At present, update_mmu_cache() and lazy_mmu_prot_update() are always 
called when ptep_set_access_flags() is called so why not move them into 
ptep_set_access_flags() and change ptep_set_access_flags() to have an 
additional boolean parameter (__update) that would when set, cause 
update_mmu_cache() and lazy_mmu_prot_update() to be called.

Well, ptep_set_access_flags() is a low level arch hook, I'd rather not
start hiding update_mmu_cache() calls in it ...

Ben.