Complete refactor of zram-swap -> zmountzmount-refactor

This renames `zram-swap` to `zmount`.

Previously, the zram-swap script did not allow any configuration without
modifying the script itself. This introduces support for a new file,
placed at `/etc/ztab`. This file is structured similarly to the fstab
file and controls most configurable aspects of the mounting process.

This also includes an example `ztab` file, as well as a Makefile which
can perform the installation process (supporting the common variable
DESTDIR for packagers).

4 files changed, 192 insertions, 77 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8a53d46
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+.DEFAULT: install
+
+install:
+	install -D -v -m 755 zmount       $(DESTDIR)/bin/zmount
+	install -D -v -m 755 ztab.example $(DESTDIR)/etc/ztab
diff --git a/zmount b/zmount
new file mode 100755
index 0000000..42721f7
--- /dev/null
+++ b/zmount
@@ -0,0 +1,178 @@
+#!/usr/bin/env bash
+# Zmount automatically configures zram devices with the ztab config file
+# Copyright (C)  2021  Aaron Ball <nullspoon@oper.io>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set -euo pipefail
+export IFS=$'\n\t'
+
+CONFIG='/etc/ztab'
+RUN='/var/run/zmount'
+
+_parseline() {
+  local -a lineargs=()
+  lineargs=($(printf '%s\n' "${1:?}" | tr ' ' '\n'))
+  if [ "${#lineargs[@]}" -ne 5 ]; then
+    printf 'ERROR: Line "%s" does not have correct columns\n' >&2
+    return 1
+  fi
+  printf '%s\n' ${lineargs[@]}
+  return 0
+}
+
+_setperms() {
+  local dir="${1}"
+  local permstr="${2}"
+  local perm
+  local -a keyval=()
+
+  [ "${permstr}" = 'none' ] && return 0
+
+  for perm in $(printf '%s\n' ${permstr} | tr ',' '\n'); do
+    keyval=($(printf '%s\n' "${perm}" | tr '=' '\n'))
+    if [ "${keyval[0]}" = 'user' ]; then
+      chown "${keyval[1]}" "${dir}"
+    elif [ "${keyval[0]}" = 'group' ]; then
+      chgrp "${keyval[1]}" "${dir}"
+    elif [ "${keyval[0]}" = 'mode' ]; then
+      chmod "${keyval[1]}" "${dir}"
+    fi
+  done
+}
+
+_setup_dev() {
+  local fs="${1}"
+  local size="${2}"
+  local dir="${3}"
+  local opts="${4:-defaults}"
+  local perms="${5:-none}"      # Default to 777 to emulate tmpfs
+
+  local dev="$(zramctl -f)"
+  local threads="$(( $(nproc) / 2 ))"
+
+  [ ! -d "${RUN}" ] && mkdir -p ${RUN}
+
+  # Check for existing mounts to avoid duplicates
+  if [ "${fs}" = 'swap' ] && [ -f "${RUN}/swap" ]; then
+    printf 'ERROR: Zswap device already detected. Skipping second.\n' >&2
+    return 1
+  elif [ -f "${RUN}/${dir//\//_}" ]; then
+    printf 'ERROR: Skipping duplicate mount dir %s\n' "${dir}" >&2
+    return 1
+  fi
+
+  # Create the zram device
+  zramctl "${dev}" -s "${size}" -t "${threads}"
+
+  if [ "${fs}" = 'swap' ]; then
+    mkswap "${dev}" 2>&1 1>/dev/null
+    swapon "${dev}"
+    printf '%s\n' "${dev}" > "${RUN}/swap"
+  else
+    if [ "${fs}" = 'btrfs' ]; then
+      mkfs.btrfs -q "${dev}"
+    elif [ "${fs}" = 'ext2' ]; then
+      mkfs.ext2 -q "${dev}"
+    elif [ "${fs}" = 'ext3' ]; then
+      mkfs.ext3 -q "${dev}"
+    elif [ "${fs}" = 'ext4' ]; then
+      mkfs.ext4 -q "${dev}"
+    elif [ "${fs}" = 'exfat' ]; then
+      mkfs.exfat -q "${dev}"
+    elif [ "${fs}" = 'vfat' ]; then
+      mkfs.vfat -q "${dev}"
+    elif [ "${fs}" = 'xfs' ]; then
+      mkfs.xfs -q "${dev}"
+    else
+      printf 'Unknown filesystem type %s\n' "${fs}"
+      return 1
+    fi
+    mount -o "${opts}" "${dev}" "${dir}"
+    printf '%s\n' "${dev}" > "${RUN}/${dir//\//_}"
+  fi
+}
+
+status() { zramctl; }
+
+start() {
+  local -a lineargs=()
+
+  for line in $(grep -v '^#' /etc/ztab); do
+    lineargs=($(_parseline "${line}"))
+
+    if [ "${lineargs[0]}" = 'swap' ]; then
