Re: [PATCH 1/6] mm/page_owner: extract skip_buddy_pages() helper to unify buddy page skipping

[Ye Liu <ye.liu@linux.dev>]

在 2026/6/25 15:13, Vlastimil Babka (SUSE) 写道:
> On 6/25/26 02:20, Andrew Morton wrote:
>> On Tue, 23 Jun 2026 14:52:26 +0800 Ye Liu <ye.liu@linux.dev> wrote:
>>
>>> Three places in page_owner.c duplicate the same pattern: check if a
>>> page is PageBuddy, read its order via buddy_order_unsafe(), advance
>>> the pfn past the buddy block if the order is valid, and continue.
>>>
>>> Consolidate them into a single inline helper skip_buddy_pages().
>>> The function returns true (skip) for any buddy page and advances
>>> @pfn past the block when the order is valid; returns false if the
>>> page is not a buddy page and should be processed normally.
>>>
>>> The old init_pages_in_zone() variant used "order > 0" as an extra
>>> guard before advancing pfn, but the continue was unconditional and
>>> (1UL << 0) - 1 == 0, so the behaviour is identical.  The comment
>>> about zone->lock is preserved in the helper's kernel-doc.
>>
>> All looks nice, thanks.
> 
> I got a bunch of "added to mm-hotfixes-unstable branch" mails, but this
> seems like cleanups and nothing urgent? Was that intended?
> 
>> A [0/N] cover letter is nice to have.
> 
> Seems like it exists, but wasn't delivered. Lore shows its message id, but
> as missing.


Apologies, I accidentally sent the cover letter only to my own address.
I'll ensure it goes to the mailing list in future submissions.         
Thanks for pointing it out.                                            


Subject: [PATCH 0/6] mm/page_owner: misc cleanups                      
                                                                       
Hi,                                                                    
                                                                       
This series collects a few cleanups for mm/page_owner.c that have been 
accumulated while reading through the file.  There is no functional    
change -- the goal is to make the code easier to read and maintain.    
                                                                       
Patch 1 consolidates three identical PageBuddy skip blocks into a      
single skip_buddy_pages() helper, eliminating the duplication and      
keeping the lockless-read comment in one place.                        
                                                                       
Patch 2 replaces the -1 magic number used for "never migrated" with    
a local MIGRATE_REASON_NONE define, making the intent explicit at      
every use site.                                                        
                                                                       
Patch 3 hoists the CONFIG_MEMCG guard out of print_page_owner_memcg()'s
body so that the real implementation and the empty stub are two clearly
separate definitions, the common kernel idiom.                         
                                                                       
Patch 4 adds a missing \n to the count_threshold debugfs attribute     
format string so that cat(1) output is properly terminated.            
                                                                       
Patch 5 moves free_ts_nsec from the allocation summary line to the     
free section in __dump_page_owner(), grouping it with free_pid and     
free_tgid where it logically belongs.  This also makes the dump        
output consistent with print_page_owner().                             
                                                                       
Patch 6 drops the redundant page_owner_ prefix from file-scoped static 
symbols (stack_fops, threshold_fops, etc.).  Since they cannot collide 
across translation units, the prefix carries no information.           
                                                                       
The series is based on v6.17-rc1 and has been compile-tested with and  
without CONFIG_MEMCG.                                                  
                                                                       
Ye Liu (6):                                                            
  mm/page_owner: extract skip_buddy_pages() helper to unify buddy page 
    skipping                                                           
  mm/page_owner: use MIGRATE_REASON_NONE instead of -1 for             
    last_migrate_reason                                                
  mm/page_owner: hoist CONFIG_MEMCG to function level for              
    print_page_owner_memcg()                                           
  mm/page_owner: add missing newline to count_threshold format string  
  mm/page_owner: move free_ts_nsec output to free section in           
    __dump_page_owner()                                                
  mm/page_owner: drop redundant page_owner prefix from static symbols  
                                                                       
 mm/page_owner.c | 121 +++++++++++++++++++++++++++---------------------
 1 file changed, 67 insertions(+), 54 deletions(-)                     


> 
>> AI review identified a few possible pre-existing issues, if you're
>> interested:
>> 	https://sashiko.dev/#/patchset/20260623065234.31866-2-ye.liu@linux.dev
>>
> 

-- 
Thanks,
Ye Liu