Merge tag 'LA.QSSI.13.0.r1-09800-qssi.0' into tachibanatachibana

"LA.QSSI.13.0.r1-09800-qssi.0"

Change-Id: I06ecf682f4d5595bce3383b6031506cc56bc0db2

21 files changed, 319 insertions, 87 deletions

diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 82b5275a3..6942d0ccd 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -1140,7 +1140,13 @@ static inline uint64_t GetIdealDataScratchSize() {
         return 0;
     }
 
-    return std::min(super_info.size, (uint64_t(s.f_frsize) * s.f_bfree) / 2);
+    auto ideal_size = std::min(super_info.size, (uint64_t(s.f_frsize) * s.f_bfree) / 2);
+
+    // Align up to the filesystem block size.
+    if (auto remainder = ideal_size % s.f_bsize; remainder > 0) {
+        ideal_size += s.f_bsize - remainder;
+    }
+    return ideal_size;
 }
 
 static bool CreateScratchOnData(std::string* scratch_device, bool* partition_exists, bool* change) {
diff --git a/fs_mgr/libdm/dm.cpp b/fs_mgr/libdm/dm.cpp
index 4034e30ab..deffae1ad 100644
--- a/fs_mgr/libdm/dm.cpp
+++ b/fs_mgr/libdm/dm.cpp
@@ -20,6 +20,7 @@
 #include <sys/ioctl.h>
 #include <sys/sysmacros.h>
 #include <sys/types.h>
+#include <sys/utsname.h>
 
 #include <chrono>
 #include <functional>
@@ -289,7 +290,7 @@ bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table) {
     return true;
 }
 
-bool DeviceMapper::LoadTableAndActivate(const std::string& name, const DmTable& table) {
+bool DeviceMapper::LoadTable(const std::string& name, const DmTable& table) {
     std::string ioctl_buffer(sizeof(struct dm_ioctl), 0);
     ioctl_buffer += table.Serialize();
 
@@ -305,9 +306,17 @@ bool DeviceMapper::LoadTableAndActivate(const std::string& name, const DmTable&
         PLOG(ERROR) << "DM_TABLE_LOAD failed";
         return false;
     }
+    return true;
+}
 
-    InitIo(io, name);
-    if (ioctl(fd_, DM_DEV_SUSPEND, io)) {
+bool DeviceMapper::LoadTableAndActivate(const std::string& name, const DmTable& table) {
+    if (!LoadTable(name, table)) {
+        return false;
+    }
+
+    struct dm_ioctl io;
+    InitIo(&io, name);
+    if (ioctl(fd_, DM_DEV_SUSPEND, &io)) {
         PLOG(ERROR) << "DM_TABLE_SUSPEND resume failed";
         return false;
     }
@@ -703,5 +712,28 @@ std::map<std::string, std::string> DeviceMapper::FindDmPartitions() {
     return dm_block_devices;
 }
 
+bool DeviceMapper::CreatePlaceholderDevice(const std::string& name) {
+    if (!CreateEmptyDevice(name)) {
+        return false;
+    }
+
+    struct utsname uts;
+    unsigned int major, minor;
+    if (uname(&uts) != 0 || sscanf(uts.release, "%u.%u", &major, &minor) != 2) {
+        LOG(ERROR) << "Could not parse the kernel version from uname";
+        return true;
+    }
+
+    // On Linux 5.15+, there is no uevent until DM_TABLE_LOAD.
+    if (major > 5 || (major == 5 && minor >= 15)) {
+        DmTable table;
+        table.Emplace<DmTargetError>(0, 1);
+        if (!LoadTable(name, table)) {
+            return false;
+        }
+    }
+    return true;
+}
+
 }  // namespace dm
 }  // namespace android
diff --git a/fs_mgr/libdm/dm_test.cpp b/fs_mgr/libdm/dm_test.cpp
index 541f254cb..4448d35c5 100644
--- a/fs_mgr/libdm/dm_test.cpp
+++ b/fs_mgr/libdm/dm_test.cpp
@@ -690,3 +690,23 @@ TEST(libdm, CreateEmptyDevice) {
     // Empty device should be in suspended state.
     ASSERT_EQ(DmDeviceState::SUSPENDED, dm.GetState("empty-device"));
 }
+
+TEST(libdm, UeventAfterLoadTable) {
+    static const char* kDeviceName = "libmd-test-uevent-load-table";
+
+    DeviceMapper& dm = DeviceMapper::Instance();
+    ASSERT_TRUE(dm.CreateEmptyDevice(kDeviceName));
+
+    DmTable table;
+    table.Emplace<DmTargetError>(0, 1);
+    ASSERT_TRUE(dm.LoadTable(kDeviceName, table));
+
+    std::string ignore_path;
+    ASSERT_TRUE(dm.WaitForDevice(kDeviceName, 5s, &ignore_path));
+
+    auto info = dm.GetDetailedInfo(kDeviceName);
+    ASSERT_TRUE(info.has_value());
+    ASSERT_TRUE(info->IsSuspended());
+
+    ASSERT_TRUE(dm.DeleteDevice(kDeviceName));
+}
diff --git a/fs_mgr/libdm/include/libdm/dm.h b/fs_mgr/libdm/include/libdm/dm.h
index 1057d7f7a..dbef8f902 100644
--- a/fs_mgr/libdm/include/libdm/dm.h
+++ b/fs_mgr/libdm/include/libdm/dm.h
@@ -75,6 +75,7 @@ class IDeviceMapper {
                               const std::chrono::milliseconds& timeout_ms) = 0;
     virtual DmDeviceState GetState(const std::string& name) const = 0;
     virtual bool LoadTableAndActivate(const std::string& name, const DmTable& table) = 0;
+    virtual bool LoadTable(const std::string& name, const DmTable& table) = 0;
     virtual bool GetTableInfo(const std::string& name, std::vector<TargetInfo>* table) = 0;
     virtual bool GetTableStatus(const std::string& name, std::vector<TargetInfo>* table) = 0;
     virtual bool GetDmDevicePathByName(const std::string& name, std::string* path) = 0;
@@ -116,7 +117,7 @@ class DeviceMapper final : public IDeviceMapper {
         bool IsBufferFull() const { return flags_ & DM_BUFFER_FULL_FLAG; }
         bool IsInactiveTablePresent() const { return flags_ & DM_INACTIVE_PRESENT_FLAG; }
         bool IsReadOnly() const { return flags_ & DM_READONLY_FLAG; }
-        bool IsSuspended() const { return flags_ & DM_SUSPEND_FLAG; }
+        bool IsSuspended() const { return !IsActiveTablePresent() || (flags_ & DM_SUSPEND_FLAG); }
     };
 
