linux-kernel - Re: [PATCH v3 5/5] mm: userfaultfd: add UFFDIO_CONTINUE_MODE

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Message-ID: <ZAaSGGzylNFCR+ql@x1n>
Date:   Mon, 6 Mar 2023 20:23:36 -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 5/5] mm: userfaultfd: add UFFDIO_CONTINUE_MODE_WP to
 install WP PTEs

On Mon, Mar 06, 2023 at 02:50:24PM -0800, Axel Rasmussen wrote:
> UFFDIO_COPY already has UFFDIO_COPY_MODE_WP, so when installing a new
> PTE to resolve a missing fault, one can install a write-protected one.
> This is useful when using UFFDIO_REGISTER_MODE_{MISSING,WP} in
> combination.
> 
> So, add an analogous UFFDIO_CONTINUE_MODE_WP, which does the same thing
> but for *minor* faults.
> 
> Update the selftest to do some very basic exercising of the new flag.
> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>

Some mentioning on the use case would be nice. :) No objection having it.

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

Thanks,

-- 
Peter Xu