diff --git a/fastboot/device/flashing.cpp b/fastboot/device/flashing.cpp
index 2347496..66b90bf 100644
--- a/fastboot/device/flashing.cpp
+++ b/fastboot/device/flashing.cpp
@@ -21,10 +21,15 @@
 
 #include <algorithm>
 #include <memory>
+#include <set>
+#include <string>
 
+#include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/strings.h>
 #include <ext4_utils/ext4_utils.h>
+#include <fs_mgr_overlayfs.h>
+#include <fstab/fstab.h>
 #include <liblp/builder.h>
 #include <liblp/liblp.h>
 #include <sparse/sparse.h>
@@ -32,13 +37,35 @@
 #include "fastboot_device.h"
 #include "utility.h"
 
+using namespace android::fs_mgr;
+using namespace std::literals;
+
 namespace {
 
 constexpr uint32_t SPARSE_HEADER_MAGIC = 0xed26ff3a;
 
-}  // namespace
+void WipeOverlayfsForPartition(FastbootDevice* device, const std::string& partition_name) {
+    // May be called, in the case of sparse data, multiple times so cache/skip.
+    static std::set<std::string> wiped;
+    if (wiped.find(partition_name) != wiped.end()) return;
+    wiped.insert(partition_name);
+    // Following appears to have a first time 2% impact on flashing speeds.
 
-using namespace android::fs_mgr;
+    // Convert partition_name to a validated mount point and wipe.
+    std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)> fstab(fs_mgr_read_fstab_default(),
+                                                               fs_mgr_free_fstab);
+    for (auto i = 0; i < fstab->num_entries; i++) {
+        const auto mount_point = fstab->recs[i].mount_point;
+        if (!mount_point) continue;
+        auto partition = android::base::Basename(mount_point);
+        if ("/"s == mount_point) partition = "system";
+        if ((partition + device->GetCurrentSlot()) == partition_name) {
+            fs_mgr_overlayfs_teardown(mount_point);
+        }
+    }
+}
+
+}  // namespace
 
 int FlashRawDataChunk(int fd, const char* data, size_t len) {
     size_t ret = 0;
@@ -101,15 +128,11 @@
     } else if (data.size() > get_block_device_size(handle.fd())) {
         return -EOVERFLOW;
     }
+    WipeOverlayfsForPartition(device, partition_name);
     return FlashBlockDevice(handle.fd(), data);
 }
 
-bool UpdateSuper(FastbootDevice* device, const std::string& partition_name, bool wipe) {
-    std::optional<std::string> super = FindPhysicalPartition(partition_name);
-    if (!super) {
-        return device->WriteFail("Could not find partition: " + partition_name);
-    }
-
+bool UpdateSuper(FastbootDevice* device, const std::string& super_name, bool wipe) {
     std::vector<char> data = std::move(device->download_data());
     if (data.empty()) {
         return device->WriteFail("No data available");
@@ -125,47 +148,17 @@
     // image.
     std::string slot_suffix = device->GetCurrentSlot();
     uint32_t slot_number = SlotNumberForSlotSuffix(slot_suffix);
-    std::unique_ptr<LpMetadata> metadata = ReadMetadata(super->c_str(), slot_number);
-    if (!metadata || wipe) {
-        if (!FlashPartitionTable(super.value(), *new_metadata.get())) {
+    if (wipe || !ReadMetadata(super_name, slot_number)) {
+        if (!FlashPartitionTable(super_name, *new_metadata.get())) {
             return device->WriteFail("Unable to flash new partition table");
         }
         return device->WriteOkay("Successfully flashed partition table");
     }
 
-    // There's a working super partition, and we don't want to wipe it - it may
-    // may contain partitions created for the user. Instead, we create a zero-
-    // sized partition for each entry in the new partition table. It is then
-    // the host's responsibility to size it correctly via resize-logical-partition.
-    std::unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(*metadata.get());
-    if (!builder) {
-        return device->WriteFail("Unable to create a metadata builder");
-    }
-    for (const auto& partition : new_metadata->partitions) {
-        std::string name = GetPartitionName(partition);
-        if (builder->FindPartition(name)) {
-            continue;
-        }
-        if (!builder->AddPartition(name, partition.attributes)) {
-            return device->WriteFail("Unable to add partition: " + name);
-        }
-    }
-
-    // The scratch partition may exist as temporary storage, created for
-    // use by adb remount for overlayfs. If we're performing a flashall
-    // operation then we want to start over with a clean slate, so we
-    // remove the scratch partition until it is requested again.
-    builder->RemovePartition("scratch");
-
-    new_metadata = builder->Export();
-    if (!new_metadata) {
-        return device->WriteFail("Unable to export new partition table");
-    }
-
     // Write the new table to every metadata slot.
     bool ok = true;
     for (size_t i = 0; i < new_metadata->geometry.metadata_slot_count; i++) {
-        ok &= UpdatePartitionTable(super.value(), *new_metadata.get(), i);
+        ok &= UpdatePartitionTable(super_name, *new_metadata.get(), i);
     }
 
     if (!ok) {
diff --git a/fastboot/device/flashing.h b/fastboot/device/flashing.h
index 89e20fc..b15f28b 100644
--- a/fastboot/device/flashing.h
+++ b/fastboot/device/flashing.h
@@ -22,4 +22,4 @@
 class FastbootDevice;
 
 int Flash(FastbootDevice* device, const std::string& partition_name);
-bool UpdateSuper(FastbootDevice* device, const std::string& partition_name, bool wipe);
+bool UpdateSuper(FastbootDevice* device, const std::string& super_name, bool wipe);
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index a6ef35b..ae2e2fe 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -50,7 +50,6 @@
 #include <cutils/partition_utils.h>
 #include <cutils/properties.h>
 #include <ext4_utils/ext4.h>
-#include <ext4_utils/ext4_crypt_init_extensions.h>
 #include <ext4_utils/ext4_sb.h>
 #include <ext4_utils/ext4_utils.h>
 #include <ext4_utils/wipe.h>
diff --git a/fs_mgr/fs_mgr_dm_linear.cpp b/fs_mgr/fs_mgr_dm_linear.cpp
index 6ddd5a8..4dacebf 100644
--- a/fs_mgr/fs_mgr_dm_linear.cpp
+++ b/fs_mgr/fs_mgr_dm_linear.cpp
@@ -75,14 +75,9 @@
                 target = std::make_unique<DmTargetZero>(sector, extent.num_sectors);
                 break;
             case LP_TARGET_TYPE_LINEAR: {
-                auto block_device = GetMetadataSuperBlockDevice(metadata);
-                if (!block_device) {
-                    LOG(ERROR) << "Could not identify the super block device";
-                    return false;
-                }
-
+                const auto& block_device = metadata.block_devices[extent.target_source];
                 std::string path;
-                if (!GetPhysicalPartitionDevicePath(*block_device, &path)) {
+                if (!GetPhysicalPartitionDevicePath(block_device, &path)) {
                     LOG(ERROR) << "Unable to complete device-mapper table, unknown block device";
                     return false;
                 }
diff --git a/fs_mgr/liblp/builder.cpp b/fs_mgr/liblp/builder.cpp
index 1b8ed57..3cd33b1 100644
--- a/fs_mgr/liblp/builder.cpp
+++ b/fs_mgr/liblp/builder.cpp
@@ -29,12 +29,19 @@
 namespace android {
 namespace fs_mgr {
 
-void LinearExtent::AddTo(LpMetadata* out) const {
-    out->extents.push_back(LpMetadataExtent{num_sectors_, LP_TARGET_TYPE_LINEAR, physical_sector_});
+bool LinearExtent::AddTo(LpMetadata* out) const {
+    if (device_index_ >= out->block_devices.size()) {
+        LERROR << "Extent references unknown block device.";
+        return false;
+    }
+    out->extents.emplace_back(
+            LpMetadataExtent{num_sectors_, LP_TARGET_TYPE_LINEAR, physical_sector_, device_index_});
+    return true;
 }
 
-void ZeroExtent::AddTo(LpMetadata* out) const {
-    out->extents.push_back(LpMetadataExtent{num_sectors_, LP_TARGET_TYPE_ZERO, 0});
+bool ZeroExtent::AddTo(LpMetadata* out) const {
+    out->extents.emplace_back(LpMetadataExtent{num_sectors_, LP_TARGET_TYPE_ZERO, 0, 0});
+    return true;
 }
 
