linux-kernel - Re: [PATCH v2 2/3] userfaultfd: UFFDIO

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Message-ID: <ZRx31TKFDGRatoC8@x1n>
Date:   Tue, 3 Oct 2023 16:21:41 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Lokesh Gidra <lokeshgidra@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Jann Horn <jannh@...gle.com>, akpm@...ux-foundation.org,
        viro@...iv.linux.org.uk, brauner@...nel.org, shuah@...nel.org,
        aarcange@...hat.com, hughd@...gle.com, mhocko@...e.com,
        axelrasmussen@...gle.com, rppt@...nel.org, willy@...radead.org,
        Liam.Howlett@...cle.com, zhangpeng362@...wei.com,
        bgeffon@...gle.com, kaleshsingh@...gle.com, ngeoffray@...gle.com,
        jdduke@...gle.com, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v2 2/3] userfaultfd: UFFDIO_REMAP uABI

On Tue, Oct 03, 2023 at 01:04:44PM -0700, Suren Baghdasaryan wrote:
> Ok, I think it makes sense to implement the strict remap logic but in
> a way that we can easily add copy fallback if that's needed in the
> future. So, I'll change UFFDIO_REMAP to UFFDIO_MOVE and will return
> some unique error, like EBUSY when the page is not PAE. If we need to
> add a copy fallback in the future, we will add a
> UFFDIO_MOVE_MODE_ALLOW_COPY flag and will implement the copy
> mechanism. Does that sound good?

For the clear failing approach, sounds all good here.

For the name, no strong opinion, but is there any strong one over MOVE?
MOVE is a fine name, however considering UFFDIO_REMAP's long history.. I
tend to prefer keeping it called as REMAP - it still sounds sane, and
anyone who knows REMAP will know this is exactly that.

Thanks,

-- 
Peter Xu