Add best-effort/allow rollback flags on WorkItem.

chrome/installer/util/delete_tree_work_item.cc

Index: chrome/installer/util/delete_tree_work_item.cc
diff --git a/chrome/installer/util/delete_tree_work_item.cc b/chrome/installer/util/delete_tree_work_item.cc
index 7dbb9e7a618c0bef29ec83a89f4ba21e4dcddda7..8fc5dadfed220c7193bab53f9d177c6374c96d90 100644
--- a/chrome/installer/util/delete_tree_work_item.cc
+++ b/chrome/installer/util/delete_tree_work_item.cc
@@ -4,158 +4,38 @@
 
 #include "chrome/installer/util/delete_tree_work_item.h"
 
-#include <algorithm>
-#include <limits>
-
 #include "base/files/file_util.h"
 #include "base/logging.h"
 
-namespace {
-
-// Casts a value of an unsigned type to a signed type of the same size provided
-// that there is no overflow.
-template<typename L, typename R>
-bool SafeCast(L left, R* right) {
-  DCHECK(right);
-  static_assert(sizeof(left) == sizeof(right),
-                "Items SafeCast is used with must be of the same size");
-  if (left > static_cast<L>(std::numeric_limits<R>::max()))
-    return false;
-  *right = static_cast<L>(left);
-  return true;
-}
-
-}  // namespace
-
-DeleteTreeWorkItem::DeleteTreeWorkItem(
-    const base::FilePath& root_path,
-    const base::FilePath& temp_path,
-    const std::vector<base::FilePath>& key_paths)
-    : root_path_(root_path),
-      temp_path_(temp_path),
-      moved_to_backup_(false) {
-  if (!SafeCast(key_paths.size(), &num_key_files_)) {
-    NOTREACHED() << "Impossibly large key_paths collection";
-  } else if (num_key_files_ != 0) {
-    key_paths_.reset(new base::FilePath[num_key_files_]);
-    key_backup_paths_.reset(new base::ScopedTempDir[num_key_files_]);
-    std::copy(key_paths.begin(), key_paths.end(), &key_paths_[0]);
-  }
-}
-
-DeleteTreeWorkItem::~DeleteTreeWorkItem() {
-}
-
-// We first try to move key_path_ to backup_path. If it succeeds, we go ahead
-// and move the rest.
-bool DeleteTreeWorkItem::Do() {
-  // Go through all the key files and see if we can open them exclusively
-  // with only the FILE_SHARE_DELETE flag.  Once we know we have all of them,
-  // we can delete them.
-  std::vector<HANDLE> opened_key_files;
-  opened_key_files.reserve(num_key_files_);
-  bool abort = false;
-  for (ptrdiff_t i = 0; !abort && i != num_key_files_; ++i) {
-    base::FilePath& key_file = key_paths_[i];
-    base::ScopedTempDir& backup = key_backup_paths_[i];
-    if (!ignore_failure_) {
-      if (!backup.CreateUniqueTempDirUnderPath(temp_path_)) {
-        PLOG(ERROR) << "Could not create temp dir in " << temp_path_.value();
-        abort = true;
-      } else if (!base::CopyFile(key_file,
-                     backup.path().Append(key_file.BaseName()))) {
-        PLOG(ERROR) << "Could not back up " << key_file.value()
-                    << " to directory " << backup.path().value();
-        abort = true;
-        if (!backup.Delete()) {
-          PLOG(ERROR) << "Could not clean up temp dir in "
-                      << temp_path_.value();
-        }
-      }
-    }
-    if (!abort) {
-      HANDLE file = ::CreateFile(key_file.value().c_str(), FILE_ALL_ACCESS,
-                                 FILE_SHARE_DELETE, NULL, OPEN_EXISTING, 0,
-                                 NULL);
-      if (file != INVALID_HANDLE_VALUE) {
-        VLOG(1) << "Acquired exclusive lock for key file: " << key_file.value();
-        opened_key_files.push_back(file);
-      } else {
-        if (::GetLastError() != ERROR_FILE_NOT_FOUND)
-          abort = true;
-        PLOG(INFO) << "Failed to open " << key_file.value();
-      }
-    }
-  }
-
-  if (!abort) {
-    // We now hold exclusive locks with "share delete" permissions for each
-    // of the key files and also have created backups of those files.
-    // We can safely delete the key files now.
-    for (ptrdiff_t i = 0; !abort && i != num_key_files_; ++i) {
-      base::FilePath& key_file = key_paths_[i];
-      if (!base::DeleteFile(key_file, true)) {
-        // This should not really be possible because of the above.
-        PLOG(DFATAL) << "Unexpectedly could not delete " << key_file.value();
-        abort = true;
-      }
-    }
-  }
-
-  std::for_each(opened_key_files.begin(), opened_key_files.end(), CloseHandle);
-  opened_key_files.clear();
+DeleteTreeWorkItem::DeleteTreeWorkItem(const base::FilePath& root_path,
+                                       const base::FilePath& temp_path)
+    : root_path_(root_path), temp_path_(temp_path) {}
 
-  if (abort) {
-    LOG(ERROR) << "Could not exclusively hold all key files.";
-    return ignore_failure_;
-  }
+DeleteTreeWorkItem::~DeleteTreeWorkItem() = default;
 
-  // Now that we've taken care of the key files, take care of the rest.
+bool DeleteTreeWorkItem::DoImpl() {
   if (root_path_.empty() || !base::PathExists(root_path_))
     return true;
 
-  if (ignore_failure_) {
-    if (DeleteRoot())
-      return true;
-    // The file cannot be removed, but perhaps it can be moved into
-    // the temporary backup path. Consumers are responsible for making
-    // a best-effort attempt to remove the backup path. SelfCleaningTempDir
-    // is generally used for the backup path, so in the
-    // worst case the file(s) will be removed after the next reboot.
-    MoveRootToBackup();
+  // If rollback is not enabled, try to delete the root without making a backup.
+  // When that fails, fall back to moving the root to the temporary backup path.
+  // Consumers are responsible for making a best-effort attempt to remove the
+  // backup path. SelfCleaningTempDir is generally used for the backup path, so
+  // in the worst case the file(s) will be removed after the next reboot.
+  if (!rollback_enabled() && DeleteRoot())
     return true;
-  }
 
   // Attempt to move the root to the backup.
   return MoveRootToBackup();
 }
 
-// If there are files in backup paths move them back.
-void DeleteTreeWorkItem::Rollback() {
-  if (ignore_failure_)
-    return;
-
+void DeleteTreeWorkItem::RollbackImpl() {
   if (moved_to_backup_) {
     base::FilePath backup = GetBackupPath();
     DCHECK(!backup.empty());
     if (base::PathExists(backup))
       base::Move(backup, root_path_);
   }
-
-  for (ptrdiff_t i = 0; i != num_key_files_; ++i) {
-    base::ScopedTempDir& backup_dir = key_backup_paths_[i];
-    if (!backup_dir.path().empty()) {
-      base::FilePath& key_file = key_paths_[i];
-      base::FilePath backup_file =
-          backup_dir.path().Append(key_file.BaseName());
-      if (base::PathExists(backup_file) &&
-          !base::Move(backup_file, key_file)) {
-        // This could happen if we could not delete the key file to begin with.
-        PLOG(WARNING) << "Rollback: Failed to move backup file back in place: "
-                      << backup_file.value() << " to " << key_file.value();
-      }
-    }
-  }
 }
 
 base::FilePath DeleteTreeWorkItem::GetBackupPath() {