On Mon, 2025-09-01 at 14:54 +0100, "Roy, Patrick" wrote:
>
> Hi Fuad!
>
> On Thu, 2025-08-28 at 11:21 +0100, Fuad Tabba wrote:
>> Hi Patrick,
>>
>> On Thu, 28 Aug 2025 at 10:39, Roy, Patrick <roypat@xxxxxxxxxxxx> wrote:
>>> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
>>> index 12a12dae727d..b52b28ae4636 100644
>>> --- a/include/linux/pagemap.h
>>> +++ b/include/linux/pagemap.h
>>> @@ -211,6 +211,7 @@ enum mapping_flags {
>>> folio contents */
>>> AS_INACCESSIBLE = 8, /* Do not attempt direct R/W access to the mapping */
>>> AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
>>> + AS_NO_DIRECT_MAP = 10, /* Folios in the mapping are not in the direct map */
>>> /* Bits 16-25 are used for FOLIO_ORDER */
>>> AS_FOLIO_ORDER_BITS = 5,
>>> AS_FOLIO_ORDER_MIN = 16,
>>> @@ -346,6 +347,21 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(struct address_spac
>>> return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
>>> }
>>>
>>> +static inline void mapping_set_no_direct_map(struct address_space *mapping)
>>> +{
>>> + set_bit(AS_NO_DIRECT_MAP, &mapping->flags);
>>> +}
>>> +
>>> +static inline bool mapping_no_direct_map(struct address_space *mapping)
>>> +{
>>> + return test_bit(AS_NO_DIRECT_MAP, &mapping->flags);
>>> +}
>>> +
>>> +static inline bool vma_is_no_direct_map(const struct vm_area_struct *vma)
>>> +{
>>> + return vma->vm_file && mapping_no_direct_map(vma->vm_file->f_mapping);
>>> +}
>>> +
>> Any reason vma is const whereas mapping in the function that it calls
>> (defined above it) isn't?
>
> Ah, I cannot say that that was a conscious decision, but rather an artifact of
> the code that I looked at for reference when writing these two simply did it
> this way. Are you saying both should be const, or neither (in my mind, both
> could be const, but the mapping_*() family of functions further up in this file
> dont take const arguments, so I'm a bit unsure now)?
Hah, just saw
https://lore.kernel.org/linux-mm/20250901123028.3383461-3-max.kellermann@xxxxxxxxx/.
Guess that means "both should be const" then :D
>> Cheers,
>> /fuad
>
> Best,
> Patrick