     // Removes a device mapper device with the given name.
@@ -199,6 +200,12 @@ class DeviceMapper final : public IDeviceMapper {
     // Returns 'true' on success, false otherwise.
     bool LoadTableAndActivate(const std::string& name, const DmTable& table) override;
 
+    // Same as LoadTableAndActivate, but there is no resume step. This puts the
+    // new table in the inactive slot.
+    //
+    // Returns 'true' on success, false otherwise.
+    bool LoadTable(const std::string& name, const DmTable& table) override;
+
     // Returns true if a list of available device mapper targets registered in the kernel was
     // successfully read and stored in 'targets'. Returns 'false' otherwise.
     bool GetAvailableTargets(std::vector<DmTargetTypeInfo>* targets);
@@ -285,6 +292,12 @@ class DeviceMapper final : public IDeviceMapper {
     // Returns mapping <partition-name, /dev/block/dm-x>
     std::map<std::string, std::string> FindDmPartitions();
 
+    // Create a placeholder device. This is useful for ensuring that a uevent is in the pipeline,
+    // to reduce the amount of time a future WaitForDevice will block. On kernels < 5.15, this
+    // simply calls CreateEmptyDevice. On 5.15 and higher, it also loads (but does not activate)
+    // a placeholder table containing dm-error.
+    bool CreatePlaceholderDevice(const std::string& name);
+
   private:
     // Maximum possible device mapper targets registered in the kernel.
     // This is only used to read the list of targets from kernel so we allocate
diff --git a/fs_mgr/libdm/include/libdm/dm_table.h b/fs_mgr/libdm/include/libdm/dm_table.h
index ee66653a5..427f34dea 100644
--- a/fs_mgr/libdm/include/libdm/dm_table.h
+++ b/fs_mgr/libdm/include/libdm/dm_table.h
@@ -31,6 +31,7 @@ namespace dm {
 class DmTable {
   public:
     DmTable() : num_sectors_(0), readonly_(false) {}
+    DmTable(DmTable&& other) = default;
 
     // Adds a target to the device mapper table for a range specified in the target object.
     // The function will return 'true' if the target was successfully added and doesn't overlap with
@@ -70,6 +71,8 @@ class DmTable {
     void set_readonly(bool readonly) { readonly_ = readonly; }
     bool readonly() const { return readonly_; }
 
+    DmTable& operator=(DmTable&& other) = default;
+
     ~DmTable() = default;
 
   private:
diff --git a/fs_mgr/libdm/include/libdm/dm_target.h b/fs_mgr/libdm/include/libdm/dm_target.h
index 954305816..09fe20012 100644
--- a/fs_mgr/libdm/include/libdm/dm_target.h
+++ b/fs_mgr/libdm/include/libdm/dm_target.h
@@ -323,6 +323,14 @@ class DmTargetUser final : public DmTarget {
     std::string control_device_;
 };
 
+class DmTargetError final : public DmTarget {
+  public:
+    DmTargetError(uint64_t start, uint64_t length) : DmTarget(start, length) {}
+
+    std::string name() const override { return "error"; }
+    std::string GetParameterString() const override { return ""; }
+};
+
 }  // namespace dm
 }  // namespace android
 
diff --git a/fs_mgr/libsnapshot/cow_reader.cpp b/fs_mgr/libsnapshot/cow_reader.cpp
index 746feeb8d..75a58a6fc 100644
--- a/fs_mgr/libsnapshot/cow_reader.cpp
+++ b/fs_mgr/libsnapshot/cow_reader.cpp
@@ -38,7 +38,7 @@ CowReader::CowReader(ReaderFlags reader_flag)
     : fd_(-1),
       header_(),
       fd_size_(0),
-      merge_op_blocks_(std::make_shared<std::vector<uint32_t>>()),
+      block_pos_index_(std::make_shared<std::vector<int>>()),
       reader_flag_(reader_flag) {}
 
 static void SHA256(const void*, size_t, uint8_t[]) {
@@ -58,13 +58,12 @@ std::unique_ptr<CowReader> CowReader::CloneCowReader() {
     cow->fd_size_ = fd_size_;
     cow->last_label_ = last_label_;
     cow->ops_ = ops_;
-    cow->merge_op_blocks_ = merge_op_blocks_;
     cow->merge_op_start_ = merge_op_start_;
-    cow->block_map_ = block_map_;
     cow->num_total_data_ops_ = num_total_data_ops_;
     cow->num_ordered_ops_to_merge_ = num_ordered_ops_to_merge_;
     cow->has_seq_ops_ = has_seq_ops_;
     cow->data_loc_ = data_loc_;
+    cow->block_pos_index_ = block_pos_index_;
     return cow;
 }
 
