scsi: libsas: Check link status in ATA prereset()

libata currently attempts to reset even if the SATA disk is unplugged.  To
avoid the meaningless reset of a missing disk, libsas should report offline
status to libata. libata already provides a .prereset callback for this
purpose. This is called by ata_eh_reset() and can be used to influence
whether a reset attempt should be made.

Add sas_ata_preset callback to check status of phy and disk. If the disk is
already offline or phy is disabled, we return -ENOENT to libata to avoid
the reset.

Link: https://lore.kernel.org/r/1595408643-63011-3-git-send-email-luojiaxing@huawei.com
Reviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libsas/sas_ata.c

@@ -507,8 +507,22 @@ void sas_ata_end_eh(struct ata_port *ap)
 	spin_unlock_irqrestore(&ha->lock, flags);
 }
 
+static int sas_ata_prereset(struct ata_link *link, unsigned long deadline)
+{
+	struct ata_port *ap = link->ap;
+	struct domain_device *dev = ap->private_data;
+	struct sas_phy *local_phy = sas_get_local_phy(dev);
+	int res = 0;
+
+	if (!local_phy->enabled || test_bit(SAS_DEV_GONE, &dev->state))
+		res = -ENOENT;
+	sas_put_local_phy(local_phy);
+
+	return res;
+}
+
 static struct ata_port_operations sas_sata_ops = {
-	.prereset		= ata_std_prereset,
+	.prereset		= sas_ata_prereset,
 	.hardreset		= sas_ata_hard_reset,
 	.error_handler		= ata_std_error_handler,
 	.post_internal_cmd	= sas_ata_post_internal,