From: Andrew Morton <akpm@linux-foundation.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Arnd Bergmann <arnd@arndb.de>,
David Hildenbrand <david@kernel.org>,
Michal Hocko <mhocko@kernel.org>, Qi Zheng <qi.zheng@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Lorenzo Stoakes <ljs@kernel.org>,
Kairui Song <kasong@tencent.com>, Barry Song <baohua@kernel.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
Baoquan He <baoquan.he@linux.dev>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Ridong Chen <chenridong@xiaomi.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/vmscan: avoid false-positive -Wuninitialized warning, again
Date: Wed, 16 Sep 2026 16:28:16 -0700 [thread overview]
Message-ID: <20260916162816.39f0f33f6a48d30a71be3575@linux-foundation.org> (raw)
In-Reply-To: <20260916083456.4136132-1-arnd@kernel.org>
On Wed, 16 Sep 2026 10:34:46 +0200 Arnd Bergmann <arnd@kernel.org> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> I previously worked around a false-postive gcc-16 warning in the
> get_tier_idx() function, by adding a fake initializer. This happens with
> the -fsanitize=bounds sanitizer when the compiler creates a specialized
> variant of isolate_folios():
>
> In function 'get_tier_idx',
> inlined from 'isolate_folios.constprop' at mm/vmscan.c:4982:9:
> mm/vmscan.c:4934:9: error: 'sp.refaulted' is used uninitialized [-Werror=uninitialized]
> 4934 | read_ctrl_pos(lruvec, type, LRU_TIER_MIN, LRU_TIER_MIN, 2, &sp);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> mm/vmscan.c: In function 'isolate_folios.constprop':
> mm/vmscan.c:4946:25: note: 'sp.refaulted' was declared here
> 4946 | struct ctrl_pos sp, pv = {};
> | ^~
>
> Adding another "= {}" would solve the problem as well, but to prevent
> this from happening again after the next code refactoring, try instead to
> prevent this by forbidding interprocedural optimizations on this function.
>
> ...
>
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3274,8 +3274,10 @@ struct ctrl_pos {
> int gain;
> };
>
> -static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier_min,
> - int tier_max, int gain, struct ctrl_pos *pos)
> +/* __noipa works around gcc-16 warning for uninitizled use of pos->refaulted */
> +static __noipa void read_ctrl_pos(struct lruvec *lruvec, int type,
> + int tier_min, int tier_max, int gain,
> + struct ctrl_pos *pos)
> {
> int i;
> struct lru_gen_folio *lrugen = &lruvec->lrugen;
Current code has changed here somewhat, but I expect the error is still
there. I fixed that "uninitizled" while in there. Altered patch is
below.
--- a/mm/vmscan.c~mm-vmscan-avoid-false-positive-wuninitialized-warning-again
+++ a/mm/vmscan.c
@@ -3195,8 +3195,12 @@ struct ctrl_pos {
int gain;
};
-static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
- struct ctrl_pos *pos)
+/*
+ * __noipa works around gcc-16 warning for uninitialized use of
+ * pos->refaulted
+ */
+static __noipa void read_ctrl_pos(struct lruvec *lruvec, int type, int tier,
+ int gain, struct ctrl_pos *pos)
{
int i;
struct lru_gen_folio *lrugen = &lruvec->lrugen;
@@ -4802,7 +4806,7 @@ static int scan_folios(unsigned long nr_
static int get_tier_idx(struct lruvec *lruvec, int type)
{
int tier;
- struct ctrl_pos sp, pv = {};
+ struct ctrl_pos sp, pv;
/*
* To leave a margin for fluctuations, use a larger gain factor (2:3).
@@ -4821,7 +4825,7 @@ static int get_tier_idx(struct lruvec *l
static int get_type_to_scan(struct lruvec *lruvec, int swappiness)
{
- struct ctrl_pos sp, pv = {};
+ struct ctrl_pos sp, pv;
if (swappiness <= MIN_SWAPPINESS + 1)
return LRU_GEN_FILE;
_
next prev parent reply other threads:[~2026-09-16 23:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 8:34 Arnd Bergmann
2026-09-16 23:08 ` Andrew Morton
2026-09-16 23:28 ` Andrew Morton [this message]
2026-09-16 23:30 ` Andrew Morton
2026-09-17 2:56 ` Baoquan He
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