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Commit 6aa77dd2 authored by Yifan Hong's avatar Yifan Hong
Browse files

libsnapshot: Cancel/merge existing update before begin 

Attempt to cancel or merge an existing update before starting
a new one.

Test: libsnapshot_test

Change-Id: Ic534db846f1fe97bd7ca1f176a9494fbc6a0f8d5
parent 0b32b199

fs_mgr/libsnapshot/include/libsnapshot/snapshot.h

+10 −2
Original line number Diff line number Diff line
@@ -127,8 +127,9 @@ class SnapshotManager final { 
    // will fail if GetUpdateState() != None.

    bool BeginUpdate();



    // Cancel an update; any snapshots will be deleted. This will fail if the

    // state != Initiated or None.

    // Cancel an update; any snapshots will be deleted. This is allowed if the

    // state == Initiated, None, or Unverified (before rebooting to the new

    // slot).

    bool CancelUpdate();



    // Mark snapshot writes as having completed. After this, new snapshots cannot
@@ -395,6 +396,13 @@ class SnapshotManager final { 
    // The reverse of MapPartitionWithSnapshot.

    bool UnmapPartitionWithSnapshot(LockedFile* lock, const std::string& target_partition_name);



    // If there isn't a previous update, return true. |needs_merge| is set to false.

    // If there is a previous update but the device has not boot into it, tries to cancel the

    //   update and delete any snapshots. Return true if successful. |needs_merge| is set to false.

    // If there is a previous update and the device has boot into it, do nothing and return true.

    //   |needs_merge| is set to true.

    bool TryCancelUpdate(bool* needs_merge);



    std::string gsid_dir_;

    std::string metadata_dir_;

    std::unique_ptr<IDeviceInfo> device_;

fs_mgr/libsnapshot/snapshot.cpp

+25 −2
Original line number Diff line number Diff line
@@ -131,6 +131,16 @@ static std::string GetSnapshotExtraDeviceName(const std::string& snapshot_name) 
}



bool SnapshotManager::BeginUpdate() {

    bool needs_merge = false;

    if (!TryCancelUpdate(&needs_merge)) {

        return false;

    }

    if (needs_merge) {

        LOG(INFO) << "Wait for merge (if any) before beginning a new update.";

        auto state = ProcessUpdateState();

        LOG(INFO) << "Merged with state = " << state;

    }



    auto file = LockExclusive();

    if (!file) return false;
@@ -143,6 +153,19 @@ bool SnapshotManager::BeginUpdate() { 
}



bool SnapshotManager::CancelUpdate() {

    bool needs_merge = false;

    if (!TryCancelUpdate(&needs_merge)) {

        return false;

    }

    if (needs_merge) {

        LOG(ERROR) << "Cannot cancel update after it has completed or started merging";

    }

    return !needs_merge;

}



bool SnapshotManager::TryCancelUpdate(bool* needs_merge) {

    *needs_merge = false;



    auto file = LockExclusive();

    if (!file) return false;
@@ -167,8 +190,8 @@ bool SnapshotManager::CancelUpdate() { 
            return RemoveAllUpdateState(file.get());

        }

    }

    LOG(ERROR) << "Cannot cancel update after it has completed or started merging";

    return false;

    *needs_merge = true;

    return true;

}



bool SnapshotManager::RemoveAllUpdateState(LockedFile* lock) {

fs_mgr/libsnapshot/snapshot_test.cpp

+1 −2
Original line number Diff line number Diff line
@@ -761,8 +761,7 @@ class SnapshotUpdateTest : public SnapshotTest { 
// Also test UnmapUpdateSnapshot unmaps everything.

// Also test first stage mount and merge after this.

TEST_F(SnapshotUpdateTest, FullUpdateFlow) {

    // OTA client calls CancelUpdate then BeginUpdate before doing anything.

    ASSERT_TRUE(sm->CancelUpdate());

    // OTA client calls BeginUpdate before doing anything.

    ASSERT_TRUE(sm->BeginUpdate());



    // OTA client blindly unmaps all partitions that are possibly mapped.