--- /usr/bin/genfstab	2012-10-04 19:08:03.000000000 -0700
+++ genfstab	2012-11-11 13:25:27.306128006 -0800
@@ -71,6 +71,20 @@
   printf '%s' "$out"
 }
 
+normalize_dm() {
+    local raw="$1" mapped canon
+    if [[ $raw == /dev/dm-[0-9]* ]]; then
+	for mapped in /dev/mapper/*; do
+	    canon=$(readlink -e "$mapped")
+	    if [[ $raw == "$canon" ]]; then
+		echo "$mapped"
+		return
+	    fi
+	done
+    fi
+    echo "$raw"
+}
+
 unmangle() {
   local i= chr= out= len=$(( ${#1} - 4 ))
 
@@ -274,7 +288,7 @@
     if [[ $type = file ]]; then
       printf '%-20s' "$device"
     else
-      write_source "$(unmangle "$device")"
+      write_source "$(normalize_dm $(unmangle "$device"))"
     fi
 
     printf '\t%-10s\t%-10s\t%-10s\t0 0\n\n' 'none' 'swap' "$options"