linux-kernel - Re: [PATCH v3 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert

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Message-ID: <CAFqt6zY9JjGhedtmhYh-+mxSMrYs6P5vtQDMSzCfL02CbLys=g@mail.gmail.com>
Date:   Sun, 9 Dec 2018 01:31:40 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        robin.murphy@....com, iamjoonsoo.kim@....com, treding@...dia.com,
        Kees Cook <keescook@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, Linux-MM <linux-mm@...ck.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range

Hi Robin,

On Fri, Dec 7, 2018 at 12:07 AM Souptick Joarder <jrdr.linux@...il.com> wrote:
>
> Convert to use vm_insert_range() to map range of kernel
> memory to user vma.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> ---
>  arch/arm/mm/dma-mapping.c | 21 +++++++--------------
>  1 file changed, 7 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 661fe48..4eec323 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma
>                     void *cpu_addr, dma_addr_t dma_addr, size_t size,
>                     unsigned long attrs)
>  {
> -       unsigned long uaddr = vma->vm_start;
> -       unsigned long usize = vma->vm_end - vma->vm_start;
> +       unsigned long page_count = vma_pages(vma);
>         struct page **pages = __iommu_get_pages(cpu_addr, attrs);
>         unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>         unsigned long off = vma->vm_pgoff;
> +       int err;
>
>         if (!pages)
>                 return -ENXIO;
>
> -       if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
> +       if (off >= nr_pages || page_count > nr_pages - off)
>                 return -ENXIO;
>
>         pages += off;
> +       err = vm_insert_range(vma, vma->vm_start, pages, page_count);

Just to clarify, do we need to adjust page_count with vma->vm_pgoff as
original code
have not consider it and run the loop for entire range irrespective of
vma->vm_pgoff value ?

> +       if (err)
> +               pr_err("Remapping memory failed: %d\n", err);
>
> -       do {
> -               int ret = vm_insert_page(vma, uaddr, *pages++);
> -               if (ret) {
> -                       pr_err("Remapping memory failed: %d\n", ret);
> -                       return ret;
> -               }
> -               uaddr += PAGE_SIZE;
> -               usize -= PAGE_SIZE;
> -       } while (usize > 0);
> -
> -       return 0;
> +       return err;
>  }
>  static int arm_iommu_mmap_attrs(struct device *dev,
>                 struct vm_area_struct *vma, void *cpu_addr,
> --
> 1.9.1
>