Description: check available disk space first to avoid filling up disks
Author: Axel Beckert <abe@debian.org>
Reviewed-By: Petter Reinholdtsen <pere@hungry.com>
Debian-Bug: https://bugs.debian.org/596187
Forwarded: not-yet

--- a/dphys-swapfile
+++ b/dphys-swapfile
@@ -29,6 +29,9 @@
 #   but is also sensible on 64bit to prevent filling /var or even / partition
 CONF_MAXSWAP=2048
 
+# restrict size to this percentage of the remaining disk space.
+CONF_MAXDISK_PCT=50
+
 
 ### ------ actual implementation from here on
 # no user settings any more below this point
@@ -78,6 +81,20 @@
     # announce end resulting config
     echo -n "want ${CONF_SWAPFILE}=${CONF_SWAPSIZE}MByte"
 
+    if [ "${CONF_MAXDISK_PCT}" != "" ] ; then
+      # check for free disk size percentage and don't overstep it
+      AVAIL_KB=$(/bin/df --output=avail "$(dirname "${CONF_SWAPFILE}")/." | tail -1)
+      if [ -n "${CONF_SWAPFILE}" -a -e "${CONF_SWAPFILE}" ]; then
+          CURRENT_SIZE_B=$(stat --printf='%s' "${CONF_SWAPFILE}")
+          AVAIL_KB=$(echo "${AVAIL_KB} ${CURRENT_SIZE_B} 1024 / + p" | dc)
+      fi
+      HALF_AVAIL_MB=$(echo "${AVAIL_KB} 2048 / p" | dc)
+      if [ "${CONF_SWAPSIZE}" -gt "${HALF_AVAIL_MB}" ] ; then
+        echo -n ", restricting to ${CONF_MAXDISK_PCT}% of remaining disk size: ${HALF_AVAIL_MB}MBytes"
+        CONF_SWAPSIZE="${HALF_AVAIL_MB}"
+      fi
+    fi
+
     if [ "${CONF_MAXSWAP}" != "" ] ; then
       # check for swap size limit and restrict to it
       if [ "${CONF_SWAPSIZE}" -gt "${CONF_MAXSWAP}" ] ; then
--- a/dphys-swapfile.8
+++ b/dphys-swapfile.8
@@ -70,6 +70,13 @@
 excess diskspace on small RAM (and disk?) systems. Defaults to 2, which gives
 swap size = 2 * RAM size.
 .TP
+.B CONF_MAXDISK_PCT
+Sets the maximal percentage of the remaining disk space which may be
+used for the swap file. Takes potentially existing dphys-swapfile swap
+files into account, i.e. adds their size to the available disk space
+before calculating the percentage. Defaults to 50. Set it to the empty
+string to disable this check.
+.TP
 .B CONF_MAXSWAP
 Set size restriction of maximal computed and absolute(!) values, in MBytes.
 Defaults to 2048 which was a former 32bit kernel limit for the swapfile size