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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4538234bc1fsm224606175e9.14.2025.07.02.04.51.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Jul 2025 04:51:55 -0700 (PDT) Message-ID: Date: Wed, 2 Jul 2025 13:51:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 19/29] mm: stop storing migration_ops in page->mapping To: Harry Yoo Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 87074140014 X-Stat-Signature: 8tgottyynukto63tohn4tqg3j8erjmea X-HE-Tag: 1751457119-105176 X-HE-Meta: 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 +wRMUAnA 6Tecw7fUlSXJkfLcpHcQiE3MUuq/f7+Wq/2DDk4QGeQ1EUYWLe75mz9XygoplpeKD2s+qpJOw9n7VH9zlJ55nd3om/wG4N4FHw4K0uW5gCj5pos825AwHY4WXPo/AojljYZDRiJP23xsJ+mpHMAXV7o+KDLJWk0qGa1//5xcsI7EievIz8VjmHtnNFuARQerGwpUh X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 02.07.25 13:43, Harry Yoo wrote: > On Wed, Jul 02, 2025 at 01:04:05PM +0200, David Hildenbrand wrote: >> 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 >>>> Signed-off-by: David Hildenbrand >>>> --- >>> >>>> +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 > > I don't understand how that's true, neither zram nor zsmalloc clears > __GFP_MOVABLE when CONFIG_COMPACTION=n? > > ...Or perhaps I'm still missing some pieces ;) You might have found a bug in zsmalloc then :) Without support for compaction, we must clear __GFP_MOVABLE in alloc_zpdesc() I assume. Do you have the capacity to look into that and send a fix if really broken? In balloon compaction code we properly handle that. > >> are not marked as having movable_ops, so we never end up in this function. > > Right. > >> See how zsmalloc.c deals with CONFIG_COMPACTION, especially how >> SetZsPageMovable() is a NOP without it. > > Right. > > Now I see what I was missing in the previous reply. > Thanks! > > Please feel free to add: > > Reviewed-by: Harry Yoo Thanks! -- Cheers, David / dhildenb