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From: Andrew Morton <akpm@linux-foundation.org>
To: Foxie Flakey <foxieflakey@gmail.com>,
	rppt@kernel.org, peterx@redhat.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] userfaultfd: reset err to be 0 when move_pages_ptes succeeded
Date: Mon, 17 Aug 2026 15:35:01 -0700	[thread overview]
Message-ID: <20260817153501.ee2ee77976e1cd5b1e1c813b@linux-foundation.org> (raw)
In-Reply-To: <20260817152605.5d2bee3fbf1a2bace4c0eff1@linux-foundation.org>

On Mon, 17 Aug 2026 15:26:05 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> > That behaviour manifested into this at userspace
> > 
> > Source:      [ .. unmapped  .. ][ .. mapped    ..]
> > Destination: [ .. mapped    .. ][ .. unmapped  ..]
> >                           ^     ^
> >                           \     Kernel moved this far in actuality
> >                            What is reported to userspace on struct
> >                            uffdio_move's move field
> > 
> > When the previous behaviour is
> > Source:      [ .. unmapped  .. ][ .. mapped    ..]
> > Destination: [ .. mapped    .. ][ .. unmapped  ..]
> >                                 ^
> >                                 Reported to user space via uffdio_move's
> >                                 move field

Also...

I assume the above illuminates lack of coverage in the uffd selftests. 
Is it hard to add a case to detect this?


  reply	other threads:[~2026-08-17 22:35 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-15 10:42 [PATCH] userfaultfd: reset err to be 0 when move_pages_ptes succeeded Foxie Flakey
2026-08-16  9:15 ` Mike Rapoport
2026-08-16  9:41   ` Foxie Flakey
2026-08-16 11:45     ` Mike Rapoport
2026-08-16 13:58       ` Foxie Flakey
2026-08-16 15:43   ` Suren Baghdasaryan
2026-08-16 15:58     ` Foxie Flakey
2026-08-17 22:26 ` Andrew Morton
2026-08-17 22:35   ` Andrew Morton [this message]
2026-08-18  1:29     ` Foxie Flakey
2026-08-18  1:13   ` Foxie Flakey

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