[PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses

[Roman Skakun <rm.skakun@gmail.com>]

This commit is dedicated to fix incorrect conversion from
cpu_addr to page address in cases when we get virtual
address which allocated in the vmalloc range.
As the result, virt_to_page() cannot convert this address
properly and return incorrect page address.

Need to detect such cases and obtains the page address using
vmalloc_to_page() instead.

Signed-off-by: Roman Skakun <roman_skakun@epam.com>
Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
---
Hey!
Thanks for suggestions, Christoph!
I updated the patch according to your advice.
But, I'm so surprised because nobody catches this problem
in the common code before. It looks a bit strange as for me. 


 kernel/dma/ops_helpers.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
index 910ae69cae77..782728d8a393 100644
--- a/kernel/dma/ops_helpers.c
+++ b/kernel/dma/ops_helpers.c
@@ -5,6 +5,14 @@
  */
 #include <linux/dma-map-ops.h>
 
+static struct page *cpu_addr_to_page(void *cpu_addr)
+{
+	if (is_vmalloc_addr(cpu_addr))
+		return vmalloc_to_page(cpu_addr);
+	else
+		return virt_to_page(cpu_addr);
+}
+
 /*
  * Create scatter-list for the already allocated DMA buffer.
  */
@@ -12,7 +20,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
 		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		 unsigned long attrs)
 {
-	struct page *page = virt_to_page(cpu_addr);
+	struct page *page = cpu_addr_to_page(cpu_addr);
 	int ret;
 
 	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
@@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 		return -ENXIO;
 
 	return remap_pfn_range(vma, vma->vm_start,
-			page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
+			page_to_pfn(cpu_addr_to_page(cpu_addr)) + vma->vm_pgoff,
 			user_count << PAGE_SHIFT, vma->vm_page_prot);
 #else
 	return -ENXIO;
-- 
2.25.1