linux-kernel - Re: [PATCH v1 23/29] mm/page-alloc: remove PageMappingFlags()

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 for Android: free password hash cracker in your pocket

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

Message-ID: <8ff24777-988a-4d1d-be97-e7184abfa998@lucifer.local>
Date: Tue, 1 Jul 2025 14:02:43 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Jerrin Shaji George <jerrin.shaji-george@...adcom.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Eugenio Pérez <eperezma@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        Zi Yan <ziy@...dia.com>, Matthew Brost <matthew.brost@...el.com>,
        Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
        Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>,
        Ying Huang <ying.huang@...ux.alibaba.com>,
        Alistair Popple <apopple@...dia.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Brendan Jackman <jackmanb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>, Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>, Peter Xu <peterx@...hat.com>,
        Xu Xin <xu.xin16@....com.cn>,
        Chengming Zhou <chengming.zhou@...ux.dev>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <nao.horiguchi@...il.com>,
        Oscar Salvador <osalvador@...e.de>, Rik van Riel <riel@...riel.com>,
        Harry Yoo <harry.yoo@...cle.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Shakeel Butt <shakeel.butt@...ux.dev>
Subject: Re: [PATCH v1 23/29] mm/page-alloc: remove PageMappingFlags()

On Mon, Jun 30, 2025 at 03:00:04PM +0200, David Hildenbrand wrote:
> We can now simply check for PageAnon() and remove PageMappingFlags().
>
> ... and while at it, use the folio instead and operate on
> folio->mapping.

Probably worth mentioning to be super crystal clear that this is because
now it's either an anon folio or a KSM folio, both of which set the
FOLIO_MAPPING_ANON flag.

I wonder if there's other places that could be fixed up similarly that do
folio_test_anon() || folio_test_ksm() or equivalent?

>
> Reviewed-by: Zi Yan <ziy@...dia.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>


> ---
>  include/linux/page-flags.h | 5 -----
>  mm/page_alloc.c            | 7 +++----
>  2 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index abed972e902e1..f539bd5e14200 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -723,11 +723,6 @@ static __always_inline bool folio_mapping_flags(const struct folio *folio)
>  	return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) != 0;
>  }
>
> -static __always_inline bool PageMappingFlags(const struct page *page)
> -{
> -	return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
> -}
> -
>  static __always_inline bool folio_test_anon(const struct folio *folio)
>  {
>  	return ((unsigned long)folio->mapping & PAGE_MAPPING_ANON) != 0;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a134b9fa9520e..a0ebcc5f54bb2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1375,10 +1375,9 @@ __always_inline bool free_pages_prepare(struct page *page,
>  			(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
>  		}
>  	}
> -	if (PageMappingFlags(page)) {
> -		if (PageAnon(page))
> -			mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
> -		page->mapping = NULL;
> +	if (folio_test_anon(folio)) {
> +		mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
> +		folio->mapping = NULL;
>  	}
>  	if (unlikely(page_has_type(page)))
>  		page->page_type = UINT_MAX;
> --
> 2.49.0
>