libsnapshot: No transition of snapuserd during second stage init

When there is a transition of daemon from selinux stage, we observe
intermittent hangs during OTA. This is a workaround wherein
we don't do the transition and allow the daemon to continue which
was spawned during selinux stage.

Bug: 179331261
Test: Incremental OTA, full OTA on pixel
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: I622a0ed8afcd404bac4919b1de00728de2c12eaf

fs_mgr/libsnapshot/snapshot.cpp

@@ -1234,6 +1234,25 @@ bool SnapshotManager::OnSnapshotMergeComplete(LockedFile* lock, const std::strin
     return true;
 }
 
+static bool DeleteDmDevice(const std::string& name, const std::chrono::milliseconds& timeout_ms) {
+    auto start = std::chrono::steady_clock::now();
+    auto& dm = DeviceMapper::Instance();
+    while (true) {
+        if (dm.DeleteDeviceIfExists(name)) {
+            break;
+        }
+        auto now = std::chrono::steady_clock::now();
+        auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(now - start);
+        if (elapsed >= timeout_ms) {
+            LOG(ERROR) << "DeleteDevice timeout: " << name;
+            return false;
+        }
+        std::this_thread::sleep_for(250ms);
+    }
+
+    return true;
+}
+
 bool SnapshotManager::CollapseSnapshotDevice(const std::string& name,
                                              const SnapshotStatus& status) {
     auto& dm = DeviceMapper::Instance();
@@ -1292,10 +1311,11 @@ bool SnapshotManager::CollapseSnapshotDevice(const std::string& name,
     if (!dm.DeleteDeviceIfExists(base_name)) {
         LOG(ERROR) << "Unable to delete base device for snapshot: " << base_name;
     }
-    auto source_name = GetSourceDeviceName(name);
-    if (!dm.DeleteDeviceIfExists(source_name)) {
-        LOG(ERROR) << "Unable to delete source device for snapshot: " << source_name;
+
+    if (!DeleteDmDevice(GetSourceDeviceName(name), 4000ms)) {
+        LOG(ERROR) << "Unable to delete source device for snapshot: " << GetSourceDeviceName(name);
     }
+
     return true;
 }
 
@@ -1387,9 +1407,6 @@ bool SnapshotManager::PerformInitTransition(InitTransition transition,
         }
 
         auto misc_name = user_cow_name;
-        if (transition == InitTransition::SELINUX_DETACH) {
-            misc_name += "-selinux";
-        }
 
         DmTable table;
         table.Emplace<DmTargetUser>(0, target.spec.length, misc_name);
@@ -2122,15 +2139,12 @@ bool SnapshotManager::UnmapCowDevices(LockedFile* lock, const std::string& name)
     CHECK(lock);
     if (!EnsureImageManager()) return false;
 
-    auto& dm = DeviceMapper::Instance();
-
     if (UpdateUsesCompression(lock) && !UnmapDmUserDevice(name)) {
         return false;
     }
 
-    auto cow_name = GetCowName(name);
-    if (!dm.DeleteDeviceIfExists(cow_name)) {
-        LOG(ERROR) << "Cannot unmap " << cow_name;
+    if (!DeleteDmDevice(GetCowName(name), 4000ms)) {
+        LOG(ERROR) << "Cannot unmap: " << GetCowName(name);
         return false;
     }
 
@@ -2155,12 +2169,11 @@ bool SnapshotManager::UnmapDmUserDevice(const std::string& snapshot_name) {
         return false;
     }
 
-    if (!EnsureSnapuserdConnected()) {
-        return false;
-    }
-    if (!snapuserd_client_->WaitForDeviceDelete(dm_user_name)) {
-        LOG(ERROR) << "Failed to wait for " << dm_user_name << " control device to delete";
-        return false;
+    if (EnsureSnapuserdConnected()) {
+        if (!snapuserd_client_->WaitForDeviceDelete(dm_user_name)) {
+            LOG(ERROR) << "Failed to wait for " << dm_user_name << " control device to delete";
+            return false;
+        }
     }
 
     // Ensure the control device is gone so we don't run into ABA problems.

fs_mgr/libsnapshot/snapuserd.cpp

@@ -534,7 +534,7 @@ bool Snapuserd::ReadMetadata() {
     bool prev_copy_op = false;
     bool metadata_found = false;
 
-    SNAP_LOG(DEBUG) << "ReadMetadata Start...";
+    SNAP_LOG(DEBUG) << "ReadMetadata: Parsing cow file";
 
     if (!reader_->Parse(cow_fd_)) {
         SNAP_LOG(ERROR) << "Failed to parse";

fs_mgr/libsnapshot/snapuserd.h

@@ -70,6 +70,11 @@ class Snapuserd final {
     const std::string& GetMiscName() { return misc_name_; }
     uint64_t GetNumSectors() { return num_sectors_; }
     bool IsAttached() const { return ctrl_fd_ >= 0; }
+    void CloseFds() {
+        ctrl_fd_ = {};
+        cow_fd_ = {};
+        backing_store_fd_ = {};
+    }
 
   private:
     bool DmuserReadRequest();

fs_mgr/libsnapshot/snapuserd_server.cpp

@@ -210,6 +210,8 @@ void SnapuserdServer::RunThread(std::shared_ptr<DmUserHandler> handler) {
         }
     }
 
+    handler->snapuserd()->CloseFds();
+
     auto misc_name = handler->misc_name();
     LOG(INFO) << "Handler thread about to exit: " << misc_name;
 

init/init.cpp

@@ -723,37 +723,6 @@ void SendLoadPersistentPropertiesMessage() {
     }
 }
 
-static Result<void> TransitionSnapuserdAction(const BuiltinArguments&) {
-    if (!SnapshotManager::IsSnapshotManagerNeeded() ||
-        !android::base::GetBoolProperty(android::snapshot::kVirtualAbCompressionProp, false)) {
-        return {};
-    }
-
-    auto sm = SnapshotManager::New();
-    if (!sm) {
-        LOG(FATAL) << "Failed to create SnapshotManager, will not transition snapuserd";
-        return {};
-    }
-
-    ServiceList& service_list = ServiceList::GetInstance();
-    auto svc = service_list.FindService("snapuserd");
-    if (!svc) {
-        LOG(FATAL) << "Failed to find snapuserd service, aborting transition";
-        return {};
-    }
-    svc->Start();
-    svc->SetShutdownCritical();
-
-    if (!sm->PerformSecondStageInitTransition()) {
-        LOG(FATAL) << "Failed to transition snapuserd to second-stage";
-    }
-
-    if (auto pid = GetSnapuserdFirstStagePid()) {
-        KillFirstStageSnapuserd(pid.value());
-    }
-    return {};
-}
-
 int SecondStageMain(int argc, char** argv) {
     if (REBOOT_BOOTLOADER_ON_PANIC) {
         InstallRebootSignalHandlers();
@@ -900,7 +869,6 @@ int SecondStageMain(int argc, char** argv) {
 
     // Queue an action that waits for coldboot done so we know ueventd has set up all of /dev...
     am.QueueBuiltinAction(wait_for_coldboot_done_action, "wait_for_coldboot_done");
-    am.QueueBuiltinAction(TransitionSnapuserdAction, "TransitionSnapuserd");
     // ... so that we can start queuing up actions that require stuff from /dev.
     am.QueueBuiltinAction(SetMmapRndBitsAction, "SetMmapRndBits");
     Keychords keychords;