linux-kernel - Re: [PATCH v5 06/21] perf script: Move find

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Message-ID: <ZylXI4zj7Hs8Uvov@google.com>
Date: Mon, 4 Nov 2024 15:22:11 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	James Clark <james.clark@...aro.org>,
	Howard Chu <howardchu95@...il.com>,
	Athira Jajeev <atrajeev@...ux.vnet.ibm.com>,
	Michael Petlan <mpetlan@...hat.com>,
	Veronika Molnarova <vmolnaro@...hat.com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	Ilya Leoshkevich <iii@...ux.ibm.com>,
	Colin Ian King <colin.i.king@...il.com>,
	Weilin Wang <weilin.wang@...el.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v5 06/21] perf script: Move find_scripts to
 browser/scripts.c

On Mon, Nov 04, 2024 at 02:20:30PM -0800, Ian Rogers wrote:
> On Mon, Nov 4, 2024 at 2:09 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > On Mon, Nov 04, 2024 at 01:06:35PM -0800, Ian Rogers wrote:
> > > On Mon, Nov 4, 2024 at 1:00 PM Namhyung Kim <namhyung@...nel.org> wrote:
> > > >
> > > > On Mon, Nov 04, 2024 at 12:48:01PM -0800, Ian Rogers wrote:
> > > > > Namhyung was asking that the c&p of code be 1 patch then "add new
> > > > > changes like using openat() on top". That is:
> > > > >
> > > > > patch 1: add is_directory_at - introduce the 2 line helper function
> > > > > patch 2: move the code
> > > > > patch 3: update the code to use is_directory_at
> > > > >
> > > > > patch 2 is known broken as patch 3 is fixing it.
> > > > >
> > > > > Hopefully this is clear.
> > > >
> > > > Actually I don't care about the patch ordering.  My request is not
> > > > to break build and just to separate different changes out. :)
> > >
> > > So, patch 2 can't be separated from patch 3 - are we agreed? So we
> > > squash patch 2 with patch 3. Patch 1 is trivial and fails to meet the
> > > bar of a meaningful change, so we squash that. We end up with this
> > > patch. If there's a later revert and a dependence of the 2 liner, just
> > > don't revert that part of the change. We've never had such a revert so
> > > it is hard to see why we need to generate so much churn because of it.
> >
> > As I said the patch 1 should be the c&p and no need to introduce
> > is_directory_at() before that.  Why not doing
> >
> >  patch1: move the code
> >  patch2: add and use is_directory_at() + openat()
> >
> > ?
> 
> Because placing all the code in 1 file expands GCC's analysis and the
> build fails. In the commit message I describe this:
> "The arrays are warned about potential buffer overflows by GCC now
> that all the code exists in a single C file."
> A standard unsound workaround to this is to change "sizeof(...)" to
> "sizeof(...) - 1", as it is ugly I added is_directory_at to not suffer
> the problem as the arrays are gone.

Ok, it's strange that this type of analysis depends on the placement.
Anyway it seems there's a problem in the code already.  Then we can fix
it first and then move.  How about this?

 patch1: add and use is_directory_at() + openat()
 patch2: move the code

Thanks,
Namhyung