[PATCH 2/2] dmabuf/tracing: Add dma-buf trace events

[Kalesh Singh]

Being able to analyze the per process usage of shared
dma buffers prodives useful insights in situations where
the system is experiencing high memory pressure. This would
allow us to see exactly which processes are holding references
to the shared buffer.

Signed-off-by: Kalesh Singh <kaleshsingh at google.com>
---
 drivers/dma-buf/dma-buf.c      | 29 +++++++++++++
 include/trace/events/dma_buf.h | 77 ++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 include/trace/events/dma_buf.h

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 1ca609f66fdf..1729191ac9ca 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -29,6 +29,9 @@
 #include <uapi/linux/dma-buf.h>
 #include <uapi/linux/magic.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/dma_buf.h>
+
 static inline int is_dma_buf_file(struct file *);
 
 struct dma_buf_list {
@@ -110,6 +113,15 @@ static struct file_system_type dma_buf_fs_type = {
 	.kill_sb = kill_anon_super,
 };
 
+static void dma_buf_vma_close(struct vm_area_struct *area)
+{
+	trace_dma_buf_map_ref_dec(current, area->vm_file);
+}
+
+static const struct vm_operations_struct dma_buf_vm_ops = {
+	.close = dma_buf_vma_close,
+};
+
 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 {
 	struct dma_buf *dmabuf;
@@ -128,6 +140,9 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 	    dmabuf->size >> PAGE_SHIFT)
 		return -EINVAL;
 
+	trace_dma_buf_map_ref_inc(current, file);
+	vma->vm_ops = &dma_buf_vm_ops;
+
 	return dmabuf->ops->mmap(dmabuf, vma);
 }
 
@@ -410,6 +425,17 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
 	spin_unlock(&dmabuf->name_lock);
 }
 
+static int dma_buf_flush(struct file *filp, fl_owner_t id)
+{
+	trace_dma_buf_fd_ref_dec(current, filp);
+	return 0;
+}
+
+static void dma_buf_fd_install(int fd, struct file *filp)
+{
+	trace_dma_buf_fd_ref_inc(current, filp);
+}
+
 static const struct file_operations dma_buf_fops = {
 	.mmap		= dma_buf_mmap_internal,
 	.llseek		= dma_buf_llseek,
@@ -417,6 +443,8 @@ static const struct file_operations dma_buf_fops = {
 	.unlocked_ioctl	= dma_buf_ioctl,
 	.compat_ioctl	= compat_ptr_ioctl,
 	.show_fdinfo	= dma_buf_show_fdinfo,
+	.fd_install	= dma_buf_fd_install,
+	.flush		= dma_buf_flush,
 };
 
 /*
@@ -1177,6 +1205,7 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
 		if (oldfile)
 			fput(oldfile);
 	}
+
 	return ret;
 
 }
diff --git a/include/trace/events/dma_buf.h b/include/trace/events/dma_buf.h
new file mode 100644
index 000000000000..05af336cd849
--- /dev/null
+++ b/include/trace/events/dma_buf.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM dma_buf
+
+#if !defined(_TRACE_DMA_BUF_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DMA_BUF_H
+
+#include <linux/dma-buf.h>
+#include <linux/tracepoint.h>
+#include <linux/types.h>
+
+#define UNKNOWN "<unknown>"
+
+#ifdef CREATE_TRACE_POINTS
+static inline struct dma_buf *dma_buffer(struct file *filp)
+{
+	return filp->private_data;
+}
+#endif
+
+DECLARE_EVENT_CLASS(dma_buf_ref_template,
+
+	TP_PROTO(struct task_struct *task, struct file *filp),
+
+	TP_ARGS(task,  filp),
+
+	TP_STRUCT__entry(
+		__field(u32, tgid)
+		__field(u32, pid)
+		__field(u64, size)
+		__field(s64, count)
+		__string(exp_name, dma_buffer(filp)->exp_name)
+		__string(name, dma_buffer(filp)->name ? dma_buffer(filp)->name : UNKNOWN)
+		__field(u64, i_ino)
+	),
+
+	TP_fast_assign(
+		__entry->tgid = task->tgid;
+		__entry->pid = task->pid;
+		__entry->size = dma_buffer(filp)->size;
+		__entry->count = file_count(filp);
+		__assign_str(exp_name, dma_buffer(filp)->exp_name);
+		__assign_str(name, dma_buffer(filp)->name ? dma_buffer(filp)->name : UNKNOWN);
+		__entry->i_ino = filp->f_inode->i_ino;
+	),
+
+	TP_printk("tgid=%u pid=%u size=%llu count=%lld exp_name=%s name=%s i_ino=%llu",
+		__entry->tgid,
+		__entry->pid,
+		__entry->size,
+		__entry->count,
+		__get_str(exp_name),
+		__get_str(name),
+		__entry->i_ino
+	)
+);
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_fd_ref_inc,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_fd_ref_dec,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_map_ref_inc,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+DEFINE_EVENT(dma_buf_ref_template, dma_buf_map_ref_dec,
+	TP_PROTO(struct task_struct *task, struct file *filp),
+	TP_ARGS(task,  filp));
+
+#endif /* _TRACE_DMA_BUF_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.28.0.163.g6104cc2f0b6-goog