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

[Hugh Dickins]

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@xxxxxxxxxx>
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>

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

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(-)