[PATCH 3/4] tracing: update file->f_pos when splice(2) it

[Lai Jiangshan <laijs@cn.fujitsu.com>]

Impact: Cleanup

These two lines:
	if (unlikely(*ppos))
		return -ESPIPE;
in tracing_buffers_splice_read() are not needed, VFS layer
has disabled seek(2).
We remove these two lines, and then we can update file->f_pos.

And tracing_buffers_read() updates file->f_pos, this fix
make tracing_buffers_splice_read() updates file->f_pos too.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2a81dec..d101c12 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3408,13 +3408,6 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 	int size, i;
 	size_t ret;
 
-	/*
-	 * We can't seek on a buffer input
-	 */
-	if (unlikely(*ppos))
-		return -ESPIPE;
-
-
 	for (i = 0; i < PIPE_BUFFERS && len; i++, len -= size) {
 		struct page *page;
 		int r;
@@ -3454,6 +3447,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		spd.partial[i].offset = 0;
 		spd.partial[i].private = (unsigned long)ref;
 		spd.nr_pages++;
+		*ppos += size;
 	}
 
 	spd.nr_pages = i;