diff --git a/include/dwarfs/block_manager.h b/include/dwarfs/block_manager.h
index 9576d3ab..69cb8f31 100644
--- a/include/dwarfs/block_manager.h
+++ b/include/dwarfs/block_manager.h
@@ -25,6 +25,7 @@
 #include <optional>
 #include <vector>
 
+#include "dwarfs/fragment_category.h"
 #include "dwarfs/gen-cpp2/metadata_types.h"
 
 namespace dwarfs {
@@ -34,13 +35,17 @@ class block_manager {
   using chunk_type = thrift::metadata::chunk;
 
   size_t get_logical_block() const;
-  void set_written_block(size_t logical_block, size_t written_block);
+  void set_written_block(size_t logical_block, size_t written_block,
+                         fragment_category::value_type category);
   void map_logical_blocks(std::vector<chunk_type>& vec);
+  std::vector<fragment_category::value_type>
+  get_written_block_categories() const;
 
  private:
   std::mutex mutable mx_;
   size_t mutable num_blocks_{0};
-  std::vector<std::optional<size_t>> block_map_;
+  std::vector<std::optional<std::pair<size_t, fragment_category::value_type>>>
+      block_map_;
 };
 
 } // namespace dwarfs
diff --git a/include/dwarfs/segmenter.h b/include/dwarfs/segmenter.h
index 0ead74db..53542f17 100644
--- a/include/dwarfs/segmenter.h
+++ b/include/dwarfs/segmenter.h
@@ -48,9 +48,8 @@ class segmenter {
     unsigned block_size_bits{22};
   };
 
-  using block_ready_cb =
-      folly::Function<void(std::shared_ptr<block_data>,
-                           folly::Function<void(size_t)> physical_block_cb)>;
+  using block_ready_cb = folly::Function<void(std::shared_ptr<block_data>,
+                                              size_t logical_block_num)>;
 
   segmenter(logger& lgr, progress& prog, std::shared_ptr<block_manager> blkmgr,
             config const& cfg, compression_constraints const& cc,
diff --git a/src/dwarfs/block_manager.cpp b/src/dwarfs/block_manager.cpp
index 6c1c8f80..e33244ab 100644
--- a/src/dwarfs/block_manager.cpp
+++ b/src/dwarfs/block_manager.cpp
@@ -35,13 +35,14 @@ size_t block_manager::get_logical_block() const {
 }
 
 void block_manager::set_written_block(size_t logical_block,
-                                      size_t written_block) {
+                                      size_t written_block,
+                                      fragment_category::value_type category) {
   std::lock_guard lock{mx_};
   assert(logical_block < num_blocks_);
   if (block_map_.size() < num_blocks_) {
     block_map_.resize(num_blocks_);
   }
-  block_map_[logical_block] = written_block;
+  block_map_[logical_block] = std::make_pair(written_block, category);
 }
 
 void block_manager::map_logical_blocks(std::vector<chunk_type>& vec) {
@@ -49,8 +50,26 @@ void block_manager::map_logical_blocks(std::vector<chunk_type>& vec) {
   for (auto& c : vec) {
     size_t block = c.get_block();
     assert(block < num_blocks_);
-    c.block() = block_map_[block].value();
+    c.block() = block_map_[block].value().first;
   }
 }
 
+std::vector<fragment_category::value_type>
+block_manager::get_written_block_categories() const {
+  std::vector<fragment_category::value_type> result;
+
+  {
+    std::lock_guard lock{mx_};
+
+    result.resize(num_blocks_);
+
+    for (auto& b : block_map_) {
+      auto& mapping = b.value();
+      result[mapping.first] = mapping.second;
+    }
+  }
+
+  return result;
+}
+
 } // namespace dwarfs
diff --git a/src/dwarfs/scanner.cpp b/src/dwarfs/scanner.cpp
index b3e6e397..dba6003a 100644
--- a/src/dwarfs/scanner.cpp
+++ b/src/dwarfs/scanner.cpp
@@ -700,9 +700,17 @@ void scanner_<LoggerPolicy>::scan(
 
         auto seg = segmenter_factory_->create(
             category, cat_size, cc, blockmgr,
-            [category, meta, &fsw](auto block, auto physical_block_cb) {
-              fsw.write_block(category, std::move(block),
-                              std::move(physical_block_cb), meta);
+            [category, meta, blockmgr, &fsw](auto block,
+                                             auto logical_block_num) {
+              fsw.write_block(
+                  category, std::move(block),
+                  [blockmgr, logical_block_num,
+                   category](auto physical_block_num) {
+                    blockmgr->set_written_block(logical_block_num,
+                                                physical_block_num,
+                                                category.value());
+                  },
+                  meta);
             });
 
         for (auto ino : span) {
@@ -862,6 +870,33 @@ void scanner_<LoggerPolicy>::scan(
   mv2.preferred_path_separator() =
       static_cast<uint32_t>(std::filesystem::path::preferred_separator);
 