 Partition::Partition(const std::string& name, const std::string& group_name, uint32_t attributes)
@@ -44,15 +51,17 @@
     size_ += extent->num_sectors() * LP_SECTOR_SIZE;
 
     if (LinearExtent* new_extent = extent->AsLinearExtent()) {
-        if (!extents_.empty() && extents_.back()->AsLinearExtent() &&
-            extents_.back()->AsLinearExtent()->end_sector() == new_extent->physical_sector()) {
-            // If the previous extent can be merged into this new one, do so
-            // to avoid creating unnecessary extents.
+        if (!extents_.empty() && extents_.back()->AsLinearExtent()) {
             LinearExtent* prev_extent = extents_.back()->AsLinearExtent();
-            extent = std::make_unique<LinearExtent>(
-                    prev_extent->num_sectors() + new_extent->num_sectors(),
-                    prev_extent->physical_sector());
-            extents_.pop_back();
+            if (prev_extent->end_sector() == new_extent->physical_sector() &&
+                prev_extent->device_index() == new_extent->device_index()) {
+                // If the previous extent can be merged into this new one, do so
+                // to avoid creating unnecessary extents.
+                extent = std::make_unique<LinearExtent>(
+                        prev_extent->num_sectors() + new_extent->num_sectors(),
+                        prev_extent->device_index(), prev_extent->physical_sector());
+                extents_.pop_back();
+            }
         }
     }
     extents_.push_back(std::move(extent));
@@ -108,9 +117,12 @@
     if (!builder) {
         return nullptr;
     }
-    BlockDeviceInfo device_info;
-    if (opener.GetInfo(super_partition, &device_info)) {
-        builder->UpdateBlockDeviceInfo(device_info);
+    for (size_t i = 0; i < builder->block_devices_.size(); i++) {
+        std::string partition_name = GetBlockDevicePartitionName(builder->block_devices_[i]);
+        BlockDeviceInfo device_info;
+        if (opener.GetInfo(partition_name, &device_info)) {
+            builder->UpdateBlockDeviceInfo(i, device_info);
+        }
     }
     return builder;
 }
@@ -120,11 +132,11 @@
     return New(PartitionOpener(), super_partition, slot_number);
 }
 
-std::unique_ptr<MetadataBuilder> MetadataBuilder::New(const BlockDeviceInfo& device_info,
-                                                      uint32_t metadata_max_size,
-                                                      uint32_t metadata_slot_count) {
+std::unique_ptr<MetadataBuilder> MetadataBuilder::New(
+        const std::vector<BlockDeviceInfo>& block_devices, const std::string& super_partition,
+        uint32_t metadata_max_size, uint32_t metadata_slot_count) {
     std::unique_ptr<MetadataBuilder> builder(new MetadataBuilder());
-    if (!builder->Init(device_info, metadata_max_size, metadata_slot_count)) {
+    if (!builder->Init(block_devices, super_partition, metadata_max_size, metadata_slot_count)) {
         return nullptr;
     }
     return builder;
@@ -156,6 +168,7 @@
 
 bool MetadataBuilder::Init(const LpMetadata& metadata) {
     geometry_ = metadata.geometry;
+    block_devices_ = metadata.block_devices;
 
     for (const auto& group : metadata.groups) {
         std::string group_name = GetPartitionGroupName(group);
@@ -164,10 +177,6 @@
         }
     }
 
-    for (const auto& block_device : metadata.block_devices) {
-        block_devices_.push_back(block_device);
-    }
-
     for (const auto& partition : metadata.partitions) {
         std::string group_name = GetPartitionGroupName(metadata.groups[partition.group_index]);
         Partition* builder =
@@ -179,7 +188,8 @@
         for (size_t i = 0; i < partition.num_extents; i++) {
             const LpMetadataExtent& extent = metadata.extents[partition.first_extent_index + i];
             if (extent.target_type == LP_TARGET_TYPE_LINEAR) {
-                auto copy = std::make_unique<LinearExtent>(extent.num_sectors, extent.target_data);
+                auto copy = std::make_unique<LinearExtent>(extent.num_sectors, extent.target_source,
+                                                           extent.target_data);
                 builder->AddExtent(std::move(copy));
             } else if (extent.target_type == LP_TARGET_TYPE_ZERO) {
                 auto copy = std::make_unique<ZeroExtent>(extent.num_sectors);
@@ -190,7 +200,37 @@
     return true;
 }
 
-bool MetadataBuilder::Init(const BlockDeviceInfo& device_info, uint32_t metadata_max_size,
+static bool VerifyDeviceProperties(const BlockDeviceInfo& device_info) {
+    if (device_info.logical_block_size % LP_SECTOR_SIZE != 0) {
+        LERROR << "Block device " << device_info.partition_name
+               << " logical block size must be a multiple of 512.";
+        return false;
+    }
+    if (device_info.size % device_info.logical_block_size != 0) {
+        LERROR << "Block device " << device_info.partition_name
+               << " size must be a multiple of its block size.";
+        return false;
+    }
+    if (device_info.alignment_offset % LP_SECTOR_SIZE != 0) {
+        LERROR << "Block device " << device_info.partition_name
+               << " alignment offset is not sector-aligned.";
+        return false;
+    }
+    if (device_info.alignment % LP_SECTOR_SIZE != 0) {
+        LERROR << "Block device " << device_info.partition_name
+               << " partition alignment is not sector-aligned.";
+        return false;
+    }
+    if (device_info.alignment_offset > device_info.alignment) {
+        LERROR << "Block device " << device_info.partition_name
+               << " partition alignment offset is greater than its alignment.";
+        return false;
+    }
+    return true;
+}
+
+bool MetadataBuilder::Init(const std::vector<BlockDeviceInfo>& block_devices,
+                           const std::string& super_partition, uint32_t metadata_max_size,
                            uint32_t metadata_slot_count) {
     if (metadata_max_size < sizeof(LpMetadataHeader)) {
         LERROR << "Invalid metadata maximum size.";
@@ -200,70 +240,102 @@
         LERROR << "Invalid metadata slot count.";
         return false;
     }
+    if (block_devices.empty()) {
+        LERROR << "No block devices were specified.";
+        return false;
+    }
 
     // Align the metadata size up to the nearest sector.
     metadata_max_size = AlignTo(metadata_max_size, LP_SECTOR_SIZE);
 
-    // Check that device properties are sane.
-    if (device_info.size % LP_SECTOR_SIZE != 0) {
-        LERROR << "Block device size must be a multiple of 512.";
+    // Validate and build the block device list.
+    uint32_t logical_block_size = 0;
+    for (const auto& device_info : block_devices) {
+        if (!VerifyDeviceProperties(device_info)) {
+            return false;
+        }
+
+        if (!logical_block_size) {
+            logical_block_size = device_info.logical_block_size;
+        }
+        if (logical_block_size != device_info.logical_block_size) {
+            LERROR << "All partitions must have the same logical block size.";
+            return false;
+        }
+
+        LpMetadataBlockDevice out = {};
+        out.alignment = device_info.alignment;
+        out.alignment_offset = device_info.alignment_offset;
+        out.size = device_info.size;
+        if (device_info.partition_name.size() >= sizeof(out.partition_name)) {
+            LERROR << "Partition name " << device_info.partition_name << " exceeds maximum length.";
+            return false;
+        }
+        strncpy(out.partition_name, device_info.partition_name.c_str(), sizeof(out.partition_name));
+
+        // In the case of the super partition, this field will be adjusted
+        // later. For all partitions, the first 512 bytes are considered
+        // untouched to be compatible code that looks for an MBR. Thus we
+        // start counting free sectors at sector 1, not 0.
+        uint64_t free_area_start = LP_SECTOR_SIZE;
+        if (out.alignment || out.alignment_offset) {
+            free_area_start = AlignTo(free_area_start, out.alignment, out.alignment_offset);
+        } else {
+            free_area_start = AlignTo(free_area_start, logical_block_size);
+        }
+        out.first_logical_sector = free_area_start / LP_SECTOR_SIZE;
+
+        // There must be one logical block of space available.
+        uint64_t minimum_size = out.first_logical_sector * LP_SECTOR_SIZE + logical_block_size;
+        if (device_info.size < minimum_size) {
+            LERROR << "Block device " << device_info.partition_name
+                   << " is too small to hold any logical partitions.";
+            return false;
+        }
+
+        // The "root" of the super partition is always listed first.
+        if (device_info.partition_name == super_partition) {
+            block_devices_.emplace(block_devices_.begin(), out);
+        } else {
+            block_devices_.emplace_back(out);
+        }
+    }
+    if (GetBlockDevicePartitionName(block_devices_[0]) != super_partition) {
+        LERROR << "No super partition was specified.";
         return false;
     }
-    if (device_info.logical_block_size % LP_SECTOR_SIZE != 0) {
-        LERROR << "Logical block size must be a multiple of 512.";
-        return false;
-    }
-    if (device_info.alignment_offset % LP_SECTOR_SIZE != 0) {
-        LERROR << "Alignment offset is not sector-aligned.";
-        return false;
-    }
-    if (device_info.alignment % LP_SECTOR_SIZE != 0) {
-        LERROR << "Partition alignment is not sector-aligned.";
-        return false;
-    }
-    if (device_info.alignment_offset > device_info.alignment) {
-        LERROR << "Partition alignment offset is greater than its alignment.";
-        return false;
-    }
+
+    LpMetadataBlockDevice& super = block_devices_[0];
 
