Port flush_cache tool.

BUG=4160

Review URL: http://codereview.chromium.org/9639
Patch from Paweł Hajdan jr.


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@5182 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 63 insertions, 0 deletions

diff --git a/base/file_util.h b/base/file_util.h
index 3df31e4..0bdb56d 100644
--- a/base/file_util.h
+++ b/base/file_util.h
@@ -389,6 +389,10 @@ bool RenameFileAndResetSecurityDescriptor(
     const std::wstring& source_file_path,
     const std::wstring& target_file_path);
 
+// Clear a specific file from the system cache. After this call, trying
+// to access this file will result in a cold load from the hard drive.
+bool EvictFileFromSystemCache(const FilePath path);
+
 }  // namespace file_util
 
 #endif  // BASE_FILE_UTIL_H_
diff --git a/base/file_util_linux.cc b/base/file_util_linux.cc
index f776c91..d2a6870 100644
--- a/base/file_util_linux.cc
+++ b/base/file_util_linux.cc
@@ -72,4 +72,16 @@ bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
   return result;
 }
 
+bool EvictFileFromSystemCache(const FilePath path) {
+  int fd = open(path.value().c_str(), O_RDONLY);
+  if (fd < 0)
+    return false;
+  if (fdatasync(fd) != 0)
+    return false;
+  if (posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED) != 0)
+    return false;
+  close(fd);
+  return true;
+}
+
 }  // namespace file_util
diff --git a/base/file_util_mac.mm b/base/file_util_mac.mm
index f7f5632..0cf63d2 100644
--- a/base/file_util_mac.mm
+++ b/base/file_util_mac.mm
@@ -28,4 +28,10 @@ bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
                    to_path.value().c_str(), NULL, COPYFILE_ALL) == 0);
 }
 
+bool EvictFileFromSystemCache(const FilePath path) {
+  // TODO(port): Implement.
+  NOTIMPLEMENTED();
+  return false;
+}
+
 }  // namespace
diff --git a/base/file_util_win.cc b/base/file_util_win.cc
index 355bdfd..5f75544 100644
--- a/base/file_util_win.cc
+++ b/base/file_util_win.cc
@@ -692,4 +692,45 @@ std::wstring FileEnumerator::Next() {
   return (file_type_ & FileEnumerator::FILES) ? cur_file : Next();
 }
 
+bool EvictFileFromSystemCache(const FilePath path) {
+  // Overwrite it with no buffering.
+  ScopedHandle file(CreateFile(path.value().c_str(),
+                               GENERIC_READ | GENERIC_WRITE,
+                               FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
+                               OPEN_EXISTING, FILE_FLAG_NO_BUFFERING, NULL));
+  if (!file.IsValid())
+    return false;
+
+  // Execute in chunks. It could be optimized. We want to do few of these since
+  // these operations will be slow without the cache.
+  char buffer[128 * 1024];
+  int total_bytes = 0;
+  DWORD bytes_read;
+  for (;;) {
+    if (!ReadFile(file, buffer, sizeof(buffer), &bytes_read, NULL))
+      return false;
+    if (bytes_read == 0)
+      break;
+
+    bool final = false;
+    if (bytes_read < sizeof(buffer))
+      final = true;
+
+    DWORD to_write = final ? sizeof(buffer) : bytes_read;
+
+    DWORD actual;
+    SetFilePointer(file, total_bytes, 0, FILE_BEGIN);
+    if (!WriteFile(file, buffer, to_write, &actual, NULL))
+      return false;
+    total_bytes += bytes_read;
+
+    if (final) {
+      SetFilePointer(file, total_bytes, 0, FILE_BEGIN);
+      SetEndOfFile(file);
+      break;
+    }
+  }
+  return true;
+}
+
 }  // namespace file_util