Merge "liblp: Store device information in a new block device table."
diff --git a/fs_mgr/fs_mgr_dm_linear.cpp b/fs_mgr/fs_mgr_dm_linear.cpp
index 804069a..6ddd5a8 100644
--- a/fs_mgr/fs_mgr_dm_linear.cpp
+++ b/fs_mgr/fs_mgr_dm_linear.cpp
@@ -33,6 +33,7 @@
 
 #include <sstream>
 
+#include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
@@ -50,8 +51,21 @@
 using DmTargetZero = android::dm::DmTargetZero;
 using DmTargetLinear = android::dm::DmTargetLinear;
 
-static bool CreateDmTable(const std::string& block_device, const LpMetadata& metadata,
-                          const LpMetadataPartition& partition, DmTable* table) {
+bool GetPhysicalPartitionDevicePath(const LpMetadataBlockDevice& block_device,
+                                    std::string* result) {
+    // Note: device-mapper will not accept symlinks, so we must use realpath
+    // here.
+    std::string name = GetBlockDevicePartitionName(block_device);
+    std::string path = "/dev/block/by-name/" + name;
+    if (!android::base::Realpath(path, result)) {
+        PERROR << "realpath: " << path;
+        return false;
+    }
+    return true;
+}
+
+static bool CreateDmTable(const LpMetadata& metadata, const LpMetadataPartition& partition,
+                          DmTable* table) {
     uint64_t sector = 0;
     for (size_t i = 0; i < partition.num_extents; i++) {
         const auto& extent = metadata.extents[partition.first_extent_index + i];
@@ -60,10 +74,22 @@
             case LP_TARGET_TYPE_ZERO:
                 target = std::make_unique<DmTargetZero>(sector, extent.num_sectors);
                 break;
-            case LP_TARGET_TYPE_LINEAR:
-                target = std::make_unique<DmTargetLinear>(sector, extent.num_sectors, block_device,
+            case LP_TARGET_TYPE_LINEAR: {
+                auto block_device = GetMetadataSuperBlockDevice(metadata);
+                if (!block_device) {
+                    LOG(ERROR) << "Could not identify the super block device";
+                    return false;
+                }
+
+                std::string path;
+                if (!GetPhysicalPartitionDevicePath(*block_device, &path)) {
+                    LOG(ERROR) << "Unable to complete device-mapper table, unknown block device";
+                    return false;
+                }
+                target = std::make_unique<DmTargetLinear>(sector, extent.num_sectors, path,
                                                           extent.target_data);
                 break;
+            }
             default:
                 LOG(ERROR) << "Unknown target type in metadata: " << extent.target_type;
                 return false;
@@ -79,13 +105,13 @@
     return true;
 }
 
-static bool CreateLogicalPartition(const std::string& block_device, const LpMetadata& metadata,
-                                   const LpMetadataPartition& partition, bool force_writable,
-                                   const std::chrono::milliseconds& timeout_ms, std::string* path) {
+static bool CreateLogicalPartition(const LpMetadata& metadata, const LpMetadataPartition& partition,
+                                   bool force_writable, const std::chrono::milliseconds& timeout_ms,
+                                   std::string* path) {
     DeviceMapper& dm = DeviceMapper::Instance();
 
     DmTable table;
-    if (!CreateDmTable(block_device, metadata, partition, &table)) {
+    if (!CreateDmTable(metadata, partition, &table)) {
         return false;
     }
     if (force_writable) {
@@ -122,7 +148,7 @@
             continue;
         }
         std::string path;
-        if (!CreateLogicalPartition(block_device, *metadata.get(), partition, false, {}, &path)) {
+        if (!CreateLogicalPartition(*metadata.get(), partition, false, {}, &path)) {
             LERROR << "Could not create logical partition: " << GetPartitionName(partition);
             return false;
         }
@@ -140,8 +166,8 @@
     }
     for (const auto& partition : metadata->partitions) {
         if (GetPartitionName(partition) == partition_name) {
-            return CreateLogicalPartition(block_device, *metadata.get(), partition, force_writable,
-                                          timeout_ms, path);
+            return CreateLogicalPartition(*metadata.get(), partition, force_writable, timeout_ms,
+                                          path);
         }
     }
     LERROR << "Could not find any partition with name: " << partition_name;
diff --git a/fs_mgr/liblp/builder.cpp b/fs_mgr/liblp/builder.cpp
index 2c57a35..4dd60e9 100644
--- a/fs_mgr/liblp/builder.cpp
+++ b/fs_mgr/liblp/builder.cpp
@@ -186,6 +186,7 @@
     header_.partitions.entry_size = sizeof(LpMetadataPartition);
     header_.extents.entry_size = sizeof(LpMetadataExtent);
     header_.groups.entry_size = sizeof(LpMetadataPartitionGroup);
+    header_.block_devices.entry_size = sizeof(LpMetadataBlockDevice);
 }
 
 bool MetadataBuilder::Init(const LpMetadata& metadata) {
@@ -198,6 +199,10 @@
         }
     }
 
