From 8696a5d11b6613e4b205e124599d7d1d9df3f4fc Mon Sep 17 00:00:00 2001
From: David Anderson <dvander@google.com>
Date: Wed, 10 Jun 2020 23:50:02 -0700
Subject: [PATCH] remount: Do not allow remounting during checkpoints.

Bug: 157540389
Test: manual test
Change-Id: I5931a583e48ddac05f319629ae2f7f5f0f6cf032
---
 fs_mgr/Android.bp         |  3 +++
 fs_mgr/fs_mgr_remount.cpp | 38 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/fs_mgr/Android.bp b/fs_mgr/Android.bp
index f5daf9174..cd6459989 100644
--- a/fs_mgr/Android.bp
+++ b/fs_mgr/Android.bp
@@ -162,10 +162,13 @@ cc_binary {
     defaults: ["fs_mgr_defaults"],
     static_libs: [
         "libavb_user",
+        "libutils",
+        "libvold_binder",
     ],
     shared_libs: [
         "libbootloader_message",
         "libbase",
+        "libbinder",
         "libcutils",
         "libcrypto",
         "libext4_utils",
diff --git a/fs_mgr/fs_mgr_remount.cpp b/fs_mgr/fs_mgr_remount.cpp
index 052efa765..b8b074e0f 100644
--- a/fs_mgr/fs_mgr_remount.cpp
+++ b/fs_mgr/fs_mgr_remount.cpp
@@ -24,6 +24,7 @@
 #include <unistd.h>
 
 #include <string>
+#include <thread>
 #include <utility>
 #include <vector>
 
@@ -31,6 +32,8 @@
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/strings.h>
+#include <android/os/IVold.h>
+#include <binder/IServiceManager.h>
 #include <bootloader_message/bootloader_message.h>
 #include <cutils/android_reboot.h>
 #include <fec/io.h>
@@ -103,8 +106,23 @@ void MyLogger(android::base::LogId id, android::base::LogSeverity severity, cons
     ::exit(0);  // SUCCESS
 }
 
+static android::sp<android::os::IVold> GetVold() {
+    while (true) {
+        if (auto sm = android::defaultServiceManager()) {
+            if (auto binder = sm->getService(android::String16("vold"))) {
+                if (auto vold = android::interface_cast<android::os::IVold>(binder)) {
+                    return vold;
+                }
+            }
+        }
+        std::this_thread::sleep_for(2s);
+    }
+}
+
 }  // namespace
 
+using namespace std::chrono_literals;
+
 enum RemountStatus {
     REMOUNT_SUCCESS = 0,
     NOT_USERDEBUG,
@@ -117,7 +135,9 @@ enum RemountStatus {
     BAD_OVERLAY,
     NO_MOUNTS,
     REMOUNT_FAILED,
-    MUST_REBOOT
+    MUST_REBOOT,
+    BINDER_ERROR,
+    CHECKPOINTING
 };
 
 static int do_remount(int argc, char* argv[]) {
@@ -194,6 +214,22 @@ static int do_remount(int argc, char* argv[]) {
         return NO_FSTAB;
     }
 
+    if (android::base::GetBoolProperty("ro.virtual_ab.enabled", false) &&
+        !android::base::GetBoolProperty("ro.virtual_ab.retrofit", false)) {
+        // Virtual A/B devices can use /data as backing storage; make sure we're
+        // not checkpointing.
+        auto vold = GetVold();
+        bool checkpointing = false;
+        if (!vold->isCheckpointing(&checkpointing).isOk()) {
+            LOG(ERROR) << "Could not determine checkpointing status.";
+            return BINDER_ERROR;
+        }
+        if (checkpointing) {
+            LOG(ERROR) << "Cannot use remount when a checkpoint is in progress.";
+            return CHECKPOINTING;
+        }
+    }
+
     // Generate the list of supported overlayfs mount points.
     auto overlayfs_candidates = fs_mgr_overlayfs_candidate_list(fstab);