Re: [PATCH v2 1/4] btrfs: drop 2K block size support

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2026/3/4 14:18, David Sterba 写道:
> On Fri, Feb 27, 2026 at 02:03:43PM +1030, Qu Wenruo wrote:
>> Commit 306a75e647fe ("btrfs: allow debug builds to accept 2K block
>> size") added a new block size, 2K as the minimal block size if the
>> kernel is built with CONFIG_BTRFS_DEBUG.
>>
>> This is to allow testing subpage routines on x86_64 (page size is fixed
>> at 4K).
>>
>> But it turns out that the support is not that widely adopted, and there
>> are extra limits inside btrfs-progs, e.g. 2K node size is not supported.
>>
>> Finally with the larger data folio support already in experimental
>> builds for a while, it's very easy to trigger a large folio and testing
>> subpage routines by just doing a 64K block sized buffered write.
>>
>> Let's just remove the seldom utilized 2K block size completely.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
> 
> Can we keep it? It's under debug and not interfering with anything but
> it can trigger different set of bugs than with the large folios.
> 

Although we can, I'd say the subpage bugs will be no different between 
using large folios and real subpage cases.

I just do not want a special case hanging there without many users.

Thanks,
Qu