+    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 =
@@ -259,9 +264,7 @@
     // 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 reserved =
-            LP_METADATA_GEOMETRY_SIZE + (uint64_t(metadata_max_size) * metadata_slot_count);
-    uint64_t total_reserved = LP_PARTITION_RESERVED_BYTES + reserved * 2;
+    uint64_t total_reserved = GetTotalMetadataSize(metadata_max_size, metadata_slot_count);
     if (device_info.size < total_reserved) {
         LERROR << "Attempting to create metadata on a block device that is too small.";
         return false;
@@ -285,12 +288,16 @@
         return false;
     }
 
-    geometry_.first_logical_sector = first_sector;
+    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_.alignment = device_info.alignment;
-    geometry_.alignment_offset = device_info.alignment_offset;
-    geometry_.block_device_size = device_info.size;
     geometry_.logical_block_size = device_info.logical_block_size;
 
     if (!AddGroup("default", 0)) {
@@ -408,9 +415,10 @@
     }
 
     // Add 0-length intervals for the first and last sectors. This will cause
-    // ExtentsToFreeList() to treat the space in between as available.
-    uint64_t last_sector = geometry_.block_device_size / LP_SECTOR_SIZE;
-    extents.emplace_back(geometry_.first_logical_sector, geometry_.first_logical_sector);
+    // 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);
 
     std::sort(extents.begin(), extents.end());
@@ -547,14 +555,18 @@
         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());
+    metadata->header.block_devices.num_entries =
+            static_cast<uint32_t>(metadata->block_devices.size());
     return metadata;
 }
 
 uint64_t MetadataBuilder::AllocatableSpace() const {
-    return geometry_.block_device_size - (geometry_.first_logical_sector * LP_SECTOR_SIZE);
+    return super_device().size - (super_device().first_logical_sector * LP_SECTOR_SIZE);
 }
 
 uint64_t MetadataBuilder::UsedSpace() const {
@@ -569,22 +581,22 @@
     // 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, geometry_.alignment, geometry_.alignment_offset);
+    uint64_t aligned = AlignTo(lba, super_device().alignment, super_device().alignment_offset);
     return AlignTo(aligned, LP_SECTOR_SIZE) / LP_SECTOR_SIZE;
 }
 
 bool MetadataBuilder::GetBlockDeviceInfo(BlockDeviceInfo* info) const {
-    info->size = geometry_.block_device_size;
-    info->alignment = geometry_.alignment;
-    info->alignment_offset = geometry_.alignment_offset;
+    info->size = super_device().size;
+    info->alignment = super_device().alignment;
+    info->alignment_offset = super_device().alignment_offset;
     info->logical_block_size = geometry_.logical_block_size;
     return true;
 }
 
 bool MetadataBuilder::UpdateBlockDeviceInfo(const BlockDeviceInfo& device_info) {
-    if (device_info.size != geometry_.block_device_size) {
+    if (device_info.size != super_device().size) {
         LERROR << "Device size does not match (got " << device_info.size << ", expected "
-               << geometry_.block_device_size << ")";
+               << super_device().size << ")";
         return false;
     }
     if (device_info.logical_block_size != geometry_.logical_block_size) {
@@ -596,10 +608,10 @@
     // 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) {
-        geometry_.alignment = device_info.alignment;
+        super_device().alignment = device_info.alignment;
     }
     if (device_info.alignment_offset) {
-        geometry_.alignment_offset = device_info.alignment_offset;
+        super_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 27ad250..c3a5ffe 100644
--- a/fs_mgr/liblp/builder_test.cpp
+++ b/fs_mgr/liblp/builder_test.cpp
@@ -132,7 +132,9 @@
     ASSERT_NE(builder, nullptr);
     unique_ptr<LpMetadata> exported = builder->Export();
     ASSERT_NE(exported, nullptr);
-    EXPECT_EQ(exported->geometry.first_logical_sector, 1536);
+    auto super_device = GetMetadataSuperBlockDevice(*exported.get());
+    ASSERT_NE(super_device, nullptr);
+    EXPECT_EQ(super_device->first_logical_sector, 1536);
 
     // Test a large alignment offset thrown in.
     device_info.alignment_offset = 753664;
@@ -140,7 +142,9 @@
     ASSERT_NE(builder, nullptr);
     exported = builder->Export();
     ASSERT_NE(exported, nullptr);
-    EXPECT_EQ(exported->geometry.first_logical_sector, 1472);
+    super_device = GetMetadataSuperBlockDevice(*exported.get());
+    ASSERT_NE(super_device, nullptr);
+    EXPECT_EQ(super_device->first_logical_sector, 1472);
 
     // Alignment offset without alignment doesn't mean anything.
     device_info.alignment = 0;
@@ -154,7 +158,9 @@
     ASSERT_NE(builder, nullptr);
     exported = builder->Export();
     ASSERT_NE(exported, nullptr);
-    EXPECT_EQ(exported->geometry.first_logical_sector, 174);
+    super_device = GetMetadataSuperBlockDevice(*exported.get());
+    ASSERT_NE(super_device, nullptr);
+    EXPECT_EQ(super_device->first_logical_sector, 174);
 
