Re: [PATCH v2 6/6] mm: Handle write faults to RO pages under the VMA lock

[Suren Baghdasaryan <surenb@google.com>]

On Fri, Oct 6, 2023 at 12:53 PM Matthew Wilcox (Oracle)
<willy@infradead.org> wrote:
>
> I think this is a pretty rare occurrence, but for consistency handle
> faults with the VMA lock held the same way that we handle other
> faults with the VMA lock held.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Reviewed-by: Suren Baghdasaryan <surenb@google.com>

> ---
>  mm/memory.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e615afd28db2..3d1bc622e344 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3301,10 +3301,9 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
>                 vm_fault_t ret;
>
>                 pte_unmap_unlock(vmf->pte, vmf->ptl);
> -               if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
> -                       vma_end_read(vmf->vma);
> -                       return VM_FAULT_RETRY;
> -               }
> +               ret = vmf_can_call_fault(vmf);
> +               if (ret)
> +                       return ret;
>
>                 vmf->flags |= FAULT_FLAG_MKWRITE;
>                 ret = vma->vm_ops->pfn_mkwrite(vmf);
> @@ -3328,10 +3327,10 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf, struct folio *folio)
>                 vm_fault_t tmp;
>
>                 pte_unmap_unlock(vmf->pte, vmf->ptl);
> -               if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
> +               tmp = vmf_can_call_fault(vmf);
> +               if (tmp) {
>                         folio_put(folio);
> -                       vma_end_read(vmf->vma);
> -                       return VM_FAULT_RETRY;
> +                       return tmp;
>                 }
>
>                 tmp = do_page_mkwrite(vmf, folio);
> --
> 2.40.1
>