Overlay Dracut Module cherrypick. (#8494)

Co-authored-by: lanzeliu <lanzeliu@microsoft.com>

Author: liulanze

SPECS/dracut/20overlayfs/overlayfs-mount.sh

@@ -1,8 +1,8 @@
-#!/bin/sh
+#!/bin/bash
 
 # Description: This script is designed to mount a DM-Verity root filesystem and
-# set up an OverlayFS. It is driven by kernel parameters and is invoked during
-# the dracut initramfs phase.
+# set up OverlayFS. It is driven by kernel parameters and is invoked during the
+# dracut initramfs phase.
 
 # Kernel Parameters:
 # - root: Specifies the path to the root filesystem. This script is designed to
@@ -12,11 +12,8 @@
 #   setups, the script will proceed with the standard OverlayFS setup, ensuring
 #   versatility in its application.
 # - rd.overlayfs: A comma-separated list defining the OverlayFS configuration.
-#   Each entry should specify the overlay, upper, and work directories for an
-#   OverlayFS instance.
-# - rd.overlayfs_persistent_volume: Specifies the path to a persistent storage
-#   volume to be used by OverlayFS. If not provided, a volatile (tmpfs) overlay
-#   is created.
+#   Each entry should specify the overlay, upper, work directories, and optional
+#   volume for an OverlayFS instance.
 
 # Behavior:
 # - Verifies the presence of the 'dracut-lib' for necessary utilities.
@@ -29,9 +26,7 @@
 #   root with the writable overlay, allowing system modifications without
 #   altering the base system.
 
-set -ex
-
-parse_cmdline_args() {
+parse_kernel_cmdline_args() {
     # Ensure that the 'dracut-lib' is present and loaded.
     type getarg >/dev/null 2>&1 || . /lib/dracut-lib.sh
 
@@ -54,49 +49,51 @@ parse_cmdline_args() {
 
     # Retrieve the OverlayFS parameters.
     [ -z "${overlayfs}" ] && overlayfs=$(getarg rd.overlayfs=)
-    # Retrieve the persistent volume for the OverlayFS.
-    [ -z "${overlayfs_persistent_volume}" ] && overlayfs_persistent_volume=$(getarg rd.overlayfs_persistent_volume=)
 }
 
-# Modified function to mount the physical partition
-mount_physical_partition() {
-    mkdir -p "${OVERLAY_MOUNT}"
-    # Leverage the partition from cmdline
-    local partition="${overlayfs_persistent_volume}"
+# Modified function to mount volatile or persistent volume.
+mount_volatile_persistent_volume() {
+    local _volume=$1
+    local _overlay_mount=$2
+
+    mkdir -p "${_overlay_mount}"
 
-    if [ -z "${partition}" ]; then
-        # Fallback to volatile overlay if no persistent volume is specified
+    if [[ "${_volume}" == "volatile" ]]; then
+        # Fallback to volatile overlay if no persistent volume is specified.
         echo "No overlayfs persistent volume specified. Creating a volatile overlay."
-        mount -t tmpfs tmpfs -o ${OVERLAY_MNT_OPTS} "${OVERLAY_MOUNT}" || \
-            die "Failed to create overlay tmpfs at ${OVERLAY_MOUNT}"
+        mount -t tmpfs tmpfs -o ${OVERLAY_MNT_OPTS} "${_overlay_mount}" || \
+            die "Failed to create overlay tmpfs at ${_overlay_mount}"
     else
         # Check if /etc/mdadm.conf exists.
         if [ -f "/etc/mdadm.conf" ]; then
-            mdadm --assemble ${partition} || \
+            mdadm --assemble ${_volume} || \
                 die "Failed to assemble RAID volume."
         fi
 
-        # Mount the specified persistent volume
-        mount "${partition}" "${OVERLAY_MOUNT}" || \
-            die "Failed to mount ${partition} at ${OVERLAY_MOUNT}"
+        # Mount the specified persistent volume.
+        mount "${_volume}" "${_overlay_mount}" || \
+            die "Failed to mount ${_volume} at ${_overlay_mount}"
     fi
 }
 
