linux-kernel - Re: [PATCH 11/13] huge_memory: Remove dead vmf_insert

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Message-ID: <ZogCDpfSyCcjVXWH@x1n>
Date: Fri, 5 Jul 2024 10:24:14 -0400
From: Peter Xu <peterx@...hat.com>
To: Alistair Popple <apopple@...dia.com>
Cc: dan.j.williams@...el.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, david@...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-mm@...ck.org, linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org, jhubbard@...dia.com, hch@....de,
	david@...morbit.com, Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH 11/13] huge_memory: Remove dead vmf_insert_pXd code

Hi, Alistair,

On Thu, Jun 27, 2024 at 10:54:26AM +1000, Alistair Popple wrote:
> Now that DAX is managing page reference counts the same as normal
> pages there are no callers for vmf_insert_pXd functions so remove
> them.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> ---
>  include/linux/huge_mm.h |   2 +-
>  mm/huge_memory.c        | 165 +-----------------------------------------
>  2 files changed, 167 deletions(-)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 9207d8e..0fb6bff 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -37,8 +37,6 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  		    pmd_t *pmd, unsigned long addr, pgprot_t newprot,
>  		    unsigned long cp_flags);
>  
> -vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write);
> -vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write);
>  vm_fault_t dax_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write);
>  vm_fault_t dax_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write);

There's a plan to support huge pfnmaps in VFIO, which may still make good
use of these functions.  I think it's fine to remove them but it may mean
we'll need to add them back when supporting pfnmaps with no memmap.

Is it still possible to make the old API generic to both service the new
dax refcount plan, but at the meantime working for pfn injections when
there's no page struct?

Thanks,

-- 
Peter Xu