linux-kernel - Re: [PATCH v1 04/23] mm/balloon_compaction: centralize basic page migration handling

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Message-ID: <2fa9f196-12e4-4c1a-a1f7-cfdded93cc94@redhat.com>
Date: Wed, 22 Oct 2025 10:37:53 +0200
From: David Hildenbrand <david@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linuxppc-dev@...ts.ozlabs.org,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, linux-doc@...r.kernel.org,
 virtualization@...ts.linux.dev, Andrew Morton <akpm@...ux-foundation.org>,
 Oscar Salvador <osalvador@...e.de>,
 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>,
 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>, Arnd Bergmann
 <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jerrin Shaji George <jerrin.shaji-george@...adcom.com>,
 Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Eugenio Pérez <eperezma@...hat.com>, Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH v1 04/23] mm/balloon_compaction: centralize basic page
 migration handling

On 21.10.25 22:50, Michael S. Tsirkin wrote:
> On Tue, Oct 21, 2025 at 02:59:09PM +0200, David Hildenbrand wrote:
>> Let's update the balloon page references, the balloon page list, the
>> BALLOON_MIGRATE counter and the isolated-pages counter in
>> balloon_page_migrate(), after letting the balloon->migratepage()
>> callback deal with the actual inflation+deflation.
>>
>> Note that we now perform the balloon list modifications outside of any
>> implementation-specific locks: which is fine, there is nothing special
>> about these page actions that the lock would be protecting.
>>
>> The old page is already no longer in the list (isolated) and the new page
>> is not yet in the list.
>>
>> Let's use -ENOENT to communicate the special "inflation of new page
>> failed after already deflating the old page" to balloon_page_migrate() so
>> it can handle it accordingly.
>>
>> While at it, rename balloon->b_dev_info to make it mach the other
> 
> match

Thanks!

-- 
Cheers

David / dhildenb