Address NBD race
diff --git a/tools/build_libvirt.sh b/tools/build_libvirt.sh
index f39f52d..a7ed411 100755
--- a/tools/build_libvirt.sh
+++ b/tools/build_libvirt.sh
@@ -229,15 +229,8 @@
ROOTFS=$VM_DIR/root
mkdir -p $ROOTFS
-# Make sure we have nbd-ness
-modprobe nbd max_part=63
-
-# Which NBD device to use?
-NBD=${NBD:-/dev/nbd$GUEST_NETWORK}
-
# Clean up from previous runs
umount $ROOTFS || echo 'ok'
-qemu-nbd -d $NBD || echo 'ok'
# Clean up old runs
cd $VM_DIR
@@ -246,12 +239,28 @@
# Create our instance fs
qemu-img create -f qcow2 -b $VM_IMAGE disk
-# Connect our nbd and wait till it is mountable
-qemu-nbd -c $NBD disk
-if ! timeout 60 sh -c "while ! [ -e ${NBD}p1 ]; do sleep 1; done"; then
- echo "Couldn't connect $NBD"
+# Make sure we have nbd-ness
+modprobe nbd max_part=63
+
+# Set up nbd
+modprobe nbd max_part=63
+for i in `seq 1 15`; do
+ if [ ! -e /sys/block/nbd$i/pid ]; then
+ NBD=/dev/nbd$i
+ # Connect to nbd and wait till it is ready
+ qemu-nbd -c $NBD disk
+ if ! timeout 60 sh -c "while ! [ -e ${NBD}p1 ]; do sleep 1; done"; then
+ echo "Couldn't connect $NBD"
+ exit 1
+ fi
+ break
+ fi
+done
+if [ -z "$NBD" ]; then
+ echo "No free NBD slots"
exit 1
fi
+NBD_DEV=`basename $NBD`
# Mount the instance
mount ${NBD}p1 $ROOTFS