linux-kernel - Re: [PATCH 2/3] drm/nouveau: use post-decrement in error handling

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Date:	Fri, 19 Feb 2016 13:32:55 +1000
From:	Ben Skeggs <skeggsb@...il.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	David Airlie <airlied@...ux.ie>
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/3] drm/nouveau: use post-decrement in error handling

On 02/16/2016 04:41 AM, Rasmus Villemoes wrote:
> We need to use post-decrement to get the dma_map_page undone also for
> i==0, and to avoid some very unpleasant behaviour if dma_map_page
> failed already at i==0.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Reviewed-by: Ben Skeggs <bskeggs@...hat.com>

> ---
>  drivers/gpu/drm/nouveau/nouveau_bo.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index 78f520d05de9..e3acc35e3805 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -1520,7 +1520,7 @@ nouveau_ttm_tt_populate(struct ttm_tt *ttm)
>  				    DMA_BIDIRECTIONAL);
>  
>  		if (dma_mapping_error(pdev, addr)) {
> -			while (--i) {
> +			while (i--) {
>  				dma_unmap_page(pdev, ttm_dma->dma_address[i],
>  					       PAGE_SIZE, DMA_BIDIRECTIONAL);
>  				ttm_dma->dma_address[i] = 0;
> 


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