     // Test a small alignment with no alignment offset.
     device_info.alignment = 11 * 1024;
@@ -162,7 +168,9 @@
     ASSERT_NE(builder, nullptr);
     exported = builder->Export();
     ASSERT_NE(exported, nullptr);
-    EXPECT_EQ(exported->geometry.first_logical_sector, 160);
+    super_device = GetMetadataSuperBlockDevice(*exported.get());
+    ASSERT_NE(super_device, nullptr);
+    EXPECT_EQ(super_device->first_logical_sector, 160);
 }
 
 TEST(liblp, InternalPartitionAlignment) {
@@ -292,6 +300,9 @@
     unique_ptr<LpMetadata> exported = builder->Export();
     EXPECT_NE(exported, nullptr);
 
+    auto super_device = GetMetadataSuperBlockDevice(*exported.get());
+    ASSERT_NE(super_device, nullptr);
+
     // Verify geometry. Some details of this may change if we change the
     // metadata structures. So in addition to checking the exact values, we
     // also check that they are internally consistent after.
@@ -300,11 +311,11 @@
     EXPECT_EQ(geometry.struct_size, sizeof(geometry));
     EXPECT_EQ(geometry.metadata_max_size, 1024);
     EXPECT_EQ(geometry.metadata_slot_count, 2);
-    EXPECT_EQ(geometry.first_logical_sector, 32);
+    EXPECT_EQ(super_device->first_logical_sector, 32);
 
     static const size_t kMetadataSpace =
             ((kMetadataSize * kMetadataSlots) + LP_METADATA_GEOMETRY_SIZE) * 2;
-    EXPECT_GE(geometry.first_logical_sector * LP_SECTOR_SIZE, kMetadataSpace);
+    EXPECT_GE(super_device->first_logical_sector * LP_SECTOR_SIZE, kMetadataSpace);
 
     // Verify header.
     const LpMetadataHeader& header = exported->header;
diff --git a/fs_mgr/liblp/images.cpp b/fs_mgr/liblp/images.cpp
index dfa37fe..46bdfa4 100644
--- a/fs_mgr/liblp/images.cpp
+++ b/fs_mgr/liblp/images.cpp
@@ -99,11 +99,12 @@
       block_size_(block_size),
       file_(nullptr, sparse_file_destroy),
       images_(images) {
+    uint64_t total_size = GetTotalSuperPartitionSize(metadata);
     if (block_size % LP_SECTOR_SIZE != 0) {
         LERROR << "Block size must be a multiple of the sector size, " << LP_SECTOR_SIZE;
         return;
     }
-    if (metadata.geometry.block_device_size % block_size != 0) {
+    if (total_size % block_size != 0) {
         LERROR << "Device size must be a multiple of the block size, " << block_size;
         return;
     }
@@ -120,7 +121,7 @@
         return;
     }
 
-    uint64_t num_blocks = metadata.geometry.block_device_size % block_size;
+    uint64_t num_blocks = total_size % block_size;
     if (num_blocks >= UINT_MAX) {
         // libsparse counts blocks in unsigned 32-bit integers, so we check to
         // make sure we're not going to overflow.
@@ -128,7 +129,10 @@
         return;
     }
 
-    file_.reset(sparse_file_new(block_size_, geometry_.block_device_size));
+    file_.reset(sparse_file_new(block_size_, total_size));
+    if (!file_) {
+        LERROR << "Could not allocate sparse file of size " << total_size;
+    }
 }
 
 bool SparseBuilder::Export(const char* file) {
@@ -333,14 +337,7 @@
 bool WriteToSparseFile(const char* file, const LpMetadata& metadata, uint32_t block_size,
                        const std::map<std::string, std::string>& images) {
     SparseBuilder builder(metadata, block_size, images);
-    if (!builder.IsValid()) {
-        LERROR << "Could not allocate sparse file of size " << metadata.geometry.block_device_size;
-        return false;
-    }
-    if (!builder.Build()) {
-        return false;
-    }
-    return builder.Export(file);
+    return builder.IsValid() && builder.Build() && builder.Export(file);
 }
 
 }  // namespace fs_mgr
diff --git a/fs_mgr/liblp/include/liblp/builder.h b/fs_mgr/liblp/include/liblp/builder.h
index 7e07df4..6d7324d 100644
--- a/fs_mgr/liblp/include/liblp/builder.h
+++ b/fs_mgr/liblp/include/liblp/builder.h
@@ -254,10 +254,14 @@
     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_;
     std::vector<std::unique_ptr<PartitionGroup>> groups_;
+    std::vector<LpMetadataBlockDevice> block_devices_;
 };
 
 // Read BlockDeviceInfo for a given block device. This always returns false
diff --git a/fs_mgr/liblp/include/liblp/liblp.h b/fs_mgr/liblp/include/liblp/liblp.h
index 5f95dca..15fcd43 100644
--- a/fs_mgr/liblp/include/liblp/liblp.h
+++ b/fs_mgr/liblp/include/liblp/liblp.h
@@ -37,6 +37,7 @@
     std::vector<LpMetadataPartition> partitions;
     std::vector<LpMetadataExtent> extents;
     std::vector<LpMetadataPartitionGroup> groups;
+    std::vector<LpMetadataBlockDevice> block_devices;
 };
 
