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-rw-r--r--include/asm-generic/fcntl.h25
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