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Date:   Mon, 10 Jul 2023 18:58:09 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Chao Yu <chao@kernel.org>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH v1 1/1] f2fs: Use return value of strreplace()
Message-ID: <ZKy3MQ4zRlvLwE1D@google.com>
References: <20230628150243.17771-1-andriy.shevchenko@linux.intel.com>
 <20230710184353.09640aee@gandalf.local.home>
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On 07/10, Steven Rostedt wrote:
> On Wed, 28 Jun 2023 18:02:43 +0300
> Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> 
> > Since strreplace() returns the pointer to the string itself,
> > we may use it directly in the code.
> > 
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > ---
> >  include/trace/events/f2fs.h | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> > index 793f82cc1515..f5994515290c 100644
> > --- a/include/trace/events/f2fs.h
> > +++ b/include/trace/events/f2fs.h
> > @@ -2234,13 +2234,11 @@ DECLARE_EVENT_CLASS(f2fs__rw_start,
> >  		 * because this screws up the tooling that parses
> >  		 * the traces.
> >  		 */
> > -		__assign_str(pathbuf, pathname);
> > -		(void)strreplace(__get_str(pathbuf), ' ', '_');
> > +		__assign_str(pathbuf, strreplace(pathname, ' ', '_'));
> 
> But this modifies the pathname that is passed into the trace event, which
> is something that a trace point should never do! In fact, the char
> *pathname, really should be a const char * (for which this would fail to
> build).
> 
> Note, I went to look for these events and I can not find where they are
> used. Should these events just be deleted?

Hmm, this was a part of upstream effort to replace the previous android_fs
tracepoints like:
https://android-review.git.corp.google.com/c/platform/system/extras/+/2223339

> 
> -- Steve
> 
> 
> >  		__entry->offset = offset;
> >  		__entry->bytes = bytes;
> >  		__entry->i_size = i_size_read(inode);
> > -		__assign_str(cmdline, command);
> > -		(void)strreplace(__get_str(cmdline), ' ', '_');
> > +		__assign_str(cmdline, strreplace(command, ' ', '_'));
> >  		__entry->pid = pid;
> >  		__entry->ino = inode->i_ino;
> >  	),