linux-kernel - Re: [PATCH] mm: Fix vmstat after removing NR

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Message-ID: <fhpxqctusqtn5cpyihf6z2esmujofi2ra7gknelms2ta4p2riv@3s7bxucy6quf>
Date: Thu, 29 May 2025 11:13:31 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	David Hildenbrand <david@...hat.com>, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, 
	vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Hongyu Ning <hongyu.ning@...ux.intel.com>, stable@...r.kernel.org, Christoph Hellwig <hch@....de>, 
	Hannes Reinecke <hare@...e.de>, Johannes Thumshirn <johannes.thumshirn@....com>, 
	Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH] mm: Fix vmstat after removing NR_BOUNCE

On Thu, May 29, 2025 at 01:38:32PM +0300, Kirill A. Shutemov wrote:
> Hongyu noticed that the nr_unaccepted counter kept growing even in the
> absence of unaccepted memory on the machine.
> 
> This happens due to a commit that removed NR_BOUNCE: it removed the
> counter from the enum zone_stat_item, but left it in the vmstat_text
> array.
> 
> As a result, all counters below nr_bounce in /proc/vmstat are
> shifted by one line, causing the numa_hit counter to be labeled as
> nr_unaccepted.
> 
> To fix this issue, remove nr_bounce from the vmstat_text array.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reported-by: Hongyu Ning <hongyu.ning@...ux.intel.com>
> Fixes: 194df9f66db8 ("mm: remove NR_BOUNCE zone stat")
> Cc: stable@...r.kernel.org
> Cc: Christoph Hellwig <hch@....de>
> Cc: Hannes Reinecke <hare@...e.de>
> Cc: Johannes Thumshirn <johannes.thumshirn@....com>
> Cc: Jens Axboe <axboe@...nel.dk>

Reviewed-by: Shakeel Butt <shakeel.butt@...ux.dev>

Can we put BUILD_BUG_ON() to avoid this situation in the future?