[PATCH 2/2] ata: libata-core: fix cancellation of a port deferred qc work

[Damien Le Moal <dlemoal@kernel.org>]

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() before locking the port and add a call to
ata_scsi_requeue_deferred_qc() to make sure there are no remaining
deferred qc.

Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
 drivers/ata/libata-core.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index beb6984b379a..54afa4df987e 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6254,9 +6254,18 @@ static void ata_port_detach(struct ata_port *ap)
 	/* Wait for any ongoing EH */
 	ata_port_wait_eh(ap);
 
+	/* Requeue any remaining deferred qc. */
+	ata_scsi_requeue_deferred_qc(ap);
+
 	mutex_lock(&ap->scsi_scan_mutex);
+
+	/* Make sure the deferred qc work finished. */
+	cancel_work_sync(&ap->deferred_qc_work);
+
 	spin_lock_irqsave(ap->lock, flags);
 
+	WARN_ON(ap->deferred_qc);
+
 	/* Remove scsi devices */
 	ata_for_each_link(link, ap, HOST_FIRST) {
 		ata_for_each_dev(dev, link, ALL) {
@@ -6269,10 +6278,6 @@ 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);
-- 
2.53.0