For snapshots, when we allocate a new inode we want to allocate an inode
number that isn't in use in any other subvolume. We won't be able to use
ITER_SLOTS for this, inode allocation needs to change to use
BTREE_ITER_ALL_SNAPSHOTS.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>