composefs: Walk parent devices to find ESP partition

The composefs BLS and UKI boot setup paths called
find_partition_of_esp() directly on the device, which fails when
the root filesystem is on an LVM logical volume (the ESP is on the
parent disk, not the LV).  The store module had the same issue via
require_single_root() + find_partition_of_esp().

Switch all call sites to find_colocated_esps() which walks up to
the physical disk(s) via find_all_roots() before searching for the
ESP, consistent with what install_systemd_boot and mount_esp_part
already do.

Assisted-by: Claude Code (Opus 4)
Signed-off-by: ckyrouac <ckyrouac@redhat.com>

Author: ckyrouac

crates/lib/src/bootc_composefs/boot.rs

@@ -529,8 +529,18 @@ pub(crate) fn setup_composefs_bls_boot(
                 ComposefsCmdline::build(&id_hex, state.composefs_options.allow_missing_verity);
             cmdline_options.extend(&Cmdline::from(&composefs_cmdline.to_string()));
 
-            // Locate ESP partition device
-            let esp_part = root_setup.device_info.find_partition_of_esp()?;
+            // Locate ESP partition device by walking up to the root disk(s)
+            let esp_part = root_setup
+                .device_info
+                .find_colocated_esps()?
+                .and_then(|mut v| {
+                    if v.is_empty() {
+                        None
+                    } else {
+                        Some(v.remove(0))
+                    }
+                })
+                .ok_or_else(|| anyhow::anyhow!("ESP partition not found"))?;
 
             (
                 root_setup.physical_root_path.clone(),
@@ -567,10 +577,18 @@ pub(crate) fn setup_composefs_bls_boot(
                 .context("Failed to create 'composefs=' parameter")?;
             cmdline.add_or_modify(&param);
 
-            // Locate ESP partition device
-            let root_dev =
-                bootc_blockdev::list_dev_by_dir(&storage.physical_root)?.require_single_root()?;
-            let esp_dev = root_dev.find_partition_of_esp()?;
+            // Locate ESP partition device by walking up to the root disk(s)
+            let root_dev = bootc_blockdev::list_dev_by_dir(&storage.physical_root)?;
+            let esp_dev = root_dev
+                .find_colocated_esps()?
+                .and_then(|mut v| {
+                    if v.is_empty() {
+                        None
+                    } else {
+                        Some(v.remove(0))
+                    }
+                })
+                .ok_or_else(|| anyhow::anyhow!("ESP partition not found"))?;
 
             (
                 Utf8PathBuf::from("/sysroot"),
@@ -1103,7 +1121,18 @@ pub(crate) fn setup_composefs_uki_boot(
         BootSetupType::Setup((root_setup, state, postfetch, ..)) => {
             state.require_no_kargs_for_uki()?;
 
-            let esp_part = root_setup.device_info.find_partition_of_esp()?;
+            // Locate ESP partition device by walking up to the root disk(s)
+            let esp_part = root_setup
+                .device_info
+                .find_colocated_esps()?
+                .and_then(|mut v| {
+                    if v.is_empty() {
+                        None
+                    } else {
+                        Some(v.remove(0))
+                    }
+                })
+                .ok_or_else(|| anyhow::anyhow!("ESP partition not found"))?;
 
             (
                 root_setup.physical_root_path.clone(),
@@ -1118,10 +1147,18 @@ pub(crate) fn setup_composefs_uki_boot(
             let sysroot = Utf8PathBuf::from("/sysroot"); // Still needed for root_path
             let bootloader = host.require_composefs_booted()?.bootloader.clone();
 
-            // Locate ESP partition device
-            let root_dev =
-                bootc_blockdev::list_dev_by_dir(&storage.physical_root)?.require_single_root()?;
-            let esp_dev = root_dev.find_partition_of_esp()?;
+            // Locate ESP partition device by walking up to the root disk(s)
+            let root_dev = bootc_blockdev::list_dev_by_dir(&storage.physical_root)?;
+            let esp_dev = root_dev
+                .find_colocated_esps()?
+                .and_then(|mut v| {
+                    if v.is_empty() {
+                        None
+                    } else {
+                        Some(v.remove(0))
+                    }
+                })
+                .ok_or_else(|| anyhow::anyhow!("ESP partition not found"))?;
 
             (
                 sysroot,

crates/lib/src/store/mod.rs

@@ -198,10 +198,18 @@ 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)?.require_single_root()?;
-                let esp_dev = root_dev.find_partition_of_esp()?;
+                // Locate ESP by walking up to the root disk(s)
+                let root_dev = bootc_blockdev::list_dev_by_dir(&physical_root)?;
+                let esp_dev = root_dev
+                    .find_colocated_esps()?
+                    .and_then(|mut v| {
+                        if v.is_empty() {
+                            None
+                        } else {
+                            Some(v.remove(0))
+                        }
+                    })
+                    .ok_or_else(|| anyhow::anyhow!("ESP partition not found"))?;
                 let esp_mount = mount_esp(&esp_dev.path())?;
 
                 let boot_dir = match get_bootloader()? {