 // Place an initial partition table on the device. This will overwrite the
@@ -69,6 +70,14 @@
 // Helper to extract safe C++ strings from partition info.
 std::string GetPartitionName(const LpMetadataPartition& partition);
 std::string GetPartitionGroupName(const LpMetadataPartitionGroup& group);
+std::string GetBlockDevicePartitionName(const LpMetadataBlockDevice& block_device);
+
+// Return the block device that houses the super partition metadata; returns
+// null on failure.
+const LpMetadataBlockDevice* GetMetadataSuperBlockDevice(const LpMetadata& metadata);
+
+// Return the total size of all partitions comprising the super partition.
+uint64_t GetTotalSuperPartitionSize(const LpMetadata& metadata);
 
 // Helper to return a slot number for a slot suffix.
 uint32_t SlotNumberForSlotSuffix(const std::string& suffix);
diff --git a/fs_mgr/liblp/include/liblp/metadata_format.h b/fs_mgr/liblp/include/liblp/metadata_format.h
index 89b219c..8a309be 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 6
+#define LP_METADATA_MAJOR_VERSION 7
 #define LP_METADATA_MINOR_VERSION 0
 
 /* Attributes for the LpMetadataPartition::attributes field.
@@ -103,42 +103,10 @@
      */
     uint32_t metadata_slot_count;
 
-    /* 48: First usable sector for allocating logical partitions. this will be
-     * the first sector after the initial geometry blocks, followed by the
-     * space consumed by metadata_max_size*metadata_slot_count*2.
-     */
-    uint64_t first_logical_sector;
-
-    /* 64: Alignment for defining partitions or partition extents. For example,
-     * an alignment of 1MiB will require that all partitions have a size evenly
-     * divisible by 1MiB, and that the smallest unit the partition can grow by
-     * is 1MiB.
-     *
-     * Alignment is normally determined at runtime when growing or adding
-     * partitions. If for some reason the alignment cannot be determined, then
-     * this predefined alignment in the geometry is used instead. By default
-     * it is set to 1MiB.
-     */
-    uint32_t alignment;
-
-    /* 68: Alignment offset for "stacked" devices. For example, if the "super"
-     * partition itself is not aligned within the parent block device's
-     * partition table, then we adjust for this in deciding where to place
-     * |first_logical_sector|.
-     *
-     * Similar to |alignment|, this will be derived from the operating system.
-     * If it cannot be determined, it is assumed to be 0.
-     */
-    uint32_t alignment_offset;
-
-    /* 72: Block device size, as specified when the metadata was created. This
-     * can be used to verify the geometry against a target device.
-     */
-    uint64_t block_device_size;
-
-    /* 76: Logical block size of the super partition block device. This is the
-     * minimal alignment for partition and extent sizes, and it must be a
-     * multiple of LP_SECTOR_SIZE.
+    /* 48: Logical block size. This is the minimal alignment for partition and
+     * extent sizes, and it must be a multiple of LP_SECTOR_SIZE. Note that
+     * this must be equal across all LUNs that comprise the super partition,
+     * and thus this field is stored in the geometry, not per-device.
      */
     uint32_t logical_block_size;
 } __attribute__((packed)) LpMetadataGeometry;
@@ -217,6 +185,8 @@
     LpMetadataTableDescriptor extents;
     /* 104: Updateable group descriptor. */
     LpMetadataTableDescriptor groups;
+    /* 116: Block device table. */
+    LpMetadataTableDescriptor block_devices;
 } __attribute__((packed)) LpMetadataHeader;
 
 /* This struct defines a logical partition entry, similar to what would be
@@ -285,6 +255,47 @@
     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.
+ */
+typedef struct LpMetadataBlockDevice {
+    /* 0: First usable sector for allocating logical partitions. this will be
+     * the first sector after the initial geometry blocks, followed by the
+     * space consumed by metadata_max_size*metadata_slot_count*2.
+     */
+    uint64_t first_logical_sector;
+
+    /* 8: Alignment for defining partitions or partition extents. For example,
+     * an alignment of 1MiB will require that all partitions have a size evenly
+     * divisible by 1MiB, and that the smallest unit the partition can grow by
+     * is 1MiB.
+     *
+     * Alignment is normally determined at runtime when growing or adding
+     * partitions. If for some reason the alignment cannot be determined, then
+     * this predefined alignment in the geometry is used instead. By default
+     * it is set to 1MiB.
+     */
+    uint32_t alignment;
+
+    /* 12: Alignment offset for "stacked" devices. For example, if the "super"
+     * partition itself is not aligned within the parent block device's
+     * partition table, then we adjust for this in deciding where to place
+     * |first_logical_sector|.
+     *
+     * Similar to |alignment|, this will be derived from the operating system.
+     * If it cannot be determined, it is assumed to be 0.
+     */
+    uint32_t alignment_offset;
+
+    /* 16: Block device size, as specified when the metadata was created. This
+     * can be used to verify the geometry against a target device.
+     */
+    uint64_t size;
+
+    /* 24: Partition name in the GPT. Any unused characters must be 0. */
+    char partition_name[36];
+} LpMetadataBlockDevice;
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
diff --git a/fs_mgr/liblp/io_test.cpp b/fs_mgr/liblp/io_test.cpp
index 2aa41f3..3889e87 100644
--- a/fs_mgr/liblp/io_test.cpp
+++ b/fs_mgr/liblp/io_test.cpp
@@ -160,7 +160,6 @@
     // Check geometry and header.
     EXPECT_EQ(exported->geometry.metadata_max_size, imported->geometry.metadata_max_size);
     EXPECT_EQ(exported->geometry.metadata_slot_count, imported->geometry.metadata_slot_count);
-    EXPECT_EQ(exported->geometry.first_logical_sector, imported->geometry.first_logical_sector);
     EXPECT_EQ(exported->header.major_version, imported->header.major_version);
     EXPECT_EQ(exported->header.minor_version, imported->header.minor_version);
     EXPECT_EQ(exported->header.header_size, imported->header.header_size);
@@ -178,6 +177,11 @@
     EXPECT_EQ(exported->extents[0].num_sectors, imported->extents[0].num_sectors);
     EXPECT_EQ(exported->extents[0].target_type, imported->extents[0].target_type);
     EXPECT_EQ(exported->extents[0].target_data, imported->extents[0].target_data);
+
+    // Check block devices table.
+    ASSERT_EQ(exported->block_devices.size(), imported->block_devices.size());
+    EXPECT_EQ(exported->block_devices[0].first_logical_sector,
+              imported->block_devices[0].first_logical_sector);
 }
 
