Re: [PATCH v2 1/2] mm: introduce memalloc_flags_move() for transferring allocation scopes

On 7/20/26 04:57, Andrew Morton wrote:
> On Sun, 19 Jul 2026 17:57:31 +0800 Yun Zhou <[email protected]> wrote:
> 
>> Add memalloc_flags_move() to transfer a saved memalloc scope from one
>> tracking variable to another.  The source is zeroed so that a
>> subsequent memalloc_flags_restore() on it becomes a no-op, effectively
>> transferring ownership of the scope to the destination.
>>
>> This is needed when a subsystem hands off an allocation context from
>> one structure to another (e.g. during transaction rolling in
>> filesystems), and needs to ensure the scope remains active without an
>> extra save/restore cycle.
>>
>> ...
>>
> 
> Thanks.  fyi, Sashiko might have found a pre-existing xfs issue:
>          https://sashiko.dev/#/patchset/[email protected]
> 

Good catch. This is indeed a pre-existing issue, and needs a separate fix.

>>   include/linux/sched/mm.h | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
> 
> This file isn't mentioned in MAINTAINERS.  Could someone please propose
> a patch?
> 
>  From the MM side, probably just place it in every record which mentions
> include/linux/mm.h - close enough.
> 
>> --- a/include/linux/sched/mm.h
>> +++ b/include/linux/sched/mm.h
>> @@ -342,6 +342,23 @@ static inline void memalloc_flags_restore(unsigned flags)
>>        current->flags &= ~flags;
>>   }
>>
>> +/**
>> + * memalloc_flags_move - transfer a memalloc scope from one tracking
>> + * variable to another.
>> + * @old_flags: pointer to the source flags (will be zeroed)
>> + *
>> + * Returns the flags value to store in the destination.  The source is
>> + * set to zero so that a subsequent memalloc_flags_restore() on it is
>> + * a no-op.
>> + */
>> +static inline unsigned int memalloc_flags_move(unsigned int *old_flags)
>> +{
>> +     unsigned int ret = *old_flags;
>> +
>> +     *old_flags = 0;
>> +     return ret;
>> +}
>> +
> 
> I've added linux-mm to cc here.  Please include it in any future
> versions of this patchset.
> 

Well, got it.

Thanks,
Yun