[PATCH] scsi: core: run queues for all non-SDEV_DEL devices from scsi_run_host_queues

[David Jeffery <djeffery@redhat.com>]

While a scsi host is in a recovery state, scsi_mq_requeue_cmd will not set
the requeue list for a requeued command to be kicked in the future. The
expectation is a call to scsi_run_host_queues will kick all scsi devices
once the recovery state is cleared.

However, scsi_run_host_queues uses shost_for_each_device which uses
scsi_device_get and so will ignore devices in a partially removed state like
SDEV_CANCEL. But these devices may also have requeued requests, leaving
their requests stuck from not being kicked and causing the removal process
of the device to hang.

scsi_run_host_queues needs to run against more devices than the macro
shost_for_each_device allows. Instead of using the too limiting
scsi_device_get state checks, only ignore devices in SDEV_DEL state or
when unable to acquire a reference. Attempt to run the queues for all other
devices when scsi_run_host_queues is called.

Fixes: 8b566edbdbfb ("scsi: core: Only kick the requeue list if necessary")
Signed-off-by: David Jeffery <djeffery@redhat.com>
---
 drivers/scsi/scsi_lib.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 6e8c7a42603e..bb7281dc3633 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -575,10 +575,27 @@ void scsi_requeue_run_queue(struct work_struct *work)
 
 void scsi_run_host_queues(struct Scsi_Host *shost)
 {
-	struct scsi_device *sdev;
+	struct scsi_device *sdev, *prev = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	__shost_for_each_device(sdev, shost) {
+		if (sdev->sdev_state == SDEV_DEL ||
+		    !get_device(&sdev->sdev_gendev))
+			continue;
+		spin_unlock_irqrestore(shost->host_lock, flags);
 
-	shost_for_each_device(sdev, shost)
+		if (prev)
+			put_device(&prev->sdev_gendev);
 		scsi_run_queue(sdev->request_queue);
+
+		prev = sdev;
+
+		spin_lock_irqsave(shost->host_lock, flags);
+	}
+	spin_unlock_irqrestore(shost->host_lock, flags);
+	if (prev)
+		put_device(&prev->sdev_gendev);
 }
 
 static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
-- 
2.53.0