lkml.org 
[lkml]   [2015]   [Feb]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC][PATCH 5/7] trace: make filter_parse_regex() provide the length of substring to compare with
On Thu,  5 Feb 2015 19:56:38 +0000
Al Viro <viro@ZenIV.linux.org.uk> wrote:

> From: Al Viro <viro@zeniv.linux.org.uk>
>
> ... by passing len by address and using it to report the length of
> substring in question.

You certainly are very verbose in your change logs.

What exactly is the purpose of this patch? Clean up? Optimization?

I can't really tell. Seems like you are just moving the strlen() from
outside the function into it.


> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -1051,7 +1051,7 @@ struct filter_pred {
> };
>
> extern enum regex_type
> -filter_parse_regex(char *buff, int len, char **search, int *not);
> +filter_parse_regex(char *buff, int *len, char **search, int *not);
> extern void print_event_filter(struct ftrace_event_file *file,
> struct trace_seq *s);
> extern int apply_event_filter(struct ftrace_event_file *file,
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 6c4a96b..6a659e1 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -321,7 +321,7 @@ static int regex_match_end(char *str, struct regex *r, int len)
> * not returns 1 if buff started with a '!'
> * 0 otherwise.
> */

@len above needs to be updated for kernel doc. The description should
also note what *len gets set to at the end.

> -enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
> +enum regex_type filter_parse_regex(char *buff, int *len, char **search, int *not)
> {
> int type = MATCH_FULL;
> int i;
> @@ -329,13 +329,13 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
> if (buff[0] == '!') {
> *not = 1;
> buff++;
> - len--;
> + (*len)--;
> } else
> *not = 0;
>
> *search = buff;
>
> - for (i = 0; i < len; i++) {
> + for (i = 0; i < *len; i++) {
> if (buff[i] == '*') {
> if (!i) {
> *search = buff + 1;
> @@ -350,6 +350,7 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
> }
> }
> }
> + *len = strlen(*search);

We could optimize this even further:

*len = &buff[i] - *search;

-- Steve

>
> return type;
> }

\
 
 \ /
  Last update: 2015-02-05 23:01    [W:0.049 / U:0.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site