Struct BackingId 

pub struct BackingId { /* private fields */ }

A reference to a previously opened fd intended to be used for passthrough

You can create these via ReplyOpen::open_backing() and send them via ReplyOpen::opened_passthrough().

When working with backing IDs you need to ensure that they live “long enough”. A good practice is to create them in the Filesystem::open() impl, store them in the struct of your Filesystem impl, then drop them in the Filesystem::release() impl. Dropping them immediately after sending them in the Filesystem::open() impl can lead to the kernel returning EIO when userspace attempts to access the file.

This is implemented as a safe wrapper around the backing_id field of the fuse_backing_map struct used by the ioctls involved in fd passthrough. It is created by performing a FUSE_DEV_IOC_BACKING_OPEN ioctl on an fd and has a Drop trait impl which makes a matching FUSE_DEV_IOC_BACKING_CLOSE call. It holds a weak reference on the fuse channel to allow it to make that call (if the channel hasn’t already been closed).

Implementations

impl BackingId

pub fn create_raw(fuse_dev: impl AsFd, fd: impl AsFd) -> Result<u32>

Creates a new backing file reference for the given file descriptor.

Usually, you will want to use ReplyOpen::open_backing() instead, since this method will return a raw backing_id value instead of a managed BackingId wrapper. As such you must manage the lifetime of the backing file yourself.

This method is useful if you want to open a backing file reference without access to a reply object.

pub fn into_raw(self) -> u32

Converts this backing file reference into the raw backing_id value as returned by the kernel.

This method transfers ownership of the backing file to the caller, who must invoke the FUSE_DEV_IOC_BACKING_CLOSE themselves once they wish to close the backing file.

The returned ID may subsequently be reopened using ReplyOpen::wrap_backing().

Trait Implementations

impl Debug for BackingId

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for BackingId

fn drop(&mut self)

Executes the destructor for this type.