diff --git a/fs_mgr/libsnapshot/cow_snapuserd_test.cpp b/fs_mgr/libsnapshot/cow_snapuserd_test.cpp
index 7eddf8c..5483fd0 100644
--- a/fs_mgr/libsnapshot/cow_snapuserd_test.cpp
+++ b/fs_mgr/libsnapshot/cow_snapuserd_test.cpp
@@ -288,20 +288,20 @@
 }
 
 void SnapuserdTest::InitCowDevices() {
-    system_blksize_ = client_->InitDmUserCow(cow_system_->path);
+    system_blksize_ = client_->InitDmUserCow(system_device_ctrl_name_, cow_system_->path,
+                                             system_a_loop_->device());
     ASSERT_NE(system_blksize_, 0);
 
-    product_blksize_ = client_->InitDmUserCow(cow_product_->path);
+    product_blksize_ = client_->InitDmUserCow(product_device_ctrl_name_, cow_product_->path,
+                                              product_a_loop_->device());
     ASSERT_NE(product_blksize_, 0);
 }
 
 void SnapuserdTest::InitDaemon() {
-    bool ok = client_->InitializeSnapuserd(cow_system_->path, system_a_loop_->device(),
-                                           GetSystemControlPath());
+    bool ok = client_->AttachDmUser(system_device_ctrl_name_);
     ASSERT_TRUE(ok);
 
-    ok = client_->InitializeSnapuserd(cow_product_->path, product_a_loop_->device(),
-                                      GetProductControlPath());
+    ok = client_->AttachDmUser(product_device_ctrl_name_);
     ASSERT_TRUE(ok);
 }
 
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd.h b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd.h
index cd8b080..aa7dc40 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd.h
@@ -61,12 +61,15 @@
 
 class Snapuserd final {
   public:
-    bool InitBackingAndControlDevice(std::string& backing_device, std::string& control_device);
-    bool InitCowDevice(std::string& cow_device);
+    Snapuserd(const std::string& misc_name, const std::string& cow_device,
+              const std::string& backing_device);
+    bool InitBackingAndControlDevice();
+    bool InitCowDevice();
     int Run();
     const std::string& GetControlDevicePath() { return control_device_; }
-    const std::string& GetCowDevice() { return cow_device_; }
+    const std::string& GetMiscName() { return misc_name_; }
     uint64_t GetNumSectors() { return num_sectors_; }
+    bool IsAttached() const { return ctrl_fd_ >= 0; }
 
   private:
     int ReadDmUserHeader();
@@ -96,6 +99,7 @@
     std::string cow_device_;
     std::string backing_store_device_;
     std::string control_device_;
+    std::string misc_name_;
 
     unique_fd cow_fd_;
     unique_fd backing_store_fd_;
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_client.h b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_client.h
index b5e5a96..0e9ba9e 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_client.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_client.h
@@ -58,9 +58,19 @@
                                                     std::chrono::milliseconds timeout_ms);
 
     bool StopSnapuserd();
-    uint64_t InitDmUserCow(const std::string& cow_device);
-    bool InitializeSnapuserd(const std::string& cow_device, const std::string& backing_device,
-                             const std::string& control_device);
+
+    // Initializing a snapuserd handler is a three-step process:
+    //
+    //  1. Client invokes InitDmUserCow. This creates the snapuserd handler and validates the
+    //     COW. The number of sectors required for the dm-user target is returned.
+    //  2. Client creates the device-mapper device with the dm-user target.
+    //  3. Client calls AttachControlDevice.
+    //
+    // The misc_name must be the "misc_name" given to dm-user in step 2.
+    //
+    uint64_t InitDmUserCow(const std::string& misc_name, const std::string& cow_device,
+                           const std::string& backing_device);
+    bool AttachDmUser(const std::string& misc_name);
 
