Add support for bsdiff of file system metadata blocks

delta_diff_generator.cc

Index: delta_diff_generator.cc
diff --git a/delta_diff_generator.cc b/delta_diff_generator.cc
index 21a4c03ad84b98decd39afa9c7a94bfd6e4f29d1..cfcfdfac73d17ec5a3876464ef47737a14cff32e 100644
--- a/delta_diff_generator.cc
+++ b/delta_diff_generator.cc
@@ -10,6 +10,13 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
+#include <base/logging.h>

[petkov, 2010/12/10 00:46:55]

move this block of includes after the c++ headers

[thieule, 2010/12/14 23:11:21]

Done.

+#include <base/string_util.h>
+#include <bzlib.h>
+

[petkov, 2010/12/10 00:46:55]

no need for blank line

[thieule, 2010/12/14 23:11:21]

Done.

+#include <ext2fs/ext2_io.h>
+#include <ext2fs/ext2fs.h>
+
 #include <algorithm>
 #include <map>
 #include <set>
@@ -17,10 +24,6 @@
 #include <utility>
 #include <vector>
 
-#include <base/logging.h>
-#include <base/string_util.h>
-#include <bzlib.h>
-
 #include "update_engine/bzip.h"
 #include "update_engine/cycle_breaker.h"
 #include "update_engine/extent_mapper.h"
@@ -241,6 +244,392 @@ bool DeltaReadFiles(Graph* graph,
   return true;
 }
 
