {
 	 * devices in order to honor physical device queue depth limits.
 	 */
 	struct hpsa_scsi_dev_t *phys_disk[RAID_MAP_MAX_ENTRIES];
+	int supports_aborts;
 #define HPSA_DO_NOT_EXPOSE	0x0
 #define HPSA_SG_ATTACH		0x1
 #define HPSA_ULD_ATTACH		0x2
@@ -257,8 +258,11 @@ struct ctlr_info {
 	struct list_head offline_device_list;
 	int	acciopath_status;
 	int	raid_offload_debug;
+	int	needs_abort_tags_swizzled;
 	struct workqueue_struct *resubmit_wq;
 	struct workqueue_struct *rescan_ctlr_wq;
+	atomic_t abort_cmds_available;
+	wait_queue_head_t abort_cmd_wait_queue;
 };
 
 struct offline_device_entry {