Refactor Session to allow users to mount it themselves #301
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There are multiple ways to mount FUSE filesystems. Processes with elevated privileges (CAP_SYS_ADMIN) can use the mount(2) syscall directly or via a suitable helper. libfuse also installs a helper program, fusermount(1), which is setuid root, to perform this mounting operation. Previously, we would attempt the syscall, and then fallback to trying fusermount (if we can find it) automatically. This is a little bit too magical, so it's better to make the option explicit.
This is a minor refactor of `Session`, to make the API slightly more flexible. Splitting `Mount` into a separate object allows callers to - Create a mount without a Session object - Create a session given an existing /dev/fuse FD One use case for this is when mounting inside containers, when you need to handle the session and mounting in separate processes. Fixes cberner#300
This was referenced Oct 14, 2024
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This is a stab at addressing #300. It's made up of three steps:
impl AsFdto Session, and split the unmount-on-drop into a separate typeEach of the commits are reviewable independently. Obviously, I'm aware these are breaking changes. I understand if you're not very inclined to accept them.
Dropping libfuse is necessary here because there's no way to tell libfuse to run a session that was mounted elsewhere, or to tell it [not] to use fusermount explicitly. Splitting out
fusermountexplicitly is necessary becausefusermountdoesn't let you send it the/dev/fuseFD; it wants to open it itself. So the create-session-and-mount-separately path only works if you don't usefusermount.