[PATCH 01/19] btrfs: require at least 4 devices for RAID 6

[Qu Wenruo]

在 2026/5/18 14:42, Christoph Hellwig 写道:
> On Fri, May 15, 2026 at 12:59:34PM -0700, H. Peter Anvin wrote:
>> I don't think this is a good idea. Error out; it is the btrfs maintainers' job to ensure user data isn't lost.
>>
>> The RAID-6 code has *never* supported only 3 units, and if it ever worked for *any* of the implementations it was purely by accident. Speaking as the original author I should know; this was deliberate as in some cases the degenerate case (3) would have required extra trays in the code to no user benefit.
>>
>> I would not be surprised if the kernel crashed or corrupted the page cache in that case.
> 
> It does, that's why I wanted to exclude it.  Anyway, for the about to be
> resent version I'll drop this btrfs patch over the stated objection and
> will otherwise not change anything.  This means the (IMHO hypothetical)
> users of this configuration will get a WARN_ON_ONCE triggered, but
> otherwise keep working (or rather not working) as before.
> 

For the btrfs part, I believe I can get the current 2-disk-raid5 and 
3-disk-raid6 to fallback to raid1 inside btrfs.

I hope the btrfs part can be finished and reach the next merge window, 
but I'm not 100% sure.

What is the planned cycle to merge this raid5/6 cleanup?

Thanks,
Qu