+  if (auto catmgr = options_.inode.categorizer_mgr) {
+    std::unordered_map<fragment_category::value_type,
+                       fragment_category::value_type>
+        category_indices;
+    std::vector<std::string> category_names;
+
+    category_indices.reserve(frag_info.info.size());
+    category_names.reserve(frag_info.info.size());
+
+    for (auto const& ci : frag_info.info) {
+      auto [it, inserted] =
+          category_indices.emplace(ci.category, category_names.size());
+      if (inserted) {
+        category_names.emplace_back(catmgr->category_name(ci.category));
+      }
+    }
+
+    auto written_categories = blockmgr->get_written_block_categories();
+
+    std::transform(written_categories.begin(), written_categories.end(),
+                   written_categories.begin(),
+                   [&](auto const& cat) { return category_indices.at(cat); });
+
+    mv2.category_names() = std::move(category_names);
+    mv2.block_categories() = std::move(written_categories);
+  }
+
   auto [schema, data] = metadata_v2::freeze(mv2);
 
   LOG_VERBOSE << "uncompressed metadata size: " << size_with_unit(data.size());
diff --git a/src/dwarfs/segmenter.cpp b/src/dwarfs/segmenter.cpp
index ccdff23b..f852f005 100644
--- a/src/dwarfs/segmenter.cpp
+++ b/src/dwarfs/segmenter.cpp
@@ -969,11 +969,7 @@ template <typename LoggerPolicy, typename SegmentingPolicy>
 void segmenter_<LoggerPolicy, SegmentingPolicy>::block_ready() {
   auto& block = blocks_.back();
   block.finalize(stats_);
-  block_ready_(block.data(), [blkmgr = blkmgr_,
-                              logical_block_num =
-                                  block.num()](size_t physical_block_num) {
-    blkmgr->set_written_block(logical_block_num, physical_block_num);
-  });
+  block_ready_(block.data(), block.num());
   ++prog_.block_count;
 }
 
diff --git a/test/segmenter_benchmark.cpp b/test/segmenter_benchmark.cpp
index e66732dd..2c3bd84f 100644
--- a/test/segmenter_benchmark.cpp
+++ b/test/segmenter_benchmark.cpp
@@ -144,13 +144,14 @@ void run_segmenter_test(unsigned iters, unsigned granularity,
 
     std::vector<std::shared_ptr<dwarfs::block_data>> written;
 
-    dwarfs::segmenter seg(lgr, prog, blkmgr, cfg, cc, total_size,
-                          [&written](std::shared_ptr<dwarfs::block_data> blk,
-                                     auto physical_block_cb) {
-                            size_t num = written.size();
-                            written.push_back(blk);
-                            physical_block_cb(num);
-                          });
+    dwarfs::segmenter seg(
+        lgr, prog, blkmgr, cfg, cc, total_size,
+        [&written, blkmgr](std::shared_ptr<dwarfs::block_data> blk,
+                           auto logical_block_num) {
+          auto physical_block_num = written.size();
+          written.push_back(blk);
+          blkmgr->set_written_block(logical_block_num, physical_block_num, 0);
+        });
 
     suspender.dismiss();
 
diff --git a/thrift/metadata.thrift b/thrift/metadata.thrift
index 0ff3b2bb..bd3faa56 100644
--- a/thrift/metadata.thrift
+++ b/thrift/metadata.thrift
@@ -361,8 +361,27 @@ struct metadata {
   // fields added with dwarfs-0.7.3, file system version 2.5 //
   //=========================================================//
 
+  // We don't need to increment the file system minor version
+  // as file systems created with this new version are still
+  // readable by older binaries as long as they don't use any
+  // unsupported features (e.g. FLAC compression).
+
   // The set of features used in this file system image. As long
   // as an older binary supports all features, it will be able
   // to use images created with newer versions.
   27: optional set<string>      features
+
+  //=========================================================//
+  // fields added with dwarfs-0.8.0, file system version 2.5 //
+  //=========================================================//
+
+  // The set of categories used in this file system image. Used
+  // for displaying and to select compression algorithms when
+  // recompressing the image.
+  28: optional list<string>     category_names
+
+  // The category of each block in the file system image. The
+  // index into this vector is the block number and the value
+  // is an index into `category_names`.
+  29: optional list<UInt32>     block_categories
 }