From afc567a4977b2d798e05153dd131a3c8d4758c0c Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@redhat.com>
Date: Sat, 25 Nov 2017 00:27:26 -0500
Subject: [PATCH] dm table: fix regression from improper dm_dev_internal.count
 refcount_t conversion
Git-commit: afc567a4977b2d798e05153dd131a3c8d4758c0c
Patch-mainline: v4.15-rc4
References: bsc#1093023

Multiple refcounts are needed if the device was already added.  The
micro-optimization of setting the refcount to 1 on first added (rather
than fall thru to a common refcount_inc) lost sight of the fact that the
refcount_inc is also needed for the case when the device already exists
and the mode need not be upgraded.

Fixes: 2a0b4682e0 ("dm: convert dm_dev_internal.count from atomic_t to refcount_t")
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-table.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 88130b5d95f9..aaffd0c0ee9a 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -453,14 +453,15 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
 
 		refcount_set(&dd->count, 1);
 		list_add(&dd->list, &t->devices);
+		goto out;
 
 	} else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
 		r = upgrade_mode(dd, mode, t->md);
 		if (r)
 			return r;
-		refcount_inc(&dd->count);
 	}
-
+	refcount_inc(&dd->count);
+out:
 	*result = dd->dm_dev;
 	return 0;
 }
-- 
2.16.3