[PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking

[Jerome Glisse]

On Fri, May 10, 2019 at 07:53:24PM +0000, Kuehling, Felix wrote:
> Don't set this flag by default in hmm_vma_do_fault. It is set
> conditionally just a few lines below. Setting it unconditionally
> can lead to handle_mm_fault doing a non-blocking fault, returning
> -EBUSY and unlocking mmap_sem unexpectedly.
> 
> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>

Reviewed-by: Jérôme Glisse <jglisse at redhat.com>

> ---
>  mm/hmm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index b65c27d5c119..3c4f1d62202f 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -339,7 +339,7 @@ struct hmm_vma_walk {
>  static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
>  			    bool write_fault, uint64_t *pfn)
>  {
> -	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
> +	unsigned int flags = FAULT_FLAG_REMOTE;
>  	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>  	struct hmm_range *range = hmm_vma_walk->range;
>  	struct vm_area_struct *vma = walk->vma;
> -- 
> 2.17.1
>