libsnapshot: Prepare removal of legacy snapshot
During OTA install, when vendor partition is on Android S, add a new flag in SnapshotUpdateStatus file to indicate that we need to support dm-snapshot based snapshot process. This will be used only during post OTA reboot.
The primary change here is the OTA install path. Earlier, dm-snapshot based approach was used; with this change, since both "snapuserd" and "update-engine" resides on system partition, OTA installation will use the userspace snapshot approach.
To maintain backward compatibility, the new flag "legacy_snapuserd" is used only after OTA reboot. This flag will make sure that update-engine will take the dm-snapshot based approach post reboot and for the entire duration of snapshot-merge.
Additionally, during first-stage init if the vendor is on Android S, then "snapuserd" binary will continue to work based off dm-snapshot as none of this change will impact the mount process.
Bug: 304829384
Test: OTA on Pixel
th - OTA from Android S to TOT with vendor on S
Change-Id: Idd9a60b09417cee141b2810e2d4b35e91c845a5c
Signed-off-by: Akilesh Kailash <akailash@google.com>
diff --git a/fs_mgr/libsnapshot/android/snapshot/snapshot.proto b/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
index f2f7fc1..076a918 100644
--- a/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
+++ b/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
@@ -212,6 +212,9 @@
// io_uring support
bool io_uring_enabled = 10;
+
+ // legacy dm-snapshot based snapuserd
+ bool legacy_snapuserd = 11;
}
// Next: 10
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index d102863..3ccc3db 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -829,6 +829,9 @@
// Set read-ahead size during OTA
void SetReadAheadSize(const std::string& entry_block_device, off64_t size_kb);
+ // Returns true post OTA reboot if legacy snapuserd is required
+ bool IsLegacySnapuserdPostReboot();
+
android::dm::IDeviceMapper& dm_;
std::unique_ptr<IDeviceInfo> device_;
std::string metadata_dir_;
@@ -839,6 +842,7 @@
std::unique_ptr<SnapuserdClient> snapuserd_client_;
std::unique_ptr<LpMetadata> old_partition_metadata_;
std::optional<bool> is_snapshot_userspace_;
+ std::optional<bool> is_legacy_snapuserd_;
};
} // namespace snapshot
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index e6c4de6..b4892b4 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -265,7 +265,6 @@
auto boot_file = GetSnapshotBootIndicatorPath();
std::string contents;
if (!android::base::ReadFileToString(boot_file, &contents)) {
- PLOG(WARNING) << "Cannot read " << boot_file;
return {};
}
return contents;
@@ -2118,6 +2117,53 @@
return update_status.io_uring_enabled();
}
+/*
+ * Please see b/304829384 for more details.
+ *
+ * In Android S, we use dm-snapshot for mounting snapshots and snapshot-merge
+ * process. If the vendor partition continues to be on Android S, then
+ * "snapuserd" binary in first stage ramdisk will be from vendor partition.
+ * Thus, we need to maintain backward compatibility.
+ *
+ * Now, We take a two step approach to maintain the backward compatibility:
+ *
+ * 1: During OTA installation, we will continue to use "user-space" snapshots
+ * for OTA installation as both update-engine and snapuserd binary will be from system partition.
+ * However, during installation, we mark "legacy_snapuserd" in
+ * SnapshotUpdateStatus file to mark that this is a path to support backward compatibility.
+ * Thus, this function will return "false" during OTA installation.
+ *
+ * 2: Post OTA reboot, there are two key steps:
+ * a: During first stage init, "init" and "snapuserd" could be from vendor
+ * partition. This could be from Android S. Thus, the snapshot mount path
+ * will be based off dm-snapshot.
+ *
+ * b: Post selinux transition, "init" and "update-engine" will be "system"
+ * partition. Now, since the snapshots are mounted off dm-snapshot,
+ * update-engine interaction with "snapuserd" should work based off
+ * dm-snapshots.
+ *
+ * TL;DR: update-engine will use the "system" snapuserd for installing new
+ * updates (this is safe as there is no "vendor" snapuserd running during
+ * installation). Post reboot, update-engine will use the legacy path when
+ * communicating with "vendor" snapuserd that was started in first-stage
+ * init. Hence, this function checks:
+ * i: Are we in post OTA reboot
+ * ii: Is the Vendor from Android 12
+ * iii: If both (i) and (ii) are true, then use the dm-snapshot based
+ * approach.
+ *
+ */
+bool SnapshotManager::IsLegacySnapuserdPostReboot() {
+ if (is_legacy_snapuserd_.has_value() && is_legacy_snapuserd_.value() == true) {
+ auto slot = GetCurrentSlot();
+ if (slot == Slot::Target) {
+ return true;
+ }
+ }
+ return false;
+}
+
bool SnapshotManager::UpdateUsesUserSnapshots() {
// This and the following function is constantly
// invoked during snapshot merge. We want to avoid
@@ -2129,7 +2175,12 @@
// during merge phase. Hence, once we know that
// the value is read from disk the very first time,
// it is safe to read successive checks from memory.
