Re: [Xen-devel] [PATCH] xen/gntdev: fix up blockable calls to mn_invl_range_start

[Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>]

On 2018/08/23 22:51, Michal Hocko wrote:
> You are right. I completely forgot I've removed in_range there. Does
> this look any better?
> 
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index e7d8bb1bee2a..30f81004ea63 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -525,14 +525,20 @@ static int mn_invl_range_start(struct mmu_notifier *mn,
>               return -EAGAIN;
>  
>       list_for_each_entry(map, &priv->maps, next) {
> -             if (!blockable && in_range(map, start, end)) {
> +             if (in_range(map, start, end)) {
> +                     if (blockable)
> +                             continue;
> +
>                       ret = -EAGAIN;
>                       goto out_unlock;
>               }

This still looks strange. in_range() returns false if map->vma == NULL.
But unmap_if_in_range() unconditionally dereferences map->vma->vm_[start|end] .
Suggestion from Boris looks better.

>               unmap_if_in_range(map, start, end);
>       }
>       list_for_each_entry(map, &priv->freeable_maps, next) {
> -             if (!blockable && in_range(map, start, end)) {
> +             if (in_range(map, start, end)) {
> +                     if (blockable)
> +                             continue;
> +                     
>                       ret = -EAGAIN;
>                       goto out_unlock;
>               }
> 


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