On 13/01/2021 19:00, David Sterba wrote: > so what changed that it's fine to use device->fs_info now while it was > not before? The time when we call btrfs_get_dev_zone_info() in "btrfs: defer loading zone info after opening trees". >From the commit message: "The current call site of btrfs_get_dev_zone_info() during the mount process is earlier than reading the trees, so we can't slice a regular device to conventional zones. This patch defers the loading of zone info to open_ctree() to load the emulated zone size from a device extent." Hope this clarifies your concerns.