[for-next-3.11][PATCH 1/8] tracing: Turn event/id->i_private into call->event.type

Steven Rostedt
2013-07-30T11:31:57Z

[-- Attachment #1: 0001-tracing-Turn-event-id-i_private-into-call-event.type.patch --]
[-- Type: text/plain, Size: 2444 bytes --]

From: Oleg Nesterov <oleg@redhat.com>

event_id_read() is racy, ftrace_event_call can be already freed
by trace_remove_event_call() callers.

Change event_create_dir() to pass "data = call->event.type", this
is all event_id_read() needs. ftrace_event_id_fops no longer needs
tracing_open_generic().

We add the new helper, event_file_data(), to read ->i_private, it
will have more users.

Note: currently ACCESS_ONCE() and "id != 0" check are not needed,
but we are going to change event_remove/rmdir to clear ->i_private.

Link: http://lkml.kernel.org/r/20130726172532.GA3605@redhat.com

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_events.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 898f868..c2d13c5 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -409,6 +409,11 @@ static void put_system(struct ftrace_subsystem_dir *dir)
mutex_unlock(&event_mutex);
}

+static void *event_file_data(struct file *filp)
+{
+ return ACCESS_ONCE(file_inode(filp)->i_private);
+}
+
/*
* Open and update trace_array ref count.
* Must have the current trace_array passed to it.
@@ -946,14 +951,18 @@ static int trace_format_open(struct inode *inode, struct file *file)
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;
+ int id = (long)event_file_data(filp);
char buf[32];
int len;

if (*ppos)
return 0;

- len = sprintf(buf, "%d\n", call->event.type);
+ if (unlikely(!id))
+ return -ENODEV;
+
+ len = sprintf(buf, "%d\n", id);
+
return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
}

@@ -1240,7 +1249,6 @@ static const struct file_operations ftrace_event_format_fops = {
};

static const struct file_operations ftrace_event_id_fops = {
- .open = tracing_open_generic,
.read = event_id_read,
.llseek = default_llseek,
};
@@ -1488,8 +1496,8 @@ event_create_dir(struct dentry *parent,

#ifdef CONFIG_PERF_EVENTS
if (call->event.type && call->class->reg)
- trace_create_file("id", 0444, file->dir, call,
- id);
+ trace_create_file("id", 0444, file->dir,
+ (void *)(long)call->event.type, id);
#endif

/*
--
1.7.10.4