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] [thread-next>] [day] [month] [year] [list]
Message-ID: <819b61fb-ebb0-4ded-a104-01ab133b6a41@redhat.com>
Date: Wed, 2 Jul 2025 13:04:05 +0200
From: David Hildenbrand <david@...hat.com>
To: Harry Yoo <harry.yoo@...cle.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>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.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>,
 Qi Zheng <zhengqi.arch@...edance.com>, Shakeel Butt <shakeel.butt@...ux.dev>
Subject: Re: [PATCH v1 19/29] mm: stop storing migration_ops in page->mapping

On 02.07.25 12:34, Harry Yoo wrote:
> On Mon, Jun 30, 2025 at 03:00:00PM +0200, David Hildenbrand wrote:
>> ... instead, look them up statically based on the page type. Maybe in the
>> future we want a registration interface? At least for now, it can be
>> easily handled using the two page types that actually support page
>> migration.
>>
>> The remaining usage of page->mapping is to flag such pages as actually
>> being movable (having movable_ops), which we will change next.
>>
>> Reviewed-by: Zi Yan <ziy@...dia.com>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
>> ---
> 
>> +static const struct movable_operations *page_movable_ops(struct page *page)
>> +{
>> +	VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page);
>> +
>> +	/*
>> +	 * If we enable page migration for a page of a certain type by marking
>> +	 * it as movable, the page type must be sticky until the page gets freed
>> +	 * back to the buddy.
>> +	 */
>> +#ifdef CONFIG_BALLOON_COMPACTION
>> +	if (PageOffline(page))
>> +		/* Only balloon compaction sets PageOffline pages movable. */
>> +		return &balloon_mops;
>> +#endif /* CONFIG_BALLOON_COMPACTION */
>> +#if defined(CONFIG_ZSMALLOC) && defined(CONFIG_COMPACTION)
>> +	if (PageZsmalloc(page))
>> +		return &zsmalloc_mops;
>> +#endif /* defined(CONFIG_ZSMALLOC) && defined(CONFIG_COMPACTION) */
> 
> What happens if:
>    CONFIG_ZSMALLOC=y
>    CONFIG_TRANSPARENT_HUGEPAGE=n
>    CONFIG_COMPACTION=n
>    CONFIG_MIGRATION=y

Pages are never allocated from ZONE_MOVABLE/CMA and are not marked as 
having movable_ops, so we never end up in this function. See how 
zsmalloc.c deals with CONFIG_COMPACTION, especially how 
SetZsPageMovable() is a NOP without it.

As a side note, both should probably be moved from COMPACTION to 
MIGRATION. Although probably in practice, anybody enabling 
CONFIG_MIGRATION likely also enables CONFIG_COMPACTION.

-- 
Cheers,

David / dhildenb


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