@@ -415,10 +414,10 @@ bool CowReader::ParseOps(std::optional<uint64_t> label) {
 //                        Replace-op-4, Zero-op-9, Replace-op-5 }
 //==============================================================
 bool CowReader::PrepMergeOps() {
-    auto merge_op_blocks = std::make_shared<std::vector<uint32_t>>();
+    auto merge_op_blocks = std::make_unique<std::vector<uint32_t>>();
     std::vector<int> other_ops;
     auto seq_ops_set = std::unordered_set<uint32_t>();
-    auto block_map = std::make_shared<std::unordered_map<uint32_t, int>>();
+    auto block_map = std::make_unique<std::unordered_map<uint32_t, int>>();
     size_t num_seqs = 0;
     size_t read;
 
@@ -477,13 +476,18 @@ bool CowReader::PrepMergeOps() {
 
     merge_op_blocks->insert(merge_op_blocks->end(), other_ops.begin(), other_ops.end());
 
+    for (auto block : *merge_op_blocks) {
+        block_pos_index_->push_back(block_map->at(block));
+    }
+
     num_total_data_ops_ = merge_op_blocks->size();
     if (header_.num_merge_ops > 0) {
         merge_op_start_ = header_.num_merge_ops;
     }
 
-    block_map_ = block_map;
-    merge_op_blocks_ = merge_op_blocks;
+    block_map->clear();
+    merge_op_blocks->clear();
+
     return true;
 }
 
@@ -589,9 +593,7 @@ const CowOperation& CowOpIter::Get() {
 class CowRevMergeOpIter final : public ICowOpIter {
   public:
     explicit CowRevMergeOpIter(std::shared_ptr<std::vector<CowOperation>> ops,
-                               std::shared_ptr<std::vector<uint32_t>> merge_op_blocks,
-                               std::shared_ptr<std::unordered_map<uint32_t, int>> map,
-                               uint64_t start);
+                               std::shared_ptr<std::vector<int>> block_pos_index, uint64_t start);
 
     bool Done() override;
     const CowOperation& Get() override;
@@ -602,17 +604,15 @@ class CowRevMergeOpIter final : public ICowOpIter {
 
   private:
     std::shared_ptr<std::vector<CowOperation>> ops_;
-    std::shared_ptr<std::vector<uint32_t>> merge_op_blocks_;
-    std::shared_ptr<std::unordered_map<uint32_t, int>> map_;
-    std::vector<uint32_t>::reverse_iterator block_riter_;
+    std::vector<int>::reverse_iterator block_riter_;
+    std::shared_ptr<std::vector<int>> cow_op_index_vec_;
     uint64_t start_;
 };
 
 class CowMergeOpIter final : public ICowOpIter {
   public:
     explicit CowMergeOpIter(std::shared_ptr<std::vector<CowOperation>> ops,
-                            std::shared_ptr<std::vector<uint32_t>> merge_op_blocks,
-                            std::shared_ptr<std::unordered_map<uint32_t, int>> map, uint64_t start);
+                            std::shared_ptr<std::vector<int>> block_pos_index, uint64_t start);
 
     bool Done() override;
     const CowOperation& Get() override;
@@ -623,26 +623,21 @@ class CowMergeOpIter final : public ICowOpIter {
 
   private:
     std::shared_ptr<std::vector<CowOperation>> ops_;
-    std::shared_ptr<std::vector<uint32_t>> merge_op_blocks_;
-    std::shared_ptr<std::unordered_map<uint32_t, int>> map_;
-    std::vector<uint32_t>::iterator block_iter_;
+    std::vector<int>::iterator block_iter_;
+    std::shared_ptr<std::vector<int>> cow_op_index_vec_;
     uint64_t start_;
 };
 
 CowMergeOpIter::CowMergeOpIter(std::shared_ptr<std::vector<CowOperation>> ops,
-                               std::shared_ptr<std::vector<uint32_t>> merge_op_blocks,
-                               std::shared_ptr<std::unordered_map<uint32_t, int>> map,
-                               uint64_t start) {
+                               std::shared_ptr<std::vector<int>> block_pos_index, uint64_t start) {
     ops_ = ops;
-    merge_op_blocks_ = merge_op_blocks;
-    map_ = map;
     start_ = start;
-
-    block_iter_ = merge_op_blocks->begin() + start;
+    cow_op_index_vec_ = block_pos_index;
+    block_iter_ = cow_op_index_vec_->begin() + start;
 }
 
 bool CowMergeOpIter::RDone() {
-    return block_iter_ == merge_op_blocks_->begin();
+    return block_iter_ == cow_op_index_vec_->begin();
 }
 
 void CowMergeOpIter::Prev() {
@@ -651,7 +646,7 @@ void CowMergeOpIter::Prev() {
 }
 
 bool CowMergeOpIter::Done() {
-    return block_iter_ == merge_op_blocks_->end();
+    return block_iter_ == cow_op_index_vec_->end();
 }
 
 void CowMergeOpIter::Next() {
@@ -661,23 +656,20 @@ void CowMergeOpIter::Next() {
 
 const CowOperation& CowMergeOpIter::Get() {
     CHECK(!Done());
-    return ops_->data()[map_->at(*block_iter_)];
+    return ops_->data()[*block_iter_];
 }
 
