linux-kernel - Re: [PATCH] mm: vmscan: Avoid signedness error for GCC 5.4

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Message-Id: <20250507110701.c2c135d3f4ed594b914da41b@linux-foundation.org>
Date: Wed, 7 May 2025 11:07:01 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: WangYuli <wangyuli@...ontech.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, yuzhao@...gle.com,
 stevensd@...omium.org, kaleshsingh@...gle.com, zhanjun@...ontech.com,
 niecheng1@...ontech.com, guanwentao@...ontech.com, Matthew Wilcox
 <willy@...radead.org>
Subject: Re: [PATCH] mm: vmscan: Avoid signedness error for GCC 5.4

On Wed, 7 May 2025 12:06:11 +0800 WangYuli <wangyuli@...ontech.com> wrote:

> Perhaps a possible approach for now could be to change this line to for 
> (i = tier % MAX_NR_TIERS; i <= min_t(int, tier, MAX_NR_TIERS - 1); i++) 
> {, which would allow us to keep the signed int type for the tier 
> variable itself.

Sure.

> Regarding the potential for a more comprehensive change in the future to 
> redefine all these "tier" variables and related ones as unsigned int, I 
> would be very grateful for your guidance on whether that's a direction 
> we should consider.

`int' is a curse.  Yes, we do this very frequently - we unthinkingly
use a signed type for a naturally unsigned concept.  Ths signed type
spreads and spreads and the incorrect signage causes (small) problems
in various places.  By then it's a big mess trying to switch to an
unsigned type.

Oh well, we just battle on.  We should at least be more vigilant about
this when adding new things.


hp2:/usr/src/25> grep "int nid" mm/*.c | wc -l
316

argh.