Re: [PATCH 4/5] block/bdev: enable large folio support for large logical block sizes

[Hannes Reinecke <hare@suse.de>]

On 5/11/24 00:35, Matthew Wilcox wrote:
> On Fri, May 10, 2024 at 12:29:05PM +0200, hare@kernel.org wrote:
>> From: Hannes Reinecke <hare@suse.de>
>>
>> Call mapping_set_folio_min_order() when modifying the logical block
>> size to ensure folios are allocated with the correct size.
> 
> This makes me nervous.  It lets the pagecache allocate folios larger
> than min_order (all the way up to PMD_ORDER).  Filesystems may not
> cope well with seeing tail pages.
> 
> I'd _like_ to be able to do this.  But I think for now we need to
> call mapping_set_folio_order_range(mapping, order, order);
> 
(Misrouted reply to the previous mail; airports make me jumpy ...)

The whole point is that these devices cannot support smaller 
allocations. We might restrict ourselves to min_order == max_order,
but we should be focussing on getting min_order working first ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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