Re: [PATCH v2 3/5] mm: userfaultfd: combine 'mode' and 'wp_copy' arguments

[Nadav Amit]

> On Feb 22, 2023, at 4:57 PM, Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
> 
> Many userfaultfd ioctl functions take both a 'mode' and a 'wp_copy'
> argument. In future commits we plan to plumb the flags through to more
> places, so we'd be proliferating the very long argument list even
> further.
> 
> Let's take the time to simplify the argument list. Combine the two
> arguments into one - and generalize, so when we add more flags in the
> future, it doesn't imply more function arguments.
> 
> Since the modes (copy, zeropage, continue) are mutually exclusive, store
> them as an integer value (0, 1, 2) in the low bits. Place combine-able
> flag bits in the high bits.
> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>

Hi Axel,

I sent a patch a long time ago called “userfaultfd: introduce uffd_flags”.
For some reason it does not appear on lore, but you were a recipient.

It was pretty similar, but one thing that I preferred in my version is
that it defined a different type to avoid confusion. Since “flags” is
a very generic name, perhaps you’d like to adapt this approach.