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|
dm_snapshot()
{
# TODO: eliminate duplication; this function exists elsewhere in a less generalized form
local ro_file rw_file cutoff_size
ro_file=$1
rw_file=$2
cutoff_size=$3
local ro_dev rw_dev size new_dev_name persist chunksize
if [ -b "$ro_file" ];
then ro_dev=$ro_file
else ro_dev=$(LoSetup -r -f --show "$ro_file") || return
fi
if [ -b "$rw_file" ];
then rw_dev=$rw_file
else rw_dev=$(LoSetup -f --show "$rw_file") || return
fi
if [ "$cutoff_size" -a "$cutoff_size" -gt 0 ]; then
size=$cutoff_size
else
size=$(blockdev --getsz "$ro_dev") || return
fi
new_dev_name=${ro_dev##*/}
persist=p
chunksize=16
dmsetup create "$new_dev_name" --table "0 $size snapshot $ro_dev $rw_dev $persist $chunksize" || return
wait_for_dm_device /dev/mapper/"$new_dev_name";
echo /dev/mapper/"$new_dev_name"
}
dm_snapshot_teardown()
{
local dev="$1"
case "$dev" in
/dev/dm-*)
dmsetup table "$dev" | (
read _ _ snapshot ro_dev rw_dev _ _
[ "$snapshot" = snapshot ] || exit 1
dmsetup remove "$dev" || exit 1
# errors ignored because the loop dev can be automatically removed upon disuse already
losetup -d /dev/block/"$rw_dev" || true
eject /dev/block/"$ro_dev" || exit 1
) || return
;;
*) return 1 ;;
esac
}
wait_for_dm_device()
{
# TODO: improve
while ! [ -e "$1" ]; do
sleep 1
done
}
mount_cdrom()
{
local cdrom_dev="$1"
local sectors md_dev=/dev/md0 cdrom_rw_file=/"${cdrom_dev##*/}".rw
sectors=$(get_cdrom_sizelimit "$cdrom_dev") || return
# TODO: do we even need this backing file? We do need to trick mdadm into
# thinking that this is a RW device, but previously we got away with just
# creating a loopback device.
dd if=/dev/zero of="$cdrom_rw_file" bs=1K count=32 || return
cdrom_rw_dev=$(dm_snapshot "$cdrom_dev" "$cdrom_rw_file" "$sectors") || return
mdadm_dup "$cdrom_rw_dev" "$md_dev" "$sectors" || return
mount -t iso9660 -r $md_dev /cdrom
}
get_cdrom_sizelimit()
{
# returns 512-byte sectors
local dev="$1" sectors
sectors=$(blockdev --getsz "$dev") || return
# Check if we can read the last 8 sectors. With a TAO CDROM, we can't --
# these sectors are faux, and not part of the ISO fs. If mdadm is allowed to
# read them, it will mark the device failed.
if dd count=2 if="$dev" bs=2048 skip=$((sectors/4 - 2)) of=/dev/null 2>/dev/null; then
echo $sectors
else
echo $((sectors - 8))
fi
}
mdadm_dup()
{
local input_dev="$1" md_name="$2" sectors="$3"
mdadm --build $md_name ${sectors:+--size=$((sectors / 2))} \
--level=1 --raid-devices=1 --force --write-mostly "$input_dev" || return
}
mdadm_subdevices()
{
local md_dev="$1"
mdadm -D "$md_dev" -Y | sed -ne 's/MD_DEVICE_.*_DEV=//p'
}
Mdadm()
{
mdadm "$@"
# r=$?
# mdadm -D "$1"
# sleep 2
# return $r
}
mdadm_copy_eject() # NOT INITRD; uses non-busybox "losetup"
{
local md_dev="$1" output_file="$2"
[ -b "$md_dev" ] || return
[ ! -e "$output_file" ] || return
local output_dev sectors
old_subdev=$(mdadm_subdevices "$md_dev"|head -n1) || return
[ -b "$old_subdev" ] || return
sectors=$(blockdev --getsz "$md_dev") || return
truncate -s $((sectors * 512)) "$output_file" || return
output_dev=$(losetup -f --show "$output_file") || return
Mdadm "$md_dev" --add "$output_dev" || return
Mdadm "$md_dev" --grow -n2 || return
mdadm_wait_remove "$md_dev" "$old_subdev" || return
Mdadm "$md_dev" --grow -n1 --force || return
dm_snapshot_teardown "$old_subdev"
}
mdadm_wait_remove()
{
# We should perhaps use mdadm --monitor's RebuildFinished event.
local dev="$1" disk="$2" tries
if ! mdadm --wait "$dev"; then
tries=1000
while ! mdadm --detail --test "$dev"; do
[ $tries -gt 0 ] || return 1
sleep 1
tries=$((tries-1))
done
fi
mdadm "$dev" --fail "$disk" || return 1
tries=100
while ! mdadm "$dev" --remove "$disk"; do
[ $tries -gt 0 ] || return 1
sleep 1
tries=$((tries-1))
done
return 0
}
|
