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(())
+    }
+}

hypha/src/ctl/cfgblk.rs

@@ -9,15 +9,21 @@ use uuid::Uuid;
 pub struct ConfigBlock<'a> {
     pub image_info: &'a ImageInfo,
     pub file: PathBuf,
+    pub dir: PathBuf,
 }
 
 impl ConfigBlock<'_> {
     pub fn new<'a>(uuid: &Uuid, image_info: &'a ImageInfo) -> Result<ConfigBlock<'a>> {
-        let mut file = std::env::temp_dir().clone();
-        file.push(format!("hypha-cfg-{}", uuid));
-        fs::create_dir_all(&file)?;
+        let mut dir = std::env::temp_dir().clone();
+        dir.push(format!("hypha-cfg-{}", uuid));
+        fs::create_dir_all(&dir)?;
+        let mut file = dir.clone();
         file.push("config.squashfs");
-        Ok(ConfigBlock { image_info, file })
+        Ok(ConfigBlock {
+            image_info,
+            file,
+            dir,
+        })
     }
 
     pub fn build(&self) -> Result<()> {

hypha/src/ctl/mod.rs

@@ -1,10 +1,12 @@
-mod cfgblk;
+pub mod cfgblk;
 
+use crate::autoloop::AutoLoop;
 use crate::ctl::cfgblk::ConfigBlock;
-use crate::error::{HyphaError, Result};
+use crate::error::Result;
 use crate::image::cache::ImageCache;
 use crate::image::name::ImageName;
 use crate::image::{ImageCompiler, ImageInfo};
+use loopdev::LoopControl;
 use std::fs;
 use std::path::PathBuf;
 use uuid::Uuid;
@@ -12,6 +14,7 @@ use xenclient::{DomainConfig, DomainDisk, XenClient};
 
 pub struct Controller {
     image_cache: ImageCache,
+    autoloop: AutoLoop,
     image: String,
     client: XenClient,
     kernel_path: String,
@@ -39,6 +42,7 @@ impl Controller {
         let image_cache = ImageCache::new(&image_cache_path)?;
         Ok(Controller {
             image_cache,
+            autoloop: AutoLoop::new(LoopControl::open()?),
             image,
             client,
             kernel_path,
@@ -60,14 +64,13 @@ impl Controller {
         let image_info = self.compile()?;
         let cfgblk = ConfigBlock::new(&uuid, &image_info)?;
         cfgblk.build()?;
-        let cfgblk_squashfs_path = cfgblk
-            .file
-            .to_str()
-            .ok_or_else(|| HyphaError::new("failed to convert config squashfs path to string"))?;
-        let image_squashfs_path = image_info
-            .image_squashfs
-            .to_str()
-            .ok_or_else(|| HyphaError::new("failed to convert image squashfs path to string"))?;
+
+        let image_squashfs_path = image_info.image_squashfs.clone();
+        let cfgblk_squashfs_path = cfgblk.file.clone();
+
+        let image_squashfs_loop = self.autoloop.loopify(&image_squashfs_path)?;
+        let cfgblk_squashfs_loop = self.autoloop.loopify(&cfgblk_squashfs_path)?;
+
         let config = DomainConfig {
             backend_domid: 0,
             name: &name,
@@ -79,17 +82,24 @@ impl Controller {
             disks: vec![
                 DomainDisk {
                     vdev: "xvda",
-                    pdev: image_squashfs_path,
+                    block: &image_squashfs_loop,
                     writable: false,
                 },
                 DomainDisk {
                     vdev: "xvdb",
-                    pdev: cfgblk_squashfs_path,
+                    block: &cfgblk_squashfs_loop,
                     writable: false,
                 },
             ],
         };
-        let domid = self.client.create(&config)?;
-        Ok(domid)
+        match self.client.create(&config) {
+            Ok(domid) => Ok(domid),
+            Err(error) => {
+                let _ = self.autoloop.unloop(&image_squashfs_loop.path);
+                let _ = self.autoloop.unloop(&cfgblk_squashfs_loop.path);
+                let _ = fs::remove_dir(&cfgblk.dir);
+                Err(error.into())
+            }
+        }
     }
 }

hypha/src/lib.rs

@@ -1,3 +1,4 @@
+pub mod autoloop;
 pub mod container;
 pub mod ctl;
 pub mod error;