Function to add loop devices, that ensures max_loop is not exceed

add-loops.sh

add-loops() {
  [[ -n ${1} && ${1} =~ ^[0-9]+$ ]] && local C=${1} || { printf "${FUNCNAME} <count>\n";return 2; }
  [[ ${EUID} = 0 ]] && export SU= || export SU=sudo
  local -a LOOP_DEVS=($(find /dev -maxdepth 1 -iregex '.*loop[0-9]+'|sort -V))
  local M=$(cat 2>/dev/null /proc/cmdline|grep -oP '(?<=max_loop=)[^ ]+')
  [[ -n ${M} && ${M} =~ ^[0-9]+$ ]] || local M=256
  [[ $((${#LOOP_DEVS[@]}+${C})) -gt ${M} ]] && { printf "Can only add up to $(($M-${#LOOP_DEVS[@]})) new devices\n";return 2; }
  local L=${LOOP_DEVS[-1]//[^0-9]/}
  local S=$(($L+1))
  local E=$(($S+$C))
  printf "Current loop device count: ${#LOOP_DEVS[@]}\n"
  printf "First new loop device: /dev/loop${S}\n"
  printf "Last new loop device: /dev/loop${E}\n"
  eval printf '%s\\n' {$S..$E}|xargs -n1 -P0 bash -c '${SU} bash -c "mknod -m0660 /dev/loop${0} b 7 ${0} && chown root.disk /dev/loop${0}"'
  local -a LOOP_DEVS=($(find /dev -maxdepth 1 -iregex '.*loop[0-9]+'|sort -V))
  printf "New loop device count: ${#LOOP_DEVS[@]}\n"
  unset SU
}

$ add-loops 10
Current loop device count: 11
First new loop device: /dev/loop11
Last new loop device: /dev/loop21
New loop device count: 22