linux-kernel - Re: [PATCH 12/12] mm: Remove devmap related functions and page table bits

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Message-ID: <CAOsKWHCEFSw6d7nC3A1Z4DKMNuUjirt-oULSr7hCWqT2GfnUDQ@mail.gmail.com>
Date: Wed, 11 Sep 2024 15:47:22 +0800
From: Chunyan Zhang <zhang.lyra@...il.com>
To: Alistair Popple <apopple@...dia.com>
Cc: dan.j.williams@...el.com, linux-mm@...ck.org, 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, 
	david@...hat.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 12/12] mm: Remove devmap related functions and page table bits

Hi Alistair,

On Tue, 10 Sept 2024 at 12:21, Alistair Popple <apopple@...dia.com> wrote:
>
> Now that DAX and all other reference counts to ZONE_DEVICE pages are
> managed normally there is no need for the special devmap PTE/PMD/PUD
> page table bits. So drop all references to these, freeing up a
> software defined page table bit on architectures supporting it.
>
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> Acked-by: Will Deacon <will@...nel.org> # arm64
> ---
>  Documentation/mm/arch_pgtable_helpers.rst     |  6 +--
>  arch/arm64/Kconfig                            |  1 +-
>  arch/arm64/include/asm/pgtable-prot.h         |  1 +-
>  arch/arm64/include/asm/pgtable.h              | 24 +--------
>  arch/powerpc/Kconfig                          |  1 +-
>  arch/powerpc/include/asm/book3s/64/hash-4k.h  |  6 +--
>  arch/powerpc/include/asm/book3s/64/hash-64k.h |  7 +--
>  arch/powerpc/include/asm/book3s/64/pgtable.h  | 52 +------------------
>  arch/powerpc/include/asm/book3s/64/radix.h    | 14 +-----
>  arch/x86/Kconfig                              |  1 +-
>  arch/x86/include/asm/pgtable.h                | 50 +-----------------
>  arch/x86/include/asm/pgtable_types.h          |  5 +--

RISC-V's references also need to be cleanup, it simply can be done by
reverting the commit

216e04bf1e4d (riscv: mm: Add support for ZONE_DEVICE)

Thanks,
Chunyan

>  include/linux/mm.h                            |  7 +--
>  include/linux/pfn_t.h                         | 20 +-------
>  include/linux/pgtable.h                       | 19 +------
>  mm/Kconfig                                    |  4 +-
>  mm/debug_vm_pgtable.c                         | 59 +--------------------
>  mm/hmm.c                                      |  3 +-
>  18 files changed, 11 insertions(+), 269 deletions(-)
>