     // We reserve a geometry block (4KB) plus space for each copy of the
     // maximum size of a metadata blob. Then, we double that space since
     // we store a backup copy of everything.
     uint64_t total_reserved = GetTotalMetadataSize(metadata_max_size, metadata_slot_count);
-    if (device_info.size < total_reserved) {
+    if (super.size < total_reserved) {
         LERROR << "Attempting to create metadata on a block device that is too small.";
         return false;
     }
 
     // Compute the first free sector, factoring in alignment.
     uint64_t free_area_start = total_reserved;
-    if (device_info.alignment || device_info.alignment_offset) {
-        free_area_start =
-                AlignTo(free_area_start, device_info.alignment, device_info.alignment_offset);
+    if (super.alignment || super.alignment_offset) {
+        free_area_start = AlignTo(free_area_start, super.alignment, super.alignment_offset);
     } else {
-        free_area_start = AlignTo(free_area_start, device_info.logical_block_size);
+        free_area_start = AlignTo(free_area_start, logical_block_size);
     }
-    uint64_t first_sector = free_area_start / LP_SECTOR_SIZE;
+    super.first_logical_sector = free_area_start / LP_SECTOR_SIZE;
 
     // There must be one logical block of free space remaining (enough for one partition).
-    uint64_t minimum_disk_size = (first_sector * LP_SECTOR_SIZE) + device_info.logical_block_size;
-    if (device_info.size < minimum_disk_size) {
+    uint64_t minimum_disk_size = (super.first_logical_sector * LP_SECTOR_SIZE) + logical_block_size;
+    if (super.size < minimum_disk_size) {
         LERROR << "Device must be at least " << minimum_disk_size << " bytes, only has "
-               << device_info.size;
+               << super.size;
         return false;
     }
 
-    block_devices_.push_back(LpMetadataBlockDevice{
-            first_sector,
-            device_info.alignment,
-            device_info.alignment_offset,
-            device_info.size,
-            "super",
-    });
-
     geometry_.metadata_max_size = metadata_max_size;
     geometry_.metadata_slot_count = metadata_slot_count;
-    geometry_.logical_block_size = device_info.logical_block_size;
+    geometry_.logical_block_size = logical_block_size;
 
     if (!AddGroup("default", 0)) {
         return false;
@@ -347,8 +419,9 @@
     for (size_t i = 1; i < extents.size(); i++) {
         const Interval& previous = extents[i - 1];
         const Interval& current = extents[i];
+        DCHECK(previous.device_index == current.device_index);
 
-        uint64_t aligned = AlignSector(previous.end);
+        uint64_t aligned = AlignSector(block_devices_[current.device_index], previous.end);
         if (aligned >= current.start) {
             // There is no gap between these two extents, try the next one.
             // Note that we check with >= instead of >, since alignment may
@@ -358,37 +431,43 @@
 
         // The new interval represents the free space starting at the end of
         // the previous interval, and ending at the start of the next interval.
-        free_regions->emplace_back(aligned, current.start);
+        free_regions->emplace_back(current.device_index, aligned, current.start);
     }
 }
 
 auto MetadataBuilder::GetFreeRegions() const -> std::vector<Interval> {
     std::vector<Interval> free_regions;
 
-    // Collect all extents in the partition table, then sort them by starting
-    // sector.
-    std::vector<Interval> extents;
+    // Collect all extents in the partition table, per-device, then sort them
+    // by starting sector.
+    std::vector<std::vector<Interval>> device_extents(block_devices_.size());
     for (const auto& partition : partitions_) {
         for (const auto& extent : partition->extents()) {
             LinearExtent* linear = extent->AsLinearExtent();
             if (!linear) {
                 continue;
             }
-            extents.emplace_back(linear->physical_sector(),
+            CHECK(linear->device_index() < device_extents.size());
+            auto& extents = device_extents[linear->device_index()];
+            extents.emplace_back(linear->device_index(), linear->physical_sector(),
                                  linear->physical_sector() + extent->num_sectors());
         }
     }
 
     // Add 0-length intervals for the first and last sectors. This will cause
     // ExtentToFreeList() to treat the space in between as available.
-    uint64_t first_sector = super_device().first_logical_sector;
-    uint64_t last_sector = super_device().size / LP_SECTOR_SIZE;
-    extents.emplace_back(first_sector, first_sector);
-    extents.emplace_back(last_sector, last_sector);
+    for (size_t i = 0; i < device_extents.size(); i++) {
+        auto& extents = device_extents[i];
+        const auto& block_device = block_devices_[i];
 
-    std::sort(extents.begin(), extents.end());
+        uint64_t first_sector = block_device.first_logical_sector;
+        uint64_t last_sector = block_device.size / LP_SECTOR_SIZE;
+        extents.emplace_back(i, first_sector, first_sector);
+        extents.emplace_back(i, last_sector, last_sector);
 
-    ExtentsToFreeList(extents, &free_regions);
+        std::sort(extents.begin(), extents.end());
+        ExtentsToFreeList(extents, &free_regions);
+    }
     return free_regions;
 }
 
@@ -443,7 +522,7 @@
         uint64_t sectors = std::min(sectors_needed, region.length());
         CHECK(sectors % sectors_per_block == 0);
 
-        auto extent = std::make_unique<LinearExtent>(sectors, region.start);
+        auto extent = std::make_unique<LinearExtent>(sectors, region.device_index, region.start);
         new_extents.push_back(std::move(extent));
         sectors_needed -= sectors;
         if (!sectors_needed) {
@@ -471,6 +550,9 @@
     metadata->header = header_;
     metadata->geometry = geometry_;
 
+    // Assign this early so the extent table can read it.
+    metadata->block_devices = block_devices_;
+
     std::map<std::string, size_t> group_indices;
     for (const auto& group : groups_) {
         LpMetadataPartitionGroup out = {};
@@ -515,13 +597,13 @@
         part.group_index = iter->second;
 
         for (const auto& extent : partition->extents()) {
-            extent->AddTo(metadata.get());
+            if (!extent->AddTo(metadata.get())) {
+                return nullptr;
+            }
         }
         metadata->partitions.push_back(part);
     }
 
-    metadata->block_devices = block_devices_;
-
     metadata->header.partitions.num_entries = static_cast<uint32_t>(metadata->partitions.size());
     metadata->header.extents.num_entries = static_cast<uint32_t>(metadata->extents.size());
     metadata->header.groups.num_entries = static_cast<uint32_t>(metadata->groups.size());
@@ -531,7 +613,11 @@
 }
 
 uint64_t MetadataBuilder::AllocatableSpace() const {
-    return super_device().size - (super_device().first_logical_sector * LP_SECTOR_SIZE);
+    uint64_t total_size = 0;
+    for (const auto& block_device : block_devices_) {
+        total_size += block_device.size - (block_device.first_logical_sector * LP_SECTOR_SIZE);
+    }
+    return total_size;
 }
 
 uint64_t MetadataBuilder::UsedSpace() const {
@@ -542,26 +628,58 @@
     return size;
 }
 
-uint64_t MetadataBuilder::AlignSector(uint64_t sector) const {
+uint64_t MetadataBuilder::AlignSector(const LpMetadataBlockDevice& block_device,
+                                      uint64_t sector) const {
     // Note: when reading alignment info from the Kernel, we don't assume it
     // is aligned to the sector size, so we round up to the nearest sector.
     uint64_t lba = sector * LP_SECTOR_SIZE;
-    uint64_t aligned = AlignTo(lba, super_device().alignment, super_device().alignment_offset);
+    uint64_t aligned = AlignTo(lba, block_device.alignment, block_device.alignment_offset);
     return AlignTo(aligned, LP_SECTOR_SIZE) / LP_SECTOR_SIZE;
 }
 
