mirror of
https://github.com/xen-project/xen.git
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Keir Fraser
1d89b44561
Allow 'file' based disks, that are blkback based disks, to be shared between the guest domain and the stubdom. It does so exploiting the same exception introduced in the previous patch "stubdoms phy disks sharing". Now we can remove the hack in stubdom-dm that forces "file" disks to be opened using blktap instead of blkback. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
382 lines
9.1 KiB
Bash
382 lines
9.1 KiB
Bash
#!/bin/bash
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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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# 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" = "$devmm" ]
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then
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echo 'local'
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return
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fi
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fi
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done
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local base_path="$XENBUS_BASE_PATH/$XENBUS_TYPE"
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for dom in $(xenstore-list "$base_path")
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do
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for dev in $(xenstore-list "$base_path/$dom")
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do
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d=$(xenstore_read_default "$base_path/$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 "$base_path/$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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##
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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 "$2")
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local result
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if [ "x$mode" = 'x!' ]
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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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if [ -n "$t" ]
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then
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p=$(xenstore_read "$XENBUS_PATH/params")
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mode=$(xenstore_read "$XENBUS_PATH/mode")
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fi
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FRONTEND_ID=$(xenstore_read "$XENBUS_PATH/frontend-id")
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FRONTEND_UUID=$(xenstore_read_default \
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"/local/domain/$FRONTEND_ID/vm" 'unknown')
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case $t in
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phy)
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dev=$(expand_dev $p)
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if [ -L "$dev" ]
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then
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dev=$(readlink -f "$dev") || fatal "$dev link does not exist."
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fi
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test -e "$dev" || fatal "$dev does not exist."
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test -b "$dev" || fatal "$dev is not a block device."
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claim_lock "block"
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check_device_sharing "$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 "$p does not exist."
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test -f "$file" || fatal "$file does not exist."
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mode=$(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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# $dev is in use. Check sharing.
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if [ "x$mode" = 'x!' ]
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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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# Canonicalise the filename for the comparison.
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# I have seen this readlink fails because the filename given by
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# losetup is only the basename. This cannot happen when the loop
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# device is set up through this script, because file is
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# canonicalised above, but it may happen when loop devices are set
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# up some other way. This readlink may also conceivably fail if
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# the file backing this loop device has been removed.
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# For maximum safety, in the case that $f does not resolve, we
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# assume that $file and $f are in the same directory.
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# If you create a loopback filesystem, remove it and continue to
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# run on it, and then create another file with the same name, then
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# this check will block that -- don't do that.
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# If you create loop devices through some other mechanism, use
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# relative filenames, and then use the same filename through this
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# script, then this check will block that -- don't do that either.
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f=$(readlink -f "$f" || echo $(dirname "$file")/$(basename "$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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release_lock "block"
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fatal 'Failed to find an unused loop device'
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fi
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if LANG=C losetup -h 2>&1 | grep read-only >/dev/null
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then
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roflag="-$mode"; roflag="${roflag#-w}"; roflag="${roflag#-!}"
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else
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roflag=''
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fi
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do_or_die losetup $roflag "$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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"")
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claim_lock "block"
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success
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release_lock "block"
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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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"")
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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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