Re: [PATCH v2 2/3] xen/heap: Split init_heap_pages() in two

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.07.2022 12:08, Julien Grall wrote:
> On 18/07/2022 10:31, Jan Beulich wrote:
>> On 15.07.2022 19:03, Julien Grall wrote:
>>> --- a/xen/common/page_alloc.c
>>> +++ b/xen/common/page_alloc.c
>>> @@ -1778,16 +1778,44 @@ int query_page_offline(mfn_t mfn, uint32_t *status)
>>>   }
>>>   
>>>   /*
>>> - * Hand the specified arbitrary page range to the specified heap zone
>>> - * checking the node_id of the previous page.  If they differ and the
>>> - * latter is not on a MAX_ORDER boundary, then we reserve the page by
>>> - * not freeing it to the buddy allocator.
>>> + * This function should only be called with valid pages from the same NUMA
>>> + * node.
>>>    */
>>> +static void _init_heap_pages(const struct page_info *pg,
>>> +                             unsigned long nr_pages,
>>> +                             bool need_scrub)
>>> +{
>>> +    unsigned long s, e;
>>> +    unsigned int nid = phys_to_nid(page_to_maddr(pg));
>>> +
>>> +    s = mfn_x(page_to_mfn(pg));
>>> +    e = mfn_x(mfn_add(page_to_mfn(pg + nr_pages - 1), 1));
>>> +    if ( unlikely(!avail[nid]) )
>>> +    {
>>> +        bool use_tail = IS_ALIGNED(s, 1UL << MAX_ORDER) &&
>>> +                        (find_first_set_bit(e) <= find_first_set_bit(s));
>>> +        unsigned long n;
>>> +
>>> +        n = init_node_heap(nid, s, nr_pages, &use_tail);
>>> +        BUG_ON(n > nr_pages);
>>> +        if ( use_tail )
>>> +            e -= n;
>>> +        else
>>> +            s += n;
>>> +    }
>>> +
>>> +    while ( s < e )
>>> +    {
>>> +        free_heap_pages(mfn_to_page(_mfn(s)), 0, need_scrub);
>>> +        s += 1UL;
>>
>> ... the more conventional s++ or ++s used here?
> 
> I would prefer to keep using "s += 1UL" here because:
>    * it will be replace with a proper order in the follow-up patch. So 
> this is temporary.

Fair enough.

Jan

>    * one could argue that if I use "s++" then I should also switch to a 
> for loop which would make sense here but not in the next patch.
> 
> Cheers,
>