Trait BlockTools

Source

pub trait BlockTools: Send + Sync {
    // Required methods
    fn attach_loop(
        &self,
        backing: &Path,
        read_only: bool,
    ) -> Result<String, SnapshotError>;
    fn detach_loop(&self, device: &str) -> Result<(), SnapshotError>;
    fn device_sectors(&self, device: &str) -> Result<u64, SnapshotError>;
}

Expand description

Loop-device and block-size operations, supplied by the composer.

Every method is synchronous and may block on a subprocess or an ioctl; CowManager calls them from spawn_blocking. Implementations are shared across sandboxes and tasks, hence Send + Sync.

Required Methods§

Source

fn attach_loop( &self, backing: &Path, read_only: bool, ) -> Result<String, SnapshotError>

Attach backing as a loop device and return the device path (/dev/loopN). Must hold up against concurrent callers in other processes: either allocate and attach in one atomic step (LOOP_CONFIGURE, util-linux losetup -f --show) or, when the tool cannot, query a free device, attach to it, and retry when another process claimed it in between (what BusyboxBlockTools does).

Source