Re: [patch 1/6] s390, block: disable fixed buffer mode when DMA support is disabled

[Heiko Carstens <heiko.carstens@de.ibm.com>]

On Tue, May 24, 2011 at 04:53:45PM -0700, David Rientjes wrote:
> dasd=fixedbuffers must create a SLAB_CACHE_DMA cache, which is not
> possible if CONFIG_ZONE_DMA is disabled (a supported configuration
> without 64-bit support).
> 
> If passed, emit a warning and disable fixed buffer mode.
> 
> Signed-off-by: David Rientjes <rientjes@google.com>

What's the reasoning here?
On s390 for !CONFIG_64BIT ZONE_DMA would be equal to ZONE_NORMAL,
that's why we only have ZONE_NORMAL. So I don't see that something
wouldn't work...

> ---
>  drivers/s390/block/dasd_devmap.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
> --- a/drivers/s390/block/dasd_devmap.c
> +++ b/drivers/s390/block/dasd_devmap.c
> @@ -282,6 +282,11 @@ dasd_parse_keyword( char *parsestring ) {
>  		return residual_str;
>  	}
>  	if (strncmp("fixedbuffers", parsestring, length) == 0) {
> +#ifndef CONFIG_ZONE_DMA
> +		DBF_EVENT(DBF_WARNING, "%s", "DMA support disabled, "
> +					"fixed buffer mode disabled.");
> +		return residual_str;
> +#endif
>  		if (dasd_page_cache)
>  			return residual_str;
>  		dasd_page_cache =