Re: [PATCH] iomap: use largest_zero_folio() in iomap_dio_zero()

[Pankaj Raghav <p.raghav@samsung.com>]

On 18/08/2025 16:12, André Almeida wrote:
> Em 18/08/2025 01:41, Christoph Hellwig escreveu:
>> On Fri, Aug 15, 2025 at 04:02:58PM +0200, Christian Brauner wrote:
>>> On Thu, 14 Aug 2025 16:21:37 +0200, Pankaj Raghav (Samsung) wrote:
>>>> iomap_dio_zero() uses a custom allocated memory of zeroes for padding
>>>> zeroes. This was a temporary solution until there was a way to 
>>>> request a
>>>> zero folio that was greater than the PAGE_SIZE.
>>>>
>>>> Use largest_zero_folio() function instead of using the custom allocated
>>>> memory of zeroes. There is no guarantee from largest_zero_folio()
>>>> function that it will always return a PMD sized folio. Adapt the 
>>>> code so
>>>> that it can also work if largest_zero_folio() returns a ZERO_PAGE.
>>>>
>>>> [...]
>>>
>>> Applied to the vfs-6.18.iomap branch of the vfs/vfs.git tree.
>>> Patches in the vfs-6.18.iomap branch should appear in linux-next soon.
>>
>> Hmm, AFAIK largest_zero_folio just showed up in mm.git a few days ago.
>> Wouldn't it be better to queue up this change there?
>>
>>
> 
> Indeed, compiling vfs/vfs.all as of today fails with:
> 
> fs/iomap/direct-io.c:281:36: error: implicit declaration of function 
> ‘largest_zero_folio’; did you mean ‘is_zero_folio’? [-Wimplicit- 
> function-declaration]
> 
> Reverting "iomap: use largest_zero_folio() in iomap_dio_zero()" fixes 
> the compilation.
> 

I also got some reports from Stephen in linux-next. As Christoph 
suggested, maybe we drop the patches from Christian's tree and queue it 
up via Andrew's tree

--
Pankaj