nova/virt/disk.py in inject_data does:
# Configure ext2fs so that it doesn't auto-check every N boots
out, err = utils.execute('tune2fs', '-c', 0, '-i', 0,
this disables both interval based and mount-count based filesystem checks on ext2 (or ext3 or ext4) file systems.
This is wrong for several reasons:
a.) Just because the user is in the unfortunate position of using file injection does not mean they want to disable filesystem checks which help to prevent data loss.
b.) I'm guessing the primary reason to modify this based on the fallacy that the first boot would then cause a filesystem check, and that filesystem check would be slow. That is not the case. A pristine image that has a filesystem check run on it due to a time interval passing happen sub-second. If the image had lots of changes since last fscheck, that is better fixed by the image author before registering.
c.) injecting a file has nothing to do with disabling filesystem checks.