flushing filesystem/flash cache?

[victorallume]

I'm trying to investigate some lfs issues on a pybd; when I change something on the filesystem (e.g. create a file or format the filesystem), the filesystem behaves as you would expect, but when I read the block device of this filesystem directly, it isn't updated and has the data that was previously there. Calling os.sync() doesn't seem to change it. Also, if I zero-out the data on the block device, the filesystem continues working. This persists through a soft reset. But if I reset the pyboard using the power button, the block device is updated. I'm not even sure if this is a cache flushing issue, as if the data was just in cache, it shouldn't appear in flash after a hard reset. I'm wondering if pyb.Flash has caching that is independent of the filesystem cache? Any suggestions?