#!/bin/sh
# defrag v0.02 by Con Kolivas <kernel@kolivas.org
# Braindead fs-agnostic defrag to rewrite files in order largest to smallest
# Run this in the directory you want all the files and subdirectories to be
# reordered. It will only affect one partition.

trap 'abort' 1 2 15

renice 19 $$ > /dev/null

abort()
{
	echo Aborting
	rm -f tmpfile dirlist
	exit 1
}

fail()
{
	echo Failed
	abort
}

declare -i filesize=0

#The maximum size of a file we can easily cache in ram
declare -i maxsize=`awk '/MemTotal/ {print $2}' /proc/meminfo`
(( maxsize-= `awk '/Mapped/ {print $2}' /proc/meminfo` ))
(( maxsize/= 2))

if [[ -a tmpfile || -a dirlist  ]] ; then
	echo dirlist or tmpfile exists
	exit 1
fi

# Sort in the following order:
# Depth of directory ascending
# Size descending
# Name

find -xdev -type f -printf "%d %s %p\n" | sort -k 1,1n -k 2nr -k 3 | awk '{print $3}' > dirlist

if (( $? )) ; then
	fail
fi

for i in `cat dirlist`
do
	if [[ ! -f $i ]]; then
		continue
	fi

	filesize=`find $i -printf "%s"`
	# read the file first to cache it in ram if possible
	if (( filesize < maxsize )) ; then
		cat $i > /dev/null
	fi
	datestamp=`find $i -printf "%s"`
	cp -a -f $i tmpfile
	if (( $? )) ; then
		fail
	fi
	# check the file hasn't been altered since we copied it
	if [[ `find $i -printf "%s"` != $datestamp ]] ; then
		echo $i changed, not overwriting
		continue
	fi

	mv -f tmpfile $i
	if (( $? )) ; then
		fail
	fi
done

rm -f dirlist