+// Read data from the specified extents.
+bool ReadExtentsData(const ext2_filsys fs,
+                     const vector<Extent>& extents,
+                     vector<char>* data) {
+  // Resize the data buffer to hold all data in the extents
+  size_t num_data_blocks = 0;
+  for (vector<Extent>::const_iterator it = extents.begin();
+       it != extents.end(); it++) {
+    num_data_blocks += it->num_blocks();
+  }
+
+  data->resize(num_data_blocks * kBlockSize);
+
+  // Read in the data blocks
+  const size_t max_read_blocks = 256;
+  vector<Block>::size_type blocks_copied_count = 0;
+  for (vector<Extent>::const_iterator it = extents.begin();
+       it != extents.end(); it++) {
+    vector<Block>::size_type blocks_read = 0;
+    while (blocks_read < it->num_blocks()) {
+      const int copy_block_cnt =
+          min(max_read_blocks,
+              static_cast<vector<char>::size_type>(
+                  it->num_blocks() - blocks_read));
+      TEST_AND_RETURN_FALSE_ERRCODE(
+          io_channel_read_blk(fs->io,
+                              it->start_block() + blocks_read,
+                              copy_block_cnt,
+                              &(*data)[blocks_copied_count * kBlockSize]));
+      blocks_read += copy_block_cnt;
+      blocks_copied_count += copy_block_cnt;
+    }
+  }
+
+  return true;
+}
+
+// Compute the bsdiff between two metadata blobs.
+bool ComputeMetadataBsdiff(const vector<char>& old_metadata,
+                           const vector<char>& new_metadata,
+                           vector<char>* bsdiff_delta) {
+  const string kTempFileTemplate("/tmp/CrAU_temp_data.XXXXXX");
+
+  // Write the metadata buffers to temporary files
+  int old_fd;
+  string temp_old_file_path;
+  TEST_AND_RETURN_FALSE(
+      utils::MakeTempFile(kTempFileTemplate, &temp_old_file_path, &old_fd));
+  TEST_AND_RETURN_FALSE(old_fd >= 0);
+  ScopedPathUnlinker temp_old_file_path_unlinker(temp_old_file_path);
+  ScopedFdCloser old_fd_closer(&old_fd);
+  TEST_AND_RETURN_FALSE(utils::WriteAll(old_fd,
+                                        &old_metadata[0],
+                                        old_metadata.size()));
+
+  int new_fd;
+  string temp_new_file_path;
+  TEST_AND_RETURN_FALSE(
+      utils::MakeTempFile(kTempFileTemplate, &temp_new_file_path, &new_fd));
+  TEST_AND_RETURN_FALSE(new_fd >= 0);
+  ScopedPathUnlinker temp_new_file_path_unlinker(temp_new_file_path);
+  ScopedFdCloser new_fd_closer(&new_fd);
+  TEST_AND_RETURN_FALSE(utils::WriteAll(new_fd,
+                                        &new_metadata[0],
+                                        new_metadata.size()));
+
+  // Perform bsdiff on these files
+  TEST_AND_RETURN_FALSE(
+      BsdiffFiles(temp_old_file_path, temp_new_file_path, bsdiff_delta));
+  CHECK_GT(bsdiff_delta->size(), 0);
+
+  return true;
+}
+
+// Add the specified metadata extents to the graph and blocks vector.
+bool AddMetadataExtents(Graph* graph,
+                        vector<Block>* blocks,
+                        const ext2_filsys fs_old,
+                        const ext2_filsys fs_new,
+                        const string& metadata_name,
+                        const vector<Extent>& extents,
+                        int data_fd,
+                        off_t* data_file_size) {
+  vector<char> data;  // Data blob that will be written to delta file.
+
+  // Read in the metadata blocks from the old and new image.
+  vector<char> old_data;
+  TEST_AND_RETURN_FALSE(ReadExtentsData(fs_old, extents, &old_data));
+
+  vector<char> new_data;
+  TEST_AND_RETURN_FALSE(ReadExtentsData(fs_new, extents, &new_data));
+
+  // Determine the best way to compress this.
+  vector<char> new_data_bz;
+  TEST_AND_RETURN_FALSE(BzipCompress(new_data, &new_data_bz));
+  CHECK(!new_data_bz.empty());
+
+  DeltaArchiveManifest_InstallOperation op;
+  size_t current_best_size = 0;
+  if (new_data.size() <= new_data_bz.size()) {
+    op.set_type(DeltaArchiveManifest_InstallOperation_Type_REPLACE);
+    current_best_size = new_data.size();
+    data = new_data;
+  } else {
+    op.set_type(DeltaArchiveManifest_InstallOperation_Type_REPLACE_BZ);
+    current_best_size = new_data_bz.size();
+    data = new_data_bz;
+  }
+
+  if (old_data == new_data) {
+    // No change in data.
+    op.set_type(DeltaArchiveManifest_InstallOperation_Type_MOVE);
+    current_best_size = 0;
+    data.clear();
+  } else {
+    // Try bsdiff of old to new data
+    vector<char> bsdiff_delta;
+    TEST_AND_RETURN_FALSE(ComputeMetadataBsdiff(old_data,
+                                                new_data,
+                                                &bsdiff_delta));
+    CHECK_GT(bsdiff_delta.size(), 0);
+
+    if (bsdiff_delta.size() < current_best_size) {
+      op.set_type(DeltaArchiveManifest_InstallOperation_Type_BSDIFF);
+      current_best_size = bsdiff_delta.size();
+      data = bsdiff_delta;
+    }
+  }
+
+  CHECK_EQ(data.size(), current_best_size);
+
+  // Set the source and dest extents to be the same since the filesystem
+  // structures are identical
+  if (op.type() == DeltaArchiveManifest_InstallOperation_Type_MOVE ||
+      op.type() == DeltaArchiveManifest_InstallOperation_Type_BSDIFF) {
+    DeltaDiffGenerator::StoreExtents(extents, op.mutable_src_extents());
+    op.set_src_length(old_data.size());
+  }
+
+  DeltaDiffGenerator::StoreExtents(extents, op.mutable_dst_extents());
+  op.set_dst_length(new_data.size());
+
+  // Write data to output file
+  if (op.type() != DeltaArchiveManifest_InstallOperation_Type_MOVE) {
+    op.set_data_offset(*data_file_size);
+    op.set_data_length(data.size());
+  }
+
+  TEST_AND_RETURN_FALSE(utils::WriteAll(data_fd, &data[0], data.size()));
+  *data_file_size += data.size();
+
+  // Now, insert into graph and blocks vector
+  graph->resize(graph->size() + 1);
+  Vertex::Index vertex = graph->size() - 1;
+  (*graph)[vertex].op = op;
+  CHECK((*graph)[vertex].op.has_type());
+  (*graph)[vertex].file_name = metadata_name;
+
+  TEST_AND_RETURN_FALSE(AddInstallOpToBlocksVector((*graph)[vertex].op,
+                                                   blocks,
+                                                   *graph,
+                                                   vertex));
+
+  return true;
+}
+
+// Reads the file system metadata extents.
+bool ReadFilesystemMetadata(Graph* graph,
+                            vector<Block>* blocks,
+                            const ext2_filsys fs_old,
+                            const ext2_filsys fs_new,
+                            int data_fd,
+                            off_t* data_file_size) {
+  LOG(INFO) << "Processing <rootfs-metadata>";
+
+  // Read all the extents that belong to the main file system metadata.
+  // The metadata blocks are at the the start of each block group and goes

