Merge tag 'block-6.0-2022-09-22' of git://git.kernel.dk/linux

Pull block fixes from Jens Axboe:
 "Fix a regression that's been plaguing us by reverting the offending
  commit, as attempts to both reproduce the issue and fix it in a saner
  fashion have failed.

  Fix for a potential oops condition in the s390 dasd block driver"

* tag 'block-6.0-2022-09-22' of git://git.kernel.dk/linux:
  Revert "block: freeze the queue earlier in del_gendisk"
  s390/dasd: fix Oops in dasd_alias_get_start_dev due to missing pavgroup

Author: torvalds

block/genhd.c

@@ -602,7 +602,6 @@ void del_gendisk(struct gendisk *disk)
 	 * Prevent new I/O from crossing bio_queue_enter().
 	 */
 	blk_queue_start_drain(q);
-	blk_mq_freeze_queue_wait(q);
 
 	if (!(disk->flags & GENHD_FL_HIDDEN)) {
 		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
@@ -626,6 +625,8 @@ void del_gendisk(struct gendisk *disk)
 	pm_runtime_set_memalloc_noio(disk_to_dev(disk), false);
 	device_del(disk_to_dev(disk));
 
+	blk_mq_freeze_queue_wait(q);
+
 	blk_throtl_cancel_bios(disk->queue);
 
 	blk_sync_queue(q);

drivers/s390/block/dasd_alias.c

@@ -675,12 +675,12 @@ int dasd_alias_remove_device(struct dasd_device *device)
 struct dasd_device *dasd_alias_get_start_dev(struct dasd_device *base_device)
 {
 	struct dasd_eckd_private *alias_priv, *private = base_device->private;
-	struct alias_pav_group *group = private->pavgroup;
 	struct alias_lcu *lcu = private->lcu;
 	struct dasd_device *alias_device;
+	struct alias_pav_group *group;
 	unsigned long flags;
 
-	if (!group || !lcu)
+	if (!lcu)
 		return NULL;
 	if (lcu->pav == NO_PAV ||
 	    lcu->flags & (NEED_UAC_UPDATE | UPDATE_PENDING))
@@ -697,6 +697,11 @@ struct dasd_device *dasd_alias_get_start_dev(struct dasd_device *base_device)
 	}
 
 	spin_lock_irqsave(&lcu->lock, flags);
+	group = private->pavgroup;
+	if (!group) {
+		spin_unlock_irqrestore(&lcu->lock, flags);
+		return NULL;
+	}
 	alias_device = group->next;
 	if (!alias_device) {
 		if (list_empty(&group->aliaslist)) {