On May 14, 2026 12:51:59 PM PDT, Goffredo Baroncelli <[email protected]> wrote: >On 13/05/2026 07.47, Christoph Hellwig wrote: >> On Tue, May 12, 2026 at 01:42:31PM +0200, David Sterba wrote: > >> >>> The degenerate modes of >>> raid0, 5, or 6 are explicit as a possible middle step when converting >>> profiles. We can use a fallback implementation for this case if the >>> accelerated implementations cannot do it. >> >> This is not about a degenerated mode. For a degenerated RAID 6, parity >> generation uses the RAID 5 XOR routines as the second parity will be >> missing. This is about generating two parities for a single data disk, >> which must be explicitly selected. >> > >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)... > >BR >GB >
That's what I'm saying – it should invoke the RAID-1 code under the cover (as with 3 disks, D = P = Q.)
