There tracing fixes:

- Use "nosteal" for ring buffer splice pages
  - Memory leak fix in error path of trace_pid_write()
  - Fix preempt_enable_no_resched() (use preempt_enable()) in ring buffer code
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Merge tag 'trace-v5.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "Three tracing fixes:

   - Use "nosteal" for ring buffer splice pages

   - Memory leak fix in error path of trace_pid_write()

   - Fix preempt_enable_no_resched() (use preempt_enable()) in ring
     buffer code"

* tag 'trace-v5.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  trace: Fix preempt_enable_no_resched() abuse
  tracing: Fix a memory leak by early error exit in trace_pid_write()
  tracing: Fix buffer_ref pipe ops

fs/splice.c

@@ -330,8 +330,8 @@ const struct pipe_buf_operations default_pipe_buf_ops = {
 	.get = generic_pipe_buf_get,
 };
 
-static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
-				    struct pipe_buffer *buf)
+int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
+			     struct pipe_buffer *buf)
 {
 	return 1;
 }

include/linux/pipe_fs_i.h

@@ -176,6 +176,7 @@ void free_pipe_info(struct pipe_inode_info *);
 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
+int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
 

kernel/trace/ring_buffer.c

@@ -762,7 +762,7 @@ u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
 
 	preempt_disable_notrace();
 	time = rb_time_stamp(buffer);
-	preempt_enable_no_resched_notrace();
+	preempt_enable_notrace();
 
 	return time;
 }

kernel/trace/trace.c

@@ -496,8 +496,10 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
 	 * not modified.
 	 */
 	pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
-	if (!pid_list)
+	if (!pid_list) {
+		trace_parser_put(&parser);
 		return -ENOMEM;
+	}
 
 	pid_list->pid_max = READ_ONCE(pid_max);
 
@@ -507,6 +509,7 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
 
 	pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
 	if (!pid_list->pids) {
+		trace_parser_put(&parser);
 		kfree(pid_list);
 		return -ENOMEM;
 	}
@@ -7025,19 +7028,23 @@ struct buffer_ref {
 	struct ring_buffer	*buffer;
 	void			*page;
 	int			cpu;
-	int			ref;
+	refcount_t		refcount;
 };
 
+static void buffer_ref_release(struct buffer_ref *ref)
+{
+	if (!refcount_dec_and_test(&ref->refcount))
+		return;
+	ring_buffer_free_read_page(ref->buffer, ref->cpu, ref->page);
+	kfree(ref);
+}
+
 static void buffer_pipe_buf_release(struct pipe_inode_info *pipe,
 				    struct pipe_buffer *buf)
 {
 	struct buffer_ref *ref = (struct buffer_ref *)buf->private;
 
-	if (--ref->ref)
-		return;
-
-	ring_buffer_free_read_page(ref->buffer, ref->cpu, ref->page);
-	kfree(ref);
+	buffer_ref_release(ref);
 	buf->private = 0;
 }
 
@@ -7046,10 +7053,10 @@ static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
 {
 	struct buffer_ref *ref = (struct buffer_ref *)buf->private;
 
-	if (ref->ref > INT_MAX/2)
+	if (refcount_read(&ref->refcount) > INT_MAX/2)
 		return false;
 
-	ref->ref++;
+	refcount_inc(&ref->refcount);
 	return true;
 }
 
@@ -7057,7 +7064,7 @@ static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
 static const struct pipe_buf_operations buffer_pipe_buf_ops = {
 	.confirm		= generic_pipe_buf_confirm,
 	.release		= buffer_pipe_buf_release,
-	.steal			= generic_pipe_buf_steal,
+	.steal			= generic_pipe_buf_nosteal,
 	.get			= buffer_pipe_buf_get,
 };
 
@@ -7070,11 +7077,7 @@ static void buffer_spd_release(struct splice_pipe_desc *spd, unsigned int i)
 	struct buffer_ref *ref =
 		(struct buffer_ref *)spd->partial[i].private;
 
-	if (--ref->ref)
-		return;
-
-	ring_buffer_free_read_page(ref->buffer, ref->cpu, ref->page);
-	kfree(ref);
+	buffer_ref_release(ref);
 	spd->partial[i].private = 0;
 }
 
@@ -7129,7 +7132,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 			break;
 		}
 
-		ref->ref = 1;
+		refcount_set(&ref->refcount, 1);
 		ref->buffer = iter->trace_buffer->buffer;
 		ref->page = ring_buffer_alloc_read_page(ref->buffer, iter->cpu_file);
 		if (IS_ERR(ref->page)) {