linux-kernel - Re: [PATCH 1/3] mm: Introduce vmf_insert_pfn

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Date:   Thu, 26 Jul 2018 17:04:44 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        linux-kernel@...r.kernel.org,
        Brajeswar Ghosh <brajeswar.linux@...il.com>,
        Sabyasachi Gupta <sabyasachi.linux@...il.com>
Subject: Re: [PATCH 1/3] mm: Introduce vmf_insert_pfn_prot

On Tue, Jul 3, 2018 at 6:09 PM, Matthew Wilcox <willy@...radead.org> wrote:
> Like vm_insert_pfn_prot(), but returns a vm_fault_t instead of an errno.
> Also unexport vm_insert_pfn_prot as it has no modular users.
>
> Signed-off-by: Matthew Wilcox <willy@...radead.org>
> ---

Any comment on this patch ?

>  include/linux/mm.h |  2 ++
>  mm/memory.c        | 47 ++++++++++++++++++++++++++++++----------------
>  2 files changed, 33 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 1a9d6bd97f00..3cb763a38642 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2441,6 +2441,8 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>                         unsigned long pfn);
>  int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
>                         unsigned long pfn, pgprot_t pgprot);
> +vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
> +                       unsigned long pfn, pgprot_t pgprot);
>  int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
>                         pfn_t pfn);
>  vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
> diff --git a/mm/memory.c b/mm/memory.c
> index b9ebd883e27c..caecb4d995ac 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1852,21 +1852,6 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>  }
>  EXPORT_SYMBOL(vm_insert_pfn);
>
> -/**
> - * vm_insert_pfn_prot - insert single pfn into user vma with specified pgprot
> - * @vma: user vma to map to
> - * @addr: target user address of this page
> - * @pfn: source kernel pfn
> - * @pgprot: pgprot flags for the inserted page
> - *
> - * This is exactly like vm_insert_pfn, except that it allows drivers to
> - * to override pgprot on a per-page basis.
> - *
> - * This only makes sense for IO mappings, and it makes no sense for
> - * cow mappings.  In general, using multiple vmas is preferable;
> - * vm_insert_pfn_prot should only be used if using multiple VMAs is
> - * impractical.
> - */
>  int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
>                         unsigned long pfn, pgprot_t pgprot)
>  {
> @@ -1893,7 +1878,37 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
>
>         return ret;
>  }
> -EXPORT_SYMBOL(vm_insert_pfn_prot);
> +
> +/**
> + * vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot
> + * @vma: user vma to map to
> + * @addr: target user address of this page
> + * @pfn: source kernel pfn
> + * @pgprot: pgprot flags for the inserted page
> + *
> + * This is exactly like vmf_insert_pfn(), except that it allows drivers to
> + * to override pgprot on a per-page basis.
> + *
> + * This only makes sense for IO mappings, and it makes no sense for
> + * COW mappings.  In general, using multiple vmas is preferable;
> + * vm_insert_pfn_prot should only be used if using multiple VMAs is
> + * impractical.
> + *
> + * Return: vm_fault_t value.
> + */
> +vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
> +                       unsigned long pfn, pgprot_t pgprot)
> +{
> +       int err = vm_insert_pfn_prot(vma, addr, pfn, pgprot);
> +
> +       if (err == -ENOMEM)
> +               return VM_FAULT_OOM;
> +       if (err < 0 && err != -EBUSY)
> +               return VM_FAULT_SIGBUS;
> +
> +       return VM_FAULT_NOPAGE;
> +}
> +EXPORT_SYMBOL(vmf_insert_pfn_prot);
>
>  static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
>  {
> --
> 2.18.0
>