Use ctime in file digest cache key

src/main/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandler.java

@@ -665,7 +665,8 @@ private static FileArtifactValue fileArtifactValueFromStat(
   }
 
   private static void setPathReadOnlyAndExecutableIfFile(Path path) throws IOException {
-    if (path.isFile(Symlinks.NOFOLLOW)) {
+    FileStatus stat = path.statIfFound(Symlinks.NOFOLLOW);
+    if (stat != null && stat.isFile() && stat.getPermissions() != 0555) {
       setPathReadOnlyAndExecutable(path);
     }
   }

src/main/java/com/google/devtools/build/lib/unix/UnixFileSystem.java

@@ -98,7 +98,10 @@ public long getNodeId() {
       return status.getInodeNumber();
     }
 
-    int getPermissions() { return status.getPermissions(); }
+    @Override
+    public int getPermissions() {
+      return status.getPermissions();
+    }
 
     @Override
     public String toString() { return status.toString(); }

src/main/java/com/google/devtools/build/lib/vfs/DigestUtils.java

@@ -54,6 +54,9 @@ private static class CacheKey {
     /** File system identifier of the file (typically the inode number). */
     private final long nodeId;
 
+    /** Last change time of the file. */
+    private final long changeTime;
+
     /** Last modification time of the file. */
     private final long modifiedTime;
 
@@ -70,6 +73,7 @@ private static class CacheKey {
     public CacheKey(Path path, FileStatus status) throws IOException {
       this.path = path.asFragment();
       this.nodeId = status.getNodeId();
+      this.changeTime = status.getLastChangeTime();
       this.modifiedTime = status.getLastModifiedTime();
       this.size = status.getSize();
     }
@@ -84,6 +88,7 @@ public boolean equals(Object object) {
         CacheKey key = (CacheKey) object;
         return path.equals(key.path)
             && nodeId == key.nodeId
+            && changeTime == key.changeTime
             && modifiedTime == key.modifiedTime
             && size == key.size;
       }
@@ -94,6 +99,7 @@ public int hashCode() {
       int result = 17;
       result = 31 * result + path.hashCode();
       result = 31 * result + Longs.hashCode(nodeId);
+      result = 31 * result + Longs.hashCode(changeTime);
       result = 31 * result + Longs.hashCode(modifiedTime);
       result = 31 * result + Longs.hashCode(size);
       return result;

src/main/java/com/google/devtools/build/lib/vfs/FileStatus.java

@@ -85,4 +85,16 @@ public interface FileStatus {
    * ought to cause the node ID of b to change, but appending / modifying b should not.
    */
   long getNodeId() throws IOException;
+
+  /**
+   * Returns the file's permissions in POSIX format (e.g. 0755) if possible without performing
+   * additional IO, otherwise (or if unsupported by the file system) returns -1.
+   *
+   * <p>If accurate group and other permissions aren't available, the returned value should attempt
+   * to mimic a umask of 022 (i.e. read and execute permissions extend to group and other, write
+   * does not).
+   */
+  default int getPermissions() {
+    return -1;
+  }
 }

src/main/java/com/google/devtools/build/lib/vfs/inmemoryfs/InMemoryContentInfo.java

@@ -120,6 +120,22 @@ public long getNodeId() {
     return System.identityHashCode(this);
   }
 
+  @Override
+  public final int getPermissions() {
+    int permissions = 0;
+    // Emulate the default umask of 022.
+    if (isReadable) {
+      permissions |= 0444;
+    }
+    if (isWritable) {
+      permissions |= 0200;
+    }
+    if (isExecutable) {
+      permissions |= 0111;
+    }
+    return permissions;
+  }
+
   @Override
   public final InMemoryContentInfo inode() {
     return this;

src/main/java/com/google/devtools/build/lib/windows/WindowsFileOperations.java

@@ -15,7 +15,9 @@
 package com.google.devtools.build.lib.windows;
 
 import com.google.devtools.build.lib.jni.JniLoader;
+import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.nio.file.AccessDeniedException;
 
 /** File operations on Windows. */
 public class WindowsFileOperations {
@@ -82,6 +84,12 @@ public Status getStatus() {
   // IS_SYMLINK_OR_JUNCTION_ERROR = 1;
   private static final int IS_SYMLINK_OR_JUNCTION_DOES_NOT_EXIST = 2;
 
