Re: [RFC] mm: fix a BUG, the page is allocated 2 times

From: yalin wang
Date: Mon Oct 12 2015 - 03:59:03 EST



> On Oct 12, 2015, at 15:38, Vlastimil Babka <vbabka@xxxxxxx> wrote:
>
> On 10/12/2015 04:40 AM, yalin wang wrote:
>> Remove unlikely(order), because we are sure order is not zero if
>> code reach here, also add if (page == NULL), only allocate page again if
>> __rmqueue_smallest() failed or alloc_flags & ALLOC_HARDER == 0
>
> The second mentioned change is actually more important as it removes a memory leak! Thanks for catching this. The problem is in patch mm-page_alloc-reserve-pageblocks-for-high-order-atomic-allocations-on-demand.patch and seems to have been due to a change in the last submitted version to make sure the tracepoint is called.
>
>> Signed-off-by: yalin wang <yalin.wang2010@xxxxxxxxx>
>> ---
>> mm/page_alloc.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 0d6f540..de82e2c 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2241,13 +2241,13 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
>> spin_lock_irqsave(&zone->lock, flags);
>>
>> page = NULL;
>> - if (unlikely(order) && (alloc_flags & ALLOC_HARDER)) {
>> + if (alloc_flags & ALLOC_HARDER) {
>> page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
>> if (page)
>> trace_mm_page_alloc_zone_locked(page, order, migratetype);
>> }
>> -
>> - page = __rmqueue(zone, order, migratetype, gfp_flags);
>> + if (page == NULL)
>
> "if (!page)" is more common and already used below.
> We could skip the check for !page in case we don't go through the ALLOC_HARDER branch, but I guess it's not worth the goto, and hopefully the compiler is smart enough anywayâ
agree with your comments,
do i need send a new patch for this ?

Thanks

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