     // Wait for snapuserd to disassociate with a dm-user control device. This
     // must ONLY be called if the control device has already been deleted.
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_server.h b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_server.h
index be48400..cadfd71 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_server.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapuserd_server.h
@@ -56,7 +56,7 @@
     const std::unique_ptr<Snapuserd>& snapuserd() const { return snapuserd_; }
     std::thread& thread() { return thread_; }
 
-    const std::string& GetControlDevice() const;
+    const std::string& GetMiscName() const;
 };
 
 class Stoppable {
@@ -85,7 +85,9 @@
     std::vector<struct pollfd> watched_fds_;
 
     std::mutex lock_;
-    std::vector<std::unique_ptr<DmUserHandler>> dm_users_;
+
+    using HandlerList = std::vector<std::shared_ptr<DmUserHandler>>;
+    HandlerList dm_users_;
 
     void AddWatchedFd(android::base::borrowed_fd fd);
     void AcceptClient();
@@ -95,7 +97,7 @@
     bool Receivemsg(android::base::borrowed_fd fd, const std::string& str);
 
     void ShutdownThreads();
-    bool WaitForDelete(const std::string& control_device);
+    bool RemoveHandler(const std::string& control_device, bool wait);
     DaemonOperations Resolveop(std::string& input);
     std::string GetDaemonStatus();
     void Parsemsg(std::string const& msg, const char delim, std::vector<std::string>& out);
@@ -103,11 +105,11 @@
     void SetTerminating() { terminating_ = true; }
     bool IsTerminating() { return terminating_; }
 
-    void RunThread(DmUserHandler* handler);
+    void RunThread(std::shared_ptr<DmUserHandler> handler);
 
-    // Remove a DmUserHandler from dm_users_, searching by its control device.
-    // If none is found, return nullptr.
-    std::unique_ptr<DmUserHandler> RemoveHandler(const std::string& control_device);
+    // Find a DmUserHandler within a lock.
+    HandlerList::iterator FindHandler(std::lock_guard<std::mutex>* proof_of_lock,
+                                      const std::string& misc_name);
 
   public:
     SnapuserdServer() { terminating_ = false; }
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index b79dbf1..6595707 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -397,7 +397,7 @@
         return false;
     }
 
-    uint64_t base_sectors = snapuserd_client_->InitDmUserCow(cow_file);
+    uint64_t base_sectors = snapuserd_client_->InitDmUserCow(misc_name, cow_file, base_device);
     if (base_sectors == 0) {
         LOG(ERROR) << "Failed to retrieve base_sectors from Snapuserd";
         return false;
@@ -410,7 +410,12 @@
     }
 
     auto control_device = "/dev/dm-user/" + misc_name;
-    return snapuserd_client_->InitializeSnapuserd(cow_file, base_device, control_device);
+    if (!android::fs_mgr::WaitForFile(control_device, timeout_ms)) {
+        LOG(ERROR) << "Timed out waiting for dm-user misc device: " << control_device;
+        return false;
+    }
+
+    return snapuserd_client_->AttachDmUser(misc_name);
 }
 
 bool SnapshotManager::MapSnapshot(LockedFile* lock, const std::string& name,
@@ -1310,28 +1315,34 @@
     size_t num_cows = 0;
     size_t ok_cows = 0;
     for (const auto& snapshot : snapshots) {
-        std::string cow_name = GetDmUserCowName(snapshot);
-        if (dm.GetState(cow_name) == DmDeviceState::INVALID) {
+        std::string user_cow_name = GetDmUserCowName(snapshot);
+        if (dm.GetState(user_cow_name) == DmDeviceState::INVALID) {
             continue;
         }
 
         DeviceMapper::TargetInfo target;
-        if (!GetSingleTarget(cow_name, TableQuery::Table, &target)) {
+        if (!GetSingleTarget(user_cow_name, TableQuery::Table, &target)) {
             continue;
         }
 
         auto target_type = DeviceMapper::GetTargetType(target.spec);
         if (target_type != "user") {
-            LOG(ERROR) << "Unexpected target type for " << cow_name << ": " << target_type;
+            LOG(ERROR) << "Unexpected target type for " << user_cow_name << ": " << target_type;
             continue;
         }
 
         num_cows++;
 
