ata: libata-core: fix cancellation of a port deferred qc work

commit 55db009 upstream.

cancel_work_sync() is a sleeping function so it cannot be called with
the spin lock of a port being held. Move the call to this function in
ata_port_detach() after EH completes, with the port lock released,
together with other work cancellation calls.

Fixes: 0ea8408 ("ata: libata-scsi: avoid Non-NCQ command starvation")
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Igor Pylypiv <ipylypiv@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: damien-lemoal

drivers/ata/libata-core.c

@@ -6163,10 +6163,6 @@ static void ata_port_detach(struct ata_port *ap)
 		}
 	}
 
-	/* Make sure the deferred qc work finished. */
-	cancel_work_sync(&ap->deferred_qc_work);
-	WARN_ON(ap->deferred_qc);
-
 	/* Tell EH to disable all devices */
 	ap->pflags |= ATA_PFLAG_UNLOADING;
 	ata_port_schedule_eh(ap);
@@ -6177,9 +6173,11 @@ static void ata_port_detach(struct ata_port *ap)
 	/* wait till EH commits suicide */
 	ata_port_wait_eh(ap);
 
-	/* it better be dead now */
+	/* It better be dead now and not have any remaining deferred qc. */
 	WARN_ON(!(ap->pflags & ATA_PFLAG_UNLOADED));
+	WARN_ON(ap->deferred_qc);
 
+	cancel_work_sync(&ap->deferred_qc_work);
 	cancel_delayed_work_sync(&ap->hotplug_task);
 	cancel_delayed_work_sync(&ap->scsi_rescan_task);