blockdev: Add find_all_roots and rename root_disk to find_single_root

This is prep for supporting multiple parent devices.

Signed-off-by: ckyrouac <ckyrouac@redhat.com>

Author: ckyrouac

crates/blockdev/src/blockdev.rs

@@ -292,7 +292,7 @@ impl Device {
     /// Returns the root device with its children (partitions) populated.
     /// If this device is already a root device, returns a clone of `self`.
     /// Fails if the device has multiple parents at any level.
-    pub fn root_disk(&self) -> Result<Device> {
+    pub fn find_single_root(&self) -> Result<Device> {
         let Some(parents) = self.list_parents()? else {
             // Already a root device; re-query to ensure children are populated
             return list_dev(Utf8Path::new(&self.path()));
@@ -316,6 +316,34 @@ impl Device {
             }
         }
     }
+
+    /// Walk the parent chain to find all root (whole disk) devices.
+    ///
+    /// Returns all root devices with their children (partitions) populated.
+    /// Unlike find_single_root, this handles devices backed by multiple
+    /// parents (e.g. RAID arrays) by following all branches of the parent tree.
+    /// If this device is already a root device, returns a single-element list.
+    pub fn find_all_roots(&self) -> Result<Vec<Device>> {
+        let Some(parents) = self.list_parents()? else {
+            // Already a root device; re-query to ensure children are populated
+            return Ok(vec![list_dev(Utf8Path::new(&self.path()))?]);
+        };
+
+        let mut roots = Vec::new();
+        let mut queue = parents;
+        while let Some(mut device) = queue.pop() {
+            match device.children.take() {
+                Some(grandparents) if !grandparents.is_empty() => {
+                    queue.extend(grandparents);
+                }
+                _ => {
+                    // Found a root; re-query to populate its actual children
+                    roots.push(list_dev(Utf8Path::new(&device.path()))?);
+                }
+            }
+        }
+        Ok(roots)
+    }
 }
 
 #[context("Listing device {dev}")]

crates/lib/src/bootc_composefs/boot.rs

@@ -545,7 +545,8 @@ pub(crate) fn setup_composefs_bls_boot(
             cmdline.add_or_modify(&param);
 
             // Locate ESP partition device
-            let root_dev = bootc_blockdev::list_dev_by_dir(&storage.physical_root)?.root_disk()?;
+            let root_dev =
+                bootc_blockdev::list_dev_by_dir(&storage.physical_root)?.find_single_root()?;
             let esp_dev = root_dev.find_partition_of_esp()?;
 
             (
@@ -1083,7 +1084,8 @@ pub(crate) fn setup_composefs_uki_boot(
             let bootloader = host.require_composefs_booted()?.bootloader.clone();
 
             // Locate ESP partition device
-            let root_dev = bootc_blockdev::list_dev_by_dir(&storage.physical_root)?.root_disk()?;
+            let root_dev =
+                bootc_blockdev::list_dev_by_dir(&storage.physical_root)?.find_single_root()?;
             let esp_dev = root_dev.find_partition_of_esp()?;
 
             (

crates/lib/src/bootloader.rs

@@ -45,7 +45,7 @@ pub(crate) fn mount_esp_part(root: &Dir, root_path: &Utf8Path, is_ostree: bool)
         root
     };
 
-    let dev = bootc_blockdev::list_dev_by_dir(physical_root)?.root_disk()?;
+    let dev = bootc_blockdev::list_dev_by_dir(physical_root)?.find_single_root()?;
     if let Some(esp_dev) = dev.find_partition_of_type(bootc_blockdev::ESP) {
         let esp_path = esp_dev.path();
         bootc_mount::mount(&esp_path, &root_path.join(&efi_path))?;

crates/lib/src/install.rs

@@ -2514,7 +2514,7 @@ pub(crate) async fn install_to_filesystem(
     // Find the real underlying backing device for the root.  This is currently just required
     // for GRUB (BIOS) and in the future zipl (I think).
     let device_info = {
-        let dev = bootc_blockdev::list_dev(Utf8Path::new(&inspect.source))?.root_disk()?;
+        let dev = bootc_blockdev::list_dev(Utf8Path::new(&inspect.source))?.find_single_root()?;
         tracing::debug!("Backing device: {}", dev.path());
         dev
     };

crates/lib/src/store/mod.rs

@@ -196,7 +196,8 @@ impl BootedStorage {
                 let composefs = Arc::new(composefs);
 
                 //TODO: this assumes a single ESP on the root device
-                let root_dev = bootc_blockdev::list_dev_by_dir(&physical_root)?.root_disk()?;
+                let root_dev =
+                    bootc_blockdev::list_dev_by_dir(&physical_root)?.find_single_root()?;
                 let esp_dev = root_dev.find_partition_of_esp()?;
                 let esp_mount = mount_esp(&esp_dev.path())?;