[RFC v2 3/6] dmabuf: Use the GPU cgroup charge/uncharge APIs

[T.J. Mercier]

This patch uses the GPU cgroup charge/uncharge APIs to charge buffers
allocated by any DMA-BUF exporter that exports a buffer with a GPU cgroup
device association.

By doing so, it becomes possible to track who allocated/exported a
DMA-BUF even after the allocating process drops all references to a
buffer.

From: Hridya Valsaraju <hridya at google.com>
Signed-off-by: Hridya Valsaraju <hridya at google.com>
Co-developed-by: T.J. Mercier <tjmercier at google.com>
Signed-off-by: T.J. Mercier <tjmercier at google.com>
---
changes in v2
- Move dma-buf cgroup charging/uncharging from a dma_buf_op defined by every
heap to a single dma-buf function for all heaps per Daniel Vetter and
Christian König.

 drivers/dma-buf/dma-buf.c | 52 +++++++++++++++++++++++++++++++++++++++
 include/linux/dma-buf.h   | 20 +++++++++++++--
 2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 602b12d7470d..83d0d1b91547 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -56,6 +56,50 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
 			     dentry->d_name.name, ret > 0 ? name : "");
 }
 
+#ifdef CONFIG_CGROUP_GPU
+static inline struct gpucg_device *
+exp_info_gpucg_dev(const struct dma_buf_export_info *exp_info)
+{
+	return exp_info->gpucg_dev;
+}
+
+static bool dmabuf_try_charge(struct dma_buf *dmabuf,
+			      struct gpucg_device *gpucg_dev)
+{
+	dmabuf->gpucg = gpucg_get(current);
+	dmabuf->gpucg_dev = gpucg_dev;
+	if (gpucg_try_charge(dmabuf->gpucg, dmabuf->gpucg_dev, dmabuf->size)) {
+		gpucg_put(dmabuf->gpucg);
+		dmabuf->gpucg = NULL;
+		dmabuf->gpucg_dev = NULL;
+		return false;
+	}
+	return true;
+}
+
+static void dmabuf_uncharge(struct dma_buf *dmabuf)
+{
+	if (dmabuf->gpucg && dmabuf->gpucg_dev) {
+		gpucg_uncharge(dmabuf->gpucg, dmabuf->gpucg_dev, dmabuf->size);
+		gpucg_put(dmabuf->gpucg);
+	}
+}
+#else /* CONFIG_CGROUP_GPU */
+static inline struct gpucg_device *exp_info_gpucg_dev(
+const struct dma_buf_export_info *exp_info)
+{
+	return NULL;
+}
+
+static inline bool dmabuf_try_charge(struct dma_buf *dmabuf,
+				     struct gpucg_device *gpucg_dev))
+{
+	return false;
+}
+
+static inline void dmabuf_uncharge(struct dma_buf *dmabuf) {}
+#endif /* CONFIG_CGROUP_GPU */
+
 static void dma_buf_release(struct dentry *dentry)
 {
 	struct dma_buf *dmabuf;
@@ -79,6 +123,8 @@ static void dma_buf_release(struct dentry *dentry)
 	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
 		dma_resv_fini(dmabuf->resv);
 
+	dmabuf_uncharge(dmabuf);
+
 	WARN_ON(!list_empty(&dmabuf->attachments));
 	module_put(dmabuf->owner);
 	kfree(dmabuf->name);
@@ -484,6 +530,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 {
 	struct dma_buf *dmabuf;
 	struct dma_resv *resv = exp_info->resv;
+	struct gpucg_device *gpucg_dev = exp_info_gpucg_dev(exp_info);
 	struct file *file;
 	size_t alloc_size = sizeof(struct dma_buf);
 	int ret;
@@ -534,6 +581,9 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 	}
 	dmabuf->resv = resv;
 
+	if (gpucg_dev && !dmabuf_try_charge(dmabuf, gpucg_dev))
+		goto err_charge;
+
 	file = dma_buf_getfile(dmabuf, exp_info->flags);
 	if (IS_ERR(file)) {
 		ret = PTR_ERR(file);
@@ -565,6 +615,8 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 	file->f_path.dentry->d_fsdata = NULL;
 	fput(file);
 err_dmabuf:
+	dmabuf_uncharge(dmabuf);
+err_charge:
 	kfree(dmabuf);
 err_module:
 	module_put(exp_info->owner);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 7ab50076e7a6..742f29c3daaf 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>
@@ -303,7 +304,7 @@ struct dma_buf {
 	/**
 	 * @size:
 	 *
-	 * Size of the buffer; invariant over the lifetime of the buffer.
+	 * Size of the buffer in bytes; invariant over the lifetime of the buffer.
 	 */
 	size_t size;
 
@@ -453,6 +454,17 @@ struct dma_buf {
 		struct dma_buf *dmabuf;
 	} *sysfs_entry;
 #endif
+
+#ifdef CONFIG_CGROUP_GPU
+	/** @gpucg: Pointer to the cgroup this buffer currently belongs to. */
+	struct gpucg *gpucg;
+
+	/** @gpucg_dev:
+	 *
+	 * Pointer to the cgroup GPU device whence this buffer originates.
+	 */
+	struct gpucg_device *gpucg_dev;
+#endif
 };
 
 /**
@@ -529,9 +541,10 @@ struct dma_buf_attachment {
  * @exp_name:	name of the exporter - useful for debugging.
  * @owner:	pointer to exporter module - used for refcounting kernel module
  * @ops:	Attach allocator-defined dma buf ops to the new buffer
- * @size:	Size of the buffer - invariant over the lifetime of the buffer
+ * @size:	Size of the buffer in bytes - invariant over the lifetime of the buffer
  * @flags:	mode flags for the file
  * @resv:	reservation-object, NULL to allocate default one
+ * @gpucg_dev:	pointer to the gpu cgroup device this buffer belongs to
  * @priv:	Attach private data of allocator to this buffer
  *
  * This structure holds the information required to export the buffer. Used
@@ -544,6 +557,9 @@ struct dma_buf_export_info {
 	size_t size;
 	int flags;
 	struct dma_resv *resv;
+#ifdef CONFIG_CGROUP_GPU
+	struct gpucg_device *gpucg_dev;
+#endif
 	void *priv;
 };
 
-- 
2.35.1.265.g69c8d7142f-goog