00-livecd.sh: fix "docache" support, unfuck the whole code

docache support was broken since the Stone age. Not all the
loop types correctly supported it because it wasn't transparent
to them and required manual hackery. Now _setup_livecd_content
transparently configures LOOP_PATH if docache is enabled.

defaults/initrd.d/00-livecd.sh

@@ -41,8 +41,7 @@ _setup_squashfs_aufs() {
     good_msg "Loading aufs"
     modprobe aufs > /dev/null 2>&1
 
-    mount -t squashfs -o loop,ro "${CDROOT_PATH}/${LOOP}" \
-        "${static}"
+    mount -t squashfs -o loop,ro "${LOOP_PATH}" "${static}"
     mount -t tmpfs none "${overlay}"
     mount -t aufs -o br:${overlay}:${static} aufs "${NEW_ROOT}"
 
@@ -71,34 +70,34 @@ _bootstrap_cd() {
         "REAL_ROOT" "${CDROOT_PATH}" ${devices}
 }
 
-_check_loop() {
-    if [ -z "${LOOP}" ] || [ ! -e "${CDROOT_PATH}/${LOOP}" ]; then
-        bad_msg "Invalid loop location: ${LOOP}"
-        bad_msg "Please export LOOP with a valid location"
-        bad_msg "or reboot and pass a proper loop=..."
-        bad_msg "kernel command line"
-        run_shell
-    fi
-}
+_setup_live_content() {
+    LOOP_PATH="${CDROOT_PATH}/${LOOP}"
 
-_cache_cd_contents() {
     # Check loop file exists and cache to ramdisk if DO_cache is enabled
     if [ "${LOOPTYPE}" != "noloop" ] && \
         [ "${LOOPTYPE}" != "sgimips" ]; then
 
-        _check_loop
+        if [ -z "${LOOP}" ] || [ ! -e "${LOOP_PATH}" ]; then
+            bad_msg "Invalid loop location: ${LOOP}"
+            bad_msg "Please export LOOP with a valid location"
+            bad_msg "or reboot and pass a proper loop=..."
+            bad_msg "kernel command line"
+            run_shell
+        fi
+
         if [ "${DO_cache}" ]; then
             good_msg "Copying loop file for caching..."
-            # Verify that the needed directory exists
-            mkdir -p "$(dirname ${NEW_ROOT}/mnt/${LOOP})"
+            local new_loop_path="/mnt/${LOOP}"
+            local new_loop_path_dir="/mnt"
 
-            cp -a "${CDROOT_PATH}/${LOOP}" "${NEW_ROOT}/mnt/${LOOP}"
+            mkdir -p "${new_loop_path_dir}" && \
+                cp -a "${LOOP_PATH}" "${new_loop_path}"
             if [ "${?}" != "0" ]; then
+                rm -rf "${new_loop_path}" 2>/dev/null
                 warn_msg "Failed to cache the loop file! Lack of RAM?"
-                rm -rf "${NEW_ROOT}/mnt/${LOOP}" 2>/dev/null
-                rm -rf "${NEW_ROOT}"/mnt/livecd.* 2>/dev/null
-                rm -rf "${NEW_ROOT}"/mnt/image.* 2>/dev/null
-                rm -rf "${NEW_ROOT}"/mnt/zisofs 2>/dev/null
+            else
+                # setup the new path to the loop file
+                LOOP_PATH="${new_loop_path}"
             fi
         fi
     fi
@@ -169,7 +168,7 @@ _livecd_mount_gcloop() {
     good_msg "Mounting gcloop filesystem"
     echo " " | losetup -E 19 -e ucl-0 -p0 \
         "${NEW_ROOT}${loop_dev}" \
-        "${CDROOT_PATH}/${LOOP}"
+        "${LOOP_PATH}"
     test_success "losetup the loop device"
 
     mount -t ext2 -o ro "${NEW_ROOT}${loop_dev}" "${NEW_ROOT}/mnt/livecd"
@@ -179,7 +178,7 @@ _livecd_mount_gcloop() {
 _livecd_mount_normal() {
     good_msg "Mounting loop filesystem"
     mount -t ext2 -o loop,ro \
-        "${CDROOT_PATH}/${LOOP}" \
+        "${LOOP_PATH}" \
         "${NEW_ROOT}/mnt/livecd"
     test_success "Mount filesystem"
 }
@@ -194,14 +193,8 @@ _livecd_mount_squashfs() {
     fi
 
     good_msg "Mounting squashfs filesystem"
-    local cached_squashfs_path="${NEW_ROOT}/mnt/${LOOP}"
-    local squashfs_path="${CDROOT_PATH}/${LOOP}"
-
-    # Upgrade to cached version if possible
-    if [ -n "${DO_cache}" ] && [ -f "${cached_squashfs_path}" ]; then
-        squashfs_path="${cached_squashfs_path}"
-    fi
 
+    local squashfs_path="${LOOP_PATH}"
     mount -t squashfs -o loop,ro "${squashfs_path}" \
         "${NEW_ROOT}/mnt/livecd" || {
         bad_msg "squashfs filesystem could not be mounted."
@@ -349,7 +342,7 @@ livecd_mount() {
     [ -z "${LOOP}" ] && LOOP=$(_find_loop)
     [ -z "${LOOPTYPE}" ] && LOOPTYPE=$(_find_looptype)
 
-    _cache_cd_contents
+    _setup_live_content
 
     # If encrypted, find key and mount, otherwise mount as usual
     if [ -n "${CRYPT_ROOTS}" ]; then
@@ -357,7 +350,7 @@ livecd_mount() {
         CRYPT_ROOTS="$(losetup -f)"  # support only one value for livecd
         good_msg "You booted an encrypted livecd"
 
-        losetup "${CRYPT_ROOTS}" "${CDROOT_PATH}/${LOOP}"
+        losetup "${CRYPT_ROOTS}" "${LOOP_PATH}"
         test_success "Preparing loop filesystem"
 
         start_luks