Re: [discuss] Re: 32-bit dma allocations on 64-bit platforms

[Andrea Arcangeli <andrea@suse.de>]

On Fri, Jun 25, 2004 at 05:50:04PM +0200, Takashi Iwai wrote:
> --- linux-2.6.7/arch/i386/kernel/pci-dma.c-dist	2004-06-24 15:56:46.017473544 +0200
> +++ linux-2.6.7/arch/i386/kernel/pci-dma.c	2004-06-25 17:43:42.509366917 +0200
> @@ -23,11 +23,22 @@ void *dma_alloc_coherent(struct device *
>  	if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
>  		gfp |= GFP_DMA;
>  
> + again:
>  	ret = (void *)__get_free_pages(gfp, get_order(size));
>  
> -	if (ret != NULL) {
> +	if (ret == NULL) {
> +		if (dev && (gfp & GFP_DMA)) {
> +			gfp &= ~GFP_DMA;

I would find cleaner to use __GFP_DMA in the whole file, this is not
about your changes, previous code used GFP_DMA too. The issue is that if
we change GFP_DMA to add a __GFP_HIGH or similar, the above will clear
the other bitflags too.

> +		    (((unsigned long)*dma_handle + size - 1) & ~(unsigned long)dev->coherent_dma_mask)) {
> +			free_pages((unsigned long)ret, get_order(size));
> +			return NULL;
> +		}

I would do the memset and setting of dma_handle after the above check.

this approch looks fine, thanks.