 // Test that we can update metadata slots without disturbing others.
@@ -206,14 +210,17 @@
     ASSERT_EQ(imported->partitions.size(), 1);
     EXPECT_EQ(GetPartitionName(imported->partitions[0]), "vendor");
 
-    uint64_t last_sector = imported->geometry.block_device_size / LP_SECTOR_SIZE;
+    auto super_device = GetMetadataSuperBlockDevice(*imported.get());
+    ASSERT_NE(super_device, nullptr);
+
+    uint64_t last_sector = super_device->size / LP_SECTOR_SIZE;
 
     // Verify that we didn't overwrite anything in the logical paritition area.
     // We expect the disk to be filled with 0xcc on creation so we can read
     // this back and compare it.
     char expected[LP_SECTOR_SIZE];
     memset(expected, 0xcc, sizeof(expected));
-    for (uint64_t i = imported->geometry.first_logical_sector; i < last_sector; i++) {
+    for (uint64_t i = super_device->first_logical_sector; i < last_sector; i++) {
         char buffer[LP_SECTOR_SIZE];
         ASSERT_GE(lseek(fd, i * LP_SECTOR_SIZE, SEEK_SET), 0);
         ASSERT_TRUE(android::base::ReadFully(fd, buffer, sizeof(buffer)));
@@ -256,7 +263,8 @@
 
     imported = ReadMetadata(fd, 0);
     ASSERT_NE(imported, nullptr);
-    imported->geometry.first_logical_sector++;
+    ASSERT_EQ(imported->block_devices.size(), 1);
+    imported->block_devices[0].first_logical_sector++;
     ASSERT_FALSE(UpdatePartitionTable(fd, *imported.get(), 1));
 
     imported = ReadMetadata(fd, 0);
@@ -329,9 +337,11 @@
     ASSERT_NE(builder, nullptr);
 
     // Compute the maximum number of partitions we can fit in 512 bytes of
-    // metadata. By default there is the header, and one partition group.
-    static const size_t kMaxPartitionTableSize =
-            kMetadataSize - sizeof(LpMetadataHeader) - sizeof(LpMetadataPartitionGroup);
+    // metadata. By default there is the header, one partition group, and a
+    // block device entry.
+    static const size_t kMaxPartitionTableSize = kMetadataSize - sizeof(LpMetadataHeader) -
+                                                 sizeof(LpMetadataPartitionGroup) -
+                                                 sizeof(LpMetadataBlockDevice);
     size_t max_partitions = kMaxPartitionTableSize / sizeof(LpMetadataPartition);
 
     // Add this number of partitions.
@@ -360,12 +370,15 @@
     // The new table should be too large to be written.
     ASSERT_FALSE(UpdatePartitionTable(fd, *exported.get(), 1));
 
+    auto super_device = GetMetadataSuperBlockDevice(*exported.get());
+    ASSERT_NE(super_device, nullptr);
+
     // Check that the first and last logical sectors weren't touched when we
     // wrote this almost-full metadata.
     char expected[LP_SECTOR_SIZE];
     memset(expected, 0xcc, sizeof(expected));
     char buffer[LP_SECTOR_SIZE];
-    ASSERT_GE(lseek(fd, exported->geometry.first_logical_sector * LP_SECTOR_SIZE, SEEK_SET), 0);
+    ASSERT_GE(lseek(fd, super_device->first_logical_sector * LP_SECTOR_SIZE, SEEK_SET), 0);
     ASSERT_TRUE(android::base::ReadFully(fd, buffer, sizeof(buffer)));
     EXPECT_EQ(memcmp(expected, buffer, LP_SECTOR_SIZE), 0);
 }
diff --git a/fs_mgr/liblp/reader.cpp b/fs_mgr/liblp/reader.cpp
index 43d8076..c34b138 100644
--- a/fs_mgr/liblp/reader.cpp
+++ b/fs_mgr/liblp/reader.cpp
@@ -108,15 +108,6 @@
         LERROR << "Metadata max size is not sector-aligned.";
         return false;
     }
-
-    // Check that the metadata area and logical partition areas don't overlap.
-    int64_t end_of_metadata =
-            GetPrimaryMetadataOffset(*geometry, geometry->metadata_slot_count - 1) +
-            geometry->metadata_max_size;
-    if (uint64_t(end_of_metadata) > geometry->first_logical_sector * LP_SECTOR_SIZE) {
-        LERROR << "Logical partition metadata overlaps with logical partition contents.";
-        return false;
-    }
     return true;
 }
 
