On Sun, Aug 01, 2021 at 11:52:16PM +0300, Matwey V. Kornilov wrote:
BTRFS volume consists of a number of subvolumes which can be mounted separately from each other. The top-level subvolume always exists even if no subvolumes were created manually. A subvolume can be denoted as the default subvolume i.e. the subvolume which is mounted by default.
The default "default subvolume" is the top-level one, but this is far from the common practices used in the wild. For instance, openSUSE provides an OS snapshot/rollback feature based on BTRFS. To achieve this, the actual OS root filesystem is located into a separate subvolume which is "default" but not "top-level". That means that the /boot/dtb/ directory is also located inside this default subvolume instead of top-level one.
However, the existing btrfs u-boot driver always uses the top-level subvolume as the filesystem root. This behaviour 1) is inconsistent with
mount /dev/sda1 /targetcommand, which mount the default subvolume 2) leads to the issues when /boot/dtb cannot be found properly (see the reference).
This patch uses the default subvolume as the filesystem root to overcome mentioned issues.
Reference: https://bugzilla.suse.com/show_bug.cgi?id=1185656 Signed-off-by: Matwey V. Kornilov matwey.kornilov@gmail.com Reviewed-by: Qu Wenruo wqu@suse.com
Applied to u-boot/master, thanks!