Re: [PATCH v1 05/10] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled()

[David Hildenbrand (Arm)]

On 3/30/26 18:19, Matthew Wilcox wrote:
> On Tue, Mar 31, 2026 at 12:09:42AM +0800, WANG Rui wrote:
>> Given the diversity of filesystems in use, each one requires dedicated
>> engineering effort to implement and validate large folio support, and
>> that assumes both sufficient resources and prioritization on the
>> filesystem side. Even after support lands, coverage across different
>> base page sizes and configurations may take additional time to mature.
>>
>> What I am really concerned about is the transition period: if filesystem
>> support is not yet broadly ready, while we have already removed the
>> fallback path, we may end up in a situation where PMD-sized mappings
>> become effectively unavailable on many systems for some time.
>>
>> This is not about the long-term direction, but about the timing and
>> practical readiness.
> 
> If we leave this fallback in place, we'll never get filesystems to move
> forward.  It's time to rip off this bandaid; they've got eight months
> before the next stable kernel.

I guess if we don't force them to work on it I guess this will never
happen. They shouldn't be holding our THP hacks we want to remove hostage.

-- 
Cheers,

David