Re: [PATCH] btrfs: add a debug accounting for eb pages contiguousness

[Qu Wenruo <wqu@suse.com>]

On 2023/7/10 13:28, Christoph Hellwig wrote:
> On Sun, Jul 09, 2023 at 12:44:33PM +0800, Qu Wenruo wrote:
>> Unfortunately __filemap_get_folio() is still only creating folios using
>> order 0, under the no_page tag:
>>
>> 	folio = filemap_alloc_folio(gfp, 0);
>>
>> So in that case, it's really no difference than find_or_create_page()
>> for new pages/folios.
> 
> You're right, willys patches to pass the order haven't actually
> made it to mainline yet, and I assumed they did.  So you'll have
> to wait another merge window.

I'm considering another solution like this:

	folio = filemap_alloc_folio();
	do_something_with_folio();
	ret = filemap_add_folio();

Which is not that complex and pretty much used everywhere in mm code.

Although I still need the old per-page allocation as a fallback, which 
may make it more complex than expected.

Thanks,
Qu