[PATCH] libata: check if port is disabled after internal command

libata core is being changed to disallow port/device disable on lower
layers.  However, some LLDDs (sata_mv) directly disable port on
command failure.  This patch makes ata_exec_internal() check whether a
port got disabled after an internal command.  If it is, AC_ERR_SYSTEM
is added to err_mask and the port gets re-enabled.

As internal command failure results in device disable for drivers
which don't implement newer reset/EH callbacks, this change results in
no behavior change for single device per port controllers.  For
slave-possible LLDDs which disable port on command failure, (1) such
drivers don't exist currently, (2) issuing command to the other device
of once-disabled port shouldn't result in catastrophe even if such
driver exists.  So, this should be enough as a temporary measure.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/scsi/libata-core.c

@@ -1009,6 +1009,22 @@ ata_exec_internal(struct ata_port *ap, struct ata_device *dev,
 
 	ata_qc_free(qc);
 
+	/* XXX - Some LLDDs (sata_mv) disable port on command failure.
+	 * Until those drivers are fixed, we detect the condition
+	 * here, fail the command with AC_ERR_SYSTEM and reenable the
+	 * port.
+	 *
+	 * Note that this doesn't change any behavior as internal
+	 * command failure results in disabling the device in the
+	 * higher layer for LLDDs without new reset/EH callbacks.
+	 *
+	 * Kill the following code as soon as those drivers are fixed.
+	 */
+	if (ap->flags & ATA_FLAG_PORT_DISABLED) {
+		err_mask |= AC_ERR_SYSTEM;
+		ata_port_probe(ap);
+	}
+
 	return err_mask;
 }