feat(cli): Add state save, restore and clear commands.

src/bin/nvmet/main.rs

@@ -1,5 +1,6 @@
 mod namespace;
 mod port;
+mod state;
 mod subsystem;
 
 use anyhow::Result;
@@ -31,6 +32,11 @@ enum CliCommands {
         #[command(subcommand)]
         namespace_command: namespace::CliNamespaceCommands,
     },
+    /// NVMe-oF Target Subsystem State Management Commands
+    State {
+        #[command(subcommand)]
+        state_command: state::CliStateCommands,
+    },
 }
 
 fn main() -> Result<()> {
@@ -44,5 +50,6 @@ fn main() -> Result<()> {
         CliCommands::Namespace { namespace_command } => {
             namespace::CliNamespaceCommands::parse(namespace_command)
         }
+        CliCommands::State { state_command } => state::CliStateCommands::parse(state_command),
     }
 }

src/bin/nvmet/state.rs

@@ -0,0 +1,69 @@
+use anyhow::{Context, Result};
+use clap::Subcommand;
+use nvmetcfg::{kernel::KernelConfig, state::State};
+use std::{fs::File, path::PathBuf};
+
+#[derive(Subcommand)]
+pub enum CliStateCommands {
+    /// Save the NVMe-oF Target configuration to file.
+    Save {
+        /// File to save the state to.
+        file: PathBuf,
+    },
+    /// Restore the NVMe-oF Target configuration from previously saved configuration.
+    Restore {
+        /// File from which to load the state.
+        file: PathBuf,
+    },
+    /// Remove all configuration of the NVMe-oF Target.
+    Clear,
+}
+
+impl CliStateCommands {
+    pub(super) fn parse(command: Self) -> Result<()> {
+        match command {
+            CliStateCommands::Save { file } => {
+                let f = File::create(file).context("Failed to open state file for writing")?;
+                let state =
+                    KernelConfig::gather_state().context("Failed to gather state for writing")?;
+                serde_yaml::to_writer(f, &state)
+                    .context("Failed to write current state to file")?;
+                println!("Sucessfully written current state to file.");
+                Ok(())
+            }
+            CliStateCommands::Restore { file } => {
+                let f = File::open(file).context("Failed to open state file for reading")?;
+                let desired: State =
+                    serde_yaml::from_reader(f).context("Failed to read from state file")?;
+                let current =
+                    KernelConfig::gather_state().context("Failed to gather state for writing")?;
+                let delta = current.get_deltas(&desired);
+                let delta_len = delta.len();
+                if delta_len == 0 {
+                    println!(
+                        "No changes made: System state has no changes compared to saved state."
+                    );
+                } else {
+                    KernelConfig::apply_delta(delta)
+                        .context("Failed to apply state delta between current and saved state")?;
+                    println!("Sucessfully applied saved state: {delta_len} state changes.");
+                }
+                Ok(())
+            }
+            CliStateCommands::Clear => {
+                let current =
+                    KernelConfig::gather_state().context("Failed to gather state for writing")?;
+                let delta = current.get_deltas(&State::default());
+                let delta_len = delta.len();
+                if delta_len == 0 {
+                    println!("No changes made: System state has no configuration.");
+                } else {
+                    KernelConfig::apply_delta(delta)
+                        .context("Failed to apply state delta between current and saved state")?;
+                    println!("Sucessfully cleared configuration: {delta_len} state changes.");
+                }
+                Ok(())
+            }
+        }
+    }
+}