From 01437a44a23478418c0018238c9f73bae59fe128 Mon Sep 17 00:00:00 2001
From: Danny Canter <danny_canter@apple.com>
Date: Wed, 12 Nov 2025 09:39:46 -0800
Subject: [PATCH] Vminitd: Sync(2) on shutdown (#400)

---
 Sources/Containerization/LinuxContainer.swift      | 2 ++
 Sources/Containerization/VirtualMachineAgent.swift | 5 +++++
 vminitd/Sources/vminitd/Application.swift          | 6 +++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Sources/Containerization/LinuxContainer.swift b/Sources/Containerization/LinuxContainer.swift
index 2ff55169..5519b2bf 100644
--- a/Sources/Containerization/LinuxContainer.swift
+++ b/Sources/Containerization/LinuxContainer.swift
@@ -563,6 +563,8 @@ extension LinuxContainer {
                         path: Self.guestRootfsPath(self.id),
                         flags: 0
                     )
+
+                    try await agent.sync()
                 }
 
                 // Lets free up the init procs resources, as this includes the open agent conn.
diff --git a/Sources/Containerization/VirtualMachineAgent.swift b/Sources/Containerization/VirtualMachineAgent.swift
index 024f1a52..80c6da48 100644
--- a/Sources/Containerization/VirtualMachineAgent.swift
+++ b/Sources/Containerization/VirtualMachineAgent.swift
@@ -42,6 +42,7 @@ public protocol VirtualMachineAgent: Sendable {
     func mkdir(path: String, all: Bool, perms: UInt32) async throws
     @discardableResult
     func kill(pid: Int32, signal: Int32) async throws -> Int32
+    func sync() async throws
     func writeFile(path: String, data: Data, flags: WriteFileFlags, mode: UInt32) async throws
 
     // Process lifecycle
@@ -89,4 +90,8 @@ extension VirtualMachineAgent {
     public func containerStatistics(containerIDs: [String]) async throws -> [ContainerStatistics] {
         throw ContainerizationError(.unsupported, message: "containerStatistics")
     }
+
+    public func sync() async throws {
+        throw ContainerizationError(.unsupported, message: "sync")
+    }
 }
diff --git a/vminitd/Sources/vminitd/Application.swift b/vminitd/Sources/vminitd/Application.swift
index af04ef2c..fd93fde4 100644
--- a/vminitd/Sources/vminitd/Application.swift
+++ b/vminitd/Sources/vminitd/Application.swift
@@ -114,7 +114,11 @@ struct Application {
         do {
             log.info("serving vminitd API")
             try await server.serve(port: vsockPort)
-            log.info("vminitd API returned")
+            log.info("vminitd API returned, syncing filesystems")
+
+            #if os(Linux)
+            Musl.sync()
+            #endif
         } catch {
             log.error("vminitd boot error \(error)")
             exit(1)