linux-kernel - Re: [PATCH v3 1/5] mm: userfaultfd: rename functions for clarity + consistency

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Date:   Mon, 6 Mar 2023 20:03:53 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Axel Rasmussen <axelrasmussen@...gle.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>, Jan Kara <jack@...e.cz>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>,
        Nadav Amit <namit@...are.com>, Shuah Khan <shuah@...nel.org>,
        James Houghton <jthoughton@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 1/5] mm: userfaultfd: rename functions for clarity +
 consistency

On Mon, Mar 06, 2023 at 02:50:20PM -0800, Axel Rasmussen wrote:
> The basic problem is, over time we've added new userfaultfd ioctls, and
> we've refactored the code so functions which used to handle only one
> case are now re-used to deal with several cases. While this happened, we
> didn't bother to rename the functions.
> 
> Similarly, as we added new functions, we cargo-culted pieces of the
> now-inconsistent naming scheme, so those functions too ended up with
> names that don't make a lot of sense.
> 
> A key point here is, "copy" in most userfaultfd code refers specifically
> to UFFDIO_COPY, where we allocate a new page and copy its contents from
> userspace. There are many functions with "copy" in the name that don't
> actually do this (at least in some cases).
> 
> So, rename things into a consistent scheme. The high level idea is that
> the call stack for userfaultfd ioctls becomes:
> 
> userfaultfd_ioctl
>   -> userfaultfd_(particular ioctl)
>     -> mfill_atomic_(particular kind of fill operation)
>       -> mfill_atomic    /* loops over pages in range */
>         -> mfill_atomic_pte    /* deals with single pages */
>           -> mfill_atomic_pte_(particular kind of fill operation)
>             -> mfill_atomic_install_pte
> 
> There are of course some special cases (shmem, hugetlb), but this is the
> general structure which all function names now adhere to.
> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>

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

-- 
Peter Xu