linux-kernel - Re: [PATCH 14/26 v5] tracing: Create seq_buf layer in trace

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Date:	Wed, 19 Nov 2014 10:08:41 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH 14/26 v5] tracing: Create seq_buf layer in trace_seq

On Wed, 19 Nov 2014 15:51:38 +0100
Petr Mladek <pmladek@...e.cz> wrote:

> On Fri 2014-11-14 23:59:01, Steven Rostedt wrote:
> > From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> > 
> > Create a seq_buf layer that trace_seq sits on. The seq_buf will not
> > be limited to page size. This will allow other usages of seq_buf
> > instead of a hard set PAGE_SIZE one that trace_seq has.
> > 
> > Link: http://lkml.kernel.org/r/20141104160221.864997179@goodmis.org
> > Link: http://lkml.kernel.org/r/20141114011412.170377300@goodmis.org
> > 
> > Tested-by: Jiri Kosina <jkosina@...e.cz>
> > Acked-by: Jiri Kosina <jkosina@...e.cz>
> > Reviewed-by: Petr Mladek <pmladek@...e.cz>
> > Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> > ---
> >  include/linux/seq_buf.h              |  81 +++++++++
> >  include/linux/trace_seq.h            |  12 +-
> >  kernel/trace/Makefile                |   1 +
> >  kernel/trace/seq_buf.c               | 341 +++++++++++++++++++++++++++++++++++
> >  kernel/trace/trace.c                 |  39 ++--
> >  kernel/trace/trace_events.c          |   6 +-
> >  kernel/trace/trace_functions_graph.c |   6 +-
> >  kernel/trace/trace_seq.c             | 177 +++++++++---------
> >  8 files changed, 538 insertions(+), 125 deletions(-)
> >  create mode 100644 include/linux/seq_buf.h
> >  create mode 100644 kernel/trace/seq_buf.c
> 
> [...]
>  
> > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > index 100288d10e1f..6d1342ae7a44 100644
> > --- a/kernel/trace/trace_functions_graph.c
> > +++ b/kernel/trace/trace_functions_graph.c
> 
> [...]
> 
> > @@ -163,21 +176,22 @@ EXPORT_SYMBOL_GPL(trace_seq_vprintf);
> >   */
> >  void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
> >  {
> > -	unsigned int len = TRACE_SEQ_BUF_LEFT(s);
> > +	unsigned int save_len = s->seq.len;
> >  	int ret;
> 
> Last but one small thing. The "ret" is assigned but not longer used.
> 
> JFYI, I have skipped this patch yesterday because it was long and already
> marked as reviewed. I could not help myself and double checked it today.
> 

OK, I'll fix that up.

> > -	if (s->full || !len)
> > +	if (s->full)
> >  		return;
> >  
> > -	ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
> > +	__trace_seq_init(s);
> > +
> > +	ret = seq_buf_bprintf(&s->seq, fmt, binary);
> >  
> >  	/* If we can't write it all, don't bother writing anything */
> > -	if (ret >= len) {
> > +	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
> > +		s->seq.len = save_len;
> >  		s->full = 1;
> >  		return;
> >  	}
> > -
> > -	s->len += ret;
> >  }
> >  EXPORT_SYMBOL_GPL(trace_seq_bprintf);
> 
> The last small thing is the same unused "ret" in trace_seq_path(). But
> this one should get fixed in "[PATCH 15/26 v5] tracing: Convert
> seq_buf_path() to be like seq_path()".

OK, I'll try to remember that :-)

> 
> Both these changes are rather cosmetic. Feel free to leave them for
> some later clean up.
> 
> 
> Eureka, I have finished review of the patchset and am happy with it \o/
> I am looking forward to see it in the main tree.

Well now it comes down to Linus or Andrew giving me the OK. I've pulled
all the trace_seq updates into my ftrace/core branch (which will be
going into my for-next branch shortly). I stopped just before this
patch. I didn't want to create the seq_buf until I knew it was going to
be used by something other than trace_seq.

> 
> Thanks a lot for the hard work.
> 

Yeah, let's hope that it was worth it.

Thanks for the in depth reviews.

-- Steve
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