[petkov, 2010/12/10 00:46:55]

typo: the the

[thieule, 2010/12/14 23:11:21]

Done.

+  // until the end of the inode table.
+  for (dgrp_t bg = 0; bg < fs_old->group_desc_count; bg++) {
+    struct ext2_group_desc* group_desc = &fs_old->group_desc[bg];
+    __u32 num_metadata_blocks = (group_desc->bg_inode_table +
+                                 fs_old->inode_blocks_per_group) -
+                                 (bg * fs_old->super->s_blocks_per_group);
+    __u32 bg_start_block = bg * fs_old->super->s_blocks_per_group;
+
+    // Due to bsdiff slowness, we're going to break each block group down

[petkov, 2010/12/10 00:46:55]

would it be better for the payload size to not break up into chunks? are you
concerned about server side performance here or client side memory use?

[thieule, 2010/12/14 23:11:21]

I ran this without breaking up into chunks and bsdiff takes ~45 minutes per
block group.  It ends up taking around 4-5 hours to generate a diff.  I
investigated further and it looks like because of the large runs of similar
values (ie. zeroes and 255), bsdiff algorithm doesn't handle it well.  The
difference in payload size was negligible.

+    // into metadata chunks and feed them to bsdiff.
+    __u32 num_chunks = 4;
+    __u32 blocks_per_chunk = num_metadata_blocks / num_chunks;
+    __u32 curr_block = bg_start_block;
+    for (__u32 chunk = 0; chunk < num_chunks; chunk++) {
+

[petkov, 2010/12/10 00:46:55]

remove blank line

[thieule, 2010/12/14 23:11:21]

Done.

+      __u32 end_block = 0;
+      if (chunk < num_chunks - 1) {
+        end_block = curr_block + blocks_per_chunk;
+      } else {
+        end_block = bg_start_block + num_metadata_blocks;
+      }
+
+      vector<Extent> extents;
+      for (__u32 i = curr_block; i < end_block; i++) {

[petkov, 2010/12/10 00:46:55]

there's an ExtentForRange utility in extent_ranges.h

[thieule, 2010/12/14 23:11:21]

Done.

+        graph_utils::AppendBlockToExtents(&extents, i);
+      }
+
+      std::stringstream metadata_name;
+      metadata_name << "<rootfs-bg-" << bg << "-" << chunk << "-metadata>";

[petkov, 2010/12/10 00:46:55]

maybe use StringPrintf instead?

[thieule, 2010/12/14 23:11:21]

Done.

