Commit cd458ba9 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

tracing: Do not (ab)use trace_seq in event_id_read()

event_id_read() has no reason to kmalloc "struct trace_seq"
(more than PAGE_SIZE!), it can use a small buffer instead.

Note: "if (*ppos) return 0" looks strange and even wrong,
simple_read_from_buffer() handles ppos != 0 case corrrectly.

And it seems that almost every user of trace_seq in this file
should be converted too. Unless you use seq_open(), trace_seq
buys nothing compared to the raw buffer, but it needs a bit
more memory and code.


Signed-off-by: default avatarOleg Nesterov <>
Signed-off-by: default avatarSteven Rostedt <>
parent 7710b639
......@@ -947,23 +947,14 @@ static ssize_t
event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
struct ftrace_event_call *call = filp->private_data;
struct trace_seq *s;
int r;
char buf[32];
int len;
if (*ppos)
return 0;
s = kmalloc(sizeof(*s), GFP_KERNEL);
if (!s)
return -ENOMEM;
trace_seq_printf(s, "%d\n", call->event.type);
r = simple_read_from_buffer(ubuf, cnt, ppos,
s->buffer, s->len);
return r;
len = sprintf(buf, "%d\n", call->event.type);
return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
static ssize_t
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