On 2014-11-17 07:59, Brendan Hide wrote: > > That leaves two aspects of this issue which I view as two separate bugs: > a) Btrfs cannot gracefully handle separate filesystems that have the same > UUID. At all. > b) Grub appears to pick the wrong filesystem when presented with two > filesystems with the same UUID. > > I feel a) is a btrfs bug. > I feel b) is a bug that is more about "ecosystem design" than grub being > silly.
Regarding a) IIRC, btrfs collects the filesystem information by UUID; if two filesystems have the same UUID (like the LVM-snapshot case), the last filesystem discovered overwrite the first one. The filesystem discovering is done in user-space; so it should be simple to skip a filesystem on a LVM-snapshot. Regarding b) I am bit confused: if I understood correctly, the root filesystem was picked from a LVM-snapshot, so grub-probe *correctly* reported that the root device is the snapshot. The problem was that during the boot filesystem discovering: first scanned the *real* device, then the LVM-snapshot; the latter overwrote the former so the system booted from the LVM-snapshot. My conclusion is that we should improve the btrfs scan so: - in udev rules, a partition that is a LVM snapshot by default should be not scanned by "btrfs dev scan" - "btrfs dev scan", during the partition discovery should skip the lvm-snapshot. BR G.Baroncelli -- gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
