#!/bin/sh
dir=$(dirname "$0")
. "$dir/block-common.sh"
expand_dev() {
local dev
case $1 in
/*)
dev=$1
;;
*)
dev=/dev/$1
;;
esac
echo -n $dev
}
##
# canonicalise_mode mode
#
# Takes the given mode, which may be r, w, ro, rw, w!, or rw!, or variations
# thereof, and canonicalises them to one of
#
# 'r': perform checks for a new read-only mount;
# 'w': perform checks for a read-write mount; or
# '!': perform no checks at all.
#
canonicalise_mode()
{
local mode="$1"
if ! expr index "$mode" 'w' >/dev/null
then
echo 'r'
elif ! expr index "$mode" '!' >/dev/null
then
echo 'w'
else
echo '!'
fi
}
##
# check_sharing device mode
#
# Check whether the device requested is already in use. To use the device in
# read-only mode, it may be in use in read-only mode, but may not be in use in
# read-write anywhere at all. To use the device in read-write mode, it must
# not be in use anywhere at all.
#
# Prints one of
#
# 'local': the device may not be used because it is mounted in the current
# (i.e. the privileged domain) in a way incompatible with the
# requested mode;
# 'ok': the device may be used.
#
check_sharing()
{
local dev="$1"
local mode="$2"
local devmm=$(device_major_minor "$dev")
local file
if [ "$mode" == 'w' ]
then
toskip="^$"
else
toskip="^[^ ]* [^ ]* [^ ]* ro[, ]"
fi
for file in $(cat /proc/mounts | grep -v "$toskip" | cut -f 1 -d ' ')
do
if [ -e "$file" ]
then
local d=$(device_major_minor "$file")
if [ "$d" == "$devmm" ]
then
echo 'local'
return
fi
fi
done
echo 'ok'
}
same_vm()
{
local otherdom="$1"
# Note that othervm can be MISSING here, because Xend will be racing with
# the hotplug scripts -- the entries in /local/domain can be removed by
# Xend before the hotplug scripts have removed the entry in
# /local/domain/0/backend/. In this case, we want to pretend that the
# VM is the same as FRONTEND_UUID, because that way the 'sharing' will be
# allowed.
local othervm=$(xenstore_read_default "/local/domain/$otherdom/vm" \
"$FRONTEND_UUID")
[ "$FRONTEND_UUID" == "$othervm" ]
}
##
# check_device_sharing dev mode
#
# Perform the sharing check for the given physical device and mode.
#
check_device_sharing()
{
local dev="$1"
local mode=$(canonicalise_mode "$2")
local result
if [ "$mode" == '!' ]
then
return 0
fi
result=$(check_sharing "$dev" "$mode")
if [ "$result" != 'ok' ]
then
do_ebusy "Device $dev is mounted " "$mode" "$result"
fi
}
##
# check_device_sharing file dev mode
#
# Perform the sharing check for the given file mounted through the given
# loopback interface, in the given mode.
#
check_file_sharing()
{
local file="$1"
local dev="$2"
local mode="$3"
result=$(check_sharing "$dev" "$mode")
if [ "$result" != 'ok' ]
then
do_ebusy "File $file is loopback-mounted through $dev,
which is mounted " "$mode" "$result"
fi
}
##
# do_ebusy prefix mode result
#
# Helper function for check_device_sharing check_file_sharing, calling ebusy
# with an error message constructed from the given prefix, mode, and result
# from a call to check_sharing.
#
do_ebusy()
{
local prefix="$1"
local mode="$2"
local result="$3"
if [ "$result" == 'guest' ]
then
dom='a guest '
when='now'
else
dom='the privileged '
when='by a guest'
fi
if [ "$mode" == 'w' ]
then
m1=''
m2=''
else
m1='read-write '
m2='read-only '
fi
release_lock "block"
ebusy \
"${prefix}${m1}in ${dom}domain,
and so cannot be mounted ${m2}${when}."
}
t=$(xenstore_read_default "$XENBUS_PATH/type" 'MISSING')
case "$command" in
add)
phys=$(xenstore_read_default "$XENBUS_PATH/physical-device" 'MISSING')
if [ "$phys" != 'MISSING' ]
then
# Depending upon the hotplug configuration, it is possible for this
# script to be called twice, so just bail.
exit 0
fi
if [ -n "$t" ]
then
p=$(xenstore_read "$XENBUS_PATH/params")
mode=$(xenstore_read "$XENBUS_PATH/mode")
fi
case $t in
phy)
dev=$(expand_dev $p)
FRONTEND_ID=$(xenstore_read "$XENBUS_PATH/frontend-id")
FRONTEND_UUID=$(xenstore_read_default \
"/local/domain/$FRONTEND_ID/vm" 'unknown')
claim_lock "block"
check_device_sharing "$dev" "$mode"
write_dev "$dev"
release_lock "block"
exit 0
;;
file)
# Canonicalise the file, for sharing check comparison, and the mode
# for ease of use here.
file=$(readlink -f "$p") || fatal "$p does not exist."
test -f "$file" || fatal "$file does not exist"
mode=$(canonicalise_mode "$mode")
claim_lock "block"
# Avoid a race with the remove if the path has been deleted, or
# otherwise changed from "InitWait" state e.g. due to a timeout
xenbus_state=$(xenstore_read_default "$XENBUS_PATH/state" 'unknown')
if [ "$xenbus_state" != '2' ]
then
release_lock "block"
fatal "Path closed or removed during hotplug add: $XENBUS_PATH state: $xenbus_state"
fi
if [ "$mode" == 'w' ] && ! stat "$file" -c %A | grep -q w
then
release_lock "block"
ebusy \
"File $file is read-only, and so I will not
mount it read-write in a guest domain."
fi
if [ "x$mode" != 'x!' ]
then
inode=$(stat -c '%i' "$file")
dev=$(stat -c '%D' "$file")
if [ -z "$inode" ] || [ -z "$dev" ]
then
fatal "Unable to lookup $file: dev: $dev inode: $inode"
fi
shared_list=$(losetup -a | grep ' \[0*'${dev}'\]:'${inode} |
cut -d : -f 1)
for dev in "$shared_list"
do
if [ -n "$dev" ]
then
check_file_sharing "$file" "$dev" "$mode"
fi
done
fi
loopdev=$(losetup -f)
if [ "$loopdev" == '' ]
then
fatal 'Failed to find an unused loop device'
fi
cmode=`canonicalise_mode $mode`
if [ "$cmode" == 'r' ]
then
do_or_die losetup -r "$loopdev" "$file"
else
do_or_die losetup "$loopdev" "$file"
fi
xenstore_write "$XENBUS_PATH/node" "$loopdev"
write_dev "$loopdev"
release_lock "block"
exit 0
;;
"")
claim_lock "block"
success
release_lock "block"
;;
esac
;;
remove)
case $t in
phy)
exit 0
;;
file)
claim_lock "block"
node=$(xenstore_read "$XENBUS_PATH/node")
losetup -d "$node"
release_lock "block"
exit 0
;;
"")
exit 0
;;
esac
;;
esac
# If we've reached here, $t is neither phy nor file, so fire a helper script.
[ -x /etc/xen/scripts/block-"$t" ] && \
/etc/xen/scripts/block-"$t" "$command" $node
