Add some comments in the zpool setup code wrt. adding/removing

disks from zpools

rust/program/zpool-setup/src/main.rs

@@ -145,6 +145,7 @@ struct ZpoolStatus {
 #[derive(Deserialize)]
 struct ZpoolStatusPool {
     state: Option<ZpoolState>,
+    vdevs: HashMap<String, ZpoolStatusVdev>,
 }
 
 #[derive(Clone, Copy, Deserialize, PartialEq)]
@@ -153,6 +154,29 @@ enum ZpoolState {
     Online,
 }
 
+#[derive(Deserialize)]
+#[serde(tag = "vdev_type")]
+enum ZpoolStatusVdev {
+    #[serde(rename = "root")]
+    Root {
+        name: String,
+        state: ZpoolState,
+        vdevs: HashMap<String, ZpoolStatusVdev>,
+    },
+    #[serde(rename = "disk")]
+    Disk {
+        name: String,
+        state: ZpoolState,
+        path: PathBuf,
+    },
+    #[serde(rename = "mirror")]
+    Mirror {
+        name: String,
+        state: ZpoolState,
+        vdevs: HashMap<String, ZpoolStatusVdev>,
+    }
+}
+
 fn setup_zpool(p: SetupZpool) -> anyhow::Result<()> {
     let disk_mapping_file = common::env::read_path_env("DISK_MAPPING_FILE")?;
     let disk_mapping = common::fs::read_to_string(&disk_mapping_file)?;
@@ -185,6 +209,13 @@ fn setup_zpool(p: SetupZpool) -> anyhow::Result<()> {
         return Err(anyhow::format_err!("Zpool {} is not online", p.pool_name));
     }
     
+    // TODO: Run through the existing VDevs and add any missing vdevs, and add any missing disks
+    // as needed to any vdevs. Not exactly sure how this should be coded, but I guess we can utilize
+    // the fact we cannot really change vdev type beyond turning a disk vdev into a mirror vdev,
+    // and any single disk can only belong to one vdev. So we can simply not support moving disks between vdevs.
+    // Also, to begin with, we can simply not support any vdev other than disk vdevs, as it doesn't make much
+    // sense for my use case.
+
     for vdev in p.vdevs.iter() {
         for member in vdev.members.iter() {
             let resolved = disk_mapping.resolve(member)?;
@@ -192,6 +223,8 @@ fn setup_zpool(p: SetupZpool) -> anyhow::Result<()> {
         }
     }
 
+    // TODO: zpool remove any extra vdevs.
+
     let mut existing_datasets = zfs::list_datasets(&p.pool_name)?;
     log::info!("Existing datasets found: {existing_datasets:?}");