libsnapshot: add GetCurrentSlot
Factor out obscure logic that reads boot indicator path.
GetCurrentSlot() returns three states:
- None (read failure)
- Old (before reboot)
- New (after reboot)
Use these "logical" slot values for simpler code.
Test: libsnapshot_test
Change-Id: I1fa2ce4916c5a1652d25682ec1f11e101c858822
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index 5738b96..eb48a76 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -496,6 +496,10 @@
// as a sanity check.
bool EnsureNoOverflowSnapshot(LockedFile* lock);
+ enum class Slot { Unknown, Source, Target };
+ friend std::ostream& operator<<(std::ostream& os, SnapshotManager::Slot slot);
+ Slot GetCurrentSlot();
+
std::string gsid_dir_;
std::string metadata_dir_;
std::unique_ptr<IDeviceInfo> device_;
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index f38db43..ce960f9 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -171,14 +171,9 @@
if (state == UpdateState::Unverified) {
// We completed an update, but it can still be canceled if we haven't booted into it.
- auto boot_file = GetSnapshotBootIndicatorPath();
- std::string contents;
- if (!android::base::ReadFileToString(boot_file, &contents)) {
- PLOG(WARNING) << "Cannot read " << boot_file << ", proceed to canceling the update:";
- return RemoveAllUpdateState(file.get());
- }
- if (device_->GetSlotSuffix() == contents) {
- LOG(INFO) << "Canceling a previously completed update";
+ auto slot = GetCurrentSlot();
+ if (slot != Slot::Target) {
+ LOG(INFO) << "Canceling previously completed updates (if any)";
return RemoveAllUpdateState(file.get());
}
}
@@ -186,6 +181,19 @@
return true;
}
+SnapshotManager::Slot SnapshotManager::GetCurrentSlot() {
+ auto boot_file = GetSnapshotBootIndicatorPath();
+ std::string contents;
+ if (!android::base::ReadFileToString(boot_file, &contents)) {
+ PLOG(WARNING) << "Cannot read " << boot_file;
+ return Slot::Unknown;
+ }
+ if (device_->GetSlotSuffix() == contents) {
+ return Slot::Source;
+ }
+ return Slot::Target;
+}
+
bool SnapshotManager::RemoveAllUpdateState(LockedFile* lock) {
if (!RemoveAllSnapshots(lock)) {
LOG(ERROR) << "Could not remove all snapshots";
@@ -505,15 +513,9 @@
return false;
}
- std::string old_slot;
- auto boot_file = GetSnapshotBootIndicatorPath();
- if (!android::base::ReadFileToString(boot_file, &old_slot)) {
- LOG(ERROR) << "Could not determine the previous slot; aborting merge";
- return false;
- }
- auto new_slot = device_->GetSlotSuffix();
- if (new_slot == old_slot) {
- LOG(ERROR) << "Device cannot merge while booting off old slot " << old_slot;
+ auto slot = GetCurrentSlot();
+ if (slot != Slot::Target) {
+ LOG(ERROR) << "Device cannot merge while not booting from new slot";
return false;
}
@@ -1097,13 +1099,11 @@
}
bool SnapshotManager::HandleCancelledUpdate(LockedFile* lock) {
- std::string old_slot;
- auto boot_file = GetSnapshotBootIndicatorPath();
- if (!android::base::ReadFileToString(boot_file, &old_slot)) {
- PLOG(ERROR) << "Unable to read the snapshot indicator file: " << boot_file;
+ auto slot = GetCurrentSlot();
+ if (slot == Slot::Unknown) {
return false;
}
- if (device_->GetSlotSuffix() != old_slot) {
+ if (slot == Slot::Target) {
// We're booted into the target slot, which means we just rebooted
// after applying the update.
if (!HandleCancelledUpdateOnNewSlot(lock)) {
@@ -1271,14 +1271,9 @@
// ultimately we'll fail to boot. Why not make it a fatal error and have
// the reason be clearer? Because the indicator file still exists, and
// if this was FATAL, reverting to the old slot would be broken.
- std::string old_slot;
- auto boot_file = GetSnapshotBootIndicatorPath();
- if (!android::base::ReadFileToString(boot_file, &old_slot)) {
- PLOG(ERROR) << "Unable to read the snapshot indicator file: " << boot_file;
- return false;
- }
- if (device_->GetSlotSuffix() == old_slot) {
- LOG(INFO) << "Detected slot rollback, will not mount snapshots.";
+ auto slot = GetCurrentSlot();
+ if (slot != Slot::Target) {
+ LOG(INFO) << "Not booting from new slot. Will not mount snapshots.";
return false;
}
@@ -2156,6 +2151,17 @@
return ok;
}
+std::ostream& operator<<(std::ostream& os, SnapshotManager::Slot slot) {
+ switch (slot) {
+ case SnapshotManager::Slot::Unknown:
+ return os << "unknown";
+ case SnapshotManager::Slot::Source:
+ return os << "source";
+ case SnapshotManager::Slot::Target:
+ return os << "target";
+ }
+}
+
bool SnapshotManager::Dump(std::ostream& os) {
// Don't actually lock. Dump() is for debugging purposes only, so it is okay
// if it is racy.
@@ -2166,11 +2172,8 @@
ss << "Update state: " << ReadUpdateState(file.get()) << std::endl;
- auto boot_file = GetSnapshotBootIndicatorPath();
- std::string boot_indicator;
- if (android::base::ReadFileToString(boot_file, &boot_indicator)) {
- ss << "Boot indicator: old slot = " << boot_indicator << std::endl;
- }
+ ss << "Current slot: " << device_->GetSlotSuffix() << std::endl;
+ ss << "Boot indicator: booting from " << GetCurrentSlot() << " slot" << std::endl;
bool ok = true;
std::vector<std::string> snapshots;
@@ -2283,11 +2286,9 @@
//
// Since the rollback is inevitable, we don't treat a HAL failure
// as an error here.
- std::string old_slot;
- auto boot_file = GetSnapshotBootIndicatorPath();
- if (android::base::ReadFileToString(boot_file, &old_slot) &&
- device_->GetSlotSuffix() != old_slot) {
- LOG(ERROR) << "Reverting to slot " << old_slot << " since update will be deleted.";
+ auto slot = GetCurrentSlot();
+ if (slot == Slot::Target) {
+ LOG(ERROR) << "Reverting to old slot since update will be deleted.";
device_->SetSlotAsUnbootable(slot_number);
}
break;