Re: [PATCH] libtracefs: Fix wrong return value in tracefs_tracing_dir_is_mounted()

[Bean Huo <beanhuo@iokpp.de>]

On Mon, 2022-11-28 at 16:41 +0100, Bean Huo wrote:
> On Mon, 2022-11-28 at 10:24 -0500, Steven Rostedt wrote:
> > On Mon, 28 Nov 2022 14:21:06 +0100
> > 
> > Bean Huo <beanhuo@iokpp.de> wrote:
> > 
> > 
> > 
> > > From: Bean Huo <beanhuo@micron.com>
> > > If it eventually mounts successfully, it should return 1 instead
> > > of
> > > 0, otherwise it will make the caller's verification logic more
> > > complicated
> > 
> > The man page shows:
> > 
> > 
> > 
> >   The tracefs_tracing_dir_is_mounted() returns 1 if the tracing
> > directory is
> > 
> >   already mounted, 0 if it is not, and -1 on error.
> > 
> > 
> > 
> > If you only want to mount it and not care if it was already mounted
> > then
> > 
> > use tracefs_tracing_dir(), as it will return the path of the mount
> > point
> > 
> > and try to mount it if it is not already, or NULL if it could not
> > mount it.
> > 
> > 
> > 
> 
> Hi Steve,
> 
> I used to reply on tracefs_tracing_dir(). But after updated the
> libtracefs yesterday, I found my app doesn't work as before, then
> checked the changelog, and switch to use
> tracefs_tracing_dir_is_mounted. 
> 
> in your latest libtracefs:
> 
> 
> const char *tracefs_tracing_dir(void) {
> 
> ...
> tracing_dir = trace_find_tracing_dir(false);//shold be changed to
> true?
> ...
> 	
> }
> 
> 
> __hidden char *trace_find_tracing_dir(bool debugfs)
> {
>         return find_tracing_dir(debugfs, false);
> }
> 
> 
> 
> static char *find_tracing_dir(bool debugfs, bool mount) {
> 
> ...
> 	if (!mount || mount_debugfs() < 0)
> 		return NULL;
> 
> 
> ...
> 
> 
> }
> 
> 


instead of changing tracefs_tracing_dir_is_mounted(), or we could
change trace_find_tracing_dir(), let it mount the tracefs in case of it
is not mounted when we call tracefs_tracing_dir():



--- a/src/tracefs-utils.c
+++ b/src/tracefs-utils.c
@@ -200,7 +200,7 @@ int tracefs_tracing_dir_is_mounted(bool mount,
const char **path)
  */
 __hidden char *trace_find_tracing_dir(bool debugfs)
 {
-       return find_tracing_dir(debugfs, false);
+       return find_tracing_dir(debugfs, true);
 }


Kind regard,
Bean