libsnapshot: Only mount snapshots in MapAllSnapshots().

By accident, this was mounting partitions as well, which caused
conflicts in partial updates where some partitions don't have snapshots.

Test: update_device.py with partial OTA
Change-Id: I2db0e6269f0a02cbe8164fa2a72b887c352f56d8

Author: dvandercorp

fs_mgr/libsnapshot/snapshot.cpp

@@ -2172,12 +2172,44 @@ bool SnapshotManager::MapAllSnapshots(const std::chrono::milliseconds& timeout_m
         return false;
     }
 
-    if (!UnmapAllSnapshots(lock.get())) {
+    std::vector<std::string> snapshots;
+    if (!ListSnapshots(lock.get(), &snapshots)) {
+        return false;
+    }
+
+    const auto& opener = device_->GetPartitionOpener();
+    auto slot_suffix = device_->GetOtherSlotSuffix();
+    auto slot_number = SlotNumberForSlotSuffix(slot_suffix);
+    auto super_device = device_->GetSuperDevice(slot_number);
+    auto metadata = android::fs_mgr::ReadMetadata(opener, super_device, slot_number);
+    if (!metadata) {
+        LOG(ERROR) << "MapAllSnapshots could not read dynamic partition metadata for device: "
+                   << super_device;
         return false;
     }
 
-    uint32_t slot = SlotNumberForSlotSuffix(device_->GetOtherSlotSuffix());
-    return MapAllPartitions(lock.get(), device_->GetSuperDevice(slot), slot, timeout_ms);
+    for (const auto& snapshot : snapshots) {
+        if (!UnmapPartitionWithSnapshot(lock.get(), snapshot)) {
+            LOG(ERROR) << "MapAllSnapshots could not unmap snapshot: " << snapshot;
+            return false;
+        }
+
+        CreateLogicalPartitionParams params = {
+                .block_device = super_device,
+                .metadata = metadata.get(),
+                .partition_name = snapshot,
+                .partition_opener = &opener,
+                .timeout_ms = timeout_ms,
+        };
+        if (!MapPartitionWithSnapshot(lock.get(), std::move(params), SnapshotContext::Mount,
+                                      nullptr)) {
+            LOG(ERROR) << "MapAllSnapshots failed to map: " << snapshot;
+            return false;
+        }
+    }
+
+    LOG(INFO) << "MapAllSnapshots succeeded.";
+    return true;
 }
 
 bool SnapshotManager::UnmapAllSnapshots() {