[PATCH 1/4] mm: introduce vma_set_file function v2

[Matthew Wilcox]

On Thu, Oct 08, 2020 at 01:23:39PM +0200, Christian König wrote:
>  drivers/dma-buf/dma-buf.c                  | 16 +++++-----------
>  drivers/gpu/drm/etnaviv/etnaviv_gem.c      |  4 +---
>  drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c |  3 +--
>  drivers/gpu/drm/i915/gem/i915_gem_mman.c   |  4 ++--
>  drivers/gpu/drm/msm/msm_gem.c              |  4 +---
>  drivers/gpu/drm/omapdrm/omap_gem.c         |  3 +--
>  drivers/gpu/drm/vgem/vgem_drv.c            |  3 +--
>  drivers/staging/android/ashmem.c           |  5 ++---
...
> +++ b/mm/mmap.c
> @@ -136,6 +136,22 @@ void vma_set_page_prot(struct vm_area_struct *vma)
>  	WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
>  }
>  
> +/*
> + * Change backing file, only valid to use during initial VMA setup.
> + */
> +struct file *vma_set_file(struct vm_area_struct *vma, struct file *file)
> +{
> +	if (file)
> +	        get_file(file);
> +
> +	swap(vma->vm_file, file);
> +
> +	if (file)
> +		fput(file);
> +
> +	return file;
> +}
> +

These users are all potentially modules.  You need an EXPORT_SYMBOL()?