Re: [PATCH] tracing: dont reset set_ftrace_filter/notrace when opened with r/w perm

[Li Zefan <lizf@cn.fujitsu.com>]

Jiri Olsa wrote:
> If user setup set_ftrace_filter/set_ftrace_notrace files and then opens them
> with read&write permissions, the previous setup will be removed.
> 

Currently:

 # echo 'sys_open sys_close' > set_ftrace_filter
 # cat set_ftrace_filter
 sys_open
 sys_close

After your patch:

 # echo 'sys_open sys_close' > set_ftrace_filter
 # cat set_ftrace_filter
 sys_close

> Tested with following program:
...
> 
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>
> 
> ---
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 4521c77..11394bc 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1661,10 +1661,6 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
>  		return -ENOMEM;
>  
>  	mutex_lock(&ftrace_regex_lock);
> -	if ((file->f_mode & FMODE_WRITE) &&
> -	    !(file->f_flags & O_APPEND))
> -		ftrace_filter_reset(enable);
> -
>  	if (file->f_mode & FMODE_READ) {
>  		iter->pg = ftrace_pages_start;
>  		iter->flags = enable ? FTRACE_ITER_FILTER :
> @@ -2260,6 +2256,9 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
>  		return 0;
>  
>  	mutex_lock(&ftrace_regex_lock);
> +	if ((file->f_mode & FMODE_WRITE) &&
> +	    !(file->f_flags & O_APPEND))
> +		ftrace_filter_reset(enable);
>  
>  	if (file->f_mode & FMODE_READ) {
>  		struct seq_file *m = file->private_data;
> --