+
if (is_snapshot_userspace_.has_value()) {
+ // Check if legacy snapuserd is running post OTA reboot
+ if (IsLegacySnapuserdPostReboot()) {
+ return false;
+ }
return is_snapshot_userspace_.value();
}
@@ -2140,13 +2191,16 @@
}
bool SnapshotManager::UpdateUsesUserSnapshots(LockedFile* lock) {
- // See UpdateUsesUserSnapshots()
- if (is_snapshot_userspace_.has_value()) {
- return is_snapshot_userspace_.value();
+ if (!is_snapshot_userspace_.has_value()) {
+ SnapshotUpdateStatus update_status = ReadSnapshotUpdateStatus(lock);
+ is_snapshot_userspace_ = update_status.userspace_snapshots();
+ is_legacy_snapuserd_ = update_status.legacy_snapuserd();
}
- SnapshotUpdateStatus update_status = ReadSnapshotUpdateStatus(lock);
- is_snapshot_userspace_ = update_status.userspace_snapshots();
+ if (IsLegacySnapuserdPostReboot()) {
+ return false;
+ }
+
return is_snapshot_userspace_.value();
}
@@ -3210,6 +3264,8 @@
// Deduce supported features.
bool userspace_snapshots = CanUseUserspaceSnapshots();
bool legacy_compression = GetLegacyCompressionEnabledProperty();
+ bool is_legacy_snapuserd = IsVendorFromAndroid12();
+
if (!vabc_disable_reason.empty()) {
if (userspace_snapshots) {
LOG(INFO) << "Userspace snapshots disabled: " << vabc_disable_reason;
@@ -3219,6 +3275,7 @@
}
userspace_snapshots = false;
legacy_compression = false;
+ is_legacy_snapuserd = false;
}
if (legacy_compression || userspace_snapshots) {
@@ -3231,6 +3288,8 @@
}
}
+ LOG(INFO) << "userspace snapshots: " << userspace_snapshots
+ << " legacy_snapuserd: " << legacy_compression;
const bool using_snapuserd = userspace_snapshots || legacy_compression;
if (!using_snapuserd) {
LOG(INFO) << "Using legacy Virtual A/B (dm-snapshot)";
@@ -3328,6 +3387,10 @@
status.set_io_uring_enabled(true);
LOG(INFO) << "io_uring for snapshots enabled";
}
+
+ if (is_legacy_snapuserd) {
+ status.set_legacy_snapuserd(true);
+ }
} else if (legacy_compression) {
LOG(INFO) << "Virtual A/B using legacy snapuserd";
} else {
@@ -3335,6 +3398,7 @@
}
is_snapshot_userspace_.emplace(userspace_snapshots);
+ is_legacy_snapuserd_.emplace(is_legacy_snapuserd);
if (!device()->IsTestDevice() && using_snapuserd) {
// Terminate stale daemon if any
diff --git a/fs_mgr/libsnapshot/utility.cpp b/fs_mgr/libsnapshot/utility.cpp
index 1ffa89c..fe2d95c 100644
--- a/fs_mgr/libsnapshot/utility.cpp
+++ b/fs_mgr/libsnapshot/utility.cpp
@@ -230,11 +230,7 @@
return fetcher->GetBoolProperty("ro.virtual_ab.userspace.snapshots.enabled", false);
}
-bool CanUseUserspaceSnapshots() {
- if (!GetUserspaceSnapshotsEnabledProperty()) {
- return false;
- }
-
+bool IsVendorFromAndroid12() {
auto fetcher = IPropertyFetcher::GetInstance();
const std::string UNKNOWN = "unknown";
@@ -243,8 +239,15 @@
// No user-space snapshots if vendor partition is on Android 12
if (vendor_release.find("12") != std::string::npos) {
- LOG(INFO) << "Userspace snapshots disabled as vendor partition is on Android: "
- << vendor_release;
+ return true;
+ }
+
+ return false;
+}
+
+bool CanUseUserspaceSnapshots() {
+ if (!GetUserspaceSnapshotsEnabledProperty()) {
+ LOG(INFO) << "Virtual A/B - Userspace snapshots disabled";
return false;
}
diff --git a/fs_mgr/libsnapshot/utility.h b/fs_mgr/libsnapshot/utility.h
index 370f3c4..f956a05 100644
--- a/fs_mgr/libsnapshot/utility.h
+++ b/fs_mgr/libsnapshot/utility.h
@@ -136,6 +136,7 @@
bool CanUseUserspaceSnapshots();
bool IsDmSnapshotTestingEnabled();
+bool IsVendorFromAndroid12();
// Swap the suffix of a partition name.
std::string GetOtherPartitionName(const std::string& name);