+        SnapshotStatus snapshot_status;
+        if (!ReadSnapshotStatus(lock.get(), snapshot, &snapshot_status)) {
+            LOG(ERROR) << "Unable to read snapshot status: " << snapshot;
+            continue;
+        }
+
         DmTable table;
-        table.Emplace<DmTargetUser>(0, target.spec.length, cow_name);
-        if (!dm.LoadTableAndActivate(cow_name, table)) {
-            LOG(ERROR) << "Unable to swap tables for " << cow_name;
+        table.Emplace<DmTargetUser>(0, target.spec.length, user_cow_name);
+        if (!dm.LoadTableAndActivate(user_cow_name, table)) {
+            LOG(ERROR) << "Unable to swap tables for " << user_cow_name;
             continue;
         }
 
@@ -1341,20 +1352,30 @@
             continue;
         }
 
-        std::string cow_device;
-        if (!dm.GetDmDevicePathByName(GetCowName(snapshot), &cow_device)) {
-            LOG(ERROR) << "Could not get device path for " << GetCowName(snapshot);
+        // If no partition was created (the COW exists entirely on /data), the
+        // device-mapper layering is different than if we had a partition.
+        std::string cow_image_name;
+        if (snapshot_status.cow_partition_size() == 0) {
+            cow_image_name = GetCowImageDeviceName(snapshot);
+        } else {
+            cow_image_name = GetCowName(snapshot);
+        }
+
+        std::string cow_image_device;
+        if (!dm.GetDmDevicePathByName(cow_image_name, &cow_image_device)) {
+            LOG(ERROR) << "Could not get device path for " << cow_image_name;
             continue;
         }
 
         // Wait for ueventd to acknowledge and create the control device node.
-        std::string control_device = "/dev/dm-user/" + cow_name;
+        std::string control_device = "/dev/dm-user/" + user_cow_name;
         if (!android::fs_mgr::WaitForFile(control_device, 10s)) {
             LOG(ERROR) << "Could not find control device: " << control_device;
             continue;
         }
 
-        uint64_t base_sectors = snapuserd_client_->InitDmUserCow(cow_device);
+        uint64_t base_sectors =
+                snapuserd_client_->InitDmUserCow(user_cow_name, cow_image_device, backing_device);
         if (base_sectors == 0) {
             // Unrecoverable as metadata reads from cow device failed
             LOG(FATAL) << "Failed to retrieve base_sectors from Snapuserd";
@@ -1363,10 +1384,10 @@
 
         CHECK(base_sectors == target.spec.length);
 
-        if (!snapuserd_client_->InitializeSnapuserd(cow_device, backing_device, control_device)) {
+        if (!snapuserd_client_->AttachDmUser(user_cow_name)) {
             // This error is unrecoverable. We cannot proceed because reads to
             // the underlying device will fail.
-            LOG(FATAL) << "Could not initialize snapuserd for " << cow_name;
+            LOG(FATAL) << "Could not initialize snapuserd for " << user_cow_name;
             return false;
         }
 
@@ -2053,13 +2074,13 @@
             return false;
         }
 
-        auto control_device = "/dev/dm-user/" + dm_user_name;
-        if (!snapuserd_client_->WaitForDeviceDelete(control_device)) {
+        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.
+        auto control_device = "/dev/dm-user/" + dm_user_name;
         if (!android::fs_mgr::WaitForFileDeleted(control_device, 10s)) {
             LOG(ERROR) << "Timed out waiting for " << control_device << " to unlink";
             return false;
diff --git a/fs_mgr/libsnapshot/snapuserd.cpp b/fs_mgr/libsnapshot/snapuserd.cpp
index 7c393fc..80b5734 100644
--- a/fs_mgr/libsnapshot/snapuserd.cpp
+++ b/fs_mgr/libsnapshot/snapuserd.cpp
@@ -66,6 +66,14 @@
     return header;
 }
 
