1 files changed, 21 insertions, 4 deletions

diff --git a/include/asm-generic/fcntl.h b/include/asm-generic/fcntl.h
index 495dc8af4044..681ddf3e844c 100644
--- a/include/asm-generic/fcntl.h
+++ b/include/asm-generic/fcntl.h
@@ -3,8 +3,6 @@
 
 #include <linux/types.h>
 
-/* open/fcntl - O_SYNC is only implemented on blocks devices and on files
-   located on an ext2 file system */
 #define O_ACCMODE       00000003
 #define O_RDONLY        00000000
 #define O_WRONLY        00000001
@@ -27,8 +25,8 @@
 #ifndef O_NONBLOCK
 #define O_NONBLOCK      00004000
 #endif
-#ifndef O_SYNC
-#define O_SYNC          00010000
+#ifndef O_DSYNC
+#define O_DSYNC         00010000        /* used to be O_SYNC, see below */
 #endif
 #ifndef FASYNC
 #define FASYNC          00020000        /* fcntl, for BSD compatibility */
@@ -51,6 +49,25 @@
 #ifndef O_CLOEXEC
 #define O_CLOEXEC       02000000        /* set close_on_exec */
 #endif
+
+/*
+ * Before Linux 2.6.32 only O_DSYNC semantics were implemented, but using
+ * the O_SYNC flag.  We continue to use the existing numerical value
+ * for O_DSYNC semantics now, but using the correct symbolic name for it.
+ * This new value is used to request true Posix O_SYNC semantics.  It is
+ * defined in this strange way to make sure applications compiled against
+ * new headers get at least O_DSYNC semantics on older kernels.
+ *
+ * This has the nice side-effect that we can simply test for O_DSYNC
+ * wherever we do not care if O_DSYNC or O_SYNC is used.
+ *
+ * Note: __O_SYNC must never be used directly.
+ */
+#ifndef O_SYNC
+#define __O_SYNC        04000000
+#define O_SYNC          (__O_SYNC|O_DSYNC)
+#endif
+
 #ifndef O_NDELAY
 #define O_NDELAY        O_NONBLOCK
 #endif