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

[G 3 <programmingkidx@gmail.com>]

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 <programmingkidx@gmail.com>
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 <programmingkidx@gmail.com>

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