mirror of
https://github.com/xen-project/xen.git
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cl349@firebug.cl.cam.ac.uk
79a13ff2fd
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
366 lines
7.8 KiB
Bash
366 lines
7.8 KiB
Bash
#!/bin/sh
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dir=$(dirname "$0")
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. "$dir/block-common.sh"
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expand_dev() {
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local dev
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case $1 in
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/*)
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dev=$1
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;;
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*)
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dev=/dev/$1
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;;
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esac
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echo -n $dev
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}
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##
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# canonicalise_mode mode
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#
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# Takes the given mode, which may be r, w, ro, rw, w!, or rw!, or variations
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# thereof, and canonicalises them to one of
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#
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# 'r': perform checks for a new read-only mount;
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# 'w': perform checks for a read-write mount; or
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# '!': perform no checks at all.
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#
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canonicalise_mode()
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{
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local mode="$1"
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if ! expr index "$mode" 'w' >/dev/null
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then
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echo 'r'
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elif ! expr index "$mode" '!' >/dev/null
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then
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echo 'w'
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else
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echo '!'
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fi
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}
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##
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# check_sharing device mode
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#
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# Check whether the device requested is already in use. To use the device in
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# read-only mode, it may be in use in read-only mode, but may not be in use in
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# read-write anywhere at all. To use the device in read-write mode, it must
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# not be in use anywhere at all.
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#
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# Prints one of
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#
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# 'local': the device may not be used because it is mounted in the current
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# (i.e. the privileged domain) in a way incompatible with the
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# requested mode;
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# 'guest': the device may not be used because it already mounted by a guest
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# in a way incompatible with the requested mode; or
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# 'ok': the device may be used.
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#
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check_sharing()
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{
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local dev="$1"
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local mode="$2"
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local devmm=$(device_major_minor "$dev")
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local file
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if [ "$mode" == 'w' ]
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then
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toskip="^$"
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else
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toskip="^[^ ]* [^ ]* [^ ]* ro "
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fi
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for file in $(cat /proc/mounts | grep -v "$toskip" | cut -f 1 -d ' ')
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do
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if [ -e "$file" ]
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then
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local d=$(device_major_minor "$file")
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if [ "$d" == "$devmm" ]
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then
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echo 'local'
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return
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fi
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fi
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done
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for dom in $(xenstore-list "$XENBUS_BASE_PATH")
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do
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for dev in $(xenstore-list "$XENBUS_BASE_PATH/$dom")
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do
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d=$(xenstore_read_default \
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"$XENBUS_BASE_PATH/$dom/$dev/physical-device" "")
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if [ "$d" == "$devmm" ]
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then
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if [ "$mode" == 'w' ]
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then
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if ! same_vm $dom
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then
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echo 'guest'
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return
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fi
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else
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local m=$(xenstore_read "$XENBUS_BASE_PATH/$dom/$dev/mode")
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m=$(canonicalise_mode "$m")
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if [ "$m" == 'w' ]
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then
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if ! same_vm $dom
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then
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echo 'guest'
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return
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fi
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fi
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fi
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fi
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done
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done
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echo 'ok'
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}
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same_vm()
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{
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local thisdom="$XENBUS_FRONTEND_ID"
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local otherdom="$1"
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local thisvm=$(xenstore-read "/local/domain/$thisdom/vm")
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local othervm=$(xenstore-read "/local/domain/$otherdom/vm")
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return [ "$thisvm" == "$othervm" ]
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}
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##
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# check_device_sharing dev mode
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#
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# Perform the sharing check for the given physical device and mode.
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#
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check_device_sharing()
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{
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local dev="$1"
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local mode=$(canonicalise_mode "$2")
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local result
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if [ "$mode" == '!' ]
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then
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return 0
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fi
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result=$(check_sharing "$dev" "$mode")
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if [ "$result" != 'ok' ]
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then
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do_ebusy "Device $dev is mounted " "$mode" "$result"
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fi
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}
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##
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# check_device_sharing file dev mode
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#
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# Perform the sharing check for the given file mounted through the given
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# loopback interface, in the given mode.
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#
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check_file_sharing()
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{
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local file="$1"
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local dev="$2"
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local mode="$3"
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result=$(check_sharing "$dev" "$mode")
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if [ "$result" != 'ok' ]
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then
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do_ebusy "File $file is loopback-mounted through $dev,
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which is mounted " "$mode" "$result"
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fi
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}
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##
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# do_ebusy prefix mode result
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#
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# Helper function for check_device_sharing check_file_sharing, calling ebusy
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# with an error message constructed from the given prefix, mode, and result
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# from a call to check_sharing.
