From: Christoph Hellwig <hch@lst.de>
Date: Wed, 18 Aug 2021 16:45:34 +0200
Subject: [PATCH] block: call bdev_add later in device_add_disk
Git-commit: 8235b5c1e8c1c0537f03a21a2e380098bed25248
Patch-mainline: v5.15-rc1
References: jsc#PED-1183

Once bdev_add is called userspace can open the block device.  Ensure
that the struct device, which is used for refcounting of the disk
besides various other things, is fully setup at that point.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/genhd.c | 36 +++++++++++++++++-------------------
 1 file changed, 17 insertions(+), 19 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index ec4be5889fbf..ab455f110be2 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -466,29 +466,14 @@ void device_add_disk(struct device *parent, struct gendisk *disk,
 
 	disk_alloc_events(disk);
 
-	if (disk->flags & GENHD_FL_HIDDEN) {
-		/*
-		 * Don't let hidden disks show up in /proc/partitions,
-		 * and don't bother scanning for partitions either.
-		 */
-		disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
-		disk->flags |= GENHD_FL_NO_PART_SCAN;
-	} else {
-		/* Register BDI before referencing it from bdev */
-		ddev->devt = MKDEV(disk->major, disk->first_minor);
-		ret = bdi_register(disk->bdi, "%u:%u",
-				   disk->major, disk->first_minor);
-		WARN_ON(ret);
-		bdi_set_owner(disk->bdi, ddev);
-		bdev_add(disk->part0, ddev->devt);
-	}
-
 	/* delay uevents, until we scanned partition table */
 	dev_set_uevent_suppress(ddev, 1);
 
 	ddev->parent = parent;
 	ddev->groups = groups;
 	dev_set_name(ddev, "%s", disk->disk_name);
+	if (!(disk->flags & GENHD_FL_HIDDEN))
+		ddev->devt = MKDEV(disk->major, disk->first_minor);
 	if (device_add(ddev))
 		return;
 	if (!sysfs_deprecated) {
@@ -521,12 +506,25 @@ void device_add_disk(struct device *parent, struct gendisk *disk,
 		disk->slave_dir = NULL;
 	}
 
-	if (!(disk->flags & GENHD_FL_HIDDEN)) {
+	if (disk->flags & GENHD_FL_HIDDEN) {
+		/*
+		 * Don't let hidden disks show up in /proc/partitions,
+		 * and don't bother scanning for partitions either.
+		 */
+		disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
+		disk->flags |= GENHD_FL_NO_PART_SCAN;
+	} else {
+		ret = bdi_register(disk->bdi, "%u:%u",
+				   disk->major, disk->first_minor);
+		WARN_ON(ret);
+		bdi_set_owner(disk->bdi, ddev);
+		bdev_add(disk->part0, ddev->devt);
+
 		disk_scan_partitions(disk);
 
 		/*
 		 * Announce the disk and partitions after all partitions are
-		 * created.
+		 * created. (for hidden disks uevents remain suppressed forever)
 		 */
 		dev_set_uevent_suppress(ddev, 0);
 		disk_uevent(disk, KOBJ_ADD);
-- 
2.35.3