+
+      LOG(INFO) << "Processing " << metadata_name.str();
+
+      TEST_AND_RETURN_FALSE(AddMetadataExtents(graph,
+                                               blocks,
+                                               fs_old,
+                                               fs_new,
+                                               metadata_name.str(),
+                                               extents,
+                                               data_fd,
+                                               data_file_size));
+
+      curr_block += blocks_per_chunk;
+    }
+  }
+
+  return true;
+}
+
+// Processes all blocks belonging to an inode
+int ProcessInodeAllBlocks(ext2_filsys fs,
+                          blk_t* blocknr,
+                          e2_blkcnt_t blockcnt,
+                          blk_t ref_blk,
+                          int ref_offset,
+                          void* priv) {
+  vector<Extent>* extents = static_cast<vector<Extent>*>(priv);
+  graph_utils::AppendBlockToExtents(extents, *blocknr);
+  return 0;
+}
+
+// Processes only indirect, double indirect or triple indirect metadata
+// blocks belonging to an inode
+int ProcessInodeMetadataBlocks(ext2_filsys fs,
+                               blk_t* blocknr,
+                               e2_blkcnt_t blockcnt,
+                               blk_t ref_blk,
+                               int ref_offset,
+                               void* priv) {
+  vector<Extent>* extents = static_cast<vector<Extent>*>(priv);
+  if (blockcnt < 0) {
+    graph_utils::AppendBlockToExtents(extents, *blocknr);
+  }
+  return 0;
+}
+
+// Read inode metadata blocks.
+bool ReadInodeMetadata(Graph* graph,
+                       vector<Block>* blocks,
+                       const ext2_filsys fs_old,
+                       const ext2_filsys fs_new,
+                       int data_fd,
+                       off_t* data_file_size) {
+  TEST_AND_RETURN_FALSE_ERRCODE(ext2fs_read_inode_bitmap(fs_old));
+
+  TEST_AND_RETURN_FALSE_ERRCODE(ext2fs_read_inode_bitmap(fs_new));
+
+  ext2_inode_scan iscan;
+  TEST_AND_RETURN_FALSE_ERRCODE(ext2fs_open_inode_scan(fs_old, 0, &iscan));
+
+  ext2_ino_t ino;
+  ext2_inode old_inode;
+  while (true) {
+    // Get the next inode on both file systems
+    errcode_t error = ext2fs_get_next_inode(iscan, &ino, &old_inode);
+    if (error) {
+      LOG(ERROR) << "Failed to retrieve next inode (" << error << ")";
+      break;
+    }
+
+    if (ino == 0) {
+      break;
+    }
+
+    if (ino == EXT2_RESIZE_INO) {
+      continue;
+    }
+
+    ext2_inode new_inode;
+    error = ext2fs_read_inode(fs_new, ino, &new_inode);
+    if (error) {
+      LOG(ERROR) << "Failed to retrieve new inode (" << error << ")";
+      continue;
+    }
+
+    // Skip inodes that are not in use
+    if (!ext2fs_test_inode_bitmap(fs_old->inode_map, ino)  ||
+        !ext2fs_test_inode_bitmap(fs_new->inode_map, ino)) {
+      continue;
+    }
+
+    // Skip inodes that have no data blocks
+    if (old_inode.i_blocks == 0 || new_inode.i_blocks == 0) {
+      continue;
+    }
+
+    // Skip inodes that are not the same type
+    bool is_old_dir = (ext2fs_check_directory(fs_old, ino) == 0);
+    bool is_new_dir = (ext2fs_check_directory(fs_new, ino) == 0);
+    if (is_old_dir != is_new_dir) {
+      continue;
+    }
+
+    // Process the inodes metadata blocks
+    // For normal files, metadata blocks are indirect, double indirect
+    // and triple indirect blocks (no data blocks). For directories and
+    // the journal, all blocks are considered metadata blocks.
+    LOG(INFO) << "Processing inode " << ino << " metadata";
+
+    bool all_blocks = ((ino == EXT2_JOURNAL_INO) || is_old_dir || is_new_dir);
+
+    vector<Extent> old_extents;
+    error = ext2fs_block_iterate2(fs_old, ino, 0, NULL,
+                                  all_blocks ? ProcessInodeAllBlocks :
+                                               ProcessInodeMetadataBlocks,
+                                  &old_extents);
+    if (error) {
+      LOG(ERROR) << "Failed to enumerate old inode " << ino
+                << " blocks (" << error << ")";
+      continue;
+    }
+
+    vector<Extent> new_extents;
+    error = ext2fs_block_iterate2(fs_new, ino, 0, NULL,
+                                  all_blocks ? ProcessInodeAllBlocks :
+                                               ProcessInodeMetadataBlocks,
+                                  &new_extents);
+    if (error) {
+      LOG(ERROR) << "Failed to enumerate new inode " << ino
+                << " blocks (" << error << ")";
+      continue;
+    }
+
+    // Skip inode if there are no metadata blocks
+    if (old_extents.size() == 0 || new_extents.size() == 0) {
+      continue;
+    }
+
+    // Make sure the two inodes have the same metadata blocks
+    if (old_extents.size() != new_extents.size()) {
+      continue;
+    }
+
+    bool same_metadata_extents = true;
+    vector<Extent>::iterator it_old;
+    vector<Extent>::iterator it_new;
+    for (it_old = old_extents.begin(),
+         it_new = new_extents.begin();
+         it_old != old_extents.end() && it_new != new_extents.end();
+         it_old++, it_new++) {
+      if (it_old->start_block() != it_new->start_block() ||
+          it_old->num_blocks() != it_new->num_blocks()) {
+            same_metadata_extents = false;
+            break;
+      }
+    }
+
+    if (!same_metadata_extents) {
+      continue;
+    }
+
+    // We have identical inode metadata blocks, we can now add them to
+    // our graph and blocks vector
+    std::stringstream metadata_name;
+    metadata_name << "<rootfs-inode-" << ino << "-metadata>";
+    TEST_AND_RETURN_FALSE(AddMetadataExtents(graph,
+                                             blocks,
+                                             fs_old,
+                                             fs_new,
+                                             metadata_name.str(),
+                                             old_extents,
+                                             data_fd,
+                                             data_file_size));
+  }
+
+  ext2fs_close_inode_scan(iscan);
+
+  return true;
+}
+
 // This class allocates non-existent temp blocks, starting from
 // kTempBlockStart. Other code is responsible for converting these
 // temp blocks into real blocks, as the client can't read or write to
@@ -620,6 +1009,52 @@ bool DeltaDiffGenerator::ReadFileToDiff(
   return true;
 }
 
