Re: [PATCH 06/11] migrate: Remove call to ->writepage

[David Hildenbrand <david@redhat.com>]

On 27.03.25 18:22, Zi Yan wrote:
> On Thu Mar 27, 2025 at 12:52 PM EDT, Matthew Wilcox wrote:
>> On Thu, Mar 27, 2025 at 11:04:57AM -0400, Zi Yan wrote:
>>> On Fri Mar 7, 2025 at 8:54 AM EST, Matthew Wilcox (Oracle) wrote:
>>>> The writepage callback is going away; filesystems must implement
>>>> migrate_folio or else dirty folios will not be migratable.
>>>
>>> What is the impact of this? Are there any filesystem that has
>>> a_ops->writepage() without migrate_folio()? I wonder if it could make
>>> the un-migratable problem worse[1] when such FS exists.
>>
>> As Christoph and I have been going through filesystems removing their
>> ->writepage operations, we've been careful to add ->migrate_folio
>> callbacks at the same time.  But we haven't fixed any out-of-tree
>> filesystems, and we can't fix the filesystems which will be written in
>> the future.
>>
>> So maybe what we should do is WARN_ON_ONCE() for filesystems which
>> have a ->writepages, but do not have a ->migrate_folio()?
> 
> Sounds good to me.

Agreed, that will also make it clear what our expectation towards 
filesystems is.

-- 
Cheers,

David / dhildenb