linux-kernel - Re: [PATCH v5 4/4] mm: Use ARRAY_END() instead of open-coding it

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Message-ID: <lo6fdczvfjb5q44euckxi5thjrply4wqk62ori4slz54ivdswj@3c234g733gzq>
Date: Thu, 11 Dec 2025 01:21:59 +0100
From: Alejandro Colomar <alx@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Christopher Bazley <chris.bazley.wg14@...il.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Marco Elver <elver@...gle.com>, Michal Hocko <mhocko@...e.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Al Viro <viro@...iv.linux.org.uk>, 
	Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Jann Horn <jannh@...gle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, "Maciej W. Rozycki" <macro@...am.me.uk>
Subject: Re: [PATCH v5 4/4] mm: Use ARRAY_END() instead of open-coding it

Hi Kees,

On Thu, Dec 11, 2025 at 08:18:56AM +0900, Kees Cook wrote:
> 
> 
> On December 11, 2025 7:46:49 AM GMT+09:00, Alejandro Colomar <alx@...nel.org> wrote:
> >Cc: Kees Cook <kees@...nel.org>
> >Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> >Signed-off-by: Alejandro Colomar <alx@...nel.org>
> 
> Hm, this seems to be missing a commit log body?

Actually, there's not much to it.  The patch uses ARRAY_END() where it
was being open-coded.  There aren't any bugs in this code, so it's
purely cosmetic (and of course, to prevent future issues, in case the
code is modified).  Maybe I could say precisely that.  What would you
say here?

> Are there other open-coded instances that could be replaced? This seems like a great task for a coccinelle script.

There are many, but I wanted to keep them out of this initial patch set,
to make it easy to apply.  When this one is applied, I could work on a
second round that replaces more of them with coccinelle.  This is just
for showing that this is beneficial, and to make sure that you ask for
more.  :)

Also, it's easier if there are few maintainers that would block an
initial patch set.  If restrict the patch set to a few files, I don't
have to deal with many of them.  Once I get used to this, I'll deal with
all of them.

> 
> -Kees

Have a lovely night!
Alex

> 
> >---
> > mm/kmemleak.c      | 2 +-
> > mm/memcontrol-v1.c | 4 ++--
> > 2 files changed, 3 insertions(+), 3 deletions(-)
> >
> >diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> >index 1ac56ceb29b6..fe33f2edfe07 100644
> >--- a/mm/kmemleak.c
> >+++ b/mm/kmemleak.c
> >@@ -510,7 +510,7 @@ static void mem_pool_free(struct kmemleak_object *object)
> > {
> > 	unsigned long flags;
> > 
> >-	if (object < mem_pool || object >= mem_pool + ARRAY_SIZE(mem_pool)) {
> >+	if (object < mem_pool || object >= ARRAY_END(mem_pool)) {
> > 		kmem_cache_free(object_cache, object);
> > 		return;
> > 	}
> >diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> >index 6eed14bff742..b2f37bd939fa 100644
> >--- a/mm/memcontrol-v1.c
> >+++ b/mm/memcontrol-v1.c
> >@@ -1794,7 +1794,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)
> > 
> > 	mem_cgroup_flush_stats(memcg);
> > 
> >-	for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
> >+	for (stat = stats; stat < ARRAY_END(stats); stat++) {
> > 		seq_printf(m, "%s=%lu", stat->name,
> > 			   mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
> > 						   false));
> >@@ -1805,7 +1805,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)
> > 		seq_putc(m, '\n');
> > 	}
> > 
> >-	for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
> >+	for (stat = stats; stat < ARRAY_END(stats); stat++) {
> > 
> > 		seq_printf(m, "hierarchical_%s=%lu", stat->name,
> > 			   mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
> 
> -- 
> Kees Cook

-- 
<https://www.alejandro-colomar.es>

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