hpsa: reserve some commands for use by driver

We need to reserve some commands for device rescans,
aborts, and the pass through ioctls, etc. so we cannot
give them all to the scsi mid layer.

This is in preparation for removing cmd_special_alloc and
cmd_special_free so that we can stop queuing commands internally
in the driver so that we can remove the locks thta protect the
queue that we will no longer have.
Reviewed-by: NScott Teel <scott.teel@pmcs.com>
Signed-off-by: NDon Brace <don.brace@pmcs.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

drivers/scsi/hpsa.c

@@ -4064,11 +4064,14 @@ static int hpsa_register_scsi(struct ctlr_info *h)
 	sh->max_cmd_len = MAX_COMMAND_SIZE;
 	sh->max_lun = HPSA_MAX_LUN;
 	sh->max_id = HPSA_MAX_LUN;
-	sh->can_queue = h->nr_cmds;
+	sh->can_queue = h->nr_cmds -
+			HPSA_CMDS_RESERVED_FOR_ABORTS -
+			HPSA_CMDS_RESERVED_FOR_DRIVER -
+			HPSA_MAX_CONCURRENT_PASSTHRUS;
 	if (h->hba_mode_enabled)
 		sh->cmd_per_lun = 7;
 	else
-		sh->cmd_per_lun = h->nr_cmds;
+		sh->cmd_per_lun = sh->can_queue;
 	sh->sg_tablesize = h->maxsgentries;
 	h->scsi_host = sh;
 	sh->hostdata[0] = (unsigned long) h;

drivers/scsi/hpsa.h

@@ -115,6 +115,8 @@ struct ctlr_info {
 	void __iomem *vaddr;
 	unsigned long paddr;
 	int 	nr_cmds; /* Number of commands allowed on this controller */
+#define HPSA_CMDS_RESERVED_FOR_ABORTS 2
+#define HPSA_CMDS_RESERVED_FOR_DRIVER 1
 	struct CfgTable __iomem *cfgtable;
 	int	interrupts_enabled;
 	int 	max_commands;