-bool MetadataBuilder::GetBlockDeviceInfo(BlockDeviceInfo* info) const {
-    info->size = super_device().size;
-    info->alignment = super_device().alignment;
-    info->alignment_offset = super_device().alignment_offset;
+bool MetadataBuilder::FindBlockDeviceByName(const std::string& partition_name,
+                                            uint32_t* index) const {
+    for (size_t i = 0; i < block_devices_.size(); i++) {
+        if (GetBlockDevicePartitionName(block_devices_[i]) == partition_name) {
+            *index = i;
+            return true;
+        }
+    }
+    return false;
+}
+
+bool MetadataBuilder::GetBlockDeviceInfo(const std::string& partition_name,
+                                         BlockDeviceInfo* info) const {
+    uint32_t index;
+    if (!FindBlockDeviceByName(partition_name, &index)) {
+        LERROR << "No device named " << partition_name;
+        return false;
+    }
+    info->size = block_devices_[index].size;
+    info->alignment = block_devices_[index].alignment;
+    info->alignment_offset = block_devices_[index].alignment_offset;
     info->logical_block_size = geometry_.logical_block_size;
+    info->partition_name = partition_name;
     return true;
 }
 
-bool MetadataBuilder::UpdateBlockDeviceInfo(const BlockDeviceInfo& device_info) {
-    if (device_info.size != super_device().size) {
+bool MetadataBuilder::UpdateBlockDeviceInfo(const std::string& partition_name,
+                                            const BlockDeviceInfo& device_info) {
+    uint32_t index;
+    if (!FindBlockDeviceByName(partition_name, &index)) {
+        LERROR << "No device named " << partition_name;
+        return false;
+    }
+    return UpdateBlockDeviceInfo(index, device_info);
+}
+
+bool MetadataBuilder::UpdateBlockDeviceInfo(size_t index, const BlockDeviceInfo& device_info) {
+    CHECK(index < block_devices_.size());
+
+    LpMetadataBlockDevice& block_device = block_devices_[index];
+    if (device_info.size != block_device.size) {
         LERROR << "Device size does not match (got " << device_info.size << ", expected "
-               << super_device().size << ")";
+               << block_device.size << ")";
         return false;
     }
     if (device_info.logical_block_size != geometry_.logical_block_size) {
@@ -573,10 +691,10 @@
     // The kernel does not guarantee these values are present, so we only
     // replace existing values if the new values are non-zero.
     if (device_info.alignment) {
-        super_device().alignment = device_info.alignment;
+        block_device.alignment = device_info.alignment;
     }
     if (device_info.alignment_offset) {
-        super_device().alignment_offset = device_info.alignment_offset;
+        block_device.alignment_offset = device_info.alignment_offset;
     }
     return true;
 }
diff --git a/fs_mgr/liblp/builder_test.cpp b/fs_mgr/liblp/builder_test.cpp
index c02242a..c27e300 100644
--- a/fs_mgr/liblp/builder_test.cpp
+++ b/fs_mgr/liblp/builder_test.cpp
@@ -27,6 +27,7 @@
 
 TEST(liblp, BuildBasic) {
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(1024 * 1024, 1024, 2);
+    ASSERT_NE(builder, nullptr);
 
     Partition* partition = builder->AddPartition("system", LP_PARTITION_ATTR_READONLY);
     ASSERT_NE(partition, nullptr);
@@ -41,6 +42,7 @@
 
 TEST(liblp, ResizePartition) {
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(1024 * 1024, 1024, 2);
+    ASSERT_NE(builder, nullptr);
 
     Partition* system = builder->AddPartition("system", LP_PARTITION_ATTR_READONLY);
     ASSERT_NE(system, nullptr);
@@ -94,6 +96,7 @@
 
 TEST(liblp, PartitionAlignment) {
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(1024 * 1024, 1024, 2);
+    ASSERT_NE(builder, nullptr);
 
     // Test that we align up to one sector.
     Partition* system = builder->AddPartition("system", LP_PARTITION_ATTR_READONLY);
@@ -120,6 +123,7 @@
 TEST(liblp, MetadataAlignment) {
     // Make sure metadata sizes get aligned up.
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(1024 * 1024, 1000, 2);
+    ASSERT_NE(builder, nullptr);
     unique_ptr<LpMetadata> exported = builder->Export();
     ASSERT_NE(exported, nullptr);
     EXPECT_EQ(exported->geometry.metadata_max_size, 1024);
@@ -127,7 +131,7 @@
 
 TEST(liblp, InternalAlignment) {
     // Test the metadata fitting within alignment.
-    BlockDeviceInfo device_info(1024 * 1024, 768 * 1024, 0, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 768 * 1024, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 2);
     ASSERT_NE(builder, nullptr);
     unique_ptr<LpMetadata> exported = builder->Export();
@@ -174,7 +178,7 @@
 }
 
 TEST(liblp, InternalPartitionAlignment) {
-    BlockDeviceInfo device_info(512 * 1024 * 1024, 768 * 1024, 753664, 4096);
+    BlockDeviceInfo device_info("super", 512 * 1024 * 1024, 768 * 1024, 753664, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 32 * 1024, 2);
 
     Partition* a = builder->AddPartition("a", 0);
@@ -394,7 +398,7 @@
     static const size_t kMetadataSize = 64 * 1024;
 
     // No space to store metadata + geometry.
-    BlockDeviceInfo device_info(kDiskSize, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", kDiskSize, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, kMetadataSize, 1);
     EXPECT_EQ(builder, nullptr);
 
@@ -441,12 +445,12 @@
 }
 
 TEST(liblp, UpdateBlockDeviceInfo) {
-    BlockDeviceInfo device_info(1024 * 1024, 4096, 1024, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 4096, 1024, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     ASSERT_NE(builder, nullptr);
 
     BlockDeviceInfo new_info;
-    ASSERT_TRUE(builder->GetBlockDeviceInfo(&new_info));
+    ASSERT_TRUE(builder->GetBlockDeviceInfo("super", &new_info));
 
     EXPECT_EQ(new_info.size, device_info.size);
     EXPECT_EQ(new_info.alignment, device_info.alignment);
@@ -455,37 +459,37 @@
 
     device_info.alignment = 0;
     device_info.alignment_offset = 2048;
-    ASSERT_TRUE(builder->UpdateBlockDeviceInfo(device_info));
-    ASSERT_TRUE(builder->GetBlockDeviceInfo(&new_info));
+    ASSERT_TRUE(builder->UpdateBlockDeviceInfo("super", device_info));
+    ASSERT_TRUE(builder->GetBlockDeviceInfo("super", &new_info));
     EXPECT_EQ(new_info.alignment, 4096);
     EXPECT_EQ(new_info.alignment_offset, device_info.alignment_offset);
 
     device_info.alignment = 8192;
     device_info.alignment_offset = 0;
-    ASSERT_TRUE(builder->UpdateBlockDeviceInfo(device_info));
-    ASSERT_TRUE(builder->GetBlockDeviceInfo(&new_info));
+    ASSERT_TRUE(builder->UpdateBlockDeviceInfo("super", device_info));
+    ASSERT_TRUE(builder->GetBlockDeviceInfo("super", &new_info));
     EXPECT_EQ(new_info.alignment, 8192);
     EXPECT_EQ(new_info.alignment_offset, 2048);
 
     new_info.size += 4096;
-    ASSERT_FALSE(builder->UpdateBlockDeviceInfo(new_info));
-    ASSERT_TRUE(builder->GetBlockDeviceInfo(&new_info));
+    ASSERT_FALSE(builder->UpdateBlockDeviceInfo("super", new_info));
+    ASSERT_TRUE(builder->GetBlockDeviceInfo("super", &new_info));
     EXPECT_EQ(new_info.size, 1024 * 1024);
 
     new_info.logical_block_size = 512;
-    ASSERT_FALSE(builder->UpdateBlockDeviceInfo(new_info));
-    ASSERT_TRUE(builder->GetBlockDeviceInfo(&new_info));
+    ASSERT_FALSE(builder->UpdateBlockDeviceInfo("super", new_info));
+    ASSERT_TRUE(builder->GetBlockDeviceInfo("super", &new_info));
     EXPECT_EQ(new_info.logical_block_size, 4096);
 }
 