 CowRevMergeOpIter::CowRevMergeOpIter(std::shared_ptr<std::vector<CowOperation>> ops,
-                                     std::shared_ptr<std::vector<uint32_t>> merge_op_blocks,
-                                     std::shared_ptr<std::unordered_map<uint32_t, int>> map,
+                                     std::shared_ptr<std::vector<int>> block_pos_index,
                                      uint64_t start) {
     ops_ = ops;
-    merge_op_blocks_ = merge_op_blocks;
-    map_ = map;
     start_ = start;
-
-    block_riter_ = merge_op_blocks->rbegin();
+    cow_op_index_vec_ = block_pos_index;
+    block_riter_ = cow_op_index_vec_->rbegin();
 }
 
 bool CowRevMergeOpIter::RDone() {
-    return block_riter_ == merge_op_blocks_->rbegin();
+    return block_riter_ == cow_op_index_vec_->rbegin();
 }
 
 void CowRevMergeOpIter::Prev() {
@@ -686,7 +678,7 @@ void CowRevMergeOpIter::Prev() {
 }
 
 bool CowRevMergeOpIter::Done() {
-    return block_riter_ == merge_op_blocks_->rend() - start_;
+    return block_riter_ == cow_op_index_vec_->rend() - start_;
 }
 
 void CowRevMergeOpIter::Next() {
@@ -696,7 +688,7 @@ void CowRevMergeOpIter::Next() {
 
 const CowOperation& CowRevMergeOpIter::Get() {
     CHECK(!Done());
-    return ops_->data()[map_->at(*block_riter_)];
+    return ops_->data()[*block_riter_];
 }
 
 std::unique_ptr<ICowOpIter> CowReader::GetOpIter() {
@@ -704,12 +696,12 @@ std::unique_ptr<ICowOpIter> CowReader::GetOpIter() {
 }
 
 std::unique_ptr<ICowOpIter> CowReader::GetRevMergeOpIter(bool ignore_progress) {
-    return std::make_unique<CowRevMergeOpIter>(ops_, merge_op_blocks_, block_map_,
+    return std::make_unique<CowRevMergeOpIter>(ops_, block_pos_index_,
                                                ignore_progress ? 0 : merge_op_start_);
 }
 
 std::unique_ptr<ICowOpIter> CowReader::GetMergeOpIter(bool ignore_progress) {
-    return std::make_unique<CowMergeOpIter>(ops_, merge_op_blocks_, block_map_,
+    return std::make_unique<CowMergeOpIter>(ops_, block_pos_index_,
                                             ignore_progress ? 0 : merge_op_start_);
 }
 
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h
index f4d5c72f3..fbdd6b98b 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h
@@ -170,9 +170,8 @@ class CowReader final : public ICowReader {
     uint64_t fd_size_;
     std::optional<uint64_t> last_label_;
     std::shared_ptr<std::vector<CowOperation>> ops_;
-    std::shared_ptr<std::vector<uint32_t>> merge_op_blocks_;
     uint64_t merge_op_start_{};
-    std::shared_ptr<std::unordered_map<uint32_t, int>> block_map_;
+    std::shared_ptr<std::vector<int>> block_pos_index_;
     uint64_t num_total_data_ops_{};
     uint64_t num_ordered_ops_to_merge_{};
     bool has_seq_ops_{};
diff --git a/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h b/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h
index c3b40dca4..1de6d9835 100644
--- a/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h
+++ b/fs_mgr/libsnapshot/include_test/libsnapshot/test_helpers.h
@@ -143,6 +143,9 @@ class DeviceMapperWrapper : public android::dm::IDeviceMapper {
     virtual DmDeviceState GetState(const std::string& name) const override {
         return impl_.GetState(name);
     }
+    virtual bool LoadTable(const std::string& name, const DmTable& table) {
+        return impl_.LoadTable(name, table);
+    }
     virtual bool LoadTableAndActivate(const std::string& name, const DmTable& table) {
         return impl_.LoadTableAndActivate(name, table);
     }
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index 019b64a44..870801ef1 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -2151,8 +2151,17 @@ bool SnapshotManager::ListSnapshots(LockedFile* lock, std::vector<std::string>*
         if (!suffix.empty() && !android::base::EndsWith(name, suffix)) {
             continue;
         }
-        snapshots->emplace_back(std::move(name));
+
+        // Insert system and product partition at the beginning so that
+        // during snapshot-merge, these partitions are merged first.
+        if (name == "system_a" || name == "system_b" || name == "product_a" ||
+            name == "product_b") {
+            snapshots->insert(snapshots->begin(), std::move(name));
+        } else {
+            snapshots->emplace_back(std::move(name));
+        }
     }
+
     return true;
 }
 
diff --git a/fs_mgr/libsnapshot/snapshot_test.cpp b/fs_mgr/libsnapshot/snapshot_test.cpp
index 6a348b4e5..c145da718 100644
--- a/fs_mgr/libsnapshot/snapshot_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_test.cpp
@@ -2755,6 +2755,10 @@ bool IsDaemonRequired() {
         return false;
     }
 
+    if (!IsCompressionEnabled()) {
+        return false;
+    }
+
     const std::string UNKNOWN = "unknown";
     const std::string vendor_release =
             android::base::GetProperty("ro.vendor.build.version.release_or_codename", UNKNOWN);
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
index 692cb740c..718c13ce0 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
@@ -143,17 +143,18 @@ void SnapshotHandler::PrepareReadAhead() {
     NotifyRAForMergeReady();
 }
 
