Re: [PATCH v3 3/9] mm: move anon-exclusive batch helper to rmap.h

[Dev Jain]

On 25/09/26 2:32 am, Barry Song wrote:
> On Thu, Sep 24, 2026 at 9:11 PM Dev Jain <dev.jain@xxxxxxx> wrote:
>>
>> In preparation for optimizing large folio unmapping, we need to reuse
>> the page_anon_exclusive_batch helper in rmap.c and rmap.h and obey the
>> existing use in mprotect.c .
>>
>> Therefore, move it from mprotect.c to rmap.h.
>>
>> While at it, change return type, start_idx and max_len to unsigned long
>> type for future proofing against THP support at >= PUD level. Also
>> shorten expected_anon_exclusive -> anon_exclusive.
> 
> I really think the `expected` prefix makes the semantics clearer, so I
> don't think it's necessary to remove it.
> 
> If you really find it too long, maybe just use
> `expected_exclusive`, since we're already in the anon context and
> know that it is definitely anon.
> 
> Another option might be to make `*exclusive` an output parameter.
> Then we wouldn't need to call
> `expected_anon_exclusive = PageAnonExclusive(first_page + batch_idx);`
> in the caller.

Ah nice! This looks much cleaner, thanks.


> 
>  static __always_inline unsigned long
> page_anon_exclusive_batch(unsigned long start_idx,
>                 unsigned long max_len, struct page *first_page, bool *exclusive)
> 
>>
>> Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
> 
> Otherwise, the patch looks good to me.
> 
> Reviewed-by: Barry Song <baohua@xxxxxxxxxx>

Thanks.

> 
>> ---
>>  include/linux/rmap.h | 17 +++++++++++++++++
>>  mm/mprotect.c        | 18 +-----------------
>>  2 files changed, 18 insertions(+), 17 deletions(-)
>>
>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
>> index 74cca0e3c7264..62ef511a6175a 100644
>> --- a/include/linux/rmap.h
>> +++ b/include/linux/rmap.h
>> @@ -106,6 +106,23 @@ enum ttu_flags {
>>
>>  #ifdef CONFIG_MMU
>>
>> +/*
>> + * Get max length of consecutive PTEs pointing to PageAnonExclusive() pages or
>> + * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce
>> + * that the PTEs point to consecutive pages of the same anon large folio.
>> + */
>> +static __always_inline unsigned long page_anon_exclusive_batch(unsigned long start_idx,
>> +               unsigned long max_len, struct page *first_page, bool anon_exclusive)
>> +{
>> +       unsigned long idx;
>> +
>> +       for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) {
>> +               if (anon_exclusive != PageAnonExclusive(first_page + idx))
>> +                       break;
>> +       }
>> +       return idx - start_idx;
>> +}
>> +
> 
> Thanks
> Barry