AU: When checking if we've visited a file before, don't follow symlinks.

delta_diff_generator.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/delta_diff_generator.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <sys/stat.h>
@@ skipping 143 matching lines @@
 
     // Make sure we visit each inode only once.
     if (utils::SetContainsKey(visited_inodes, fs_iter.GetStat().st_ino))
       continue;
     visited_inodes.insert(fs_iter.GetStat().st_ino);
     if (fs_iter.GetStat().st_size == 0)
       continue;
 
     LOG(INFO) << "Encoding file " << fs_iter.GetPartialPath();
 
     // We can't visit each dst image inode more than once, as that would

[petkov, 2011/02/22 23:25:32]

Update the comment to reflect the fact that we never diff symlinks...

     // duplicate work. Here, we avoid visiting each source image inode
     // more than once. Technically, we could have multiple operations
     // that read the same blocks from the source image for diffing, but
     // we choose not to to avoid complexity. Eventually we will move away
     // from using a graph/cycle detection/etc to generate diffs, and at that
     // time, it will be easy (non-complex) to have many operations read
     // from the same source blocks. At that time, this code can die. -adlr
-    bool should_diff_from_source = true;
+    bool should_diff_from_source = false;
     string src_path = old_root + fs_iter.GetPartialPath();
-    if (utils::FileExists(src_path.c_str())) {
-      struct stat src_stbuf;
-      TEST_AND_RETURN_FALSE_ERRNO(0 == stat(src_path.c_str(), &src_stbuf));
+    struct stat src_stbuf;
+    if (0 == lstat(src_path.c_str(), &src_stbuf) &&
+        S_ISREG(src_stbuf.st_mode)) {
       should_diff_from_source = !utils::SetContainsKey(visited_src_inodes,
                                                        src_stbuf.st_ino);
       visited_src_inodes.insert(src_stbuf.st_ino);
     }
 
     TEST_AND_RETURN_FALSE(DeltaReadFile(graph,
                                         Vertex::kInvalidIndex,
                                         blocks,
                                         (should_diff_from_source ?
                                          old_root :
@@ skipping 1439 matching lines @@
   dummy_extent->set_start_block(kSparseHole);
   dummy_extent->set_num_blocks((signature_blob_length + kBlockSize - 1) /
                                kBlockSize);
 }
 
 const char* const kBsdiffPath = "bsdiff";
 const char* const kBspatchPath = "bspatch";
 const char* const kDeltaMagic = "CrAU";
 
 };  // namespace chromeos_update_engine