-void SnapshotHandler::CheckMergeCompletionStatus() {
+bool SnapshotHandler::CheckMergeCompletionStatus() {
     if (!merge_initiated_) {
         SNAP_LOG(INFO) << "Merge was not initiated. Total-data-ops: "
                        << reader_->get_num_total_data_ops();
-        return;
+        return false;
     }
 
     struct CowHeader* ch = reinterpret_cast<struct CowHeader*>(mapped_addr_);
 
     SNAP_LOG(INFO) << "Merge-status: Total-Merged-ops: " << ch->num_merge_ops
                    << " Total-data-ops: " << reader_->get_num_total_data_ops();
+    return true;
 }
 
 bool SnapshotHandler::ReadMetadata() {
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
index 83d40f635..c6805e5d9 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
@@ -18,6 +18,9 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/time.h>
+#include <unistd.h>
 
 #include <condition_variable>
 #include <cstring>
@@ -54,6 +57,8 @@ static_assert(PAYLOAD_BUFFER_SZ >= BLOCK_SZ);
 
 static constexpr int kNumWorkerThreads = 4;
 
+static constexpr int kNiceValueForMergeThreads = -5;
+
 #define SNAP_LOG(level) LOG(level) << misc_name_ << ": "
 #define SNAP_PLOG(level) PLOG(level) << misc_name_ << ": "
 
@@ -274,7 +279,7 @@ class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {
     const bool& IsAttached() const { return attached_; }
     void AttachControlDevice() { attached_ = true; }
 
-    void CheckMergeCompletionStatus();
+    bool CheckMergeCompletionStatus();
     bool CommitMerge(int num_merge_ops);
 
     void CloseFds() { cow_fd_ = {}; }
@@ -305,6 +310,8 @@ class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {
 
     // State transitions for merge
     void InitiateMerge();
+    void MonitorMerge();
+    void WakeupMonitorMergeThread();
     void WaitForMergeComplete();
     bool WaitForMergeBegin();
     void NotifyRAForMergeReady();
@@ -333,6 +340,7 @@ class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {
     void SetSocketPresent(bool socket) { is_socket_present_ = socket; }
     void SetIouringEnabled(bool io_uring_enabled) { is_io_uring_enabled_ = io_uring_enabled; }
     bool MergeInitiated() { return merge_initiated_; }
+    bool MergeMonitored() { return merge_monitored_; }
     double GetMergePercentage() { return merge_completion_percentage_; }
 
     // Merge Block State Transitions
@@ -407,6 +415,7 @@ class SnapshotHandler : public std::enable_shared_from_this<SnapshotHandler> {
     double merge_completion_percentage_;
 
     bool merge_initiated_ = false;
+    bool merge_monitored_ = false;
     bool attached_ = false;
     bool is_socket_present_;
     bool is_io_uring_enabled_ = false;
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp
index c26a2cd5c..63f47d6f0 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_merge.cpp
@@ -71,16 +71,16 @@ int Worker::PrepareMerge(uint64_t* source_offset, int* pending_ops,
 }
 
 bool Worker::MergeReplaceZeroOps() {
-    // Flush every 8192 ops. Since all ops are independent and there is no
+    // Flush after merging 2MB. Since all ops are independent and there is no
     // dependency between COW ops, we will flush the data and the number
-    // of ops merged in COW file for every 8192 ops. If there is a crash,
-    // we will end up replaying some of the COW ops which were already merged.
-    // That is ok.
+    // of ops merged in COW block device. If there is a crash, we will
+    // end up replaying some of the COW ops which were already merged. That is
+    // ok.
     //
-    // Why 8192 ops ? Increasing this may improve merge time 3-4 seconds but
-    // we need to make sure that we checkpoint; 8k ops seems optimal. In-case
-    // if there is a crash merge should always make forward progress.
-    int total_ops_merged_per_commit = (PAYLOAD_BUFFER_SZ / BLOCK_SZ) * 32;
+    // Although increasing this greater than 2MB may help in improving merge
+    // times; however, on devices with low memory, this can be problematic
+    // when there are multiple merge threads in parallel.
+    int total_ops_merged_per_commit = (PAYLOAD_BUFFER_SZ / BLOCK_SZ) * 2;
     int num_ops_merged = 0;
 
     SNAP_LOG(INFO) << "MergeReplaceZeroOps started....";
@@ -543,6 +543,10 @@ bool Worker::RunMergeThread() {
         return true;
     }
 
+    if (setpriority(PRIO_PROCESS, gettid(), kNiceValueForMergeThreads)) {
+        SNAP_PLOG(ERROR) << "Failed to set priority for TID: " << gettid();
+    }
+
     SNAP_LOG(INFO) << "Merge starting..";
 
     if (!Init()) {
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
index fa2866f39..b9e4255b2 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_readahead.cpp
@@ -727,6 +727,10 @@ bool ReadAhead::RunThread() {
 
     InitializeIouring();
 
+    if (setpriority(PRIO_PROCESS, gettid(), kNiceValueForMergeThreads)) {
+        SNAP_PLOG(ERROR) << "Failed to set priority for TID: " << gettid();
+    }
+
     while (!RAIterDone()) {
         if (!ReadAheadIOStart()) {
             break;
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
index 82b2b25dd..5d93f01a7 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
@@ -59,6 +59,14 @@ DaemonOps UserSnapshotServer::Resolveop(std::string& input) {
     return DaemonOps::INVALID;
 }
 
