On Mon, Jun 19 2017, Vlastimil Babka <vbabka@xxxxxxx> wrote:
> On 06/19/2017 03:54 PM, Hao Lee wrote:
>> The variable current_order decreases from MAX_ORDER-1 to order, so the
>> condition current_order <= MAX_ORDER-1 is always true.
>>
>> Signed-off-by: Hao Lee <haolee.swjtu@xxxxxxxxx>
>
> Sounds right.
>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
current_order and order are both unsigned, and if order==0,
current_order >= order is always true, and we may decrement
current_order past 0 making it UINT_MAX... A comment would be in order,
though.
>> ---
>> mm/page_alloc.c | 5 ++---
>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 2302f25..9120c2b 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2215,9 +2215,8 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
>> bool can_steal;
>>
>> /* Find the largest possible block of pages in the other list */
>> - for (current_order = MAX_ORDER-1;
>> - current_order >= order && current_order <= MAX_ORDER-1;
>> - --current_order) {
>> + for (current_order = MAX_ORDER-1; current_order >= order;
>> + --current_order) {
>> area = &(zone->free_area[current_order]);
>> fallback_mt = find_suitable_fallback(area, current_order,
>> start_migratetype, false, &can_steal);
>>
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