linux-kernel - [PATCH 3.14 60/70] dma-debug: Fix dma_debug

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Date:	Tue, 23 Feb 2016 19:34:09 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Daniel Mentz <danielmentz@...gle.com>,
	Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 3.14 60/70] dma-debug: Fix dma_debug_entry offset calculation

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Mentz <danielmentz@...gle.com>

commit 0354aec19ce3d355c6213b0434064efc25c9b22c upstream.

dma-debug uses struct dma_debug_entry to keep track of dma coherent
memory allocation requests. The virtual address is converted into a pfn
and an offset. Previously, the offset was calculated using an incorrect
bit mask.  As a result, we saw incorrect error messages from dma-debug
like the following:

"DMA-API: exceeded 7 overlapping mappings of cacheline 0x03e00000"

Cacheline 0x03e00000 does not exist on our platform.

Fixes: 0abdd7a81b7e ("dma-debug: introduce debug_dma_assert_idle()")
Signed-off-by: Daniel Mentz <danielmentz@...gle.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 lib/dma-debug.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -1440,7 +1440,7 @@ void debug_dma_alloc_coherent(struct dev
 	entry->type      = dma_debug_coherent;
 	entry->dev       = dev;
 	entry->pfn	 = page_to_pfn(virt_to_page(virt));
-	entry->offset	 = (size_t) virt & PAGE_MASK;
+	entry->offset	 = (size_t) virt & ~PAGE_MASK;
 	entry->size      = size;
 	entry->dev_addr  = dma_addr;
 	entry->direction = DMA_BIDIRECTIONAL;
@@ -1456,7 +1456,7 @@ void debug_dma_free_coherent(struct devi
 		.type           = dma_debug_coherent,
 		.dev            = dev,
 		.pfn		= page_to_pfn(virt_to_page(virt)),
-		.offset		= (size_t) virt & PAGE_MASK,
+		.offset		= (size_t) virt & ~PAGE_MASK,
 		.dev_addr       = addr,
 		.size           = size,
 		.direction      = DMA_BIDIRECTIONAL,