[PATCH 1/4] scsi: core: Revert "Call blk_mq_free_tag_set() earlier"

[Bart Van Assche <bvanassche@acm.org>]

Revert the patch series "Call blk_mq_free_tag_set() earlier" because it
introduces a deadlock if the scsi_remove_host() caller holds a reference
on a device, target or host.

Reported-by: syzbot+bafeb834708b1bb750bc@syzkaller.appspotmail.com
Fixes: f323896fe6fa ("scsi: core: Call blk_mq_free_tag_set() earlier")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/hosts.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 0738238ed6cc..20c1f5420ba6 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -197,8 +197,6 @@ void scsi_remove_host(struct Scsi_Host *shost)
 	 * the dependent SCSI targets and devices are gone before returning.
 	 */
 	wait_event(shost->targets_wq, atomic_read(&shost->target_count) == 0);
-
-	scsi_mq_destroy_tags(shost);
 }
 EXPORT_SYMBOL(scsi_remove_host);
 
@@ -309,8 +307,8 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	return error;
 
 	/*
-	 * Any resources associated with the SCSI host in this function except
-	 * the tag set will be freed by scsi_host_dev_release().
+	 * Any host allocation in this function will be freed in
+	 * scsi_host_dev_release().
 	 */
  out_del_dev:
 	device_del(&shost->shost_dev);
@@ -326,7 +324,6 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	pm_runtime_disable(&shost->shost_gendev);
 	pm_runtime_set_suspended(&shost->shost_gendev);
 	pm_runtime_put_noidle(&shost->shost_gendev);
-	scsi_mq_destroy_tags(shost);
  fail:
 	return error;
 }
@@ -360,6 +357,9 @@ static void scsi_host_dev_release(struct device *dev)
 		kfree(dev_name(&shost->shost_dev));
 	}
 
+	if (shost->tag_set.tags)
+		scsi_mq_destroy_tags(shost);
+
 	kfree(shost->shost_data);
 
 	ida_free(&host_index_ida, shost->host_no);