+Snapuserd::Snapuserd(const std::string& misc_name, const std::string& cow_device,
+                     const std::string& backing_device) {
+    misc_name_ = misc_name;
+    cow_device_ = cow_device;
+    backing_store_device_ = backing_device;
+    control_device_ = "/dev/dm-user/" + misc_name;
+}
+
 // Construct kernel COW header in memory
 // This header will be in sector 0. The IO
 // request will always be 4k. After constructing
@@ -672,9 +680,7 @@
     return true;
 }
 
-bool Snapuserd::InitCowDevice(std::string& cow_device) {
-    cow_device_ = cow_device;
-
+bool Snapuserd::InitCowDevice() {
     cow_fd_.reset(open(cow_device_.c_str(), O_RDWR));
     if (cow_fd_ < 0) {
         PLOG(ERROR) << "Open Failed: " << cow_device_;
@@ -691,11 +697,7 @@
     return ReadMetadata();
 }
 
-bool Snapuserd::InitBackingAndControlDevice(std::string& backing_device,
-                                            std::string& control_device) {
-    backing_store_device_ = backing_device;
-    control_device_ = control_device;
-
+bool Snapuserd::InitBackingAndControlDevice() {
     backing_store_fd_.reset(open(backing_store_device_.c_str(), O_RDONLY));
     if (backing_store_fd_ < 0) {
         PLOG(ERROR) << "Open Failed: " << backing_store_device_;
diff --git a/fs_mgr/libsnapshot/snapuserd_client.cpp b/fs_mgr/libsnapshot/snapuserd_client.cpp
index d7fdb43..a5d2061 100644
--- a/fs_mgr/libsnapshot/snapuserd_client.cpp
+++ b/fs_mgr/libsnapshot/snapuserd_client.cpp
@@ -183,10 +183,8 @@
     return true;
 }
 
-bool SnapuserdClient::InitializeSnapuserd(const std::string& cow_device,
-                                          const std::string& backing_device,
-                                          const std::string& control_device) {
-    std::string msg = "start," + cow_device + "," + backing_device + "," + control_device;
+bool SnapuserdClient::AttachDmUser(const std::string& misc_name) {
+    std::string msg = "start," + misc_name;
     if (!Sendmsg(msg)) {
         LOG(ERROR) << "Failed to send message " << msg << " to snapuserd daemon";
         return false;
@@ -202,8 +200,10 @@
     return true;
 }
 
-uint64_t SnapuserdClient::InitDmUserCow(const std::string& cow_device) {
-    std::string msg = "init," + cow_device;
+uint64_t SnapuserdClient::InitDmUserCow(const std::string& misc_name, const std::string& cow_device,
+                                        const std::string& backing_device) {
+    std::vector<std::string> parts = {"init", misc_name, cow_device, backing_device};
+    std::string msg = android::base::Join(parts, ",");
     if (!Sendmsg(msg)) {
         LOG(ERROR) << "Failed to send message " << msg << " to snapuserd daemon";
         return 0;
@@ -213,7 +213,7 @@
 
     std::vector<std::string> input = android::base::Split(str, ",");
 
-    if (input[0] != "success") {
+    if (input.empty() || input[0] != "success") {
         LOG(ERROR) << "Failed to receive number of sectors for " << msg << " from snapuserd daemon";
         return 0;
     }
diff --git a/fs_mgr/libsnapshot/snapuserd_server.cpp b/fs_mgr/libsnapshot/snapuserd_server.cpp
index 3aa6136..9d065b6 100644
--- a/fs_mgr/libsnapshot/snapuserd_server.cpp
+++ b/fs_mgr/libsnapshot/snapuserd_server.cpp
@@ -74,7 +74,7 @@
     StopThreads();
 
