Re: [Xen-devel] [PATCH v5 3/8] mm: Scrub pages in alloc_heap_pages() if needed

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> 06/22/17 8:55 PM >>>
> @@ -862,10 +879,19 @@ static struct page_info *alloc_heap_pages(
>      if ( d != NULL )
>          d->last_alloc_node = node;
>  
> +    need_scrub = !!first_dirty_pg && !(memflags & MEMF_no_scrub);

No need for !! here. But I wonder whether that part of the check is really
useful anyway, considering the sole use ...

>      for ( i = 0; i < (1 << order); i++ )
>      {
>          /* Reference count must continuously be zero for free pages. */
> -        BUG_ON(pg[i].count_info != PGC_state_free);
> +        BUG_ON((pg[i].count_info & ~PGC_need_scrub) != PGC_state_free);
> +
> +        if ( test_bit(_PGC_need_scrub, &pg[i].count_info) )
> +        {
> +            if ( need_scrub )
> +                scrub_one_page(&pg[i]);

... here. If it isn't, I think the local variable isn't warranted either.
If you agree, the thus adjusted patch can have
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
(otherwise I'll wait with it to understand the reason first).

Jan

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