[PATCH v2] btrfs: remove BUG_ON in btrfs_rm_dev_replace_free_srcdev()

[Anand Jain <anand.jain@oracle.com>]

Use ASSERT instead of BUG_ON.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
V2: Accepts David suggestion to keep the check as ASSERT.
    Adds more comments to explain the context.

 fs/btrfs/volumes.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 93afc7d49d4d..94a9e69e844b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2015,19 +2015,20 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info,
 	}
 
 	btrfs_close_bdev(srcdev);
-
 	call_rcu(&srcdev->rcu, free_device);
 
-	/*
-	 * unless fs_devices is seed fs, num_devices shouldn't go
-	 * zero
-	 */
-	BUG_ON(!fs_devices->num_devices && !fs_devices->seeding);
-
 	/* if this is no devs we rather delete the fs_devices */
 	if (!fs_devices->num_devices) {
 		struct btrfs_fs_devices *tmp_fs_devices;
 
+		/*
+		 * In a mounted FS, num_devices can't be zero unless
+		 * its a seed. Where in case of seed device being replaced,
+		 * the replace target added to the sprout FS, so there
+		 * will be no more device left under the seed FS.
+		 */
+		ASSERT(fs_devices->seeding);
+
 		tmp_fs_devices = fs_info->fs_devices;
 		while (tmp_fs_devices) {
 			if (tmp_fs_devices->seed == fs_devices) {
-- 
2.13.1