+      printf 'Setting up %s zswap\n' "${lineargs[1]}"
+    else
+      printf 'Setting up %s zram dev on %s\n' "${lineargs[1]}" "${lineargs[2]}"
+    fi
+    _setup_dev ${lineargs[@]}
+    _setperms "${lineargs[2]}" "${lineargs[4]}"
+  done
+}
+
+
+stop() {
+  local -a lineargs=()
+  local fs size dir
+
+  for line in $(grep -v '^#' /etc/ztab); do
+    lineargs=($(_parseline "${line}"))
+    fs="${lineargs[0]}"
+    size="${lineargs[1]}"
+    dir="${lineargs[2]}"
+    # Ignore opts and perms column
+
+    if [ "${fs}" = 'swap' ] && [ -f "${RUN}/swap" ]; then
+      dev="$(cat ${RUN}/swap)"
+      printf 'Stopping %s (mounted as swap)\n' "${dev}"
+      swapoff "${dev}"
+      rm -f "${RUN}/swap"
+    else
+      if [ ! -f "${RUN}/${dir//\//_}" ]; then
+        printf '%s is already unmounted from %s\n' "${fs}" "${dir}"
+        continue
+      fi
+      dev="$(cat ${RUN}/${dir//\//_})"
+      printf 'Stopping %s (mounted on %s)\n' "${dev}" "${dir}"
+      umount "${dir}" || :   # Ignore unmount failures
+      rm -f "${RUN}/${dir//\//_}"
+    fi
+    zramctl "${dev}" -r
+  done
+}
+
+
+main() {
+  if [ ${UID} -ne 0 ]; then
+    printf 'Must be run as root\n' >&2
+    return 1
+  fi
+
+  # Make sure the zram module is loaded
+  modprobe zram
+
+  if [ "${1:-}" = 'start' ]; then
+    start
+  elif [ "${1:-}" = 'stop' ]; then
+    stop
+  elif [ "${1:-}" = 'status' ]; then
+    status
+  else
+    printf 'usage: %s [start|stop|status]\n' "${0}"
+    return 1
+  fi
+}
+
+main ${@}
diff --git a/zram-swap b/zram-swap
deleted file mode 100755
index 0041234..0000000
--- a/zram-swap
+++ /dev/null
@@ -1,77 +0,0 @@
-#!/usr/bin/env bash
-# Zram-swap automatically compresses half of ram for swap usage
-# Copyright (C)  2021  Aaron Ball <nullspoon@oper.io>
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-set -euo pipefail
-export IFS=$'\n\t'
-
-RUNFILE='/var/run/zram-swap'
-MEMTOTAL=$(sed -n 's/^MemTotal: \+\([0-9]\+\) kB/\1/p' /proc/meminfo)
-
-status() {
-  if [ -f "${RUNFILE}" ]; then
-    zramctl $(cat "${RUNFILE}")
-  else
-    printf 'stopped\n'
-  fi
-}
-
-start() {
-  [ $(status) != 'stopped' ] && printf 'Already running\n' && return 1
-
-  local unused="$(zramctl -f)"
-  # Size is 1/2 of total memory
-  local size="$(( MEMTOTAL / 1024 / 2 ))M"
-  # Thread count is half of cpu
-  local threads="$(( $(nproc) / 2 ))"
-
-  # Create the zram device
-  zramctl "${unused}" -s "${size}" -t "${threads}"
-  mkswap "${unused}"
-  swapon "${unused}"
-  printf '%s\n' "${unused}" > "${RUNFILE}"
-}
-
-stop() {
-  [ $(status) = 'stopped' ] && printf 'Already stopped\n' && return 1
-  local zram="$(cat ${RUNFILE})"
-  swapoff ${zram}
-  zramctl -r "${zram}"
-  rm -f "${RUNFILE}"
-}
-
-main() {
-  if [ ${UID} -ne 0 ]; then
-    printf 'Must be run as root\n' >&2
-    return 1
-  fi
-
-  # Make sure the zram module is loaded
-  modprobe zram
-
-  if [ "${1:-}" = 'start' ]; then
-    start
-  elif [ "${1:-}" = 'stop' ]; then
-    stop
-  elif [ "${1:-}" = 'status' ]; then
-    status
-  else
-    printf 'usage: %s [start|stop|status]\n' "${0}"
-    exit 1
-  fi
-}
-
-main ${@}
diff --git a/ztab.example b/ztab.example
new file mode 100644
index 0000000..d1f4544
--- /dev/null
+++ b/ztab.example
@@ -0,0 +1,9 @@
+#
+# /etc/ztab: Zram file system information
+#
+# <file system>  <size>  <dir>              <options>           <perms>
+
+# swap           8G      none               none                none
+# ext4           10G     /tmp               defaults,relatime   mode=777
+# ext4           16G     /var/pkgmk         defaults,noatime    user=jcricket,group=public,mode=750
+# ext3           512M    /mnt               defaults            none