[RFC][PATCH 2/3] dma-buf: heaps: Add a WARN_ON should the vmap_cnt go negative

[John Stultz]

We shouldn't vunmap more then we vmap, but if we do, make
sure we complain loudly.

Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Sandeep Patil <sspatil@xxxxxxxxxx>
Cc: Daniel Mentz <danielmentz@xxxxxxxxxx>
Cc: Chris Goldsworthy <cgoldswo@xxxxxxxxxxxxxx>
Cc: Ørjan Eide <orjan.eide@xxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
Cc: Simon Ser <contact@xxxxxxxxxxx>
Cc: James Jones <jajones@xxxxxxxxxx>
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
 drivers/dma-buf/heaps/cma_heap.c    | 1 +
 drivers/dma-buf/heaps/system_heap.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index 5e7c3436310c..877353e8014f 100644
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -231,6 +231,7 @@ static void cma_heap_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
 	struct cma_heap_buffer *buffer = dmabuf->priv;
 
 	mutex_lock(&buffer->lock);
+	WARN_ON(buffer->vmap_cnt == 0);
 	if (!--buffer->vmap_cnt) {
 		vunmap(buffer->vaddr);
 		buffer->vaddr = NULL;
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 405351aad2a8..2321c91891f6 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -273,6 +273,7 @@ static void system_heap_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
 	struct system_heap_buffer *buffer = dmabuf->priv;
 
 	mutex_lock(&buffer->lock);
+	WARN_ON(buffer->vmap_cnt == 0);
 	if (!--buffer->vmap_cnt) {
 		vunmap(buffer->vaddr);
 		buffer->vaddr = NULL;
-- 
2.17.1