Re: [PATCH] mm/sparse: simplify the vmemmap alignment check

[Kaitao Cheng]

在 2026/10/29 00:08, Mike Rapoport 写道:
> Hi,
> 
> On Wed, Oct 28, 2026 at 08:11:29PM +0800, Kaitao Cheng wrote:
>> From: Kaitao Cheng <chengkaitao@xxxxxxxxxx>
>>
>> sparse_init() is called only once during boot, and the vmemmap alignment
>> check is outside any loop, so VM_WARN_ON_ONCE() provides no benefit over
>> VM_WARN_ON() here.
>>
>> Use VM_WARN_ON() and fold compound_info_has_mask() into its condition,
>> preserving short-circuit evaluation.
> 
> Do you think it's worth the churn?

I think saving two lines of code is nice. It also eliminates a variable,
even if only in debug kernels.

I’ll send a v2 following Muchun’s suggestion. If the consensus is that
this change isn’t worth merging, please feel free to ignore this email.

>> Signed-off-by: Kaitao Cheng <chengkaitao@xxxxxxxxxx>
>> ---
>>  mm/sparse.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 6acb628c8a73..248bee2d39b9 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -277,10 +277,8 @@ static void __init sparse_metadata_init(void)
>>   */
>>  void __init sparse_init(void)
>>  {
>> -	if (compound_info_has_mask()) {
>> -		VM_WARN_ON_ONCE(!IS_ALIGNED((unsigned long) pfn_to_page(0),
>> -				    MAX_FOLIO_VMEMMAP_ALIGN));
>> -	}
>> +	VM_WARN_ON(compound_info_has_mask() && !IS_ALIGNED(
>> +		   (unsigned long)pfn_to_page(0), MAX_FOLIO_VMEMMAP_ALIGN));
>>  
>>  	sparse_metadata_init();
>>  	sparse_init_subsection_map();
>> -- 
>> 2.53.0
>>
> 

-- 
Thanks
Kaitao Cheng