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Date: Wed, 18 Mar 2015 13:21:45 +0200
From: Boaz Harrosh <boaz@...xistor.com>
To: Dan Williams <dan.j.williams@...el.com>,
linux-kernel@...r.kernel.org
CC: axboe@...nel.dk, linux-raid@...r.kernel.org, riel@...hat.com,
linux-nvdimm@...ts.01.org, hch@...radead.org, mgorman@...e.de,
linux-fsdevel@...r.kernel.org
Subject: Re: [Linux-nvdimm] [RFC PATCH 3/7] dma-mapping: allow archs to optionally
specify a ->map_pfn() operation
On 03/16/2015 10:25 PM, Dan Williams wrote:
> This is in support of enabling block device drivers to perform DMA
> to/from persistent memory which may not have a backing struct page
> entry.
>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
> arch/Kconfig | 3 +++
> include/asm-generic/dma-mapping-common.h | 30 ++++++++++++++++++++++++++++++
> include/linux/dma-debug.h | 23 +++++++++++++++++++----
> include/linux/dma-mapping.h | 8 +++++++-
> lib/dma-debug.c | 4 ++--
> 5 files changed, 61 insertions(+), 7 deletions(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 05d7a8a458d5..80ea3e124494 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -203,6 +203,9 @@ config HAVE_DMA_ATTRS
> config HAVE_DMA_CONTIGUOUS
> bool
>
> +config HAVE_DMA_PFN
> + bool
> +
> config GENERIC_SMP_IDLE_THREAD
> bool
>
> diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h
> index 3378dcf4c31e..58fad817e51a 100644
> --- a/include/asm-generic/dma-mapping-common.h
> +++ b/include/asm-generic/dma-mapping-common.h
> @@ -17,9 +17,15 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
>
> kmemcheck_mark_initialized(ptr, size);
> BUG_ON(!valid_dma_direction(dir));
> +#ifdef CONFIG_HAVE_DMA_PFN
> + addr = ops->map_pfn(dev, page_to_pfn_typed(virt_to_page(ptr)),
> + (unsigned long)ptr & ~PAGE_MASK, size,
> + dir, attrs);
> +#else
Yes our beloved Kernel is full of #ifdef(s) in the middle of the code
Very beautiful
> addr = ops->map_page(dev, virt_to_page(ptr),
> (unsigned long)ptr & ~PAGE_MASK, size,
> dir, attrs);
> +#endif
> debug_dma_map_page(dev, virt_to_page(ptr),
> (unsigned long)ptr & ~PAGE_MASK, size,
> dir, addr, true);
> @@ -68,6 +74,29 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
> ops->unmap_sg(dev, sg, nents, dir, attrs);
> }
>
> +#ifdef CONFIG_HAVE_DMA_PFN
> +static inline dma_addr_t dma_map_pfn(struct device *dev, __pfn_t pfn,
> + size_t offset, size_t size,
> + enum dma_data_direction dir)
> +{
> + struct dma_map_ops *ops = get_dma_ops(dev);
> + dma_addr_t addr;
> +
> + BUG_ON(!valid_dma_direction(dir));
> + addr = ops->map_pfn(dev, pfn, offset, size, dir, NULL);
> + debug_dma_map_pfn(dev, pfn, offset, size, dir, addr, false);
> +
> + return addr;
> +}
> +
> +static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
> + size_t offset, size_t size,
> + enum dma_data_direction dir)
> +{
> + kmemcheck_mark_initialized(page_address(page) + offset, size);
> + return dma_map_pfn(dev, page_to_pfn_typed(page), offset, size, dir);
> +}
> +#else
And in the middle of source code files
> static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
> size_t offset, size_t size,
> enum dma_data_direction dir)
> @@ -82,6 +111,7 @@ static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
>
> return addr;
> }
> +#endif /* CONFIG_HAVE_DMA_PFN */
>
> static inline void dma_unmap_page(struct device *dev, dma_addr_t addr,
> size_t size, enum dma_data_direction dir)
> diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
> index fe8cb610deac..eb3e69c61e5e 100644
> --- a/include/linux/dma-debug.h
> +++ b/include/linux/dma-debug.h
> @@ -34,10 +34,18 @@ extern void dma_debug_init(u32 num_entries);
>
> extern int dma_debug_resize_entries(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_map_pfn(struct device *dev, __pfn_t pfn, size_t offset,
> + size_t size, int direction, dma_addr_t dma_addr,
> + bool map_single);
> +
> +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)
> +{
> + return debug_dma_map_pfn(dev, page_to_pfn_typed(page), offset, size,
> + direction, dma_addr, map_single);
> +}
>
> extern void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
>
> @@ -109,6 +117,13 @@ static inline void debug_dma_map_page(struct device *dev, struct page *page,
> {
> }
>
> +static inline void debug_dma_map_pfn(struct device *dev, __pfn_t pfn,
> + size_t offset, size_t size,
> + int direction, dma_addr_t dma_addr,
> + bool map_single)
> +{
> +}
> +
> static inline void debug_dma_mapping_error(struct device *dev,
> dma_addr_t dma_addr)
> {
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index c3007cb4bfa6..6411621e4179 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -26,11 +26,17 @@ struct dma_map_ops {
>
> int (*get_sgtable)(struct device *dev, struct sg_table *sgt, void *,
> dma_addr_t, size_t, struct dma_attrs *attrs);
> -
> +#ifdef CONFIG_HAVE_DMA_PFN
> + dma_addr_t (*map_pfn)(struct device *dev, __pfn_t pfn,
> + unsigned long offset, size_t size,
> + enum dma_data_direction dir,
> + struct dma_attrs *attrs);
> +#else
And in the middle of structures
> dma_addr_t (*map_page)(struct device *dev, struct page *page,
> unsigned long offset, size_t size,
> enum dma_data_direction dir,
> struct dma_attrs *attrs);
> +#endif
> void (*unmap_page)(struct device *dev, dma_addr_t dma_handle,
> size_t size, enum dma_data_direction dir,
> struct dma_attrs *attrs);
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index 9722bd2dbc9b..a447730fff97 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -1250,7 +1250,7 @@ out:
> put_hash_bucket(bucket, &flags);
> }
>
> -void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
> +void debug_dma_map_pfn(struct device *dev, __pfn_t pfn, size_t offset,
> size_t size, int direction, dma_addr_t dma_addr,
> bool map_single)
> {
> @@ -1268,7 +1268,7 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
>
> entry->dev = dev;
> entry->type = dma_debug_page;
> - entry->pfn = page_to_pfn(page);
> + entry->pfn = pfn.pfn;
> entry->offset = offset,
> entry->dev_addr = dma_addr;
> entry->size = size;
>
This is exactly what I meant. It is not only two different code paths it is
two different compilation paths. This is a maintenance nightmare. And a sure
bit rot.
Real nice for nothing
Thanks, but no thanks
Boaz
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