linux-kernel - Re: [PATCH 1/2] mm/gup: Remove dead pgmap refcounting code

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Message-ID: <68b7974488914_75e310062@dwillia2-mobl4.notmuch>
Date: Tue, 2 Sep 2025 18:17:56 -0700
From: <dan.j.williams@...el.com>
To: Alistair Popple <apopple@...dia.com>, <linux-mm@...ck.org>,
	<akpm@...ux-foundation.org>
CC: <david@...hat.com>, <osalvador@...e.de>, <jgg@...pe.ca>,
	<jhubbard@...dia.com>, <peterx@...hat.com>, <linux-kernel@...r.kernel.org>,
	<dan.j.williams@...el.com>, Alistair Popple <apopple@...dia.com>
Subject: Re: [PATCH 1/2] mm/gup: Remove dead pgmap refcounting code

Alistair Popple wrote:
> Prior to aed877c2b425 ("device/dax: properly refcount device dax pages
> when mapping") ZONE_DEVICE pages were not fully reference counted when
> mapped into user page tables. Instead GUP would take a reference on the
> associated pgmap to ensure the results of pfn_to_page() remained valid.
> 
> This is no longer required and most of the code was removed by
> fd2825b0760a ("mm/gup: remove pXX_devmap usage from get_user_pages()").
> Finish cleaning this up by removing the dead calls to put_dev_pagemap()
> and the temporary context struct.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>

Looks good, thanks for this work Alistair.

Reviewed-by: Dan Williams <dan.j.williams@...el.com>