restic/vendor/bazil.org/fuse/doc/mount-sequence.md
2017-07-23 14:25:38 +02:00

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# The mount sequence
FUSE mounting is a little bit tricky. There's a userspace helper tool
that performs the handshake with the kernel, and then steps out of the
way. This helper behaves differently on different platforms, forcing a
more complex API on us.
## Successful runs
On Linux, the mount is immediate and file system accesses wait until
the requests are served.
![Diagram of Linux FUSE mount sequence](mount-linux.seq.png)
On OS X, the mount becomes visible only after `InitRequest` (and maybe
more) have been served.
![Diagram of OSXFUSE mount sequence](mount-osx.seq.png)
## Errors
Let's see what happens if `InitRequest` gets an error response. On
Linux, the mountpoint is there but all operations will fail:
![Diagram of Linux error handling](mount-linux-error-init.seq.png)
On OS X, the mount never happened:
![Diagram of OS X error handling](mount-osx-error-init.seq.png)