Re: [PATCH v3 10/14] mm/page-flags: introduce folio_test_fs_private()

[Zi Yan]

On Tue Sep 8, 2026 at 12:59 PM EDT, David Hildenbrand (Arm) wrote:
> On 9/8/26 04:56, Zi Yan wrote:
>> folio_test_fs_private() wraps folio->private != NULL check and excludes
>> swapcache and hugetlb folios, since swapcache uses swp_entry_t overlapping
>> with folio->private and hugetlb sets its own flags in folio->private.
>> Replace open code with the helper, since core MM does this check
>> frequently.
>> 
>> No functional change intended.
>> 
>> Assisted-by: Claude:claude-opus-4-8
>> Assisted-by: Codex:gpt-5
>> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
>> To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> To: David Hildenbrand <david@xxxxxxxxxx>
>> To: Steven Rostedt <rostedt@xxxxxxxxxxx>
>> To: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
>> To: Lorenzo Stoakes <ljs@xxxxxxxxxx>
>> Cc: "Liam R. Howlett" <liam@xxxxxxxxxxxxx>
>> Cc: Vlastimil Babka <vbabka@xxxxxxxxxx>
>> Cc: Mike Rapoport <rppt@xxxxxxxxxx>
>> Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
>> Cc: Zi Yan <ziy@xxxxxxxxxx>
>> Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>> Cc: Nico Pache <nico.pache@xxxxxxxxx>
>> Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
>> Cc: Dev Jain <dev.jain@xxxxxxx>
>> Cc: Barry Song <baohua@xxxxxxxxxx>
>> Cc: Lance Yang <lance.yang@xxxxxxxxx>
>> Cc: Usama Arif <usama.arif@xxxxxxxxx>
>> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
>> Cc: Joshua Hahn <joshua.hahnjy@xxxxxxxxx>
>> Cc: Rakie Kim <rakie.kim@xxxxxx>
>> Cc: Byungchul Park <byungchul@xxxxxx>
>> Cc: Gregory Price <gourry@xxxxxxxxxx>
>> Cc: Ying Huang <ying.huang@xxxxxxxxxxxxxxxxx>
>> Cc: Alistair Popple <apopple@xxxxxxxxxx>
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
>> Cc: linux-mm@xxxxxxxxx
>> Cc: linux-trace-kernel@xxxxxxxxxxxxxxx
>> ---
>>  include/linux/mm.h             |  4 +---
>>  include/linux/page-flags.h     | 26 +++++++++++++++++++++++---
>>  include/trace/events/pagemap.h |  4 +---
>>  mm/huge_memory.c               |  4 +---
>>  mm/migrate.c                   |  3 +--
>>  mm/page-writeback.c            |  5 +----
>>  mm/vmscan.c                    |  3 +--
>>  7 files changed, 29 insertions(+), 20 deletions(-)
>> 
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 5eb8a62fafb56..c861525cda83f 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -3053,9 +3053,7 @@ static inline int folio_expected_ref_count(const struct folio *folio)
>>  		 * One reference from filesystem private data.
>>  		 * Use data_race() since folio might not be locked.
>>  		 */
>> -		ref_count += data_race(folio_test_private(folio)) &&
>> -			     !folio_test_hugetlb(folio) &&
>> -			     !folio_test_swapbacked(folio);
>> +		ref_count += data_race(folio_test_fs_private(folio));
>>  	}
>
> Lol :) That's what I meant with folio_has_attached_private()
>
> (I think I prefer that name as it matches folio_attach_private(), but I might be
> biased ;) )

I can rename it, since it sounds more generic than "fs private".
>
>
> This really should be sqashed into the previous patch, OR, have a prep patch
> that only replaces these instances and uses folio_test_private() until you
> convert it to folio->private in the second patch.
>
> In short: touch these call sites only once, not twice in a row.

Will squash it to the prior patch.

-- 
Best Regards,
Yan, Zi