Merge pull request #130 from cloudbuilders/fix_races

Address races in NBD and images

tools/build_libvirt.sh

@@ -229,15 +229,8 @@ EOF
 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 +239,27 @@ rm -f $VM_DIR/disk
 # Create our instance fs
 qemu-img create -f qcow2 -b $VM_IMAGE disk
 
-# Connect our nbd and wait till it is mountable
+# Make sure we have nbd-ness
+modprobe nbd max_part=63
+
+# Set up nbd
+for i in `seq 0 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 $ROOTFS
@@ -344,9 +352,6 @@ echo "export PS1='${debian_chroot:+($debian_chroot)}\\u@\\H:\\w\\$ '" >> $ROOTFS
 # Give stack ownership over $DEST so it may do the work needed
 chroot $ROOTFS chown -R stack $DEST
 
-# GRUB 2 wants to see /dev
-mount -o bind /dev $ROOTFS/dev
-
 # Set the hostname
 echo $GUEST_NAME > $ROOTFS/etc/hostname
 
@@ -355,6 +360,9 @@ if ! grep -q $GUEST_NAME $ROOTFS/etc/hosts; then
     echo "$GUEST_IP $GUEST_NAME" >> $ROOTFS/etc/hosts
 fi
 
+# GRUB 2 wants to see /dev
+mount -o bind /dev $ROOTFS/dev
+
 # Change boot params so that we get a console log
 G_DEV_UUID=`blkid -t LABEL=cloudimg-rootfs -s UUID -o value | head -1`
 sed -e "s/GRUB_TIMEOUT=.*$/GRUB_TIMEOUT=3/" -i $ROOTFS/etc/default/grub

tools/get_uec_image.sh

@@ -51,6 +51,7 @@ fi
 # Default args
 DIST_NAME=$1
 IMG_FILE=$2
+IMG_FILE_TMP=`mktemp $IMG_FILE.XXXXXX`
 
 case $FORMAT in
     kvm|qcow2)  FORMAT=qcow2
@@ -88,11 +89,6 @@ case $DIST_NAME in
                 ;;
 esac
 
-# Set up nbd
-modprobe nbd max_part=63
-NBD=${NBD:-/dev/nbd9}
-NBD_DEV=`basename $NBD`
-
 # Prepare the base image
 
 # Get the UEC image
@@ -103,24 +99,37 @@ fi
 
 if [ "$FORMAT" = "qcow2" ]; then
     # Just copy image
-    cp -p $CACHEDIR/$UEC_NAME-disk1.img $IMG_FILE
+    cp -p $CACHEDIR/$UEC_NAME-disk1.img $IMG_FILE_TMP
 else
     # Convert image
-    qemu-img convert -O $QFORMAT $CACHEDIR/$UEC_NAME-disk1.img $IMG_FILE
+    qemu-img convert -O $QFORMAT $CACHEDIR/$UEC_NAME-disk1.img $IMG_FILE_TMP
 fi
 
 # Resize the image if necessary
 if [ $ROOTSIZE -gt 2000 ]; then
     # Resize the container
-    qemu-img resize $IMG_FILE +$((ROOTSIZE - 2000))M
+    qemu-img resize $IMG_FILE_TMP +$((ROOTSIZE - 2000))M
 fi
 
+# 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 $IMG_FILE
+        qemu-nbd -c $NBD $IMG_FILE_TMP
-if ! timeout 60 sh -c "while ! [ -e /sys/block/$NBD_DEV/pid ]; do sleep 1; done"; then
+        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`
 
 # Resize partition 1 to full size of the disk image
 echo "d
@@ -153,3 +162,5 @@ rm -f $MNTDIR/etc/resolv.conf
 umount $MNTDIR
 rmdir $MNTDIR
 qemu-nbd -d $NBD
+
+mv $IMG_FILE_TMP $IMG_FILE