hypha: implement loop device support directly to avoid devd

hypha/src/autoloop.rs

@@ -0,0 +1,36 @@
+use crate::error::{HyphaError, Result};
+use loopdev::{LoopControl, LoopDevice};
+use std::path::Path;
+use xenclient::BlockDeviceRef;
+
+pub struct AutoLoop {
+    control: LoopControl,
+}
+
+impl AutoLoop {
+    pub(crate) fn new(control: LoopControl) -> AutoLoop {
+        AutoLoop { control }
+    }
+
+    pub fn loopify(&self, file: &Path) -> Result<BlockDeviceRef> {
+        let device = self.control.next_free()?;
+        device.with().read_only(true).attach(file)?;
+        let path = device
+            .path()
+            .ok_or(HyphaError::new("unable to get loop device path"))?
+            .to_str()
+            .ok_or(HyphaError::new(
+                "unable to convert loop device path to string",
+            ))?
+            .to_string();
+        let major = device.major()?;
+        let minor = device.minor()?;
+        Ok(BlockDeviceRef { path, major, minor })
+    }
+
+    pub fn unloop(&self, device: &str) -> Result<()> {
+        let device = LoopDevice::open(device)?;
+        device.detach()?;
+        Ok(())
+    }
+}