[PATCH v2 1/1] block: blk-merge: don't merge the pages with non-contiguous descriptors

On Wed, 2013-01-16 at 23:14 +0000, Russell King - ARM Linux wrote:

On Wed, Jan 16, 2013 at 10:32:35AM +0000, James Bottomley wrote:

quoted

On Wed, 2013-01-16 at 12:07 +0530, Subhash Jadavani wrote:

quoted

Now consider this call stack from MMC block driver (this is on the ARmv7 
based board):
     [   98.918174] [<c001b50c>] (v7_dma_inv_range+0x30/0x48) from 
[<c0017b8c>] (dma_cache_maint_page+0x1c4/0x24c)
     [   98.927819] [<c0017b8c>] (dma_cache_maint_page+0x1c4/0x24c) from 
[<c0017c28>] (___dma_page_cpu_to_dev+0x14/0x1c)
     [   98.937982] [<c0017c28>] (___dma_page_cpu_to_dev+0x14/0x1c) from 
[<c0017ff8>] (dma_map_sg+0x3c/0x114)

OK, so this is showing that ARM itself is making the assumption that the
pages are contiguous in the page offset map.

Fix this by doing the increment via the pfn, which will do the right
thing whatever the memory model.

Signed-off-by: James Bottomley <redacted>

Ok.  What would you like the patch summary line for this to be -
the existing one seems to be a little wrong given the content of
this patch...

how about

arm: fix struct page iterator in dma_cache_maint() to work with
sparsemem

?

James

quoted

---

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 6b2fb87..ab88c5b 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c

@@ -809,7 +809,7 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset,
 			op(vaddr, len, dir);
 		}
 		offset = 0;
-		page++;
+		page = pfn_to_page(page_to_pfn(page) + 1);
 		left -= len;
 	} while (left);
 }

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