@@ -195,7 +186,8 @@
     }
     if (!ValidateTableBounds(header, header.partitions) ||
         !ValidateTableBounds(header, header.extents) ||
-        !ValidateTableBounds(header, header.groups)) {
+        !ValidateTableBounds(header, header.groups) ||
+        !ValidateTableBounds(header, header.block_devices)) {
         LERROR << "Logical partition metadata has invalid table bounds.";
         return false;
     }
@@ -294,6 +286,28 @@
         metadata->groups.push_back(group);
     }
 
+    cursor = buffer.get() + header.block_devices.offset;
+    for (size_t i = 0; i < header.block_devices.num_entries; i++) {
+        LpMetadataBlockDevice device = {};
+        memcpy(&device, cursor, sizeof(device));
+        cursor += header.block_devices.entry_size;
+
+        metadata->block_devices.push_back(device);
+    }
+
+    const LpMetadataBlockDevice* super_device = GetMetadataSuperBlockDevice(*metadata.get());
+    if (!super_device) {
+        LERROR << "Metadata does not specify a super device.";
+        return nullptr;
+    }
+
+    // Check that the metadata area and logical partition areas don't overlap.
+    uint64_t metadata_region =
+            GetTotalMetadataSize(geometry.metadata_max_size, geometry.metadata_slot_count);
+    if (metadata_region > super_device->first_logical_sector * LP_SECTOR_SIZE) {
+        LERROR << "Logical partition metadata overlaps with logical partition contents.";
+        return nullptr;
+    }
     return metadata;
 }
 
@@ -374,5 +388,9 @@
     return NameFromFixedArray(group.name, sizeof(group.name));
 }
 
+std::string GetBlockDevicePartitionName(const LpMetadataBlockDevice& block_device) {
+    return NameFromFixedArray(block_device.partition_name, sizeof(block_device.partition_name));
+}
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/liblp/utility.cpp b/fs_mgr/liblp/utility.cpp
index 0556833..518920d 100644
--- a/fs_mgr/liblp/utility.cpp
+++ b/fs_mgr/liblp/utility.cpp
@@ -66,11 +66,8 @@
 
 int64_t GetPrimaryMetadataOffset(const LpMetadataGeometry& geometry, uint32_t slot_number) {
     CHECK(slot_number < geometry.metadata_slot_count);
-
     int64_t offset = LP_PARTITION_RESERVED_BYTES + (LP_METADATA_GEOMETRY_SIZE * 2) +
                      geometry.metadata_max_size * slot_number;
-    CHECK(offset + geometry.metadata_max_size <=
-          int64_t(geometry.first_logical_sector * LP_SECTOR_SIZE));
     return offset;
 }
 
@@ -81,6 +78,18 @@
     return start + int64_t(geometry.metadata_max_size * slot_number);
 }
 
+uint64_t GetTotalMetadataSize(uint32_t metadata_max_size, uint32_t max_slots) {
+    return LP_PARTITION_RESERVED_BYTES +
+           (LP_METADATA_GEOMETRY_SIZE + metadata_max_size * max_slots) * 2;
+}
+
+const LpMetadataBlockDevice* GetMetadataSuperBlockDevice(const LpMetadata& metadata) {
+    if (metadata.block_devices.empty()) {
+        return nullptr;
+    }
+    return &metadata.block_devices[0];
+}
+
 void SHA256(const void* data, size_t length, uint8_t out[32]) {
     SHA256_CTX c;
     SHA256_Init(&c);
@@ -100,5 +109,13 @@
     return suffix[1] - 'a';
 }
 
+uint64_t GetTotalSuperPartitionSize(const LpMetadata& metadata) {
+    uint64_t size = 0;
+    for (const auto& block_device : metadata.block_devices) {
+        size += block_device.size;
+    }
+    return size;
+}
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/liblp/utility.h b/fs_mgr/liblp/utility.h
index 61e7d31..65e643b 100644
--- a/fs_mgr/liblp/utility.h
+++ b/fs_mgr/liblp/utility.h
@@ -23,7 +23,7 @@
 
 #include <android-base/logging.h>
 
-#include "liblp/metadata_format.h"
+#include "liblp/liblp.h"
 
 #define LP_TAG "[liblp]"
 #define LWARN LOG(WARNING) << LP_TAG
@@ -50,6 +50,10 @@
 // device.
 int64_t GetBackupMetadataOffset(const LpMetadataGeometry& geometry, uint32_t slot_number);
 