+UserSnapshotServer::UserSnapshotServer() {
+    monitor_merge_event_fd_.reset(eventfd(0, EFD_CLOEXEC));
+    if (monitor_merge_event_fd_ == -1) {
+        PLOG(FATAL) << "monitor_merge_event_fd_: failed to create eventfd";
+    }
+    terminating_ = false;
+}
+
 UserSnapshotServer::~UserSnapshotServer() {
     // Close any client sockets that were added via AcceptClient().
     for (size_t i = 1; i < watched_fds_.size(); i++) {
@@ -249,7 +257,7 @@ bool UserSnapshotServer::Receivemsg(android::base::borrowed_fd fd, const std::st
                     return Sendmsg(fd, "fail");
                 }
 
-                if (!StartMerge(*iter)) {
+                if (!StartMerge(&lock, *iter)) {
                     return Sendmsg(fd, "fail");
                 }
 
@@ -298,7 +306,7 @@ void UserSnapshotServer::RunThread(std::shared_ptr<UserSnapshotDmUserHandler> ha
     }
 
     handler->snapuserd()->CloseFds();
-    handler->snapuserd()->CheckMergeCompletionStatus();
+    bool merge_completed = handler->snapuserd()->CheckMergeCompletionStatus();
     handler->snapuserd()->UnmapBufferRegion();
 
     auto misc_name = handler->misc_name();
@@ -306,7 +314,11 @@ void UserSnapshotServer::RunThread(std::shared_ptr<UserSnapshotDmUserHandler> ha
 
     {
         std::lock_guard<std::mutex> lock(lock_);
-        num_partitions_merge_complete_ += 1;
+        if (merge_completed) {
+            num_partitions_merge_complete_ += 1;
+            active_merge_threads_ -= 1;
+            WakeupMonitorMergeThread();
+        }
         handler->SetThreadTerminated();
         auto iter = FindHandler(&lock, handler->misc_name());
         if (iter == dm_users_.end()) {
@@ -418,6 +430,9 @@ void UserSnapshotServer::JoinAllThreads() {
 
         if (th.joinable()) th.join();
     }
+
+    stop_monitor_merge_thread_ = true;
+    WakeupMonitorMergeThread();
 }
 
 void UserSnapshotServer::AddWatchedFd(android::base::borrowed_fd fd, int events) {
@@ -502,13 +517,24 @@ bool UserSnapshotServer::StartHandler(const std::shared_ptr<UserSnapshotDmUserHa
     return true;
 }
 
-bool UserSnapshotServer::StartMerge(const std::shared_ptr<UserSnapshotDmUserHandler>& handler) {
+bool UserSnapshotServer::StartMerge(std::lock_guard<std::mutex>* proof_of_lock,
+                                    const std::shared_ptr<UserSnapshotDmUserHandler>& handler) {
+    CHECK(proof_of_lock);
+
     if (!handler->snapuserd()->IsAttached()) {
         LOG(ERROR) << "Handler not attached to dm-user - Merge thread cannot be started";
         return false;
     }
 
-    handler->snapuserd()->InitiateMerge();
+    handler->snapuserd()->MonitorMerge();
+
+    if (!is_merge_monitor_started_.has_value()) {
+        std::thread(&UserSnapshotServer::MonitorMerge, this).detach();
+        is_merge_monitor_started_ = true;
+    }
+
+    merge_handlers_.push(handler);
+    WakeupMonitorMergeThread();
     return true;
 }
 
@@ -590,6 +616,42 @@ bool UserSnapshotServer::RemoveAndJoinHandler(const std::string& misc_name) {
     return true;
 }
 
+void UserSnapshotServer::WakeupMonitorMergeThread() {
+    uint64_t notify = 1;
+    ssize_t rc = TEMP_FAILURE_RETRY(write(monitor_merge_event_fd_.get(), &notify, sizeof(notify)));
+    if (rc < 0) {
+        PLOG(FATAL) << "failed to notify monitor merge thread";
+    }
+}
+
+void UserSnapshotServer::MonitorMerge() {
+    while (!stop_monitor_merge_thread_) {
+        uint64_t testVal;
+        ssize_t ret =
+                TEMP_FAILURE_RETRY(read(monitor_merge_event_fd_.get(), &testVal, sizeof(testVal)));
+        if (ret == -1) {
+            PLOG(FATAL) << "Failed to read from eventfd";
+        } else if (ret == 0) {
+            LOG(FATAL) << "Hit EOF on eventfd";
+        }
+
+        LOG(INFO) << "MonitorMerge: active-merge-threads: " << active_merge_threads_;
+        {
+            std::lock_guard<std::mutex> lock(lock_);
+            while (active_merge_threads_ < kMaxMergeThreads && merge_handlers_.size() > 0) {
+                auto handler = merge_handlers_.front();
+                merge_handlers_.pop();
+                LOG(INFO) << "Starting merge for partition: "
+                          << handler->snapuserd()->GetMiscName();
+                handler->snapuserd()->InitiateMerge();
+                active_merge_threads_ += 1;
+            }
+        }
+    }
+
+    LOG(INFO) << "Exiting MonitorMerge: size: " << merge_handlers_.size();
+}
+
 bool UserSnapshotServer::WaitForSocket() {
     auto scope_guard = android::base::make_scope_guard([this]() -> void { JoinAllThreads(); });
 
@@ -646,6 +708,7 @@ bool UserSnapshotServer::WaitForSocket() {
     if (!StartWithSocket(true)) {
         return false;
     }
+
     return Run();
 }
 
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h
index 34e7941bc..e0844aeb1 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.h
@@ -15,6 +15,7 @@
 #pragma once
 
