[PATCH v1 5/6] perf: Drop PERF_FLAG_FD_OUTPUT

[Alexander Shishkin <alexander.shishkin@linux.intel.com>]

Since commit:

  ac9721f3f54b ("perf_events: Fix races and clean up perf_event and perf_mmap_data interaction")

... PERF_FLAG_FD_OUTPUT has been always returning -EINVAL. This can be
either fixed by supplying enough context information to the set_output
path to validate the request, or it can simply be dropped. The fact that
in 8 years since it last worked, nobody (except Vince [1]) seems to
notice, this patch drops it.

[1] https://lkml.org/lkml/2015/1/9/479

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 kernel/events/core.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 70918ed33143..9bf5c7abb621 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -344,7 +344,6 @@ static void event_function_local(struct perf_event *event, event_f func, void *d
 }
 
 #define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
-		       PERF_FLAG_FD_OUTPUT  |\
 		       PERF_FLAG_PID_CGROUP |\
 		       PERF_FLAG_FD_CLOEXEC |\
 		       PERF_FLAG_FD_SAMPLE)
@@ -9997,7 +9996,7 @@ SYSCALL_DEFINE5(perf_event_open,
 		struct perf_event_attr __user *, attr_uptr,
 		pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
 {
-	struct perf_event *group_leader = NULL, *output_event = NULL;
+	struct perf_event *group_leader = NULL;
 	struct perf_event *sample_event = NULL;
 	struct perf_event *event, *sibling;
 	struct perf_event_attr attr;
@@ -10067,8 +10066,6 @@ SYSCALL_DEFINE5(perf_event_open,
 		if (err)
 			goto err_fd;
 		group_leader = group.file->private_data;
-		if (flags & PERF_FLAG_FD_OUTPUT)
-			output_event = group_leader;
 		if (flags & PERF_FLAG_FD_SAMPLE)
 			sample_event = group_leader;
 		if (flags & PERF_FLAG_FD_NO_GROUP)
@@ -10223,12 +10220,6 @@ SYSCALL_DEFINE5(perf_event_open,
 			goto err_context;
 	}
 
-	if (output_event) {
-		err = perf_event_set_output(event, output_event);
-		if (err)
-			goto err_context;
-	}
-
 	event_file = anon_inode_getfile("[perf_event]", &perf_fops, event,
 					f_flags);
 	if (IS_ERR(event_file)) {
-- 
2.17.1