+// Return the total space at the start of the super partition that must be set
+// aside from headers/metadata and backups.
+uint64_t GetTotalMetadataSize(uint32_t metadata_max_size, uint32_t max_slots);
+
 // Cross-platform helper for lseek64().
 int64_t SeekFile64(int fd, int64_t offset, int whence);
 
diff --git a/fs_mgr/liblp/utility_test.cpp b/fs_mgr/liblp/utility_test.cpp
index 8baf9e7..bdf6dfd 100644
--- a/fs_mgr/liblp/utility_test.cpp
+++ b/fs_mgr/liblp/utility_test.cpp
@@ -36,10 +36,6 @@
                                    {0},
                                    16384,
                                    4,
-                                   10000,
-                                   0,
-                                   0,
-                                   1024 * 1024,
                                    4096};
     static const uint64_t start = LP_PARTITION_RESERVED_BYTES;
     EXPECT_EQ(GetPrimaryMetadataOffset(geometry, 0), start + 8192);
diff --git a/fs_mgr/liblp/writer.cpp b/fs_mgr/liblp/writer.cpp
index f857d8c..ddae842 100644
--- a/fs_mgr/liblp/writer.cpp
+++ b/fs_mgr/liblp/writer.cpp
@@ -43,9 +43,7 @@
 static bool CompareGeometry(const LpMetadataGeometry& g1, const LpMetadataGeometry& g2) {
     return g1.metadata_max_size == g2.metadata_max_size &&
            g1.metadata_slot_count == g2.metadata_slot_count &&
-           g1.block_device_size == g2.block_device_size &&
-           g1.logical_block_size == g2.logical_block_size &&
-           g1.first_logical_sector == g2.first_logical_sector;
+           g1.logical_block_size == g2.logical_block_size;
 }
 
 std::string SerializeMetadata(const LpMetadata& input) {
@@ -59,15 +57,18 @@
                         metadata.extents.size() * sizeof(LpMetadataExtent));
     std::string groups(reinterpret_cast<const char*>(metadata.groups.data()),
                        metadata.groups.size() * sizeof(LpMetadataPartitionGroup));
+    std::string block_devices(reinterpret_cast<const char*>(metadata.block_devices.data()),
+                              metadata.block_devices.size() * sizeof(LpMetadataBlockDevice));
 
     // Compute positions of tables.
     header.partitions.offset = 0;
     header.extents.offset = header.partitions.offset + partitions.size();
     header.groups.offset = header.extents.offset + extents.size();
-    header.tables_size = header.groups.offset + groups.size();
+    header.block_devices.offset = header.groups.offset + groups.size();
+    header.tables_size = header.block_devices.offset + block_devices.size();
 
     // Compute payload checksum.
-    std::string tables = partitions + extents + groups;
+    std::string tables = partitions + extents + groups + block_devices;
     SHA256(tables.data(), tables.size(), header.tables_checksum);
 
     // Compute header checksum.
@@ -105,14 +106,20 @@
                              uint64_t(geometry.metadata_max_size) * geometry.metadata_slot_count;
     uint64_t total_reserved = reserved_size * 2;
 
+    const LpMetadataBlockDevice* super_device = GetMetadataSuperBlockDevice(metadata);
+    if (!super_device) {
+        LERROR << "Logical partition metadata does not have a super block device.";
+        return false;
+    }
+
     if (total_reserved > blockdevice_size ||
-        total_reserved > geometry.first_logical_sector * LP_SECTOR_SIZE) {
+        total_reserved > super_device->first_logical_sector * LP_SECTOR_SIZE) {
         LERROR << "Not enough space to store all logical partition metadata slots.";
         return false;
     }
-    if (blockdevice_size != metadata.geometry.block_device_size) {
+    if (blockdevice_size != super_device->size) {
         LERROR << "Block device size " << blockdevice_size
-               << " does not match metadata requested size " << metadata.geometry.block_device_size;
+               << " does not match metadata requested size " << super_device->size;
         return false;
     }
 
@@ -125,11 +132,11 @@
     }
 
     // Make sure all linear extents have a valid range.
-    uint64_t last_sector = geometry.block_device_size / LP_SECTOR_SIZE;
+    uint64_t last_sector = super_device->size / LP_SECTOR_SIZE;
     for (const auto& extent : metadata.extents) {
         if (extent.target_type == LP_TARGET_TYPE_LINEAR) {
             uint64_t physical_sector = extent.target_data;
-            if (physical_sector < geometry.first_logical_sector ||
+            if (physical_sector < super_device->first_logical_sector ||
                 physical_sector + extent.num_sectors > last_sector) {
                 LERROR << "Extent table entry is out of bounds.";
                 return false;
@@ -139,10 +146,28 @@
     return true;
 }
 
