linux-kernel - Re: [PATCH v4 10/25] mm/mm_init: Move p2pdma page refcount initialisation to p2pdma

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Message-ID: <4446a9c9-613b-4303-9a06-686fb10af363@redhat.com>
Date: Fri, 20 Dec 2024 19:29:18 +0100
From: David Hildenbrand <david@...hat.com>
To: Alistair Popple <apopple@...dia.com>
Cc: akpm@...ux-foundation.org, dan.j.williams@...el.com, linux-mm@...ck.org,
 lina@...hilina.net, zhang.lyra@...il.com, gerald.schaefer@...ux.ibm.com,
 vishal.l.verma@...el.com, dave.jiang@...el.com, logang@...tatee.com,
 bhelgaas@...gle.com, jack@...e.cz, jgg@...pe.ca, catalin.marinas@....com,
 will@...nel.org, mpe@...erman.id.au, npiggin@...il.com,
 dave.hansen@...ux.intel.com, ira.weiny@...el.com, willy@...radead.org,
 djwong@...nel.org, tytso@....edu, linmiaohe@...wei.com, peterx@...hat.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
 nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 linux-xfs@...r.kernel.org, jhubbard@...dia.com, hch@....de,
 david@...morbit.com
Subject: Re: [PATCH v4 10/25] mm/mm_init: Move p2pdma page refcount
 initialisation to p2pdma


>>
>>
>> But that's a bit weird: we call __init_single_page()->init_page_count() to
>> initialize it to 1, to then set it back to 0.
>>
>>
>> Maybe we can just pass to __init_single_page() the refcount we want to have
>> directly? Can be a patch on top of course.
> 
> Once the dust settles on this series we won't need the pgmap->type check at
> all because all ZONE_DEVICE pages will get an initial count of 0. I have some
> follow up clean-ups for after this series is applied (particularly with regards
> to pgmap refcounts), so if it's ok I'd rather do this as a follow-up.

Sure. For ordinary memory hotplug I'll also convert it to start with 
refcount=0 soonish, so there we're also simply pass 0 to __init_single_page.

-- 
Cheers,

David / dhildenb