+  // Keep GET_CHANGE_TIME_* values in sync with src/main/native/windows/file.cc.
+  private static final int GET_CHANGE_TIME_SUCCESS = 0;
+  //  private static final int GET_CHANGE_TIME_ERROR = 1;
+  private static final int GET_CHANGE_TIME_DOES_NOT_EXIST = 2;
+  private static final int GET_CHANGE_TIME_ACCESS_DENIED = 3;
+
   // Keep CREATE_JUNCTION_* values in sync with src/main/native/windows/file.h.
   private static final int CREATE_JUNCTION_SUCCESS = 0;
   // CREATE_JUNCTION_ERROR = 1;
@@ -114,6 +122,9 @@ public Status getStatus() {
   private static native int nativeIsSymlinkOrJunction(
       String path, boolean[] result, String[] error);
 
+  private static native int nativeGetChangeTime(
+      String path, boolean followReparsePoints, long[] result, String[] error);
+
   private static native boolean nativeGetLongPath(String path, String[] result, String[] error);
 
   private static native int nativeCreateJunction(String name, String target, String[] error);
@@ -143,6 +154,25 @@ public static boolean isSymlinkOrJunction(String path) throws IOException {
     throw new IOException(String.format("Cannot tell if '%s' is link: %s", path, error[0]));
   }
 
+  /** Returns the time at which the file was last changed, including metadata changes. */
+  public static long getLastChangeTime(String path, boolean followReparsePoints)
+      throws IOException {
+    long[] result = new long[] {0};
+    String[] error = new String[] {null};
+    switch (nativeGetChangeTime(asLongPath(path), followReparsePoints, result, error)) {
+      case GET_CHANGE_TIME_SUCCESS:
+        return result[0];
+      case GET_CHANGE_TIME_DOES_NOT_EXIST:
+        throw new FileNotFoundException(path);
+      case GET_CHANGE_TIME_ACCESS_DENIED:
+        throw new AccessDeniedException(path);
+      default:
+        // This is GET_CHANGE_TIME_ERROR (1). The JNI code puts a custom message in 'error[0]'.
+        break;
+    }
+    throw new IOException(String.format("Cannot get last change time of '%s': %s", path, error[0]));
+  }
+
   /**
    * Returns the long path associated with the input `path`.
    *

src/main/java/com/google/devtools/build/lib/windows/WindowsFileSystem.java

@@ -156,6 +156,8 @@ protected FileStatus stat(PathFragment path, boolean followSymlinks) throws IOEx
     }
 
     final boolean isSymbolicLink = !followSymlinks && fileIsSymbolicLink(file);
+    final long lastChangeTime =
+        WindowsFileOperations.getLastChangeTime(getNioPath(path).toString(), followSymlinks);
     FileStatus status =
         new FileStatus() {
           @Override
@@ -193,15 +195,20 @@ public long getLastModifiedTime() throws IOException {
 
           @Override
           public long getLastChangeTime() {
-            // This is the best we can do with Java NIO...
-            return attributes.lastModifiedTime().toMillis();
+            return lastChangeTime;
           }
 
           @Override
           public long getNodeId() {
             // TODO(bazel-team): Consider making use of attributes.fileKey().
             return -1;
           }
+
+          @Override
+          public int getPermissions() {
+            // Files on Windows are implicitly readable and executable.
+            return 0555 | (attributes.isReadOnly() ? 0 : 0200);
+          }
         };
 
     return status;

src/main/native/windows/file-jni.cc

@@ -62,6 +62,29 @@ Java_com_google_devtools_build_lib_windows_WindowsFileOperations_nativeIsSymlink
   return static_cast<jint>(result);
 }
 
+extern "C" JNIEXPORT jint JNICALL
+Java_com_google_devtools_build_lib_windows_WindowsFileOperations_nativeGetChangeTime(
+    JNIEnv* env, jclass clazz, jstring path, jboolean follow_reparse_points,
+    jlongArray result_holder, jobjectArray error_msg_holder) {
+  std::wstring wpath(bazel::windows::GetJavaWstring(env, path));
+  std::wstring error;
+  jlong ctime = 0;
+  int result =
+      bazel::windows::GetChangeTime(wpath.c_str(), follow_reparse_points,
+                                    reinterpret_cast<int64_t*>(&ctime), &error);
+  if (result == bazel::windows::GetChangeTimeResult::kSuccess) {
+    env->SetLongArrayRegion(result_holder, 0, 1, &ctime);
+  } else {
+    if (!error.empty() && CanReportError(env, error_msg_holder)) {
+      ReportLastError(
+          bazel::windows::MakeErrorMessage(
+              WSTR(__FILE__), __LINE__, L"nativeGetChangeTime", wpath, error),
+          env, error_msg_holder);
+    }
+  }
+  return static_cast<jint>(result);
+}
+
 extern "C" JNIEXPORT jboolean JNICALL
 Java_com_google_devtools_build_lib_windows_WindowsFileOperations_nativeGetLongPath(
     JNIEnv* env, jclass clazz, jstring path, jobjectArray result_holder,

src/main/native/windows/file.cc

@@ -21,6 +21,7 @@
 #include <WinIoCtl.h>
 #include <stdint.h>  // uint8_t
 #include <versionhelpers.h>
+#include <winbase.h>
 #include <windows.h>
 