 TEST(liblp, InvalidBlockSize) {
-    BlockDeviceInfo device_info(1024 * 1024, 0, 0, 513);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 0, 0, 513);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     EXPECT_EQ(builder, nullptr);
 }
 
 TEST(liblp, AlignedExtentSize) {
-    BlockDeviceInfo device_info(1024 * 1024, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     ASSERT_NE(builder, nullptr);
 
@@ -497,13 +501,13 @@
 
 TEST(liblp, AlignedFreeSpace) {
     // Only one sector free - at least one block is required.
-    BlockDeviceInfo device_info(10240, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", 10240, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 512, 1);
     ASSERT_EQ(builder, nullptr);
 }
 
 TEST(liblp, HasDefaultGroup) {
-    BlockDeviceInfo device_info(1024 * 1024, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     ASSERT_NE(builder, nullptr);
 
@@ -511,7 +515,7 @@
 }
 
 TEST(liblp, GroupSizeLimits) {
-    BlockDeviceInfo device_info(1024 * 1024, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     ASSERT_NE(builder, nullptr);
 
@@ -530,6 +534,9 @@
 constexpr unsigned long long operator"" _GiB(unsigned long long x) {  // NOLINT
     return x << 30;
 }
+constexpr unsigned long long operator"" _MiB(unsigned long long x) {  // NOLINT
+    return x << 20;
+}
 
 TEST(liblp, RemoveAndAddFirstPartition) {
     auto builder = MetadataBuilder::New(10_GiB, 65536, 2);
@@ -555,7 +562,7 @@
 }
 
 TEST(liblp, ListGroups) {
-    BlockDeviceInfo device_info(1024 * 1024, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     ASSERT_NE(builder, nullptr);
     ASSERT_TRUE(builder->AddGroup("example", 0));
@@ -565,7 +572,7 @@
 }
 
 TEST(liblp, RemoveGroupAndPartitions) {
-    BlockDeviceInfo device_info(1024 * 1024, 0, 0, 4096);
+    BlockDeviceInfo device_info("super", 1024 * 1024, 0, 0, 4096);
     unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(device_info, 1024, 1);
     ASSERT_NE(builder, nullptr);
     ASSERT_TRUE(builder->AddGroup("example", 0));
@@ -580,3 +587,48 @@
     builder->RemoveGroupAndPartitions("default");
     ASSERT_NE(builder->FindPartition("system"), nullptr);
 }
+
+TEST(liblp, MultipleBlockDevices) {
+    std::vector<BlockDeviceInfo> partitions = {
+            BlockDeviceInfo("system_a", 256_MiB, 786432, 229376, 4096),
+            BlockDeviceInfo("vendor_a", 128_MiB, 786432, 753664, 4096),
+            BlockDeviceInfo("product_a", 64_MiB, 786432, 753664, 4096),
+    };
+    unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(partitions, "system_a", 65536, 2);
+    ASSERT_NE(builder, nullptr);
+    EXPECT_EQ(builder->AllocatableSpace(), 467238912);
+
+    // Create a partition that spans 3 devices.
+    Partition* p = builder->AddPartition("system_a", 0);
+    ASSERT_NE(p, nullptr);
+    ASSERT_TRUE(builder->ResizePartition(p, 466976768));
+
+    unique_ptr<LpMetadata> metadata = builder->Export();
+    ASSERT_NE(metadata, nullptr);
+    ASSERT_EQ(metadata->block_devices.size(), 3);
+    EXPECT_EQ(GetBlockDevicePartitionName(metadata->block_devices[0]), "system_a");
+    EXPECT_EQ(metadata->block_devices[0].size, 256_MiB);
+    EXPECT_EQ(metadata->block_devices[0].alignment, 786432);
+    EXPECT_EQ(metadata->block_devices[0].alignment_offset, 229376);
+    EXPECT_EQ(GetBlockDevicePartitionName(metadata->block_devices[1]), "vendor_a");
+    EXPECT_EQ(metadata->block_devices[1].size, 128_MiB);
+    EXPECT_EQ(metadata->block_devices[1].alignment, 786432);
+    EXPECT_EQ(metadata->block_devices[1].alignment_offset, 753664);
+    EXPECT_EQ(GetBlockDevicePartitionName(metadata->block_devices[2]), "product_a");
+    EXPECT_EQ(metadata->block_devices[2].size, 64_MiB);
+    EXPECT_EQ(metadata->block_devices[2].alignment, 786432);
+    EXPECT_EQ(metadata->block_devices[2].alignment_offset, 753664);
+    ASSERT_EQ(metadata->extents.size(), 3);
+    EXPECT_EQ(metadata->extents[0].num_sectors, 522304);
+    EXPECT_EQ(metadata->extents[0].target_type, LP_TARGET_TYPE_LINEAR);
+    EXPECT_EQ(metadata->extents[0].target_data, 1984);
+    EXPECT_EQ(metadata->extents[0].target_source, 0);
+    EXPECT_EQ(metadata->extents[1].num_sectors, 260672);
+    EXPECT_EQ(metadata->extents[1].target_type, LP_TARGET_TYPE_LINEAR);
+    EXPECT_EQ(metadata->extents[1].target_data, 1472);
+    EXPECT_EQ(metadata->extents[1].target_source, 1);
+    EXPECT_EQ(metadata->extents[2].num_sectors, 129088);
+    EXPECT_EQ(metadata->extents[2].target_type, LP_TARGET_TYPE_LINEAR);
+    EXPECT_EQ(metadata->extents[2].target_data, 1472);
+    EXPECT_EQ(metadata->extents[2].target_source, 2);
+}
diff --git a/fs_mgr/liblp/include/liblp/builder.h b/fs_mgr/liblp/include/liblp/builder.h
index a090889..f9de106 100644
--- a/fs_mgr/liblp/include/liblp/builder.h
+++ b/fs_mgr/liblp/include/liblp/builder.h
@@ -41,7 +41,7 @@
     explicit Extent(uint64_t num_sectors) : num_sectors_(num_sectors) {}
     virtual ~Extent() {}
 
-    virtual void AddTo(LpMetadata* out) const = 0;
+    virtual bool AddTo(LpMetadata* out) const = 0;
     virtual LinearExtent* AsLinearExtent() { return nullptr; }
 
     uint64_t num_sectors() const { return num_sectors_; }
@@ -54,16 +54,18 @@
 // This corresponds to a dm-linear target.
 class LinearExtent final : public Extent {
   public:
-    LinearExtent(uint64_t num_sectors, uint64_t physical_sector)
-        : Extent(num_sectors), physical_sector_(physical_sector) {}
+    LinearExtent(uint64_t num_sectors, uint32_t device_index, uint64_t physical_sector)
+        : Extent(num_sectors), device_index_(device_index), physical_sector_(physical_sector) {}
 
-    void AddTo(LpMetadata* metadata) const override;
+    bool AddTo(LpMetadata* metadata) const override;
     LinearExtent* AsLinearExtent() override { return this; }
 
     uint64_t physical_sector() const { return physical_sector_; }
     uint64_t end_sector() const { return physical_sector_ + num_sectors_; }
+    uint32_t device_index() const { return device_index_; }
 
   private:
+    uint32_t device_index_;
     uint64_t physical_sector_;
 };
 
@@ -72,7 +74,7 @@
   public:
     explicit ZeroExtent(uint64_t num_sectors) : Extent(num_sectors) {}
 
-    void AddTo(LpMetadata* out) const override;
+    bool AddTo(LpMetadata* out) const override;
 };
 
 class PartitionGroup final {
@@ -122,15 +124,17 @@
 
 class MetadataBuilder {
   public:
-    // Construct an empty logical partition table builder. The block device size
-    // and maximum metadata size must be specified, as this will determine which
-    // areas of the physical partition can be flashed for metadata vs for logical
-    // partitions.
+    // Construct an empty logical partition table builder given the specified
+    // map of partitions that are available for storing logical partitions.
+    //
+    // At least one partition in the list must be the "super" device, where
+    // metadata will be stored.
     //
     // If the parameters would yield invalid metadata, nullptr is returned. This
-    // could happen if the block device size is too small to store the metadata
-    // and backup copies.
-    static std::unique_ptr<MetadataBuilder> New(const BlockDeviceInfo& device_info,
+    // could happen if the super device is too small to store all required
+    // metadata.
+    static std::unique_ptr<MetadataBuilder> New(const std::vector<BlockDeviceInfo>& block_devices,
+                                                const std::string& super_partition,
                                                 uint32_t metadata_max_size,
                                                 uint32_t metadata_slot_count);
 
