Wikidpad. You need a part of disk where both Windows and Linux can write.

When you create a new wiki, there is an option "only use ascii in file names", I am not sure what it means, but it would be probably a good idea to use it, to prevent possible problems with different encoding on different systems.

If you choose an option "Sqlite compact", all wiki pages will be in one file; the default option is one file per page. It depends on what you want. I prefer less files. But with the one file per page, you could use external tools to search in the pages; as a Linux user you will probably want this.