trace: Convert trace/seq to use copy_splice_read()

For the splice from the trace seq buffer, just use copy_splice_read().

In the future, something better can probably be done by gifting pages from
seq->buf into the pipe, but that would require changing seq->buf into a
vmap over an array of pages.

Signed-off-by: David Howells <[email protected]>
cc: Christoph Hellwig <[email protected]>
cc: Al Viro <[email protected]>
cc: Jens Axboe <[email protected]>
cc: Steven Rostedt <[email protected]>
cc: Masami Hiramatsu <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: dhowells

kernel/trace/trace.c

@@ -5171,7 +5171,7 @@ static const struct file_operations tracing_fops = {
 	.open		= tracing_open,
 	.read		= seq_read,
 	.read_iter	= seq_read_iter,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.write		= tracing_write_stub,
 	.llseek		= tracing_lseek,
 	.release	= tracing_release,