Re: [PATCH v5 6/6] mm: handle userfaults under VMA lock

Suren Baghdasaryan
2023-06-29T00:19:50Z

On Wed, Jun 28, 2023 at 10:32 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Wed, Jun 28, 2023 at 10:25:29AM -0700, Suren Baghdasaryan wrote:
> > Enable handle_userfault to operate under VMA lock by releasing VMA lock
> > instead of mmap_lock and retrying. Note that FAULT_FLAG_RETRY_NOWAIT
> > should never be used when handling faults under per-VMA lock protection
> > because that would break the assumption that lock is dropped on retry.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>
> Maybe the sanitize_fault_flags() changes suite more in patch 3, but not a
> big deal I guess.

IIUC FAULT_FLAG_RETRY_NOWAIT comes into play in this patchset only in
the context of uffds, therefore that check seems to be needed when we
enable per-VMA lock uffd support, which is this patch. Does that make
sense?

>
> Acked-by: Peter Xu <peterx@redhat.com>

Thanks!

>
> Thanks!
>
> --
> Peter Xu
>