+bool DeltaDiffGenerator::DeltaReadMetadata(Graph* graph,
+                                           vector<Block>* blocks,
+                                           const string& old_image,
+                                           const string& new_image,
+                                           int data_fd,
+                                           off_t* data_file_size) {
+  // Open the two file systems.
+  ext2_filsys fs_old;
+  TEST_AND_RETURN_FALSE_ERRCODE(ext2fs_open(old_image.c_str(), 0, 0, 0,
+                                            unix_io_manager, &fs_old));
+  ScopedExt2fsCloser fs_old_closer(fs_old);
+
+  ext2_filsys fs_new;
+  TEST_AND_RETURN_FALSE_ERRCODE(ext2fs_open(new_image.c_str(), 0, 0, 0,
+                                            unix_io_manager, &fs_new));
+  ScopedExt2fsCloser fs_new_closer(fs_new);
+
+  // Make sure these two file systems are the same.

[petkov, 2010/12/10 00:46:55]

clarify that if they aren't the same we'll just send the metadata as a full
update.

[thieule, 2010/12/14 23:11:21]

Done.

+  if (fs_old->blocksize != fs_new->blocksize ||
+      fs_old->fragsize != fs_new->fragsize ||
+      fs_old->group_desc_count != fs_new->group_desc_count ||
+      fs_old->inode_blocks_per_group != fs_new->inode_blocks_per_group ||
+      fs_old->super->s_inodes_count != fs_new->super->s_inodes_count ||
+      fs_old->super->s_blocks_count != fs_new->super->s_blocks_count) {
+    return true;
+  }
+
+  // Process the main file system metadata (superblock, inode tables, etc)
+  TEST_AND_RETURN_FALSE(ReadFilesystemMetadata(graph,
+                                               blocks,
+                                               fs_old,
+                                               fs_new,
+                                               data_fd,
+                                               data_file_size));
+
+  // Process each inode metadata blocks.
+  TEST_AND_RETURN_FALSE(ReadInodeMetadata(graph,
+                                          blocks,
+                                          fs_old,
+                                          fs_new,
+                                          data_fd,
+                                          data_file_size));
+
+  return true;
+}
+
 bool DeltaDiffGenerator::InitializePartitionInfo(bool is_kernel,
                                                  const string& partition,
                                                  PartitionInfo* info) {
@@ -1390,6 +1825,16 @@ bool DeltaDiffGenerator::GenerateDeltaUpdateFile(
       LOG(INFO) << "done reading normal files";
       CheckGraph(graph);
 
+      LOG(INFO) << "Starting metadata processing";
+      TEST_AND_RETURN_FALSE(DeltaReadMetadata(&graph,
+                                              &blocks,
+                                              old_image,
+                                              new_image,
+                                              fd,
+                                              &data_file_size));
+      LOG(INFO) << "Done metadata processing";
+      CheckGraph(graph);
+
       graph.resize(graph.size() + 1);
       TEST_AND_RETURN_FALSE(ReadUnwrittenBlocks(blocks,
                                                 fd,