On Fri, Jul 24, 2015 at 1:47 PM, Ming Lin [off-list ref] wrote:

And I want to learn how the btree node insert/delete/update happens on
disk. These maybe too detail. I'm going to write a small tool to dump
the file system. Then I could understand better the on disk btree
format.

Here is my simple tool to dump parts of the on-disk format.
http://www.minggr.net/cgit/cgit.cgi/bcache-tools/commit/?id=deb258e2

It's not in good shape, but simple enough to learn the on-disk format.