Index: os-prober/os-probes/common/50mounted-tests
===================================================================
--- os-prober.orig/os-probes/common/50mounted-tests
+++ os-prober/os-probes/common/50mounted-tests
@@ -72,9 +72,7 @@ mounted=
 
 if [ "$types" = btrfs ]; then
 	partition="$BTRFSDEV"
-fi
-
-if type grub2-mount >/dev/null 2>&1 && \
+elif type grub2-mount >/dev/null 2>&1 && \
    type grub2-probe >/dev/null 2>&1 && \
    grub2-mount "$partition" "$tmpmnt" 2>/dev/null; then
 	mounted=1
@@ -110,7 +108,11 @@ if [ "$mounted" ]; then
 		fi
 	done
 fi
-do_unmount
+
+if [ "$types" != "btrfs" ]; then
+	do_unmount
+	exit 1
+fi
 
 # all btrfs processing here.  Handle both unmounted and
 # mounted subvolumes.
@@ -125,9 +127,9 @@ if [ "$types" = btrfs ]; then
 		exit 1
 	fi
 	# besides regular subvols, get ro and snapshot so thet can be excluded
-        subvols=$(btrfs subvolume list "$tmpmnt" | cut -d ' ' -f 9)
-        rosubvols=$(btrfs subvolume list -r "$tmpmnt" | cut -d ' ' -f 9)
-        sssubvols=$(btrfs subvolume list -s "$tmpmnt" | cut -d ' ' -f 14)
+        subvols=$(btrfs subvolume list -a "$tmpmnt" | cut -d ' ' -f 9 | sed -e s!^\<FS_TREE\>/!!)
+        rosubvols=$(btrfs subvolume list -r -a "$tmpmnt" | cut -d ' ' -f 9 | sed -e s!^\<FS_TREE\>/!!)
+        sssubvols=$(btrfs subvolume list -s -a "$tmpmnt" | cut -d ' ' -f 14 | sed -e s!^\<FS_TREE\>/!!)
         if ! umount "$tmpmnt"; then
             warn "failed to umount btrfs volume on $tmpmnt"
             rmdir "$tmpmnt" || true