Improve available capacity checking (#240)

* Improve available capacity checking

* Fixed expression

README.md

@@ -268,3 +268,21 @@ This invocation calls the `tart pull` implicitly (if the image is not being pres
   Tart is limited by functionality of Apple's `Virtualization.Framework`. At the moment `Virtualization.Framework`
   doesn't support nested virtualization.
 </details>
+
+<details>
+  <summary>Changing the default NAT subnet</summary>
+
+  To change the default network to `192.168.77.1`:
+
+  ```
+  sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.vmnet.plist Shared_Net_Address -string 192.168.77.1
+  ```
+
+  Note that even through a network would normally be specified as `192.168.77.0`, the [vmnet framework](https://developer.apple.com/documentation/vmnet) seems to treat this as a starting address too and refuses to pick up such network-like values.
+
+  The default subnet mask `255.255.255.0` should suffice for most use-cases, however, you can also change it to `255.255.0.0`, for example:
+
+  ```
+  sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.vmnet.plist Shared_Net_Mask -string 255.255.0.0
+  ```
+</details>

Sources/tart/Commands/Clone.swift

@@ -34,6 +34,11 @@ struct Clone: AsyncParsableCommand {
       let sourceVM = try VMStorageHelper.open(sourceName)
 
       let tmpVMDir = try VMDirectory.temporary()
+
+      // Lock the temporary VM directory to prevent it's garbage collection
+      let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+      try tmpVMDirLock.lock()
+
       try await withTaskCancellationHandler(operation: {
         let lock = try FileLock(lockURL: Config().tartHomeDir)
         try lock.lock()

Sources/tart/Commands/Create.swift

@@ -27,6 +27,11 @@ struct Create: AsyncParsableCommand {
   func run() async throws {
     do {
       let tmpVMDir = try VMDirectory.temporary()
+
+      // Lock the temporary VM directory to prevent it's garbage collection
+      let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+      try tmpVMDirLock.lock()
+
       try await withTaskCancellationHandler(operation: {
         if let fromIPSW = fromIPSW {
           if fromIPSW == "latest" {

Sources/tart/Commands/Run.swift

@@ -47,8 +47,10 @@ struct Run: AsyncParsableCommand {
   @Option(help: ArgumentHelp("""
                              Additional directory shares with an optional read-only specifier\n(e.g. --dir=\"build:~/src/build\" --dir=\"sources:~/src/sources:ro\")
                              """, discussion: """
+                                              Requires host to be macOS 13.0 (Ventura) or newer.
                                               All shared directories are automatically mounted to "/Volumes/My Shared Files" directory on macOS,
                                               while on Linux you have to do it manually: "mount -t virtiofs com.apple.virtio-fs.automount /mount/point".
+                                              For macOS guests, they must be running macOS 13.0 (Ventura) or newer.
                                               """, valueName: "name:path[:ro]"))
   var dir: [String] = []
 
@@ -126,8 +128,9 @@ struct Run: AsyncParsableCommand {
   func additionalDiskAttachments() throws -> [VZDiskImageStorageDeviceAttachment] {
     var result: [VZDiskImageStorageDeviceAttachment] = []
     let readOnlySuffix = ":ro"
+    let expandedDiskPaths = disk.map { NSString(string:$0).expandingTildeInPath }
 
-    for rawDisk in disk {
+    for rawDisk in expandedDiskPaths {
       if rawDisk.hasSuffix(readOnlySuffix) {
         result.append(try VZDiskImageStorageDeviceAttachment(
           url: URL(fileURLWithPath: String(rawDisk.prefix(rawDisk.count - readOnlySuffix.count))),
@@ -166,7 +169,7 @@ struct Run: AsyncParsableCommand {
 
       let (name, path) = (String(splits[0]), String(splits[1]))
 
