[Qemu-devel] [PATCH] Substitute O_DSYNC with O_SYNC or O_FSYNC when needed.

[G 3]

On Jul 1, 2009, at 9:54 AM, Christoph Hellwig wrote:

> On Fri, Jun 26, 2009 at 03:02:47PM -0400, G 3 wrote:
> > /* OS X does not have O_DSYNC */
> > #ifndef O_DSYNC
> > #ifdef O_SYNC                           /* Works on Mac OS 10.4 and
> > greater */
> > #define O_DSYNC O_SYNC
> > #elif defined(O_FSYNC)          /* Works on Mac OS 10.3 and under */
> > #define O_DSYNC O_FSYNC
> > #else                                           /* If no substitute is
> > available */
> > #define O_DSYNC 0                       
> > #endif
> > #endif
>
> This still does the NULL sync which can cause silent data loss if no
> O_*SYNC is available.  If you want to be safe and support either O_SYNC
> or O_FSYNC as O_DSYNC replacement the following should be enough:
>
> /*
>  * MacOS X does not have O_DSYNC, and in earlier version no O_SYNC 
> either.
>  */
> #ifndef O_DSYNC
> #ifdef O_SYNC   
> #define O_DSYNC O_SYNC
> #else
> #define O_DSYNC O_FSYNC
> #endif
> #endif


This patch should be what you want.

commit b32354139556d1a807d04aa54ed82610e0f4507a
Author: John Arbuckle <address@hidden>
Date:   Wed Jul 1 13:24:37 2009 -0400

    Substitute O_DSYNC with O_SYNC or O_FSYNC when needed.

    Signed-off-by: John Arbuckle <address@hidden>

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 8b1e67c..17338ee 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -81,7 +81,11 @@

 /* OS X does not have O_DSYNC */
 #ifndef O_DSYNC
+#ifdef O_SYNC
 #define O_DSYNC O_SYNC
+#elif defined(O_FSYNC)
+#define O_DSYNC O_FSYNC
+#endif
 #endif