Open Source Summit North America 2018

User file systems offer numerous advantages over their in- kernel implementations, such as ease of development and better system reliability. However, they incur heavy performance penalty due to user-kernel round-trip communication. We, however, observe that existing user file system frameworks, such as FUSE are highly general: they implement a minimal interposition layer in the kernel that simply forward all low-level requests to the user-space.

This work introduces ExtFUSE, a framework for developing extensible user file systems that allows applications to also register “thin” eBPF request handlers in the kernel to meet their specific needs, while retaining the complex functionality in user-space. Our evaluation with multiple FUSE file systems, such as Android sdcard and Gluster shows that ExtFUSE can substantially improve their performance with less than few hundreds of lines of eBPF code on average.