-static bool WritePrimaryMetadata(int fd, const LpMetadataGeometry& geometry, uint32_t slot_number,
+// Check that the given region is within metadata bounds.
+static bool ValidateMetadataRegion(const LpMetadata& metadata, uint64_t start, size_t size) {
+    const LpMetadataBlockDevice* super_device = GetMetadataSuperBlockDevice(metadata);
+    if (!super_device) {
+        LERROR << __PRETTY_FUNCTION__ << " could not locate super block device in metadata";
+        return false;
+    }
+    if (start + size >= super_device->first_logical_sector * LP_SECTOR_SIZE) {
+        LERROR << __PRETTY_FUNCTION__ << " write of " << size << " bytes at " << start
+               << " overlaps with logical partition contents";
+        return false;
+    }
+    return true;
+}
+
+static bool WritePrimaryMetadata(int fd, const LpMetadata& metadata, uint32_t slot_number,
                                  const std::string& blob,
                                  const std::function<bool(int, const std::string&)>& writer) {
-    int64_t primary_offset = GetPrimaryMetadataOffset(geometry, slot_number);
+    int64_t primary_offset = GetPrimaryMetadataOffset(metadata.geometry, slot_number);
+    if (!ValidateMetadataRegion(metadata, primary_offset, blob.size())) {
+        return false;
+    }
     if (SeekFile64(fd, primary_offset, SEEK_SET) < 0) {
         PERROR << __PRETTY_FUNCTION__ << " lseek failed: offset " << primary_offset;
         return false;
@@ -154,18 +179,15 @@
     return true;
 }
 
-static bool WriteBackupMetadata(int fd, const LpMetadataGeometry& geometry, uint32_t slot_number,
+static bool WriteBackupMetadata(int fd, const LpMetadata& metadata, uint32_t slot_number,
                                 const std::string& blob,
                                 const std::function<bool(int, const std::string&)>& writer) {
-    int64_t backup_offset = GetBackupMetadataOffset(geometry, slot_number);
-    int64_t abs_offset = SeekFile64(fd, backup_offset, SEEK_SET);
-    if (abs_offset == (int64_t)-1) {
-        PERROR << __PRETTY_FUNCTION__ << " lseek failed: offset " << backup_offset;
+    int64_t backup_offset = GetBackupMetadataOffset(metadata.geometry, slot_number);
+    if (!ValidateMetadataRegion(metadata, backup_offset, blob.size())) {
         return false;
     }
-    if (abs_offset >= int64_t(geometry.first_logical_sector) * LP_SECTOR_SIZE) {
-        PERROR << __PRETTY_FUNCTION__ << " backup offset " << abs_offset
-               << " is within logical partition bounds, sector " << geometry.first_logical_sector;
+    if (SeekFile64(fd, backup_offset, SEEK_SET) < 0) {
+        PERROR << __PRETTY_FUNCTION__ << " lseek failed: offset " << backup_offset;
         return false;
     }
     if (!writer(fd, blob)) {
@@ -175,18 +197,18 @@
     return true;
 }
 
-static bool WriteMetadata(int fd, const LpMetadataGeometry& geometry, uint32_t slot_number,
+static bool WriteMetadata(int fd, const LpMetadata& metadata, uint32_t slot_number,
                           const std::string& blob,
                           const std::function<bool(int, const std::string&)>& writer) {
     // Make sure we're writing to a valid metadata slot.
-    if (slot_number >= geometry.metadata_slot_count) {
+    if (slot_number >= metadata.geometry.metadata_slot_count) {
         LERROR << "Invalid logical partition metadata slot number.";
         return false;
     }
-    if (!WritePrimaryMetadata(fd, geometry, slot_number, blob, writer)) {
+    if (!WritePrimaryMetadata(fd, metadata, slot_number, blob, writer)) {
         return false;
     }
-    if (!WriteBackupMetadata(fd, geometry, slot_number, blob, writer)) {
+    if (!WriteBackupMetadata(fd, metadata, slot_number, blob, writer)) {
         return false;
     }
     return true;
@@ -237,7 +259,7 @@
 
     bool ok = true;
     for (size_t i = 0; i < metadata.geometry.metadata_slot_count; i++) {
-        ok &= WriteMetadata(fd, metadata.geometry, i, metadata_blob, DefaultWriter);
+        ok &= WriteMetadata(fd, metadata, i, metadata_blob, DefaultWriter);
     }
     return ok;
 }
@@ -289,7 +311,7 @@
             LERROR << "Error serializing primary metadata to repair corrupted backup";
             return false;
         }
-        if (!WriteBackupMetadata(fd, geometry, slot_number, old_blob, writer)) {
+        if (!WriteBackupMetadata(fd, metadata, slot_number, old_blob, writer)) {
             LERROR << "Error writing primary metadata to repair corrupted backup";
             return false;
         }
@@ -301,14 +323,14 @@
             LERROR << "Error serializing primary metadata to repair corrupted backup";
             return false;
         }
-        if (!WritePrimaryMetadata(fd, geometry, slot_number, old_blob, writer)) {
+        if (!WritePrimaryMetadata(fd, metadata, slot_number, old_blob, writer)) {
             LERROR << "Error writing primary metadata to repair corrupted backup";
             return false;
         }
     }
 
     // Both copies should now be in sync, so we can continue the update.
-    return WriteMetadata(fd, geometry, slot_number, blob, writer);
+    return WriteMetadata(fd, metadata, slot_number, blob, writer);
 }
 
 bool FlashPartitionTable(const std::string& block_device, const LpMetadata& metadata) {