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#
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do_ebusy()
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{
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local prefix="$1"
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local mode="$2"
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local result="$3"
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if [ "$result" == 'guest' ]
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then
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dom='a guest '
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when='now'
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else
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dom='the privileged '
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when='by a guest'
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fi
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if [ "$mode" == 'w' ]
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then
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m1=''
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m2=''
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else
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m1='read-write '
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m2='read-only '
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fi
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release_lock "block"
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ebusy \
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"${prefix}${m1}in ${dom}domain,
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and so cannot be mounted ${m2}${when}."
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}
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t=$(xenstore_read_default "$XENBUS_PATH/type" 'MISSING')
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case "$command" in
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add)
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phys=$(xenstore_read_default "$XENBUS_PATH/physical-device" 'MISSING')
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if [ "$phys" != 'MISSING' ]
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then
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# Depending upon the hotplug configuration, it is possible for this
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# script to be called twice, so just bail.
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exit 0
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fi
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p=$(xenstore_read "$XENBUS_PATH/params")
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mode=$(xenstore_read "$XENBUS_PATH/mode")
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case $t in
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phy)
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dev=$(expand_dev $p)
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claim_lock "block"
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check_device_sharing "$dev" "$mode"
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write_dev "$dev"
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release_lock "block"
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exit 0
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;;
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file)
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# Canonicalise the file, for sharing check comparison, and the mode
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# for ease of use here.
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file=$(readlink -f "$p") || fatal "$p does not exist."
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mode=$(canonicalise_mode "$mode")
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claim_lock "block"
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if [ "$mode" == 'w' ] && ! stat "$file" -c %A | grep -q w
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then
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release_lock "block"
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ebusy \
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"File $file is read-only, and so I will not
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mount it read-write in a guest domain."
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fi
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loopdev=''
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for dev in /dev/loop*
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do
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if [ ! -b "$dev" ]
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then
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continue
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fi
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f=$(losetup "$dev" 2>/dev/null) || f=''
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if [ "$f" ]
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then
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# $dev is in use. Check sharing.
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if [ "$mode" == '!' ]
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then
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continue
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fi
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f=$(echo "$f" | sed -e 's/.*(\(.*\)).*/\1/g')
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# $f is the filename, as read from losetup, but the loopback
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# driver truncates filenames at 64 characters, so we need to go
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# trawling through the store if it's longer than that. Truncation
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# is indicated by an asterisk at the end of the filename.
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if expr index "$f" '*' >/dev/null
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then
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found=""
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for dom in $(xenstore-list "$XENBUS_BASE_PATH")
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do
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for domdev in $(xenstore-list "$XENBUS_BASE_PATH/$dom")
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do
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d=$(xenstore_read_default \
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"$XENBUS_BASE_PATH/$dom/$domdev/node" "")
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if [ "$d" == "$dev" ]
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then
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f=$(xenstore_read "$XENBUS_BASE_PATH/$dom/$domdev/params")
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found=1
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break 2
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fi
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done
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done
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if [ ! "$found" ]
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then
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# This loopback device is in use by someone else, so skip it.
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log debug "Loopback sharing check skips device $dev."
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continue
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fi
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fi
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f=$(readlink -f "$f")
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if [ "$f" == "$file" ]
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then
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check_file_sharing "$file" "$dev" "$mode"
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fi
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else
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# $dev is not in use, so we'll remember it for use later; we want
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# to finish the sharing check first.
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if [ "$loopdev" == '' ]
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then
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loopdev="$dev"
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fi
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fi
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done
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if [ "$loopdev" == '' ]
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then
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fatal 'Failed to find an unused loop device'
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fi
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do_or_die losetup "$loopdev" "$file"
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xenstore_write "$XENBUS_PATH/node" "$loopdev"
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write_dev "$loopdev"
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release_lock "block"
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exit 0
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;;
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esac
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;;
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remove)
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case $t in
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phy)
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exit 0
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;;
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file)
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node=$(xenstore_read "$XENBUS_PATH/node")
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losetup -d "$node"
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exit 0
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;;
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esac
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;;
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esac
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# If we've reached here, $t is neither phy nor file, so fire a helper script.
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[ -x /etc/xen/scripts/block-"$t" ] && \
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/etc/xen/scripts/block-"$t" "$command" $node
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