On Thu, Jan 23, 2014 at 01:28:54PM +0100, Joshua Schüler wrote: > btrfs guarantees backward compatibility since 3.13(?), but never > guaranteed forward compatibility. Isnt' this the opposite way? Forward means that old fs will be mountable on a newer kernel. I don't know what you mean by 'backward compatibility is guaranteed since 3.13'. There are some features that get turned on automatically if used for the first time, but not all of them prevent mounting on an older kernel. Exmaple is the uuid tree, "generation v2" that's been introduced with send. Older kernel ignores the changes and newer kernel is usually able to recognize that the data are not all-ok and recovers itself or allows the user to do so manually. > So it is not yet supported to mount the fs with an older kernel once > it was mounted with a newer one. That's right, but in practice is not that bad. > Especially when using features that are under heavy development right now. Which features do you mean? Once a feature is introduced, the format and incompatibility bits should not change. The code may change, and does of course, but always in a compatible way. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
