Re: [Qemu-devel] [PATCH v7 3/6] libnvdimm: add dax_dev sync flag

[Dan Williams]

On Thu, Apr 25, 2019 at 10:02 PM Pankaj Gupta <address@hidden> wrote:
>
> This patch adds 'DAXDEV_SYNC' flag which is set
> for nd_region doing synchronous flush. This later
> is used to disable MAP_SYNC functionality for
> ext4 & xfs filesystem for devices don't support
> synchronous flush.
>
> Signed-off-by: Pankaj Gupta <address@hidden>
[..]
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 0dd316a74a29..c97fc0cc7167 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -7,6 +7,9 @@
>  #include <linux/radix-tree.h>
>  #include <asm/pgtable.h>
>
> +/* Flag for synchronous flush */
> +#define DAXDEV_F_SYNC true

I'd feel better, i.e. it reads more canonically, if this was defined
as (1UL << 0) and the argument to alloc_dax() was changed to 'unsigned
long flags' rather than a bool.