composefs-backend: Deleting deployments

Add a command to delete a composefs native deployment

Deleting a deployment would mean, deleting the EROFS image, the
bootloader entries for that deployment and deleting any objects in the
composefs repository that are only referenced by said deployment.

Also refactor some functions and add error contexts in some places

Signed-off-by: Pragyan Poudyal <[email protected]>

composefs-backend: Deleting staged deployment

Signed-off-by: Pragyan Poudyal <[email protected]>

Author: Johan-Liebert1

crates/lib/src/bootc_composefs/boot.rs

@@ -64,7 +64,7 @@ const SYSTEMD_LOADER_CONF_PATH: &str = "loader/loader.conf";
 /// directory specified by the BLS spec. We do this because we want systemd-boot to only look at
 /// our config files and not show the actual UKIs in the bootloader menu
 /// This is relative to the ESP
-const SYSTEMD_UKI_DIR: &str = "EFI/Linux/bootc";
+pub(crate) const SYSTEMD_UKI_DIR: &str = "EFI/Linux/bootc";
 
 pub(crate) enum BootSetupType<'a> {
     /// For initial setup, i.e. install to-disk
@@ -211,9 +211,9 @@ fn compute_boot_digest(
 /// Given the SHA256 sum of current VMlinuz + Initrd combo, find boot entry with the same SHA256Sum
 ///
 /// # Returns
-/// Returns the verity of the deployment that has a boot digest same as the one passed in
+/// Returns the verity of all deployments that have a boot digest same as the one passed in
 #[context("Checking boot entry duplicates")]
-fn find_vmlinuz_initrd_duplicates(digest: &str) -> Result<Option<String>> {
+pub(crate) fn find_vmlinuz_initrd_duplicates(digest: &str) -> Result<Option<Vec<String>>> {
     let deployments = Dir::open_ambient_dir(STATE_DIR_ABS, ambient_authority());
 
     let deployments = match deployments {
@@ -223,7 +223,7 @@ fn find_vmlinuz_initrd_duplicates(digest: &str) -> Result<Option<String>> {
         Err(e) => anyhow::bail!(e),
     };
 
-    let mut symlink_to: Option<String> = None;
+    let mut symlink_to: Option<Vec<String>> = None;
 
     for depl in deployments.entries()? {
         let depl = depl?;
@@ -243,8 +243,10 @@ fn find_vmlinuz_initrd_duplicates(digest: &str) -> Result<Option<String>> {
         match ini.get::<String>(ORIGIN_KEY_BOOT, ORIGIN_KEY_BOOT_DIGEST) {
             Some(hash) => {
                 if hash == digest {
-                    symlink_to = Some(depl_file_name.to_string());
-                    break;
+                    match symlink_to {
+                        Some(ref mut prev) => prev.push(depl_file_name.to_string()),
+                        None => symlink_to = Some(vec![depl_file_name.to_string()]),
+                    }
                 }
             }
 
@@ -479,6 +481,8 @@ pub(crate) fn setup_composefs_bls_boot(
 
             match find_vmlinuz_initrd_duplicates(&boot_digest)? {
                 Some(symlink_to) => {
+                    let symlink_to = &symlink_to[0];
+
                     match bls_config.cfg_type {
                         BLSConfigType::NonEFI {
                             ref mut linux,