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Date:   Wed, 6 May 2020 18:11:17 -0700
From:   Brian Geffon <>
To:     Joel Fernandes <>
Cc:     Andrew Morton <>,
        "Michael S . Tsirkin" <>,
        LKML <>,
        linux-mm <>,
        Andrea Arcangeli <>,
        Sonny Rao <>,
        Minchan Kim <>,
        "Kirill A . Shutemov" <>
Subject: Re: [PATCH] userfaultfd: fix remap event with MREMAP_DONTUNMAP.

> > -       mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
> > +       mremap_userfaultfd_complete(&uf, addr, ret, old_len);
> Not super familiar with this code, but thought I'd ask, does ret
> to be checked for -ENOMEM before calling mremap_userfaultfd_complete?
> Sorry if I missed something.

No, mremap_userfaultfd_complete will do a check similar to
offset_in_page() by checking the page mask.
It does (to & ~PAGE_MASK) to check for a non-aligned "to" value, so we're good.

Additionally, earlier in the process then ctx will be null because we
will have never called mremap_userfaultfd_prep,
and mremap_userfaultfd_complete will check if there is a context
before proceeding.


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