[RFC 4/6] dma-buf: Add DMA-BUF exporter op to charge a DMA-BUF to a cgroup.

[Hridya Valsaraju <hridya@google.com>]

The optional exporter op provides a way for processes to transfer
charge of a buffer to a different process. This is essential for the
cases where a central allocator process does allocations for various
subsystems, hands over the fd to the client who
requested the memory and drops all references to the allocated memory.

Signed-off-by: Hridya Valsaraju <hridya@google.com>
---
 include/linux/dma-buf.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 7ab50076e7a6..d5e52f81cc6f 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -13,6 +13,7 @@
 #ifndef __DMA_BUF_H__
 #define __DMA_BUF_H__
 
+#include <linux/cgroup_gpu.h>
 #include <linux/dma-buf-map.h>
 #include <linux/file.h>
 #include <linux/err.h>
@@ -285,6 +286,23 @@ struct dma_buf_ops {
 
 	int (*vmap)(struct dma_buf *dmabuf, struct dma_buf_map *map);
 	void (*vunmap)(struct dma_buf *dmabuf, struct dma_buf_map *map);
+
+	/**
+	 * @charge_to_cgroup:
+	 *
+	 * This is called by an exporter to charge a buffer to the specified
+	 * cgroup. The caller must hold a reference to @gpucg obtained via
+	 * gpucg_get(). The DMA-BUF will be uncharged from the cgroup it is
+	 * currently charged to before being charged to @gpucg. The caller must
+	 * belong to the cgroup the buffer is currently charged to.
+	 *
+	 * This callback is optional.
+	 *
+	 * Returns:
+	 *
+	 * 0 on success or negative error code on failure.
+	 */
+	int (*charge_to_cgroup)(struct dma_buf *dmabuf, struct gpucg *gpucg);
 };
 
 /**
-- 
2.34.1.703.g22d0c6ccf7-goog