Re: [PATCH v2 1/3] mm/hmm: make full use of walk_page_range()

[Jason Gunthorpe <jgg@mellanox.com>]

On Tue, Oct 15, 2019 at 01:48:12PM -0700, Ralph Campbell wrote:

> +static bool hmm_range_needs_fault(unsigned long addr, unsigned long end,
> +				  const struct hmm_vma_walk *hmm_vma_walk)

This has a very similar name to hmm_range_need_fault(), and seems like
it does the same thing?

> +static int hmm_vma_walk_test(unsigned long start, unsigned long end,
> +			     struct mm_walk *walk)
> +{
> +	struct hmm_vma_walk *hmm_vma_walk = walk->private;
> +	struct hmm_range *range = hmm_vma_walk->range;
> +	struct vm_area_struct *vma = walk->vma;
> +
> +	/* If range is no longer valid, force retry. */
> +	if (!range->valid)
> +		return -EBUSY;
> +
> +	/*
> +	 * Skip vma ranges that don't have struct page backing them or
> +	 * map I/O devices directly.
> +	 */
> +	if (vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP))
> +		return -EFAULT;
> +
> +	/*
> +	 * If the vma does not allow read access, then assume that it does not
> +	 * allow write access either. HMM does not support architectures
> +	 * that allow write without read.
> +	 */
> +	if (!(vma->vm_flags & VM_READ)) {
> +		/*
> +		 * Check to see if a fault is requested for any page in the
> +		 * range.
> +		 */
> +		if (hmm_range_needs_fault(start, end, hmm_vma_walk))
> +			return -EFAULT;

Is this change to call hmm_range_needs_fault another bug fix?

Jason