@@ -150,11 +154,20 @@
     // This method is for testing or changing off-line tables.
     static std::unique_ptr<MetadataBuilder> New(const LpMetadata& metadata);
 
+    // Helper function for a single super partition, for tests.
+    static std::unique_ptr<MetadataBuilder> New(const BlockDeviceInfo& device_info,
+                                                uint32_t metadata_max_size,
+                                                uint32_t metadata_slot_count) {
+        return New({device_info}, device_info.partition_name, metadata_max_size,
+                   metadata_slot_count);
+    }
+
     // Wrapper around New() with a BlockDeviceInfo that only specifies a device
     // size. This is a convenience method for tests.
     static std::unique_ptr<MetadataBuilder> New(uint64_t blockdev_size, uint32_t metadata_max_size,
                                                 uint32_t metadata_slot_count) {
-        BlockDeviceInfo device_info(blockdev_size, 0, 0, kDefaultBlockSize);
+        BlockDeviceInfo device_info(LP_METADATA_DEFAULT_PARTITION_NAME, blockdev_size, 0, 0,
+                                    kDefaultBlockSize);
         return New(device_info, metadata_max_size, metadata_slot_count);
     }
 
@@ -209,8 +222,8 @@
     // Remove all partitions belonging to a group, then remove the group.
     void RemoveGroupAndPartitions(const std::string& group_name);
 
-    bool GetBlockDeviceInfo(BlockDeviceInfo* info) const;
-    bool UpdateBlockDeviceInfo(const BlockDeviceInfo& info);
+    bool GetBlockDeviceInfo(const std::string& partition_name, BlockDeviceInfo* info) const;
+    bool UpdateBlockDeviceInfo(const std::string& partition_name, const BlockDeviceInfo& info);
 
   private:
     MetadataBuilder();
@@ -218,19 +231,27 @@
     MetadataBuilder(MetadataBuilder&&) = delete;
     MetadataBuilder& operator=(const MetadataBuilder&) = delete;
     MetadataBuilder& operator=(MetadataBuilder&&) = delete;
-    bool Init(const BlockDeviceInfo& info, uint32_t metadata_max_size, uint32_t metadata_slot_count);
+    bool Init(const std::vector<BlockDeviceInfo>& block_devices, const std::string& super_partition,
+              uint32_t metadata_max_size, uint32_t metadata_slot_count);
     bool Init(const LpMetadata& metadata);
     bool GrowPartition(Partition* partition, uint64_t aligned_size);
     void ShrinkPartition(Partition* partition, uint64_t aligned_size);
-    uint64_t AlignSector(uint64_t sector) const;
+    uint64_t AlignSector(const LpMetadataBlockDevice& device, uint64_t sector) const;
     uint64_t TotalSizeOfGroup(PartitionGroup* group) const;
+    bool UpdateBlockDeviceInfo(size_t index, const BlockDeviceInfo& info);
+    bool FindBlockDeviceByName(const std::string& partition_name, uint32_t* index) const;
 
     struct Interval {
+        uint32_t device_index;
         uint64_t start;
         uint64_t end;
 
-        Interval(uint64_t start, uint64_t end) : start(start), end(end) {}
+        Interval(uint32_t device_index, uint64_t start, uint64_t end)
+            : device_index(device_index), start(start), end(end) {}
         uint64_t length() const { return end - start; }
+
+        // Note: the device index is not included in sorting (intervals are
+        // sorted in per-device lists).
         bool operator<(const Interval& other) const {
             return (start == other.start) ? end < other.end : start < other.start;
         }
@@ -239,9 +260,6 @@
     void ExtentsToFreeList(const std::vector<Interval>& extents,
                            std::vector<Interval>* free_regions) const;
 
-    const LpMetadataBlockDevice& super_device() const { return block_devices_[0]; }
-    LpMetadataBlockDevice& super_device() { return block_devices_[0]; }
-
     LpMetadataGeometry geometry_;
     LpMetadataHeader header_;
     std::vector<std::unique_ptr<Partition>> partitions_;
diff --git a/fs_mgr/liblp/include/liblp/metadata_format.h b/fs_mgr/liblp/include/liblp/metadata_format.h
index 8a309be..1e40df3 100644
--- a/fs_mgr/liblp/include/liblp/metadata_format.h
+++ b/fs_mgr/liblp/include/liblp/metadata_format.h
@@ -38,7 +38,7 @@
 #define LP_METADATA_HEADER_MAGIC 0x414C5030
 
 /* Current metadata version. */
-#define LP_METADATA_MAJOR_VERSION 7
+#define LP_METADATA_MAJOR_VERSION 8
 #define LP_METADATA_MINOR_VERSION 0
 
 /* Attributes for the LpMetadataPartition::attributes field.
@@ -240,6 +240,13 @@
      * ZERO: This field must be 0.
      */
     uint64_t target_data;
+
+    /* 20: Contents depends on target_type.
+     *
+     * LINEAR: Must be an index into the block devices table.
+     * ZERO: This field must be 0.
+     */
+    uint32_t target_source;
 } __attribute__((packed)) LpMetadataExtent;
 
 /* This struct defines an entry in the groups table. Each group has a maximum
@@ -255,8 +262,9 @@
     uint64_t maximum_size;
 } LpMetadataPartitionGroup;
 
-/* This struct defines an entry in the block_devices table. There must be
- * exactly one device, corresponding to the super partition.
+/* This struct defines an entry in the block_devices table. There must be at
+ * least one device, and the first device must represent the partition holding
+ * the super metadata.
  */
 typedef struct LpMetadataBlockDevice {
     /* 0: First usable sector for allocating logical partitions. this will be
diff --git a/fs_mgr/liblp/include/liblp/partition_opener.h b/fs_mgr/liblp/include/liblp/partition_opener.h
index fe61b9c..e506bd5 100644
--- a/fs_mgr/liblp/include/liblp/partition_opener.h
+++ b/fs_mgr/liblp/include/liblp/partition_opener.h
@@ -27,12 +27,13 @@
 
 struct BlockDeviceInfo {
     BlockDeviceInfo() : size(0), alignment(0), alignment_offset(0), logical_block_size(0) {}
-    BlockDeviceInfo(uint64_t size, uint32_t alignment, uint32_t alignment_offset,
-                    uint32_t logical_block_size)
+    BlockDeviceInfo(const std::string& partition_name, uint64_t size, uint32_t alignment,
+                    uint32_t alignment_offset, uint32_t logical_block_size)
         : size(size),
           alignment(alignment),
           alignment_offset(alignment_offset),
-          logical_block_size(logical_block_size) {}
+          logical_block_size(logical_block_size),
+          partition_name(partition_name) {}
     // Size of the block device, in bytes.
     uint64_t size;
     // Optimal target alignment, in bytes. Partition extents will be aligned to
@@ -44,6 +45,9 @@
     uint32_t alignment_offset;
     // Block size, for aligning extent sizes and partition sizes.
     uint32_t logical_block_size;
+    // The physical partition name for this block device, as it would appear in
+    // the GPT or under /dev/block/by-name.
+    std::string partition_name;
 };
 
 // Test-friendly interface for interacting with partitions.
diff --git a/fs_mgr/liblp/io_test.cpp b/fs_mgr/liblp/io_test.cpp
index 9c675fe..603e5c0 100644
--- a/fs_mgr/liblp/io_test.cpp
+++ b/fs_mgr/liblp/io_test.cpp
@@ -128,7 +128,7 @@
 // Flashing metadata should not work if the metadata was created for a larger
 // disk than the destination disk.
 TEST(liblp, ExportDiskTooSmall) {
-    unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(kDiskSize + 1024, 512, 2);
+    unique_ptr<MetadataBuilder> builder = MetadataBuilder::New(kDiskSize + 4096, 512, 2);
     ASSERT_NE(builder, nullptr);
     unique_ptr<LpMetadata> exported = builder->Export();
     ASSERT_NE(exported, nullptr);
@@ -581,7 +581,7 @@
     unique_fd fd = CreateFakeDisk();
     ASSERT_GE(fd, 0);
 