     // Acquire the thread list within the lock.
-    std::vector<std::unique_ptr<DmUserHandler>> dm_users;
+    std::vector<std::shared_ptr<DmUserHandler>> dm_users;
     {
         std::lock_guard<std::mutex> guard(lock_);
         dm_users = std::move(dm_users_);
@@ -87,8 +87,8 @@
     }
 }
 
-const std::string& DmUserHandler::GetControlDevice() const {
-    return snapuserd_->GetControlDevicePath();
+const std::string& DmUserHandler::GetMiscName() const {
+    return snapuserd_->GetMiscName();
 }
 
 bool SnapuserdServer::Sendmsg(android::base::borrowed_fd fd, const std::string& msg) {
@@ -126,16 +126,16 @@
     switch (op) {
         case DaemonOperations::INIT: {
             // Message format:
-            // init,<cow_device_path>
+            // init,<misc_name>,<cow_device_path>,<control_device>
             //
             // Reads the metadata and send the number of sectors
-            if (out.size() != 2) {
+            if (out.size() != 4) {
                 LOG(ERROR) << "Malformed init message, " << out.size() << " parts";
                 return Sendmsg(fd, "fail");
             }
 
-            auto snapuserd = std::make_unique<Snapuserd>();
-            if (!snapuserd->InitCowDevice(out[1])) {
+            auto snapuserd = std::make_unique<Snapuserd>(out[1], out[2], out[3]);
+            if (!snapuserd->InitCowDevice()) {
                 LOG(ERROR) << "Failed to initialize Snapuserd";
                 return Sendmsg(fd, "fail");
             }
@@ -145,6 +145,10 @@
             auto handler = std::make_unique<DmUserHandler>(std::move(snapuserd));
             {
                 std::lock_guard<std::mutex> lock(lock_);
+                if (FindHandler(&lock, out[1]) != dm_users_.end()) {
+                    LOG(ERROR) << "Handler already exists: " << out[1];
+                    return Sendmsg(fd, "fail");
+                }
                 dm_users_.push_back(std::move(handler));
             }
 
@@ -152,37 +156,30 @@
         }
         case DaemonOperations::START: {
             // Message format:
-            // start,<cow_device_path>,<source_device_path>,<control_device>
+            // start,<misc_name>
             //
             // Start the new thread which binds to dm-user misc device
-            if (out.size() != 4) {
+            if (out.size() != 2) {
                 LOG(ERROR) << "Malformed start message, " << out.size() << " parts";
                 return Sendmsg(fd, "fail");
             }
 
-            bool found = false;
-            {
-                std::lock_guard<std::mutex> lock(lock_);
-                auto iter = dm_users_.begin();
-                while (iter != dm_users_.end()) {
-                    if ((*iter)->snapuserd()->GetCowDevice() == out[1]) {
-                        if (!((*iter)->snapuserd()->InitBackingAndControlDevice(out[2], out[3]))) {
-                            LOG(ERROR) << "Failed to initialize control device: " << out[3];
-                            break;
-                        }
-                        (*iter)->thread() = std::thread(
-                                std::bind(&SnapuserdServer::RunThread, this, (*iter).get()));
-                        found = true;
-                        break;
-                    }
-                    iter++;
-                }
-            }
-            if (found) {
-                return Sendmsg(fd, "success");
-            } else {
+            std::lock_guard<std::mutex> lock(lock_);
+            auto iter = FindHandler(&lock, out[1]);
+            if (iter == dm_users_.end()) {
+                LOG(ERROR) << "Could not find handler: " << out[1];
                 return Sendmsg(fd, "fail");
             }
+            if ((*iter)->snapuserd()->IsAttached()) {
+                LOG(ERROR) << "Tried to re-attach control device: " << out[1];
+                return Sendmsg(fd, "fail");
+            }
+            if (!((*iter)->snapuserd()->InitBackingAndControlDevice())) {
+                LOG(ERROR) << "Failed to initialize control device: " << out[1];
+                return Sendmsg(fd, "fail");
+            }
+            (*iter)->thread() = std::thread(std::bind(&SnapuserdServer::RunThread, this, *iter));
+            return Sendmsg(fd, "success");
         }
         case DaemonOperations::STOP: {
             // Message format: stop
@@ -207,12 +204,12 @@
         }
         case DaemonOperations::DELETE: {
             // Message format:
-            // delete,<control_device_path>
+            // delete,<misc_name>
             if (out.size() != 2) {
                 LOG(ERROR) << "Malformed delete message, " << out.size() << " parts";
                 return Sendmsg(fd, "fail");
             }
-            if (!WaitForDelete(out[1])) {
+            if (!RemoveHandler(out[1], true)) {
                 return Sendmsg(fd, "fail");
             }
             return Sendmsg(fd, "success");
@@ -225,8 +222,8 @@
     }
 }
 
