Please try this patch:
---
>From f42fb98cc627f9b960fd5b9a3a229da5c5dcf54a Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Fri, 10 Apr 2020 07:14:13 +0200
Subject: block: fix busy device checking in blk_drop_partitions again
The previous fix had an off by one in the bd_openers checking, counting
the callers blkdev_get.
Fixes: d3ef5536274f ("block: fix busy device checking in blk_drop_partitions")
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/partitions/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 1a0a829d8416..bc1ded1331b1 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -496,7 +496,7 @@ int blk_drop_partitions(struct gendisk *disk, struct block_device *bdev)
if (!disk_part_scan_enabled(disk))
return 0;
- if (bdev->bd_part_count || bdev->bd_openers)
+ if (bdev->bd_part_count || bdev->bd_openers > 1)
return -EBUSY;
res = invalidate_partition(disk, 0);
if (res)
--
2.25.1