 #include <poll.h>
+#include <sys/eventfd.h>
 
 #include <cstdio>
 #include <cstring>
@@ -22,6 +23,8 @@
 #include <future>
 #include <iostream>
 #include <mutex>
+#include <optional>
+#include <queue>
 #include <sstream>
 #include <string>
 #include <thread>
@@ -34,6 +37,7 @@ namespace android {
 namespace snapshot {
 
 static constexpr uint32_t kMaxPacketSize = 512;
+static constexpr uint8_t kMaxMergeThreads = 2;
 
 enum class DaemonOps {
     INIT,
@@ -84,13 +88,19 @@ class UserSnapshotServer {
     std::vector<struct pollfd> watched_fds_;
     bool is_socket_present_ = false;
     int num_partitions_merge_complete_ = 0;
+    int active_merge_threads_ = 0;
+    bool stop_monitor_merge_thread_ = false;
     bool is_server_running_ = false;
     bool io_uring_enabled_ = false;
+    std::optional<bool> is_merge_monitor_started_;
+
+    android::base::unique_fd monitor_merge_event_fd_;
 
     std::mutex lock_;
 
     using HandlerList = std::vector<std::shared_ptr<UserSnapshotDmUserHandler>>;
     HandlerList dm_users_;
+    std::queue<std::shared_ptr<UserSnapshotDmUserHandler>> merge_handlers_;
 
     void AddWatchedFd(android::base::borrowed_fd fd, int events);
     void AcceptClient();
@@ -108,6 +118,8 @@ class UserSnapshotServer {
     bool IsTerminating() { return terminating_; }
 
     void RunThread(std::shared_ptr<UserSnapshotDmUserHandler> handler);
+    void MonitorMerge();
+
     void JoinAllThreads();
     bool StartWithSocket(bool start_listening);
 
@@ -119,7 +131,7 @@ class UserSnapshotServer {
     void TerminateMergeThreads(std::lock_guard<std::mutex>* proof_of_lock);
 
   public:
-    UserSnapshotServer() { terminating_ = false; }
+    UserSnapshotServer();
     ~UserSnapshotServer();
 
     bool Start(const std::string& socketname);
@@ -133,9 +145,11 @@ class UserSnapshotServer {
                                                           const std::string& backing_device,
                                                           const std::string& base_path_merge);
     bool StartHandler(const std::shared_ptr<UserSnapshotDmUserHandler>& handler);
-    bool StartMerge(const std::shared_ptr<UserSnapshotDmUserHandler>& handler);
+    bool StartMerge(std::lock_guard<std::mutex>* proof_of_lock,
+                    const std::shared_ptr<UserSnapshotDmUserHandler>& handler);
     std::string GetMergeStatus(const std::shared_ptr<UserSnapshotDmUserHandler>& handler);
 
+    void WakeupMonitorMergeThread();
     void SetTerminating() { terminating_ = true; }
     void ReceivedSocketSignal() { received_socket_signal_ = true; }
     void SetServerRunning() { is_server_running_ = true; }
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp
index d4e1d7c7e..28c9f688a 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_transitions.cpp
@@ -165,6 +165,13 @@ using namespace android;
 using namespace android::dm;
 using android::base::unique_fd;
 
+void SnapshotHandler::MonitorMerge() {
+    {
+        std::lock_guard<std::mutex> lock(lock_);
+        merge_monitored_ = true;
+    }
+}
+
 // This is invoked once primarily by update-engine to initiate
 // the merge
 void SnapshotHandler::InitiateMerge() {
@@ -361,10 +368,16 @@ void SnapshotHandler::WaitForMergeComplete() {
 
 std::string SnapshotHandler::GetMergeStatus() {
     bool merge_not_initiated = false;
+    bool merge_monitored = false;
     bool merge_failed = false;
 
     {
         std::lock_guard<std::mutex> lock(lock_);
+
+        if (MergeMonitored()) {
+            merge_monitored = true;
+        }
+
         if (!MergeInitiated()) {
             merge_not_initiated = true;
         }
@@ -387,6 +400,12 @@ std::string SnapshotHandler::GetMergeStatus() {
             return "snapshot-merge-complete";
         }
 
+        // Merge monitor thread is tracking the merge but the merge thread
+        // is not started yet.
+        if (merge_monitored) {
+            return "snapshot-merge";
+        }
+
         // Return the state as "snapshot". If the device was rebooted during
         // merge, we will return the status as "snapshot". This is ok, as
         // libsnapshot will explicitly resume the merge. This is slightly
diff --git a/fs_mgr/libsnapshot/vts_ota_config_test.cpp b/fs_mgr/libsnapshot/vts_ota_config_test.cpp
index afc2d81a4..02bcc3438 100644
--- a/fs_mgr/libsnapshot/vts_ota_config_test.cpp
+++ b/fs_mgr/libsnapshot/vts_ota_config_test.cpp
@@ -17,7 +17,14 @@
 #include <android-base/properties.h>
 #include <gtest/gtest.h>
 
+static int GetVsrLevel() {
+    return android::base::GetIntProperty("ro.vendor.api_level", -1);
+}
+
 TEST(VAB, Enabled) {
     ASSERT_TRUE(android::base::GetBoolProperty("ro.virtual_ab.enabled", false));
+    if (GetVsrLevel() < __ANDROID_API_T__) {
+        GTEST_SKIP();
+    }
     ASSERT_TRUE(android::base::GetBoolProperty("ro.virtual_ab.userspace.snapshots.enabled", false));
 }
diff --git a/fs_mgr/tests/vts_fs_test.cpp b/fs_mgr/tests/vts_fs_test.cpp
index aac2cfd9b..ae8e45992 100644
--- a/fs_mgr/tests/vts_fs_test.cpp
+++ b/fs_mgr/tests/vts_fs_test.cpp
@@ -28,8 +28,8 @@ static int GetVsrLevel() {
 }
 
