The VM object being returned, or NULL if the caller wants to test for the existence of the VM object).
VFS(9) invokes VOP_CREATEVOBJECT when it needs to create a VM object for the given vnode(9). File system code may pass this call down to the underlying file system. This VOP can be called multiple times, and file system code should ignore any additional calls, exiting with a zero return code.
VOP_DESTROYVOBJECT is called when a vnode(9) is recycled.
VOP_GETVOBJECT should be used by all kernel code to get a VM object. The returned VM object may belong to a different file system in the case of stacked mounts.
VFS(9) has three functions which perform standard operations by creating and destroying VM objects. These functions are: vop_stdcreatevobject, vop_stddestroyvobject and vop_stdgetvobject.
Note: a vnode(9) should be locked on entry and must be left locked on exit.
