From: Shakeel Butt <shakeel.butt@linux.dev>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@surriel.com>,
Song Liu <songliubraving@fb.com>,
Kiryl Shutsemau <kas@kernel.org>,
Usama Arif <usamaarif642@gmail.com>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Nico Pache <npache@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>,
Lance Yang <lance.yang@linux.dev>,
Meta kernel team <kernel-team@meta.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: khugepaged: fix NR_FILE_PAGES accounting in collapse_file()
Date: Thu, 29 Jan 2026 16:47:52 -0800 [thread overview]
Message-ID: <aXv_HI8JM9mZCr4-@linux.dev> (raw)
In-Reply-To: <aXvjdArhPpUNF8BI@casper.infradead.org>
On Thu, Jan 29, 2026 at 10:47:16PM +0000, Matthew Wilcox wrote:
> On Thu, Jan 29, 2026 at 10:40:54AM -0800, Shakeel Butt wrote:
> > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
>
> Are you sure this is the right Fixes? 99cb0dbd47a1 wasn't cgroup
> aware:
>
> if (nr_none) {
> struct zone *zone = page_zone(new_page);
>
> __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
> - __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
> + if (is_shmem)
> + __mod_node_page_state(zone->zone_pgdat,
> + NR_SHMEM, nr_none);
> }
>
> b8eddff8886b added cgroup support:
>
> if (is_shmem)
> - __inc_node_page_state(new_page, NR_SHMEM_THPS);
> + __inc_lruvec_page_state(new_page, NR_SHMEM_THPS);
> else {
> - __inc_node_page_state(new_page, NR_FILE_THPS);
> + __inc_lruvec_page_state(new_page, NR_FILE_THPS);
> filemap_nr_thps_inc(mapping);
> }
>
> which would seem like the right Fixes: to me?
>
b8eddff8886b is about different stats NR_SHMEM_THPS & NR_FILE_THPS.
However as Johannes responded this code was broken even before memcg
awareness for NR_FILE_PAGES and NR_SHMEM.
I will send v2 with correct handling of NR_SHMEM as well.
next prev parent reply other threads:[~2026-01-30 0:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-29 18:40 Shakeel Butt
2026-01-29 18:50 ` Andrew Morton
2026-01-29 18:55 ` Shakeel Butt
2026-01-29 22:47 ` Matthew Wilcox
2026-01-30 0:47 ` Shakeel Butt [this message]
2026-01-29 22:49 ` Usama Arif
2026-01-30 0:32 ` Johannes Weiner
2026-01-30 0:50 ` Shakeel Butt
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