Re: [PATCH] ftrace: don't increment @pos in g_start()

[Wang Liming]

Li Zefan wrote:
> Li Zefan wrote:
> > Liming Wang wrote:
> > > how about this one?
> > Yeah, this should work, and cleaner than my version.
>
> Hmmm, the patch is cleaner in diffstat but the resulted code
> isn't..
>
> After yours:
>    text    data     bss     dec     hex filename
>   14879    5480    4240   24599    6017 kernel/trace/ftrace.o
>
> After mine:
>    text    data     bss     dec     hex filename
>   14873    5480    4240   24593    6011 kernel/trace/ftrace.o
Hmmm, if you prefer to smaller target size, I don't care.
But in my system, I got the same size:

  text    data     bss     dec     hex filename
  14330    5019     104   19453    4bfd kernel/trace/ftrace.o

I use objdump to compute the actual size of all modified functions:

After mine:
func	size
g_start 0x50
g_next  0x70

After yours:
func	 size
__g_next 0x70
g_next   0x20
g_start  0x30

I used Steve git tree and commit e482f8395f215e0ad6557b2722cd9b9b308035c4.
My gcc version is :
gcc version 4.2.4

I don't know where the difference.

Liming Wang

> > > It's wrong to increment @pos in g_start(). It causes some entries
> > > lost when reading set_graph_function, if the output of the file
> > > is large than PAGE_SIZE.
> > >
> > > [ Impact: fix missing entries when reading set_graph_function ]
> > >
> > > Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
> > > Signed-off-by: Liming Wang <liming.wang@xxxxxxxxxxxxx>
> > > ---
> > >  kernel/trace/ftrace.c |   14 +++++---------
> > >  1 files changed, 5 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > > index 134e580..1beaac6 100644
> > > --- a/kernel/trace/ftrace.c
> > > +++ b/kernel/trace/ftrace.c
> > > @@ -2495,29 +2495,25 @@ static void *
> > >  g_next(struct seq_file *m, void *v, loff_t *pos)
> > >  {
> > >  	unsigned long *array = m->private;
> > > -	int index = *pos;
> > >  
> > > -	(*pos)++;
> > > +	if (v)
> > > +		(*pos)++;
> > >  
> > > -	if (index >= ftrace_graph_count)
> > > +	if (*pos >= ftrace_graph_count)
> > >  		return NULL;
> > >  
> > > -	return &array[index];
> > > +	return &array[*pos];
> > >  }
> > >  
> > >  static void *g_start(struct seq_file *m, loff_t *pos)
> > >  {
> > > -	void *p = NULL;
> > > -
> > >  	mutex_lock(&graph_lock);
> > >  
> > >  	/* Nothing, tell g_show to print all functions are enabled */
> > >  	if (!ftrace_graph_count && !*pos)
> > >  		return (void *)1;
> > >  
> > > -	p = g_next(m, p, pos);
> > > -
> > > -	return p;
> > > +	return g_next(m, NULL, pos);
> > >  }
> > >  
> > >  static void g_stop(struct seq_file *m, void *p)

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