Only that I re-read some code and had to trace the path to convince myself once again that it is fine.
Note that the pmap_extract_and_hold() caller may not fall back to the slow path in some cases, e.g., if VM_PROT_QUICK_NOFAULT is specified.
I do not agree. VM_PROT_QUICK_NOFAULT only makes vm_fault_quick...() to not ignore TDP_NOFAULTING. In this case, the code that set TDP_NOFAULTING typically has to handle EFAULT by some means, which is to call vm_fault() explicitly. This is how vn_io_fault() works.