Revert "block: take bd_mutex around delete_partitions in del_gendisk"

hulk inclusion
category: bugfix
bugzilla: 55097
CVE: NA

-------------------------------------------------

This reverts commit 10097449.

The patch set for partition symlink cleanup will introduce
deadlock for nbd, loop and xen-blkfront driver, so revert it.
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

block/genhd.c

@@ -764,7 +764,6 @@ void del_gendisk(struct gendisk *disk)
 {
 	struct disk_part_iter piter;
 	struct hd_struct *part;
-	struct block_device *bdev;
 
 	blk_integrity_del(disk);
 	disk_del_events(disk);
@@ -774,14 +773,6 @@ void del_gendisk(struct gendisk *disk)
 	 * disk is marked as dead (GENHD_FL_UP cleared).
 	 */
 	down_write(&disk->lookup_sem);
-
-	/*
-	 * If bdev is null, that menas memory allocate fail. Then
-	 * add_partitions can also fail.
-	 */
-	bdev = bdget_disk(disk, 0);
-	if (bdev)
-		mutex_lock(&bdev->bd_mutex);
 	/* invalidate stuff */
 	disk_part_iter_init(&piter, disk,
 			     DISK_PITER_INCL_EMPTY | DISK_PITER_REVERSE);
@@ -791,8 +782,6 @@ void del_gendisk(struct gendisk *disk)
 		delete_partition(disk, part->partno);
 	}
 	disk_part_iter_exit(&piter);
-	if (bdev)
-		mutex_unlock(&bdev->bd_mutex);
 
 	invalidate_partition(disk, 0);
 	bdev_unhash_inode(disk_devt(disk));