efi: during installation using blockdev to find esp partition

instead of `partlabel`

Copy Dusty's comment from https://github.com/coreos/bootupd/pull/932/files#r2112567301:

During `bootc install to-disk` the esp device is not mounted but
we can call `get_esp_device()` and it will find the device via
the `/dev/disk/by-partlabel/` symlink. When running `cosa build` and
building a disk image using `OSBuild` the EFI partitions is mounted
but no udev `/dev/disk/by-partlabel/` symlinks exist because it's
just a chroot and not a full linux environment. In that case
fallback to using `blockdev` to find the partition.

Even better, get rid of `self.get_esp_device()` altogether and just
use `blockdev`

Author: HuijingHei

src/bootupd.rs

@@ -328,8 +328,21 @@ pub(crate) fn status() -> Result<Status> {
     // Process the remaining components not installed
     log::trace!("Remaining known components: {}", known_components.len());
     for (name, _) in known_components {
-        // Only run `query_adopt_state()` is enough
-        // When do adopt and update for each component, will check more
+        // To determine if not-installed components can be adopted:
+        //
+        // `query_adopt_state()` checks for existing installation state,
+        // such as a `version` in `/sysroot/.coreos-aleph-version.json`,
+        // or the presence of `/ostree/deploy`.
+        //
+        // `component.query_adopt()` performs additional checks,
+        // including hardware/device requirements.
+        // For example, it will skip BIOS adoption if the system is booted via EFI
+        // and lacks a BIOS_BOOT partition.
+        //
+        // Once a component is determined to be adoptable, it is added to the
+        // adoptable list, and adoption proceeds automatically.
+        //
+        // Therefore, calling `query_adopt_state()` alone is sufficient.
         if let Some(adopt_ver) = crate::component::query_adopt_state()? {
             ret.adoptable.insert(name.to_string(), adopt_ver);
         } else {

src/efi.rs

@@ -61,21 +61,6 @@ pub(crate) struct Efi {
 }
 
 impl Efi {
-    // Get esp device via EFI partlabel
-    fn get_esp_device(&self) -> Option<PathBuf> {
-        let esp_devices = [COREOS_ESP_PART_LABEL, ANACONDA_ESP_PART_LABEL]
-            .into_iter()
-            .map(|p| Path::new("/dev/disk/by-partlabel/").join(p));
-        let mut esp_device = None;
-        for path in esp_devices {
-            if path.exists() {
-                esp_device = Some(path);
-                break;
-            }
-        }
-        return esp_device;
-    }
-
     // Get mounted point for esp
     pub(crate) fn get_mounted_esp(&self, root: &Path) -> Result<Option<PathBuf>> {
         // First check all potential mount points without holding the borrow
@@ -321,11 +306,13 @@ impl Component for Efi {
         log::debug!("Found metadata {}", meta.version);
         let srcdir_name = component_updatedirname(self);
         let ft = crate::filetree::FileTree::new_from_dir(&src_root.sub_dir(&srcdir_name)?)?;
-        // get esp device via /dev/disk/by-partlabel
-        let esp_device = self
-            .get_esp_device()
+
+        // Using `blockdev` to find the partition instead of partlabel because
+        // we know the target install toplevel device already.
+        let esp_device = blockdev::get_esp_partition(device)?
             .ok_or_else(|| anyhow::anyhow!("Failed to find ESP device"))?;
-        let destpath = &self.ensure_mounted_esp(Path::new(dest_root), &esp_device)?;
+
+        let destpath = &self.ensure_mounted_esp(Path::new(dest_root), Path::new(&esp_device))?;
 
         let destd = &openat::Dir::open(destpath)
             .with_context(|| format!("opening dest dir {}", destpath.display()))?;