linux-kernel - Re: [PATCH 09/18] dma-debug: add checking for map/unmap

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Date:	Thu, 19 Mar 2009 10:39:30 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	joerg.roedel@....com
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 09/18] dma-debug: add checking for map/unmap_page/single

On Fri, 6 Mar 2009 14:30:20 +0100
Joerg Roedel <joerg.roedel@....com> wrote:

> Impact: add debug callbacks for dma_{un}map_[page|single]
> 
> Signed-off-by: Joerg Roedel <joerg.roedel@....com>
> ---
>  include/linux/dma-debug.h |   23 +++++++++++++++++++
>  lib/dma-debug.c           |   53 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 76 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
> index 345d538..65f7352 100644
> --- a/include/linux/dma-debug.h
> +++ b/include/linux/dma-debug.h
> @@ -28,12 +28,35 @@ struct device;
>  
>  extern void dma_debug_init(u32 num_entries);
>  
> +extern void debug_dma_map_page(struct device *dev, struct page *page,
> +			       size_t offset, size_t size,
> +			       int direction, dma_addr_t dma_addr,
> +			       bool map_single);
> +
> +extern void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
> +				 size_t size, int direction, bool map_single);
> +
> +
>  #else /* CONFIG_DMA_API_DEBUG */
>  
>  static inline void dma_debug_init(u32 num_entries)
>  {
>  }
>  
> +static inline void debug_dma_map_page(struct device *dev, struct page *page,
> +				      size_t offset, size_t size,
> +				      int direction, dma_addr_t dma_addr,
> +				      bool map_single)
> +{
> +}
> +
> +static inline void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
> +					size_t size, int direction,
> +					bool map_single)
> +{
> +}
> +
> +
>  #endif /* CONFIG_DMA_API_DEBUG */
>  
>  #endif /* __DMA_DEBUG_H */
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index d0cb47a..a2ed2b7 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -566,3 +566,56 @@ out:
>  
>  }
>  
> +void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
> +			size_t size, int direction, dma_addr_t dma_addr,
> +			bool map_single)
> +{
> +	struct dma_debug_entry *entry;
> +
> +	if (unlikely(global_disable))
> +		return;
> +
> +	if (unlikely(dma_mapping_error(dev, dma_addr)))
> +		return;
> +
> +	entry = dma_entry_alloc();
> +	if (!entry)
> +		return;
> +
> +	entry->dev       = dev;
> +	entry->type      = dma_debug_page;
> +	entry->paddr     = page_to_phys(page) + offset;
> +	entry->dev_addr  = dma_addr;
> +	entry->size      = size;
> +	entry->direction = direction;
> +
> +	if (map_single) {
> +		entry->type = dma_debug_single;
> +		check_for_stack(dev, page_address(page) + offset);

Why you don't call check_for_stack() for dma_map_page()?

page_address(page) could be invalid with dma_map_page() so the check
can be pointless. However, you call check_for_stack() with dma_map_sg,
which the check can be pointless too with; I think that you call
check_for_stack() in an inconsistent way.
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