David Hildenbrand <david@xxxxxxxxxx> writes: > On 28.07.22 10:45, Alistair Popple wrote: >> >> Looks like the original patch might need rebasing. I am about to post a >> clean-up for the tortured logic in check_and_migrate_movable_pages() so >> can incorporate it there, but I'm wondering what the consensus was for >> pinning of zero pfn? > > We have to keep it working right now, but in most cases (inside > MAP_PRIVATE regions) it's shaky and undesired. Ok. Well I've looked at this now so may as well stick Reviewed-by: Alistair Popple <apopple@xxxxxxxxxx> on it. However I think it needs rebasing, should I send an updated version? >> >> Currently my clean-up will result in PUP returning an error for the zero >> pfn rather than looping indefinitely in the kernel. However it wasn't >> clear from this thread if returning an error is ok, or if R/O pinning >> of the zero pfn should succeed? > > I'm working on proper COW breaking in MAP_PRIVATE mappings, which will, > for example, unshare the shared zeropage and properly replace it by > exclusive anon pages first in the FOLL_LONGTERM case.
