[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.sem...@linaro.org>
Cc: Liam Mark <lm...@codeaurora.org>
Cc: Laura Abbott <labb...@kernel.org>
Cc: Brian Starkey <brian.star...@arm.com>
Cc: Hridya Valsaraju <hri...@google.com>
Cc: Suren Baghdasaryan <sur...@google.com>
Cc: Sandeep Patil <sspa...@google.com>
Cc: Daniel Mentz <danielme...@google.com>
Cc: Chris Goldsworthy <cgold...@codeaurora.org>
Cc: Ørjan Eide <orjan.e...@arm.com>
Cc: Robin Murphy <robin.mur...@arm.com>
Cc: Ezequiel Garcia <ezequ...@collabora.com>
Cc: Simon Ser <cont...@emersion.fr>
Cc: James Jones <jajo...@nvidia.com>
Cc: linux-me...@vger.kernel.org
Cc: dri-de...@lists.freedesktop.org
Suggested-by: Suren Baghdasaryan <sur...@google.com>
Signed-off-by: John Stultz <john.stu...@linaro.org>
---
 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