On Fri, 1 Nov 2024 18:50:33 +0000 Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> > > Locking around VMAs is complicated and confusing. While we have a number of > disparate comments scattered around the place, we seem to be reaching a > level of complexity that justifies a serious effort at clearly documenting > how locks are expected to be interacted with when it comes to interacting > with mm_struct and vm_area_struct objects. > > This is especially pertinent as regards efforts to find sensible > abstractions for these fundamental objects within the kernel rust > abstraction whose compiler strictly requires some means of expressing these > rules (and through this expression can help self-document these > requirements as well as enforce them which is an exciting concept). > > The document limits scope to mmap and VMA locks and those that are > immediately adjacent and relevant to them - so additionally covers page > table locking as this is so very closely tied to VMA operations (and relies > upon us handling these correctly). > > The document tries to cover some of the nastier and more confusing edge > cases and concerns especially around lock ordering and page table teardown. > What is missed is the clear guide to the correct locking order. Is the order below correct for instance? lock vma lock vma->vm_mm
