#!/bin/bash
# invoked by backup scripts as
#    remountrocp snap $vardir $device $mountpoint
#		remounts $mountpoint readonly
#		copies data to $vardir/snap-mount
#		remounts $mountpoint readwrite
#    remountrocp drop $vardir
#		deletes $vardir/snap-mount

set -e
snapkind=remountrocp
: ${lvm_vg:=}
remountrocp_fs=ext2
. ${CHIARK_BACKUP_SHAREDIR:-/usr/share/chiark-backup}/snap-common

#---------- clean up anything

vgroup=$lvm_vg
lvmdropcore

lastsettings="$vardir/remountrocp-settings"
test ! -f $lastsettings || . $lastsettings

if test "$opmode" = drop; then
	test -z "$last_mountpoint" || mount -o remount,rw $last_mountpoint
	rm -f $lastsettings
	echo 'remountrocp snap dropped'
	exit 0
fi

#---------- create snapshot

if [ -z "$lvm_lvsize_opts" ]; then
	lvmextentscore1

	df_out="$(really df -P --block-size=$extsize $mountpoint)"
	extents2="$(printf "%s" "$df_out" | awk '/^\// {print $3}')"
	extents2=$(( ($extents2*150+102399)/102400 + 4 ))

	lvmextentscore2
fi

lvmcreatecore1

cat >$lastsettings.new <<END
last_mountpoint=$mountpoint
END
mv -f $lastsettings.new $lastsettings

lvcreate \
	$lvm_lvtools_opts \
	$lvm_lvsize_opts \
	-n $lvm_lv \
	$lvm_lvcreate_opts \
	$vgroup \
	$lvm_lvcreate_args

mkfs -t $remountrocp_fs -q "$lvpath"

mkdir -- "$snmnt"
mount -t $remountrocp_fs $lvm_mount_opts "$lvpath" "$snmnt"
echo ' copy filesystem created and mounted'

attempts=10
while true; do
	if mount -o remount,ro "$mountpoint"; then break; fi
	attempts=$(( $attempts - 1 ))
	if [ $attempts = 0 ]; then
		echo >&2 'cannot remount readonly'
		exit 1
	fi
	sleep 1
done
trap "set +e; mount -o remount,rw $mountpoint; exit 12" 0
echo ' source remounted readonly, copying...'
cp -ax -- "$mountpoint/." "$snmnt/."
echo ' finalising...'
mount -o remount,rw "$mountpoint"
trap '' 0
mount -o remount,ro "$lvpath"

echo 'remountrocp snap activated'