-      result.append(DirectoryShare(name: name, path: URL(fileURLWithPath: path), readOnly: readOnly))
+      result.append(DirectoryShare(name: name, path: URL(fileURLWithPath: NSString(string: path).expandingTildeInPath), readOnly: readOnly))
     }
 
     return result

Sources/tart/Config.swift

@@ -3,6 +3,7 @@ import Foundation
 struct Config {
   let tartHomeDir: URL
   let tartCacheDir: URL
+  let tartTmpDir: URL
 
   init() throws {
     var tartHomeDir: URL
@@ -14,11 +15,27 @@ struct Config {
               .homeDirectoryForCurrentUser
               .appendingPathComponent(".tart", isDirectory: true)
     }
-
     self.tartHomeDir = tartHomeDir
-    tartCacheDir = tartHomeDir.appendingPathComponent("cache", isDirectory: true)
 
+    tartCacheDir = tartHomeDir.appendingPathComponent("cache", isDirectory: true)
     try FileManager.default.createDirectory(at: tartCacheDir, withIntermediateDirectories: true)
+
+    tartTmpDir = tartHomeDir.appendingPathComponent("tmp", isDirectory: true)
+    try FileManager.default.createDirectory(at: tartTmpDir, withIntermediateDirectories: true)
+  }
+
+  func gc() throws {
+    for entry in try FileManager.default.contentsOfDirectory(at: tartTmpDir,
+        includingPropertiesForKeys: [], options: []) {
+      let lock = try FileLock(lockURL: entry)
+      if try !lock.trylock() {
+        continue
+      }
+
+      try FileManager.default.removeItem(at: entry)
+
+      try lock.unlock()
+    }
   }
 
   static func jsonEncoder() -> JSONEncoder {

Sources/tart/Root.swift

@@ -36,6 +36,9 @@ struct Root: AsyncParsableCommand {
     do {
       var command = try parseAsRoot()
 
+      // Run garbage-collection before each command (shouldn't take too long)
+      try Config().gc()
+
       if var asyncCommand = command as? AsyncParsableCommand {
         try await asyncCommand.run()
       } else {

Sources/tart/VMDirectory.swift

@@ -29,7 +29,7 @@ struct VMDirectory: Prunable {
   }
 
   static func temporary() throws -> VMDirectory {
-    let tmpDir = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    let tmpDir = try Config().tartTmpDir.appendingPathComponent(UUID().uuidString)
     try FileManager.default.createDirectory(at: tmpDir, withIntermediateDirectories: false)
 
     return VMDirectory(baseURL: tmpDir)

Sources/tart/VMStorageOCI.swift

@@ -150,14 +150,20 @@ class VMStorageOCI: PrunableStorage {
     if !exists(digestName) {
       let tmpVMDir = try VMDirectory.temporary()
 
+      // Lock the temporary VM directory to prevent it's garbage collection
+      let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+      try tmpVMDirLock.lock()
+
       // Try to reclaim some cache space if we know the VM size in advance
       if let uncompressedDiskSize = manifest.uncompressedDiskSize() {
         let requiredCapacityBytes = UInt64(uncompressedDiskSize + 128 * 1024 * 1024)
 
-        let attrs = try Config().tartCacheDir.resourceValues(forKeys: [.volumeAvailableCapacityForImportantUsageKey])
-        let availableCapacityBytes = UInt64(attrs.volumeAvailableCapacityForImportantUsage!)
+        let attrs = try Config().tartCacheDir.resourceValues(forKeys: [.volumeAvailableCapacityForImportantUsageKey, .volumeAvailableCapacityKey])
+        let availableCapacityBytes = max(UInt64(attrs.volumeAvailableCapacityForImportantUsage!), UInt64(attrs.volumeAvailableCapacity!))
 
-        if availableCapacityBytes < requiredCapacityBytes {
+        // There is a suspicious that occasionally capacity is returned as zero which can't be true.
+        // Let's validate to avoid unnecessary pruning.
+        if 0 < availableCapacityBytes && availableCapacityBytes < requiredCapacityBytes {
           try Prune.pruneReclaim(reclaimBytes: requiredCapacityBytes - availableCapacityBytes)
         }
       }