# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID c08cfaf353c60781f9b7baa5a8d91dfda6eca880
# Parent cfcf9212a90bb01e5f343a3407b0d32d07ab45a3
Added device-sharing checks for loopback-mounted files. The existing
check_sharing functions have been rejigged slightly so that the file-specific
stuff can share the code therein. This separates the actual test from the
generation of the error message, and introduces the canonicalise_mode function.
This also restores the broken teardown functionality for file: devices -- the
writing of XENBUS_PATH/node had been removed, but this is required for file
device teardown.
Signed-off-by: Ewan Mellor <ewan@xxxxxxxxxxxxx>
diff -r cfcf9212a90b -r c08cfaf353c6 tools/examples/block
--- a/tools/examples/block Sun Nov 27 00:10:14 2005
+++ b/tools/examples/block Sun Nov 27 00:56:34 2005
@@ -1,4 +1,6 @@
#!/bin/sh
+
+set -x
dir=$(dirname "$0")
. "$dir/block-common.sh"
@@ -17,8 +19,24 @@
}
+canonicalise_mode()
+{
+ local mode="$1"
+
+ if ! expr index "$mode" 'w' >/dev/null
+ then
+ echo 'ro'
+ elif ! expr index "$mode" '!' >/dev/null
+ then
+ echo 'rw'
+ else
+ echo 'no'
+ fi
+}
+
+
##
-# check_sharing device device_major_minor writable
+# check_sharing device device_major_minor 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
@@ -27,13 +45,13 @@
#
check_sharing()
{
-
local dev="$1"
- local devmm="$2"
- local writable="$3"
+ local mode="$2"
+
+ local devmm=$(device_major_minor "$dev")
local file
- if [ "$writable" ]
+ if [ "$mode" == 'rw' ]
then
toskip="^$"
else
@@ -48,18 +66,8 @@
if [ "$d" == "$devmm" ]
then
- if [ "$writable" ]
- then
- m1=""
- m2=""
- else
- m1="read-write "
- m2="read-only "
- fi
-
- ebusy \
-"Device $dev is mounted ${m1}in the privileged domain,
-and so cannot be mounted ${m2}by a guest."
+ echo 'local'
+ return
fi
fi
done
@@ -71,73 +79,182 @@
local d=$(cat "$file")
if [ "$d" == "$devmm" ]
then
- if [ "$writable" ]
- then
- ebusy \
-"Device $dev is already mounted in a guest domain, and so
-cannot be mounted read-write now."
+ if [ "$mode" == 'rw' ]
+ then
+ echo 'guest'
+ return
else
local m=$(cat "${file/physical_device/mode}")
if expr index "$m" 'w' >/dev/null
then
- ebusy \
-"Device $dev is already mounted read-write in a guest domain,
-and so cannot be mounted read-only again."
+ echo 'guest'
+ return
fi
fi
fi
fi
done
+
+ echo 'ok'
}
check_device_sharing()
{
local dev="$1"
- local devmm=$(device_major_minor "$dev")
- local mode=$(xenstore_read "$XENBUS_PATH/mode")
-
- if ! expr index "$mode" 'w' >/dev/null
- then
- # No w implies read-only use; sharing with writers must be prevented.
- check_sharing "$dev" "$devmm" ""
- elif ! expr index "$mode" '!' >/dev/null
- then
- # No exclamation mark implies all sharing must be prevented.
- check_sharing "$dev" "$devmm" 1
- fi
-}
-
-
-t=$(xenstore_read_default "$XENBUS_PATH/type" "MISSING")
-
-case "$command" in
+ local mode=$(canonicalise_mode "$2")
+ local result
+
+ if [ "$mode" == 'no' ]
+ then
+ return 0
+ fi
+
+ result=$(check_sharing "$dev" "$mode")
+
+ if [ "$result" != 'ok' ]
+ then
+ do_ebusy "Device $dev is mounted " "$mode" "$result"
+ fi
+}
+
+
+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()
+{
+ 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 [ "$mode" == 'rw' ]
+ then
+ m1=''
+ m2=''
+ else
+ m1='read-write '
+ m2='read-only '
+ fi
+
+ ebusy \
+"${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" ]
+ phys=$(xenstore_read_default "$XENBUS_PATH/physical-device" 'MISSING')
+ if [ "$phys" != 'MISSING' ]
then
# Depending upon the hotplug configuration, it is possible for this
# script to be called twice, so just bail.
exit 0
fi
+
p=$(xenstore_read "$XENBUS_PATH/params")
+ mode=$(xenstore_read "$XENBUS_PATH/mode")
+
case $t in
phy)
dev=$(expand_dev $p)
- check_device_sharing "$dev"
+ check_device_sharing "$dev" "$mode"
write_dev "$dev"
exit 0
;;
file)
- for dev in /dev/loop* ; do
- if losetup $dev $p; then
- write_dev "$dev"
- exit 0
- fi
- done
- exit 1
+ # Canonicalise the file, for sharing check comparison, and the mode
+ # for ease of use here.
+ file=$(readlink -f "$p")
+ mode=$(canonicalise_mode "$mode")
+
+ if [ "$mode" == 'rw' ] && ! stat "$file" -c %A | grep w >&/dev/null
+ then
+ ebusy \
+"File $file is read-only, and so I will not
+mount it read-write in a guest domain."
+ fi
+
+ loopdev=''
+
+ for dev in /dev/loop*
+ do
+ if [ ! -b "$dev" ]
+ then
+ continue
+ fi
+
+ f=$(losetup "$dev" 2>/dev/null) || f='()'
+ f=$(echo "$f" | sed -e 's/.*(\(.*\)).*/\1/g')
+
+ log err "$file $f $dev"
+
+ if [ "$f" ]
+ then
+ # $dev is in use. Check sharing.
+
+ if [ "$mode" == 'no' ]
+ then
+ continue
+ fi
+
+ f=$(readlink -f "$f")
+
+ if [ "$f" == "$file" ]
+ then
+ check_file_sharing "$file" "$dev" "$mode"
+ fi
+ else
+ # $dev is not in use, so we'll remember it for use later; we want
+ # to finish the sharing check first.
+
+ if [ "$loopdev" == '' ]
+ then
+ loopdev="$dev"
+ fi
+ fi
+ done
+
+ if [ "$loopdev" == '' ]
+ then
+ fatal 'Failed to find an unused loop device'
+ fi
+
+ if losetup "$loopdev" "$file"
+ then
+ xenstore_write "$XENBUS_PATH/node" "$loopdev"
+ write_dev "$loopdev"
+ exit 0
+ else
+ fatal "losetup $loopdev $file failed"
+ fi
;;
esac
;;
@@ -150,7 +267,7 @@
file)
node=$(xenstore_read "$XENBUS_PATH/node")
- losetup -d $node
+ losetup -d "$node"
exit 0
;;
esac
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