[PATCH v4] dma-buf: system_heap: Use 'for_each_sgtable_sg' in pages free flow

[guangming.cao at mediatek.com]

From: Guangming <Guangming.Cao at mediatek.com>

For previous version, it uses 'sg_table.nent's to traverse sg_table in pages
free flow.
However, 'sg_table.nents' is reassigned in 'dma_map_sg', it means the number of
created entries in the DMA adderess space.
So, use 'sg_table.nents' in pages free flow will case some pages can't be freed.

Here we should use sg_table.orig_nents to free pages memory, but use the
sgtable helper 'for each_sgtable_sg'(, instead of the previous rather common
helper 'for_each_sg' which maybe cause memory leak) is much better.

Fixes: d963ab0f15fb0 ("dma-buf: system_heap: Allocate higher order pages if available")
Signed-off-by: Guangming <Guangming.Cao at mediatek.com>
Reviewed-by: Robin Murphy <robin.murphy at arm.com>
Cc: <stable at vger.kernel.org> # 5.11.*
---
v4: Correct commit message
    1. Cc stable at vger.kernel.org in commit message and add required kernel version.
    2. Add reviewed-by since patch V2 and V4 are same and V2 is reviewed by Robin.
    3. There is no new code change in V4.
V3: Cc stable at vger.kernel.org
    1. This patch needs to be merged stable branch, add stable at vger.kernel.org
       in mail list.
    2. Correct some spelling mistake.
    3. There is No new code change in V3.
V2: use 'for_each_sgtable_sg' to 'replece for_each_sg' as suggested by Robin.

---
 drivers/dma-buf/heaps/system_heap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 23a7e74ef966..8660508f3684 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -289,7 +289,7 @@ static void system_heap_dma_buf_release(struct dma_buf *dmabuf)
 	int i;
 
 	table = &buffer->sg_table;
-	for_each_sg(table->sgl, sg, table->nents, i) {
+	for_each_sgtable_sg(table, sg, i) {
 		struct page *page = sg_page(sg);
 
 		__free_pages(page, compound_order(page));
-- 
2.17.1