Re: [PATCH 01/19] btrfs: require at least 4 devices for RAID 6
Goffredo Baroncelli <[email protected]>
| Newsgroups | gmane.linux.ports.riscv,gmane.linux.kernel,gmane.linux.ports.arm.kernel,gmane.linux.ports.ppc64.devel,gmane.linux.kernel.cryptoapi,gmane.comp.file-systems.btrfs,gmane.linux.kernel.cross-arch,gmane.linux.raid |
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| Message-ID | <[email protected]> |
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 -- gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5