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Subject[RFC][PATCH] dma-heap: Add proper kref handling on dma-buf heaps
Date
Add proper refcounting on the dma_heap structure.
While existing heaps are built-in, we may eventually
have heaps loaded from modules, and we'll need to be
able to properly handle the references to the heaps

Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Andrew F. Davis <afd@ti.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Liam Mark <lmark@codeaurora.org>
Cc: Laura Abbott <labbott@kernel.org>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
drivers/dma-buf/dma-heap.c | 31 +++++++++++++++++++++++++++----
include/linux/dma-heap.h | 6 ++++++
2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index afd22c9dbdcf..90c3720acc1c 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -40,6 +40,8 @@ struct dma_heap {
dev_t heap_devt;
struct list_head list;
struct cdev heap_cdev;
+ int minor;
+ struct kref refcount;
};

static LIST_HEAD(heap_list);
@@ -190,11 +192,31 @@ void *dma_heap_get_drvdata(struct dma_heap *heap)
return heap->priv;
}

+static void dma_heap_release(struct kref *ref)
+{
+ struct dma_heap *heap = container_of(ref, struct dma_heap, refcount);
+
+ /* Remove heap from the list */
+ mutex_lock(&heap_list_lock);
+ list_del(&heap->list);
+ mutex_unlock(&heap_list_lock);
+
+ device_destroy(dma_heap_class, heap->heap_devt);
+ cdev_del(&heap->heap_cdev);
+ xa_erase(&dma_heap_minors, heap->minor);
+
+ kfree(heap);
+}
+
+void dma_heap_put(struct dma_heap *h)
+{
+ kref_put(&h->refcount, dma_heap_release);
+}
+
struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
{
struct dma_heap *heap, *h, *err_ret;
struct device *dev_ret;
- unsigned int minor;
int ret;

if (!exp_info->name || !strcmp(exp_info->name, "")) {
@@ -223,12 +245,13 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
if (!heap)
return ERR_PTR(-ENOMEM);

+ kref_init(&heap->refcount);
heap->name = exp_info->name;
heap->ops = exp_info->ops;
heap->priv = exp_info->priv;

/* Find unused minor number */
- ret = xa_alloc(&dma_heap_minors, &minor, heap,
+ ret = xa_alloc(&dma_heap_minors, &heap->minor, heap,
XA_LIMIT(0, NUM_HEAP_MINORS - 1), GFP_KERNEL);
if (ret < 0) {
pr_err("dma_heap: Unable to get minor number for heap\n");
@@ -237,7 +260,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
}

/* Create device */
- heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), minor);
+ heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), heap->minor);

cdev_init(&heap->heap_cdev, &dma_heap_fops);
ret = cdev_add(&heap->heap_cdev, heap->heap_devt, 1);
@@ -267,7 +290,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
err2:
cdev_del(&heap->heap_cdev);
err1:
- xa_erase(&dma_heap_minors, minor);
+ xa_erase(&dma_heap_minors, heap->minor);
err0:
kfree(heap);
return err_ret;
diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
index 454e354d1ffb..c1572f29cfac 100644
--- a/include/linux/dma-heap.h
+++ b/include/linux/dma-heap.h
@@ -56,4 +56,10 @@ void *dma_heap_get_drvdata(struct dma_heap *heap);
*/
struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info);

+/**
+ * dma_heap_put - drops a reference to a dmabuf heaps, potentially freeing it
+ * @heap: heap pointer
+ */
+void dma_heap_put(struct dma_heap *heap);
+
#endif /* _DMA_HEAPS_H */
--
2.17.1
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