-void SnapuserdServer::RunThread(DmUserHandler* handler) {
-    LOG(INFO) << "Entering thread for handler: " << handler->GetControlDevice();
+void SnapuserdServer::RunThread(std::shared_ptr<DmUserHandler> handler) {
+    LOG(INFO) << "Entering thread for handler: " << handler->GetMiscName();
 
     while (!StopRequested()) {
         if (handler->snapuserd()->Run() < 0) {
@@ -235,15 +232,11 @@
         }
     }
 
-    LOG(INFO) << "Exiting thread for handler: " << handler->GetControlDevice();
+    LOG(INFO) << "Exiting thread for handler: " << handler->GetMiscName();
 
-    if (auto client = RemoveHandler(handler->GetControlDevice())) {
-        // The main thread did not receive a WaitForDelete request for this
-        // control device. Since we transferred ownership within the lock,
-        // we know join() was never called, and will never be called. We can
-        // safely detach here.
-        client->thread().detach();
-    }
+    // If the main thread called /emoveHandler, the handler was already removed
+    // from within the lock, and calling RemoveHandler again has no effect.
+    RemoveHandler(handler->GetMiscName(), false);
 }
 
 bool SnapuserdServer::Start(const std::string& socketname) {
@@ -336,34 +329,37 @@
     SetTerminating();
 }
 
-std::unique_ptr<DmUserHandler> SnapuserdServer::RemoveHandler(const std::string& control_device) {
-    std::unique_ptr<DmUserHandler> client;
-    {
-        std::lock_guard<std::mutex> lock(lock_);
-        auto iter = dm_users_.begin();
-        while (iter != dm_users_.end()) {
-            if ((*iter)->GetControlDevice() == control_device) {
-                client = std::move(*iter);
-                iter = dm_users_.erase(iter);
-                break;
-            }
-            iter++;
+auto SnapuserdServer::FindHandler(std::lock_guard<std::mutex>* proof_of_lock,
+                                  const std::string& misc_name) -> HandlerList::iterator {
+    CHECK(proof_of_lock);
+
+    for (auto iter = dm_users_.begin(); iter != dm_users_.end(); iter++) {
+        if ((*iter)->GetMiscName() == misc_name) {
+            return iter;
         }
     }
-    return client;
+    return dm_users_.end();
 }
 
-bool SnapuserdServer::WaitForDelete(const std::string& control_device) {
-    auto client = RemoveHandler(control_device);
+bool SnapuserdServer::RemoveHandler(const std::string& misc_name, bool wait) {
+    std::shared_ptr<DmUserHandler> handler;
+    {
+        std::lock_guard<std::mutex> lock(lock_);
 
-    // Client already deleted.
-    if (!client) {
-        return true;
+        auto iter = FindHandler(&lock, misc_name);
+        if (iter == dm_users_.end()) {
+            // Client already deleted.
+            return true;
+        }
+        handler = std::move(*iter);
+        dm_users_.erase(iter);
     }
 
-    auto& th = client->thread();
-    if (th.joinable()) {
+    auto& th = handler->thread();
+    if (th.joinable() && wait) {
         th.join();
+    } else if (handler->snapuserd()->IsAttached()) {
+        th.detach();
     }
     return true;
 }