On 15/05/2026 06.37, Christoph Hellwig wrote:
On Thu, May 14, 2026 at 09:51:59PM +0200, Goffredo Baroncelli wrote:
I think that the David concern is : "what happens for an already
existing btrfs raid6 3 disks filesystem when the user upgrade the kernel ?"
(I am thinking when a new BG needs to be allocated)...
Then it will cleanly fail to mount instead of constantly corrupting data
and memory with every write, yes. Which clearly suggest that such
file systems don't exist in the wild.
But if btrfs wants to keep supporting this I'll just add a _unsafe
version without the check in the core library.
I am not arguing about this part. My point is that the change shouldn't have
impacted the
BTRFS interface versus the user (as patch 01/19 does), but instead the change
should
have modify the interface raid code <-> btrfs (e.g. doing a memcpy....), or at
least the
cover letter should warn that the raid6 code requires a number of disk >= 4,
pointing
to BTRFS as "client doing wrong things".
At least, the message was received: don't relay to the raid6 code when the
number of disk is
less than 4.
BR
GB
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