On 04/05/2023 16:28, Goffredo Baroncelli wrote: > [...] > Hi Guilherme, > > did you tried to run "btrfs dev scan --forget /dev/sd.." before > mount the filesystem ? > > Assuming that you have two devices /dev/sdA and /dev/sdB with two btrfs > filesystem with the same uuid, you should mount /dev/sdA > > btrfs dev scan --forget /dev/sdB # you can use event /dev/sdA > mount /dev/sdA /mnt/target > > and to mount /dev/sdB > > btrfs dev scan --forget /dev/sdA # you can use event /dev/sdB > mount /dev/sdB /mnt/target > > I made a quick test using two loop devices and it seems that it works > reliably. Hi Goffredo, thanks for your suggestion! This seems interesting with regards the second patch here..indeed, I can mount any of the 2 filesystems if I use the forget option - interesting option, wasn't aware of that. But unfortunately it seems limited to mounting one device at a time, and we need to be able to mount *both* of them, due to an installation step. If I try to forget the device that is mounted, it gets (obviously) a "busy device" error. Is there any missing step from my side, or mounting both devices is really a limitation when using the forget option? > > Another option should be make a kernel change that "forget" the device > before mounting *if* the filesystem is composed by only one device ( > and another few exceptions like the filesystem is already mounted). > > This would avoid all the problem related to make a "temporary" uuid. I guess again this would be useful in the scope of the second patch here...we could check the way you're proposing instead of having the module parameter. In a way this is similar to the forget approach, right? But it's kind of an "automatic" forget heh How btrfs would know it is a case for single-device filesystem? In other words: how would we distinguish between the cases we want to auto-forget before mounting, and the cases in which this behavior is undesired? Thanks again for your feedback, it is much appreciated. Cheers, Guilherme
