Create zap for root vdev

And add it to the AVZ, this is not backwards compatible with older pools
due to an assertion in spa_sync() that verifies the number of ZAPs of
all vdevs matches the number of ZAPs in the AVZ.

Granted, the assertion only applies to #DEBUG builds - still, a feature
flag is introduced to avoid the assertion, com.klarasystems:vdev_zaps_v2

Notably, this allows to get/set properties on the root vdev:

    % zpool set user:prop=value <pool> root-0

Before this commit, it was already possible to get/set properties on
top-level vdevs with the syntax <type>-<vdev_id> (e.g. mirror-0):

    % zpool set user:prop=value <pool> mirror-0

This syntax also applies to the root vdev as it is is of type 'root'
with a vdev_id of 0, root-0. The keyword 'root' as an alias for
'root-0'.

The following tests have been added:

    - zpool get all properties from root vdev
    - zpool set a property on root vdev
    - verify root vdev ZAP is created

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Rob Wing <[email protected]>
Sponsored-by: Seagate Technology
Submitted-by: Klara, Inc.
Closes #14405

1 files changed, 1 insertions, 0 deletions

diff --git a/include/sys/vdev_impl.h b/include/sys/vdev_impl.h
index 7cfffe3b4..ea3043c82 100644
--- a/include/sys/vdev_impl.h
+++ b/include/sys/vdev_impl.h
@@ -277,6 +277,7 @@ struct vdev {
 	kthread_t	*vdev_open_thread; /* thread opening children	*/
 	kthread_t	*vdev_validate_thread; /* thread validating children */
 	uint64_t	vdev_crtxg;	/* txg when top-level was added */
+	uint64_t	vdev_root_zap;
 
 	/*
 	 * Top-level vdev state.