composefs: Fix unqueuing rollback

We were simply checking to booted system's verity and simply setting the
corresponding boot entry as the secondary boot entry, even if rollback
was already queued. Update the code to actually consider the bootloader
entries as the source of truth, similar to what ostree does

Signed-off-by: Pragyan Poudyal <pragyanpoudyal41999@gmail.com>

Author: Johan-Liebert1

crates/lib/src/bootc_composefs/rollback.rs

@@ -114,36 +114,34 @@ fn rollback_grub_uki_entries(boot_dir: &Dir) -> Result<()> {
 /// - Grub Type1 boot entries
 /// - Systemd Typ1 boot entries
 /// - Systemd UKI (Type2) boot entries [since we use BLS entries for systemd boot]
+///
+/// Cases
+/// 1. We're actually booted into the deployment that has it's sort_key as 0
+///    a. Just swap the primary and secondary bootloader entries
+///    b. If they're already swapped (rollback was queued), re-swap them (unqueue rollback)
+///
+/// 2. We're booted into the depl with sort_key 1 (choose the rollback deployment on boot screen)
+///    a. Here we assume that rollback is queued as there's no way to differentiate between this
+///    case and Case 1-b. This is what ostree does as well
 #[context("Rolling back {bootloader} entries")]
 fn rollback_composefs_entries(boot_dir: &Dir, bootloader: Bootloader) -> Result<()> {
-    use crate::bootc_composefs::state::get_booted_bls;
-
     // Get all boot entries sorted in descending order by sort-key
     let mut all_configs = get_sorted_type1_boot_entries(&boot_dir, false)?;
 
     // TODO(Johan-Liebert): Currently assuming there are only two deployments
     assert!(all_configs.len() == 2);
 
-    // Identify which entry is the currently booted one
-    let booted_bls = get_booted_bls(&boot_dir)?;
-    let booted_verity = booted_bls.get_verity()?;
-
     // For rollback: previous gets primary sort-key, booted gets secondary sort-key
     // Use "bootc" as default os_id for rollback scenarios
     // TODO: Extract actual os_id from deployment
     let os_id = "bootc";
 
-    for cfg in &mut all_configs {
-        let cfg_verity = cfg.get_verity()?;
-
-        if cfg_verity == booted_verity {
-            // This is the currently booted deployment - it should become secondary
-            cfg.sort_key = Some(secondary_sort_key(os_id));
-        } else {
-            // This is the previous deployment - it should become primary (rollback target)
-            cfg.sort_key = Some(primary_sort_key(os_id));
-        }
-    }
+    // This is the currently booted deployment - it should become secondary
+    // OR if rollback was queued, it would become primary
+    all_configs[0].sort_key = Some(primary_sort_key(os_id));
+    // This is the previous deployment - it should become primary (rollback target)
+    // OR if rollback was queued, it would become secondary
+    all_configs[1].sort_key = Some(secondary_sort_key(os_id));
 
     // Write these
     boot_dir
@@ -156,9 +154,8 @@ fn rollback_composefs_entries(boot_dir: &Dir, bootloader: Bootloader) -> Result<
 
     // Write the BLS configs in there
     for cfg in all_configs {
-        let cfg_verity = cfg.get_verity()?;
         // After rollback: previous deployment becomes primary, booted becomes secondary
-        let priority = if cfg_verity == booted_verity {
+        let priority = if cfg.sort_key == Some(secondary_sort_key(os_id)) {
             FILENAME_PRIORITY_SECONDARY
         } else {
             FILENAME_PRIORITY_PRIMARY