 #include <memory>
@@ -119,6 +120,54 @@ int IsSymlinkOrJunction(const WCHAR* path, bool* result, wstring* error) {
   }
 }
 
+int GetChangeTime(const WCHAR* path, bool follow_reparse_points,
+                  int64_t* result, wstring* error) {
+  if (!IsAbsoluteNormalizedWindowsPath(path)) {
+    if (error) {
+      *error = MakeErrorMessage(WSTR(__FILE__), __LINE__, L"GetChangeTime",
+                                path, L"expected an absolute Windows path");
+    }
+    return GetChangeTimeResult::kError;
+  }
+
+  AutoHandle handle;
+  DWORD flags = FILE_FLAG_BACKUP_SEMANTICS;
+  if (!follow_reparse_points) {
+    flags |= FILE_FLAG_OPEN_REPARSE_POINT;
+  }
+  handle = CreateFileW(path, 0,
+                       FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                       nullptr, OPEN_EXISTING, flags, nullptr);
+
+  if (!handle.IsValid()) {
+    DWORD err = GetLastError();
+    if (err == ERROR_FILE_NOT_FOUND || err == ERROR_PATH_NOT_FOUND) {
+      return GetChangeTimeResult::kDoesNotExist;
+    } else if (err == ERROR_ACCESS_DENIED) {
+      return GetChangeTimeResult::kAccessDenied;
+    }
+    if (error) {
+      *error =
+          MakeErrorMessage(WSTR(__FILE__), __LINE__, L"CreateFileW", path, err);
+    }
+    return GetChangeTimeResult::kError;
+  }
+
+  FILE_BASIC_INFO info;
+  if (!GetFileInformationByHandleEx(handle, FileBasicInfo, (LPVOID)&info,
+                                    sizeof(FILE_BASIC_INFO))) {
+    DWORD err = GetLastError();
+    if (error) {
+      *error = MakeErrorMessage(WSTR(__FILE__), __LINE__,
+                                L"GetFileInformationByHandleEx", path, err);
+    }
+    return GetChangeTimeResult::kError;
+  }
+
+  *result = info.ChangeTime.QuadPart;
+  return GetChangeTimeResult::kSuccess;
+}
+
 wstring GetLongPath(const WCHAR* path, unique_ptr<WCHAR[]>* result) {
   if (!IsAbsoluteNormalizedWindowsPath(path)) {
     return MakeErrorMessage(WSTR(__FILE__), __LINE__, L"GetLongPath", path,

src/main/native/windows/file.h

@@ -82,6 +82,16 @@ struct IsSymlinkOrJunctionResult {
   };
 };
 
+// Keep in sync with j.c.g.devtools.build.lib.windows.WindowsFileOperations
+struct GetChangeTimeResult {
+  enum {
+    kSuccess = 0,
+    kError = 1,
+    kDoesNotExist = 2,
+    kAccessDenied = 3,
+  };
+};
+
 // Keep in sync with j.c.g.devtools.build.lib.windows.WindowsFileOperations
 struct DeletePathResult {
   enum {
@@ -136,6 +146,13 @@ struct ReadSymlinkOrJunctionResult {
 // see http://superuser.com/a/343079. In Bazel we only ever create junctions.
 int IsSymlinkOrJunction(const WCHAR* path, bool* result, wstring* error);
 
+// Retrieves the FILETIME at which `path` was last changed, including metadata.
+//
+// `path` should be an absolute, normalized, Windows-style path, with "\\?\"
+// prefix if it's longer than MAX_PATH.
+int GetChangeTime(const WCHAR* path, bool follow_reparse_points,
+                  int64_t* result, wstring* error);
+
 // Computes the long version of `path` if it has any 8dot3 style components.
 // Returns the empty string upon success, or a human-readable error message upon
 // failure.

src/test/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandlerTest.java

@@ -300,9 +300,10 @@ public void resettingOutputs() throws Exception {
 
     // Reset this output, which will make the handler stat the file again.
     handler.resetOutputs(ImmutableList.of(artifact));
-    chmodCalls.clear(); // Permit a second chmod call for the artifact.
+    chmodCalls.clear();
     assertThat(handler.getMetadata(artifact).getSize()).isEqualTo(10);
-    assertThat(chmodCalls).containsExactly(outputPath);
+    // The handler should not have chmodded the file as it already has the correct permission.
+    assertThat(chmodCalls).isEmpty();
   }
 
   @Test