-    BlockDeviceInfo device_info(kDiskSize, 0, 0, 512);
+    BlockDeviceInfo device_info("super", kDiskSize, 0, 0, 512);
     unique_ptr<MetadataBuilder> builder =
             MetadataBuilder::New(device_info, kMetadataSize, kMetadataSlots);
     ASSERT_NE(builder, nullptr);
diff --git a/fs_mgr/liblp/partition_opener.cpp b/fs_mgr/liblp/partition_opener.cpp
index 7381eed..77b0e62 100644
--- a/fs_mgr/liblp/partition_opener.cpp
+++ b/fs_mgr/liblp/partition_opener.cpp
@@ -24,6 +24,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <android-base/file.h>
+
 #include "utility.h"
 
 namespace android {
@@ -68,6 +70,7 @@
 
     device_info->alignment_offset = static_cast<uint32_t>(alignment_offset);
     device_info->logical_block_size = static_cast<uint32_t>(logical_block_size);
+    device_info->partition_name = android::base::Basename(block_device);
     return true;
 #else
     (void)block_device;
diff --git a/fs_mgr/liblp/reader.cpp b/fs_mgr/liblp/reader.cpp
index 070573c..a02e746 100644
--- a/fs_mgr/liblp/reader.cpp
+++ b/fs_mgr/liblp/reader.cpp
@@ -274,6 +274,12 @@
         memcpy(&extent, cursor, sizeof(extent));
         cursor += header.extents.entry_size;
 
+        if (extent.target_type == LP_TARGET_TYPE_LINEAR &&
+            extent.target_source >= header.block_devices.num_entries) {
+            LERROR << "Logical partition extent has invalid block device.";
+            return nullptr;
+        }
+
         metadata->extents.push_back(extent);
     }
 
diff --git a/fs_mgr/tests/adb-remount-test.sh b/fs_mgr/tests/adb-remount-test.sh
index 497f33f..b6a8eef 100755
--- a/fs_mgr/tests/adb-remount-test.sh
+++ b/fs_mgr/tests/adb-remount-test.sh
@@ -267,8 +267,33 @@
   B="`adb_cat /vendor/hello`" ||
   die "re-read vendor hello after reboot"
 check_eq "${A}" "${B}" vendor after reboot
+
+adb reboot-fastboot &&
+  fastboot flash vendor &&
+  fastboot reboot ||
+  die "fastbootd flash vendor"
+adb_wait &&
+  adb_root &&
+  adb_wait &&
+  adb_sh df -k </dev/null | head -1 &&
+  adb_sh df -k </dev/null | grep "^overlay " &&
+  adb_sh df -k </dev/null | grep "^overlay .* /system\$" >/dev/null ||
+  die  "overlay system takeover after flash vendor"
+adb_sh df -k </dev/null | grep "^overlay .* /vendor\$" >/dev/null &&
+  die  "overlay minus vendor takeover after flash vendor"
+B="`adb_cat /system/hello`" ||
+  die "re-read system hello after flash vendor"
+check_eq "${A}" "${B}" system after flash vendor
+adb_root &&
+  adb_wait ||
+  die "adb root"
+B="`adb_cat /vendor/hello`" &&
+  die "re-read vendor hello after flash vendor"
+check_eq "cat: /vendor/hello: No such file or directory" "${B}" vendor after flash vendor
+
 adb remount &&
-  adb_sh rm /system/hello /vendor/hello </dev/null ||
+  ( adb_sh rm /vendor/hello </dev/null 2>/dev/null || true ) &&
+  adb_sh rm /system/hello </dev/null ||
   die "cleanup hello"
 B="`adb_cat /system/hello`" &&
   die "re-read system hello after rm"
diff --git a/init/Android.bp b/init/Android.bp
index c793971..ff3b61f 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -74,6 +74,7 @@
         "libdl",
         "libext4_utils",
         "libfs_mgr",
+        "libfscrypt",
         "libhidl-gen-utils",
         "libkeyutils",
         "liblog",
diff --git a/init/Android.mk b/init/Android.mk
index ef08329..c85727c 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -73,6 +73,7 @@
     libsquashfs_utils \
     liblogwrap \
     libext4_utils \
+    libfscrypt \
     libseccomp_policy \
     libcrypto_utils \
     libsparse \
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 7da2526..5d62c0b 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -50,9 +50,9 @@
 #include <android-base/unique_fd.h>
 #include <bootloader_message/bootloader_message.h>
 #include <cutils/android_reboot.h>
-#include <ext4_utils/ext4_crypt.h>
-#include <ext4_utils/ext4_crypt_init_extensions.h>
 #include <fs_mgr.h>
+#include <fscrypt/fscrypt.h>
+#include <fscrypt/fscrypt_init_extensions.h>
 #include <selinux/android.h>
 #include <selinux/label.h>
 #include <selinux/selinux.h>
@@ -307,8 +307,8 @@
         }
     }
 
-    if (e4crypt_is_native()) {
-        if (e4crypt_set_directory_policy(args[1].c_str())) {
+    if (fscrypt_is_native()) {
+        if (fscrypt_set_directory_policy(args[1].c_str())) {
             return reboot_into_recovery(
                 {"--prompt_and_wipe_data", "--reason=set_policy_failed:"s + args[1]});
         }
@@ -517,8 +517,8 @@
         return reboot_into_recovery(options);
         /* If reboot worked, there is no return. */
     } else if (code == FS_MGR_MNTALL_DEV_FILE_ENCRYPTED) {
-        if (e4crypt_install_keyring()) {
-            return Error() << "e4crypt_install_keyring() failed";
+        if (fscrypt_install_keyring()) {
+            return Error() << "fscrypt_install_keyring() failed";
         }
         property_set("ro.crypto.state", "encrypted");
         property_set("ro.crypto.type", "file");
@@ -528,8 +528,8 @@
         ActionManager::GetInstance().QueueEventTrigger("nonencrypted");
         return Success();
     } else if (code == FS_MGR_MNTALL_DEV_IS_METADATA_ENCRYPTED) {
-        if (e4crypt_install_keyring()) {
-            return Error() << "e4crypt_install_keyring() failed";
+        if (fscrypt_install_keyring()) {
+            return Error() << "fscrypt_install_keyring() failed";
         }
         property_set("ro.crypto.state", "encrypted");
         property_set("ro.crypto.type", "file");
@@ -539,8 +539,8 @@
         ActionManager::GetInstance().QueueEventTrigger("nonencrypted");
         return Success();
     } else if (code == FS_MGR_MNTALL_DEV_NEEDS_METADATA_ENCRYPTION) {
-        if (e4crypt_install_keyring()) {
-            return Error() << "e4crypt_install_keyring() failed";
+        if (fscrypt_install_keyring()) {
+            return Error() << "fscrypt_install_keyring() failed";
         }
         property_set("ro.crypto.state", "encrypted");
         property_set("ro.crypto.type", "file");
@@ -1016,7 +1016,7 @@
     }
     service->AddReapCallback([reboot_reason](const siginfo_t& siginfo) {
         if (siginfo.si_code != CLD_EXITED || siginfo.si_status != 0) {
-            if (e4crypt_is_native()) {
+            if (fscrypt_is_native()) {
                 LOG(ERROR) << "Rebooting into recovery, reason: " << reboot_reason;
                 if (auto result = reboot_into_recovery(
                             {"--prompt_and_wipe_data", "--reason="s + reboot_reason});
@@ -1038,7 +1038,7 @@
 static Result<Success> do_installkey(const BuiltinArguments& args) {
     if (!is_file_crypto()) return Success();
 
-    auto unencrypted_dir = args[1] + e4crypt_unencrypted_folder;
+    auto unencrypted_dir = args[1] + fscrypt_unencrypted_folder;
     if (!make_dir(unencrypted_dir, 0700) && errno != EEXIST) {
         return ErrnoError() << "Failed to create " << unencrypted_dir;
     }
diff --git a/libziparchive/zip_archive.cc b/libziparchive/zip_archive.cc
index 9d6d919..9eb7f2c 100644
--- a/libziparchive/zip_archive.cc
+++ b/libziparchive/zip_archive.cc
@@ -34,6 +34,10 @@
 #include <memory>
 #include <vector>
 
