Re: [RFC patch 29/41] btrfs: ref-verify: Simplify stack trace retrieval

[Thomas Gleixner]

On Wed, 10 Apr 2019, Johannes Thumshirn wrote:

> On Wed, Apr 10, 2019 at 12:28:23PM +0200, Thomas Gleixner wrote:
> > Replace the indirection through struct stack_trace with an invocation of
> > the storage array based interface.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: David Sterba <dsterba@xxxxxxxx>
> > Cc: Chris Mason <clm@xxxxxx>
> > Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
> > Cc: linux-btrfs@xxxxxxxxxxxxxxx
> > ---
> >  fs/btrfs/ref-verify.c |   15 ++-------------
> >  1 file changed, 2 insertions(+), 13 deletions(-)
> > 
> > --- a/fs/btrfs/ref-verify.c
> > +++ b/fs/btrfs/ref-verify.c
> > @@ -205,28 +205,17 @@ static struct root_entry *lookup_root_en
> >  #ifdef CONFIG_STACKTRACE
> >  static void __save_stack_trace(struct ref_action *ra)
> >  {
> > -	struct stack_trace stack_trace;
> > -
> > -	stack_trace.max_entries = MAX_TRACE;
> > -	stack_trace.nr_entries = 0;
> > -	stack_trace.entries = ra->trace;
> > -	stack_trace.skip = 2;
> > -	save_stack_trace(&stack_trace);
> > -	ra->trace_len = stack_trace.nr_entries;
> > +	ra->trace_len = stack_trace_save(ra->trace, MAX_TRACE, 2);
> 
> 
> Stupid question: why are you passing a '2' for 'skipnr' and in
> stack_trace_save() from your series you set stack_trace::skip as skipnr + 1. 
> 
> Wouldn't this result in a stack_trace::skip = 3? Or is it the number of
> functions to be skipped and you don't want to have stack_trace_save() saved as
> well? 

Correct. The extra call will shift the skipped one up, so I compensate for that.

Thanks,

	tglx