btrfs: remove BUG_ON in btrfs_rm_dev_replace_free_srcdev()

That was only an extra check to tackle a few bugs around this area, now
its safe to remove it.  Replace it by an ASSERT.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 11d7707a3fb3cea133ad5efad133290f83a13769..f1ecb938ba4d71b4a83c1be50bf5880bc86add38 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2016,19 +2016,20 @@ 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;
 
+               /*
+                * On a mounted FS, num_devices can't be zero unless it's a
+                * seed. In case of a 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) {