+#if defined(__APPLE__)
+#define lseek64 lseek
+#endif
+
 #if defined(__BIONIC__)
 #include <android/fdsan.h>
 #endif
diff --git a/libziparchive/zip_archive_test.cc b/libziparchive/zip_archive_test.cc
index af9f4c8..0ea7d5d 100644
--- a/libziparchive/zip_archive_test.cc
+++ b/libziparchive/zip_archive_test.cc
@@ -348,7 +348,7 @@
   // Read the file back to a buffer and make sure the contents are
   // the same as the memory buffer we extracted directly to.
   std::vector<uint8_t> file_contents(kAbUncompressedSize);
-  ASSERT_EQ(0, lseek64(tmp_output_file.fd, 0, SEEK_SET));
+  ASSERT_EQ(0, lseek(tmp_output_file.fd, 0, SEEK_SET));
   ASSERT_TRUE(android::base::ReadFully(tmp_output_file.fd, &file_contents[0], file_contents.size()));
   ASSERT_EQ(file_contents, buffer);
 
@@ -392,7 +392,7 @@
 
   // Assert that the first 8 bytes of the file haven't been clobbered.
   uint8_t read_buffer[data_size];
-  ASSERT_EQ(0, lseek64(tmp_file.fd, 0, SEEK_SET));
+  ASSERT_EQ(0, lseek(tmp_file.fd, 0, SEEK_SET));
   ASSERT_TRUE(android::base::ReadFully(tmp_file.fd, read_buffer, data_size));
   ASSERT_EQ(0, memcmp(read_buffer, data, data_size));
 
@@ -404,7 +404,7 @@
 
   // Assert that the total length of the file is sane
   ASSERT_EQ(static_cast<ssize_t>(data_size + kATxtContents.size()),
-            lseek64(tmp_file.fd, 0, SEEK_END));
+            lseek(tmp_file.fd, 0, SEEK_END));
 }
 
 #if !defined(_WIN32)
diff --git a/lmkd/lmkd.c b/lmkd/lmkd.c
index e3c4ccc..c9c9e8e 100644
--- a/lmkd/lmkd.c
+++ b/lmkd/lmkd.c
@@ -1260,6 +1260,8 @@
     return maxprocp;
 }
 
+static int last_killed_pid = -1;
+
 /* Kill one process specified by procp.  Returns the size of the process killed */
 static int kill_one_process(struct proc* procp) {
     int pid = procp->pid;
@@ -1304,6 +1306,8 @@
 
     TRACE_KILL_END();
 
+    last_killed_pid = pid;
+
     if (r) {
         ALOGE("kill(%d): errno=%d", pid, errno);
         goto out;
@@ -1331,14 +1335,12 @@
 }
 
 /*
- * Find processes to kill to free required number of pages.
- * If pages_to_free is set to 0 only one process will be killed.
- * Returns the size of the killed processes.
+ * Find one process to kill at or above the given oom_adj level.
+ * Returns size of the killed process.
  */
-static int find_and_kill_processes(int min_score_adj, int pages_to_free) {
+static int find_and_kill_process(int min_score_adj) {
     int i;
-    int killed_size;
-    int pages_freed = 0;
+    int killed_size = 0;
 
 #ifdef LMKD_LOG_STATS
     bool lmk_state_change_start = false;
@@ -1363,20 +1365,12 @@
                                                   LMK_STATE_CHANGE_START);
                 }
 #endif
-
-                pages_freed += killed_size;
-                if (pages_freed >= pages_to_free) {
-
-#ifdef LMKD_LOG_STATS
-                    if (enable_stats_log && lmk_state_change_start) {
-                        stats_write_lmk_state_changed(log_ctx, LMK_STATE_CHANGED,
-                                LMK_STATE_CHANGE_STOP);
-                    }
-#endif
-                    return pages_freed;
-                }
+                break;
             }
         }
+        if (killed_size) {
+            break;
+        }
     }
 
 #ifdef LMKD_LOG_STATS
@@ -1385,7 +1379,7 @@
     }
 #endif
 
-    return pages_freed;
+    return killed_size;
 }
 
 static int64_t get_memory_usage(struct reread_data *file_data) {
@@ -1445,6 +1439,23 @@
         level - 1 : level);
 }
 
+static bool is_kill_pending(void) {
+    char buf[24];
+
+    if (last_killed_pid < 0) {
+        return false;
+    }
+
+    snprintf(buf, sizeof(buf), "/proc/%d/", last_killed_pid);
+    if (access(buf, F_OK) == 0) {
+        return true;
+    }
+
+    // reset last killed PID because there's nothing pending
+    last_killed_pid = -1;
+    return false;
+}
+
 static void mp_event_common(int data, uint32_t events __unused) {
     int ret;
     unsigned long long evcount;
@@ -1459,7 +1470,6 @@
     enum vmpressure_level level = (enum vmpressure_level)data;
     long other_free = 0, other_file = 0;
     int min_score_adj;
-    int pages_to_free = 0;
     int minfree = 0;
     static struct reread_data mem_usage_file_data = {
         .filename = MEMCG_MEMORY_USAGE,
@@ -1490,7 +1500,11 @@
     }
 
     if (kill_timeout_ms) {
-        if (get_time_diff_ms(&last_kill_tm, &curr_tm) < kill_timeout_ms) {
+        // If we're within the timeout, see if there's pending reclaim work
+        // from the last killed process. If there is (as evidenced by
+        // /proc/<pid> continuing to exist), skip killing for now.
+        if ((get_time_diff_ms(&last_kill_tm, &curr_tm) < kill_timeout_ms) &&
+            (low_ram_device || is_kill_pending())) {
             kill_skip_count++;
             return;
         }
@@ -1537,9 +1551,6 @@
             return;
         }
 
-        /* Free up enough pages to push over the highest minfree level */
-        pages_to_free = lowmem_minfree[lowmem_targets_size - 1] -
-            ((other_free < other_file) ? other_free : other_file);
         goto do_kill;
     }
 
@@ -1595,7 +1606,7 @@
 do_kill:
     if (low_ram_device) {
         /* For Go devices kill only one task */
-        if (find_and_kill_processes(level_oomadj[level], 0) == 0) {
+        if (find_and_kill_process(level_oomadj[level]) == 0) {
             if (debug_process_killing) {
                 ALOGI("Nothing to kill");
             }
@@ -1619,10 +1630,7 @@
                 return;
             }
             /* Free up enough memory to downgrate the memory pressure to low level */
-            if (mi.field.nr_free_pages < low_pressure_mem.max_nr_free_pages) {
-                pages_to_free = low_pressure_mem.max_nr_free_pages -
-                    mi.field.nr_free_pages;
-            } else {
+            if (mi.field.nr_free_pages >= low_pressure_mem.max_nr_free_pages) {
                 if (debug_process_killing) {
                     ALOGI("Ignoring pressure since more memory is "
                         "available (%" PRId64 ") than watermark (%" PRId64 ")",
@@ -1633,7 +1641,7 @@
             min_score_adj = level_oomadj[level];
         }
 
-        pages_freed = find_and_kill_processes(min_score_adj, pages_to_free);
+        pages_freed = find_and_kill_process(min_score_adj);
 
         if (pages_freed == 0) {
             /* Rate limit kill reports when nothing was reclaimed */
@@ -1641,25 +1649,24 @@
                 report_skip_count++;
                 return;
             }
+        } else {
+            /* If we killed anything, update the last killed timestamp. */
+            last_kill_tm = curr_tm;
         }
 
         /* Log meminfo whenever we kill or when report rate limit allows */
         meminfo_log(&mi);
-        if (pages_freed >= pages_to_free) {
-            /* Reset kill time only if reclaimed enough memory */
-            last_kill_tm = curr_tm;
-        }
 
         if (use_minfree_levels) {
-            ALOGI("Killing to reclaim %ldkB, reclaimed %ldkB, cache(%ldkB) and "
+            ALOGI("Reclaimed %ldkB, cache(%ldkB) and "
                 "free(%" PRId64 "kB)-reserved(%" PRId64 "kB) below min(%ldkB) for oom_adj %d",
-                pages_to_free * page_k, pages_freed * page_k,
+                pages_freed * page_k,
                 other_file * page_k, mi.field.nr_free_pages * page_k,
                 zi.field.totalreserve_pages * page_k,
                 minfree * page_k, min_score_adj);
         } else {
-            ALOGI("Killing to reclaim %ldkB, reclaimed %ldkB at oom_adj %d",
-                pages_to_free * page_k, pages_freed * page_k, min_score_adj);
+            ALOGI("Reclaimed %ldkB at oom_adj %d",
+                pages_freed * page_k, min_score_adj);
         }
 
         if (report_skip_count > 0) {