Re: [PATCH] f2fs: Fix f2fs_truncate_partial_nodes ftrace event

Kajetan Puchalski
2023-08-14T14:39:53Z

On Mon, Aug 14, 2023 at 02:32:53PM +0100, Kajetan Puchalski wrote:
> On Mon, Mar 06, 2023 at 12:25:49PM +0000, Douglas RAILLARD wrote:
> > From: Douglas Raillard <douglas.raillard@arm.com>
> >
> > Fix the nid_t field so that its size is correctly reported in the text
> > format embedded in trace.dat files. As it stands, it is reported as
> > being of size 4:
> >
> > field:nid_t nid[3]; offset:24; size:4; signed:0;
> >
> > Instead of 12:
> >
> > field:nid_t nid[3]; offset:24; size:12; signed:0;
> >
> > This also fixes the reported offset of subsequent fields so that they
> > match with the actual struct layout.
> >
> >
> > Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
> > ---
> > include/trace/events/f2fs.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> > index 31d994e6b4ca..8d053838d6cf 100644
> > --- a/include/trace/events/f2fs.h
> > +++ b/include/trace/events/f2fs.h
> > @@ -512,7 +512,7 @@ TRACE_EVENT(f2fs_truncate_partial_nodes,
> > TP_STRUCT__entry(
> > __field(dev_t, dev)
> > __field(ino_t, ino)
> > - __field(nid_t, nid[3])
> > + __array(nid_t, nid, 3)
> > __field(int, depth)
> > __field(int, err)
> > ),
> > --
> > 2.25.1
>
> Hi,
>
> Just wanted to flag that I noticed this breaks Perfetto tracing on
> Android, at least as of Android 13. I'm not sure if it's been fixed in newer
> versions. Looks like the version of Perfetto in Android 13 is expecting
> the previous (ie broken) field format to be there and its entire ftrace
> collector fails as a result:
>
> E/perfetto( 3532): ranslation_table.cc:133 Failed to infer ftrace field type for "f2fs_truncate_partial_nodes.nid" (type:"nid_t nid[3]" size:12 signed:0) (errno: 2, No such file or directory)
> I/perfetto( 3640): probes.cc:65 Hard resetting ftrace state.
>
> For my own purposes I just reverted these two:
> * 0b04d4c0542e8573a837b1d81b94209e48723b25 (f2fs: Fix f2fs_truncate_partial_nodes ftrace event)
> * f82e7ca019dfad3b006fd3b772f7ac569672db55 (tracing: Error if a trace event has an array for a __field()
>
> and now it works fine so not the biggest deal but this should probably
> be addressed, I imagine more likely on the Perfetto side.

Added context here, it is just caused by the parser implementation in Perfetto