linux-kernel - Re: [PATCH v6 13/26] mm/memory: Add vmf_insert_page

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Message-ID: <6785baa0b6b03_20fa294dd@dwillia2-xfh.jf.intel.com.notmuch>
Date: Mon, 13 Jan 2025 17:15:12 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Alistair Popple <apopple@...dia.com>, <akpm@...ux-foundation.org>,
	<dan.j.williams@...el.com>, <linux-mm@...ck.org>
CC: <alison.schofield@...el.com>, Alistair Popple <apopple@...dia.com>,
	<lina@...hilina.net>, <zhang.lyra@...il.com>,
	<gerald.schaefer@...ux.ibm.com>, <vishal.l.verma@...el.com>,
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Subject: Re: [PATCH v6 13/26] mm/memory: Add vmf_insert_page_mkwrite()

Alistair Popple wrote:
> Currently to map a DAX page the DAX driver calls vmf_insert_pfn. This
> creates a special devmap PTE entry for the pfn but does not take a
> reference on the underlying struct page for the mapping. This is
> because DAX page refcounts are treated specially, as indicated by the
> presence of a devmap entry.
> 
> To allow DAX page refcounts to be managed the same as normal page
> refcounts introduce vmf_insert_page_mkwrite(). This will take a
> reference on the underlying page much the same as vmf_insert_page,
> except it also permits upgrading an existing mapping to be writable if
> requested/possible.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> 
> ---
> 
> Updates from v2:
> 
>  - Rename function to make not DAX specific
> 
>  - Split the insert_page_into_pte_locked() change into a separate
>    patch.
> 
> Updates from v1:
> 
>  - Re-arrange code in insert_page_into_pte_locked() based on comments
>    from Jan Kara.
> 
>  - Call mkdrity/mkyoung for the mkwrite case, also suggested by Jan.
> ---
>  include/linux/mm.h |  2 ++
>  mm/memory.c        | 36 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+)

Looks good to me, you can add:

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