improve btrfs handling devtools patches

bin/mkchroot.in

@@ -81,7 +81,7 @@ umask 0022
 
 lock 9 "${working_dir}.lock" "Locking chroot"
 
-if [[ $(stat -f -c %T "$working_dir") == btrfs ]]; then
+if is_btrfs "$working_dir"; then
 	rmdir "$working_dir"
 	if ! btrfs subvolume create "$working_dir"; then
 		die "Couldn't create subvolume for '%s'" "$working_dir"

bin/mkchrootpkg.in

@@ -128,11 +128,9 @@ create_chroot() {
         slock 8 "$chrootdir/root.lock" "Locking clean chroot"
 
         stat_busy "Creating clean working copy [$copy]"
-        if [[ "$chroottype" == btrfs ]] && ! mountpoint -q "$copydir"; then
-            if [[ -d $copydir ]]; then
-                btrfs subvolume delete "$copydir" >/dev/null ||
+        if is_btrfs "$chrootdir" && ! mountpoint -q "$copydir"; then
+            subvolume_delete_recursive "$copydir" ||
                 die "Unable to delete subvolume %s" "$copydir"
-            fi
             btrfs subvolume snapshot "$chrootdir/root" "$copydir" >/dev/null ||
                 die "Unable to create subvolume %s" "$copydir"
         else
@@ -151,7 +149,7 @@ create_chroot() {
 
 clean_temporary() {
     stat_busy "Removing temporary copy [$copy]"
-    if [[ "$chroottype" == btrfs ]] && ! mountpoint -q "$copydir"; then
+    if is_btrfs "$chrootdir" && ! mountpoint -q "$copydir"; then
         btrfs subvolume delete "$copydir" >/dev/null ||
             die "Unable to delete subvolume %s" "$copydir"
     else

lib/util-pkg.sh

@@ -209,9 +209,7 @@ chroot_clean(){
 
         lock 9 "${copy}.lock" "Locking chroot copy '${copy}'"
 
-        if [[ "$(stat -f -c %T "${copy}")" == btrfs ]]; then
-            { type -P btrfs && btrfs subvolume delete "${copy}"; } &>/dev/null
-        fi
+        subvolume_delete_recursive "${copy}"
         rm -rf --one-file-system "${copy}"
     done
     exec 9>&-

lib/util.sh

@@ -760,3 +760,22 @@ run(){
         $1 $2
     fi
 }
+
+is_btrfs() {
+    [[ -e "$1" && "$(stat -f -c %T "$1")" == btrfs ]]
+}
+
+subvolume_delete_recursive() {
+    local subvol
+
+    is_btrfs "$1" || return 0
+
+    while IFS= read -d $'\0' -r subvol; do
+        if ! btrfs subvolume delete "$subvol" &>/dev/null; then
+            error "Unable to delete subvolume %s" "$subvol"
+            return 1
+        fi
+    done < <(find "$1" -xdev -depth -inum 256 -print0)
+
+    return 0
+}