 TEST(fs, ErofsSupported) {
-    // S and higher for this test.
-    if (GetVsrLevel() < __ANDROID_API_S__) {
+    // T-launch GKI kernels and higher must support EROFS.
+    if (GetVsrLevel() < __ANDROID_API_T__) {
         GTEST_SKIP();
     }
 
diff --git a/fs_mgr/tools/dmctl.cpp b/fs_mgr/tools/dmctl.cpp
index 62ca1620b..10efd0cab 100644
--- a/fs_mgr/tools/dmctl.cpp
+++ b/fs_mgr/tools/dmctl.cpp
@@ -33,6 +33,7 @@
 #include <ios>
 #include <iostream>
 #include <map>
+#include <optional>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -183,6 +184,8 @@ class TargetParser final {
             }
             std::string control_device = NextArg();
             return std::make_unique<DmTargetUser>(start_sector, num_sectors, control_device);
+        } else if (target_type == "error") {
+            return std::make_unique<DmTargetError>(start_sector, num_sectors);
         } else {
             std::cerr << "Unrecognized target type: " << target_type << std::endl;
             return nullptr;
@@ -206,16 +209,26 @@ class TargetParser final {
     char** argv_;
 };
 
-static bool parse_table_args(DmTable* table, int argc, char** argv) {
+struct TableArgs {
+    DmTable table;
+    bool suspended = false;
+};
+
+static std::optional<TableArgs> parse_table_args(int argc, char** argv) {
+    TableArgs out;
+
     // Parse extended options first.
     int arg_index = 1;
     while (arg_index < argc && argv[arg_index][0] == '-') {
         if (strcmp(argv[arg_index], "-ro") == 0) {
-            table->set_readonly(true);
+            out.table.set_readonly(true);
+            arg_index++;
+        } else if (strcmp(argv[arg_index], "-suspended") == 0) {
+            out.suspended = true;
             arg_index++;
         } else {
             std::cerr << "Unrecognized option: " << argv[arg_index] << std::endl;
-            return -EINVAL;
+            return {};
         }
     }
 
@@ -223,37 +236,44 @@ static bool parse_table_args(DmTable* table, int argc, char** argv) {
     TargetParser parser(argc - arg_index, argv + arg_index);
     while (parser.More()) {
         std::unique_ptr<DmTarget> target = parser.Next();
-        if (!target || !table->AddTarget(std::move(target))) {
-            return -EINVAL;
+        if (!target || !out.table.AddTarget(std::move(target))) {
+            return {};
         }
     }
 
-    if (table->num_targets() == 0) {
+    if (out.table.num_targets() == 0) {
         std::cerr << "Must define at least one target." << std::endl;
-        return -EINVAL;
+        return {};
     }
-    return 0;
+    return {std::move(out)};
 }
 
 static int DmCreateCmdHandler(int argc, char** argv) {
     if (argc < 1) {
-        std::cerr << "Usage: dmctl create <dm-name> [-ro] <targets...>" << std::endl;
+        std::cerr << "Usage: dmctl create <dm-name> [--suspended] [-ro] <targets...>" << std::endl;
         return -EINVAL;
     }
     std::string name = argv[0];
 
-    DmTable table;
-    int ret = parse_table_args(&table, argc, argv);
-    if (ret) {
-        return ret;
+    auto table_args = parse_table_args(argc, argv);
+    if (!table_args) {
+        return -EINVAL;
     }
 
     std::string ignore_path;
     DeviceMapper& dm = DeviceMapper::Instance();
-    if (!dm.CreateDevice(name, table, &ignore_path, 5s)) {
+    if (!dm.CreateEmptyDevice(name)) {
         std::cerr << "Failed to create device-mapper device with name: " << name << std::endl;
         return -EIO;
     }
+    if (!dm.LoadTable(name, table_args->table)) {
+        std::cerr << "Failed to load table for dm device: " << name << std::endl;
+        return -EIO;
+    }
+    if (!table_args->suspended && !dm.ChangeState(name, DmDeviceState::ACTIVE)) {
+        std::cerr << "Failed to activate table for " << name << std::endl;
+        return -EIO;
+    }
     return 0;
 }
 
@@ -269,7 +289,6 @@ static int DmDeleteCmdHandler(int argc, char** argv) {
         std::cerr << "Failed to delete [" << name << "]" << std::endl;
         return -EIO;
     }
-
     return 0;
 }
 
@@ -280,17 +299,20 @@ static int DmReplaceCmdHandler(int argc, char** argv) {
     }
     std::string name = argv[0];
 
-    DmTable table;
-    int ret = parse_table_args(&table, argc, argv);
-    if (ret) {
-        return ret;
+    auto table_args = parse_table_args(argc, argv);
+    if (!table_args) {
+        return -EINVAL;
     }
 
     DeviceMapper& dm = DeviceMapper::Instance();
-    if (!dm.LoadTableAndActivate(name, table)) {
+    if (!dm.LoadTable(name, table_args->table)) {
         std::cerr << "Failed to replace device-mapper table to: " << name << std::endl;
         return -EIO;
     }
+    if (!table_args->suspended && !dm.ChangeState(name, DmDeviceState::ACTIVE)) {
+        std::cerr << "Failed to activate table for " << name << std::endl;
+        return -EIO;
+    }
     return 0;
 }