Re: [PATCH v5 09/13] osdep: move O_DSYNC and O_DIRECT defines from file-posix

[Daniel P . Berrangé]

On Thu, May 23, 2024 at 04:55:18PM +0200, Stefano Garzarella wrote:
> These defines are also useful for vhost-user-blk when it is compiled
> in some POSIX systems that do not define them, so let's move them to
> “qemu/osdep.h”.
> 
> Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>  include/qemu/osdep.h | 14 ++++++++++++++
>  block/file-posix.c   | 14 --------------
>  2 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index f61edcfdc2..e165b5cb1b 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -325,6 +325,20 @@ void QEMU_ERROR("code path is reachable")
>  #define ESHUTDOWN 4099
>  #endif
>  
> +/* 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
> +
> +/* Approximate O_DIRECT with O_DSYNC if O_DIRECT isn't available */
> +#ifndef O_DIRECT
> +#define O_DIRECT O_DSYNC
> +#endif

Please don't do this - we can't be confident that all code in
QEMU will be OK with O_DIRECT being simulated in this way.

I'm not convinced that the O_DSYNC simulation is a good idea
to do tree-wide either.

With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|