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From: "=?utf-8?B?6ZmI5Y2O5omN?=" <chenhc@lemote.com>
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Subject: Re: [PATCH V5 2/3] mm: dmapool: Align to ARCH_DMA_MINALIGN innon-coherent DMA mode
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Hi, Christoph,

Maybe you missed something.
1, pool_alloc_page() use dma_alloc_coherent() to allocate pool pages, and of course these pages are aligned to  ARCH_DMA_MINALIGN.
2, dma_pool_alloc() is the element allocator, but it doesn't use dma_alloc_coherent(). Elements only align to pool->size, but pool->size is usually less than ARCH_DMA_MINALIGN.
3, ARCH_DMA_MINALIGN is now only used in serveral drivers, no dma_ops use it.

Huacai
 
------------------ Original ------------------
From:  "Christoph Hellwig"<hch@infradead.org>;
Date:  Mon, Sep 18, 2017 01:22 PM
To:  "Huacai Chen"<chenhc@lemote.com>;
Cc:  "Andrew Morton"<akpm@linux-foundation.org>; "Fuxin Zhang"<zhangfx@lemote.com>; "linux-mm"<linux-mm@kvack.org>; "linux-kernel"<linux-kernel@vger.kernel.org>; "stable"<stable@vger.kernel.org>;
Subject:  Re: [PATCH V5 2/3] mm: dmapool: Align to ARCH_DMA_MINALIGN innon-coherent DMA mode
 
The dmapool code uses dma_alloc_coherent to allocate each element,
and dma_alloc_coherent must align to ARCH_DMA_MINALIGN already.
If you implementation doesn't do that it needs to be fixed.