Re: [PATCH v4 04/10] userfaultfd/shmem: support minor fault registration for shmem

Hugh Dickins
2021-04-27T02:24:06Z

On Tue, 20 Apr 2021, Axel Rasmussen wrote:

> This patch allows shmem-backed VMAs to be registered for minor faults.
> Minor faults are appropriately relayed to userspace in the fault path,
> for VMAs with the relevant flag.
>
> This commit doesn't hook up the UFFDIO_CONTINUE ioctl for shmem-backed
> minor faults, though, so userspace doesn't yet have a way to resolve
> such faults.
>
> Acked-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>

And if this "04/10" had been numbered 03/10, I would have said
Acked-by: Hugh Dickins <hughd@google.com>

Just read the comment above: "so userspace doesn't yet have a way to
resolve such faults" - if it doesn't by this stage, we're in trouble.

> ---
> fs/userfaultfd.c | 6 +++---
> include/uapi/linux/userfaultfd.h | 7 ++++++-
> mm/memory.c | 8 +++++---
> mm/shmem.c | 12 +++++++++++-
> 4 files changed, 25 insertions(+), 8 deletions(-)