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

[<guangming.cao@mediatek.com>]

From: Guangming <Guangming.Cao@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@mediatek.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Cc: <stable@vger.kernel.org> # 5.11.*
---
v4: Correct commit message
    1. Cc stable@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@vger.kernel.org
    1. This patch needs to be merged stable branch, add stable@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