linux-kernel - Re: [PATCH] mm: khugepaged: fix NR_FILE_PAGES accounting in collapse

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aXv_5Gl6L-1eXYQd@linux.dev>
Date: Thu, 29 Jan 2026 16:50:57 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Rik van Riel <riel@...riel.com>, Song Liu <songliubraving@...com>, 
	Kiryl Shutsemau <kas@...nel.org>, Usama Arif <usamaarif642@...il.com>, 
	David Hildenbrand <david@...nel.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	"Liam R . Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>, 
	Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>, 
	Lance Yang <lance.yang@...ux.dev>, Meta kernel team <kernel-team@...a.com>, linux-mm@...ck.org, 
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: khugepaged: fix NR_FILE_PAGES accounting in
 collapse_file()

On Thu, Jan 29, 2026 at 07:32:14PM -0500, Johannes Weiner wrote:
> On Thu, Jan 29, 2026 at 10:40:54AM -0800, Shakeel Butt wrote:
> > @@ -2200,8 +2200,8 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
> >  	else
> >  		lruvec_stat_mod_folio(new_folio, NR_FILE_THPS, HPAGE_PMD_NR);
> >  
> > +	lruvec_stat_mod_folio(new_folio, NR_FILE_PAGES, HPAGE_PMD_NR);
> 
> The memcg breakage is more visible, but I think this has been broken
> for NUMA stats even longer. new_folio could also come from a different
> node than the subpages, after all.

Indeed you are right, so I should blame Kiryl instead of Song :P

> 
> >  	if (nr_none) {
> > -		lruvec_stat_mod_folio(new_folio, NR_FILE_PAGES, nr_none);
> >  		/* nr_none is always 0 for non-shmem. */
> >  		lruvec_stat_mod_folio(new_folio, NR_SHMEM, nr_none);
> 
> So AFAICT NR_SHMEM needs the same treatment.
> 
> It looks like that's been broken since f3f0e1d2150b ("khugepaged: add
> support of collapse for tmpfs/shmem pages").

Thanks, I will send v2 with correct handling of NR_SHMEM as well.