-create_overlay() {
-    local _dir=$1
-    local _mounted_dir="${VERITY_MOUNT}/${_dir}"
+create_overlayfs() {
+    local _lower=$1
     local _upper=$2
     local _work=$3
 
-    [ -d "$_mounted_dir" ] || die "Unable to create overlay as $_dir does not exist"
+    [ -d "$_lower" ] || die "Unable to create overlay as $_lower does not exist"
 
     mkdir -p "${_upper}" && \
     mkdir -p "${_work}" && \
-    mount -t overlay overlay -o ro,lowerdir="${_mounted_dir}",upperdir="${_upper}",workdir="${_work}" "${_mounted_dir}" || \
-        die "Failed to mount overlay in ${_mounted_dir}"
+    mount -t overlay overlay -o ro,lowerdir="${_lower}",upperdir="${_upper}",workdir="${_work}" "${_lower}" || \
+        die "Failed to mount overlay in ${_lower}"
 }
 
-mount_root() {
+mount_overlayfs() {
+    local cnt=0
+    local overlay_mount_with_cnt
+    declare -A volume_mount_map
+
     if [ "$is_verity" = true ]; then
         echo "Mounting DM-Verity Target"
         mkdir -p "${VERITY_MOUNT}"
@@ -109,19 +106,34 @@ mount_root() {
             die "Failed to mount root"
     fi
 
-    mount_physical_partition
-
     echo "Starting to create OverlayFS"
     for _group in ${overlayfs}; do
-        IFS=',' read -r overlay upper work <<< "$_group"
-        echo "Creating OverlayFS with overlay: $overlay, upper: ${OVERLAY_MOUNT}/${upper}, work: ${OVERLAY_MOUNT}/${work}"
-        create_overlay "$overlay" "${OVERLAY_MOUNT}/${upper}" "${OVERLAY_MOUNT}/${work}"
+        IFS=',' read -r overlay upper work volume <<< "$_group"
+
+        if [[ "$volume" == "" ]]; then
+            overlay_mount_with_cnt="${OVERLAY_MOUNT}/${cnt}"
+            mount_volatile_persistent_volume "volatile" $overlay_mount_with_cnt
+        else
+            if [[ -n "${volume_mount_map[$volume]}" ]]; then
+                # Volume already mounted, retrieve existing mount point from map.
+                overlay_mount_with_cnt=${volume_mount_map[$volume]}
+            else
+                # Not in map, so mount and update the map.
+                overlay_mount_with_cnt="${OVERLAY_MOUNT}/${cnt}"
+                mount_volatile_persistent_volume $volume $overlay_mount_with_cnt
+                volume_mount_map[$volume]=$overlay_mount_with_cnt
+            fi
+        fi
+        cnt=$((cnt + 1))
+
+        echo "Creating OverlayFS with overlay: $overlay, upper: ${overlay_mount_with_cnt}/${upper}, work: ${overlay_mount_with_cnt}/${work}"
+        create_overlayfs "${VERITY_MOUNT}/${overlay}" "${overlay_mount_with_cnt}/${upper}" "${overlay_mount_with_cnt}/${work}"
     done
 
     echo "Done Verity Root Mounting and OverlayFS Mounting"
     # Re-mount the verity mount along with overlayfs to the sysroot.
     mount --rbind "${VERITY_MOUNT}" "${NEWROOT}"
 }
 
-parse_cmdline_args
-mount_root
+parse_kernel_cmdline_args
+mount_overlayfs

SPECS/dracut/dracut.signatures.json

@@ -5,6 +5,6 @@
   "megaraid.conf": "914824cdbe0c525b71efa05a75e453335b0068beb8bc28bef2a5866d74bf7dd4",
   "mkinitrd": "32a0e19de954a356a0f1903a1f75d3266493b55d71b0eeab6bd07b585e955dcf",
   "module-setup.sh": "330af5c105793fb37434730ce0ff59467a9cc60a81a5e32193dc53235e9744c1",
-  "overlayfs-mount.sh": "63552c4115b5c37ed04c5311367301483e2dfe1091dc5717b2bd22d9cdda044b"
+  "overlayfs-mount.sh": "d6c064e383f00abae1ee621b9657e439e698dba5d49807e38c94fac795f45ea4"
  }
 }