Re: [PATCH 4/8] mm: FOLL_DUMP replace FOLL_ANON

Rik van Riel
2009-09-08T19:00:05Z

Hugh Dickins wrote:
> The "FOLL_ANON optimization" and its use_zero_page() test have caused
> confusion and bugs: why does it test VM_SHARED? for the very good but
> unsatisfying reason that VMware crashed without. As we look to maybe
> reinstating anonymous use of the ZERO_PAGE, we need to sort this out.
>
> Easily done: it's silly for __get_user_pages() and follow_page() to
> be guessing whether it's safe to assume that they're being used for
> a coredump (which can take a shortcut snapshot where other uses must
> handle a fault) - just tell them with GUP_FLAGS_DUMP and FOLL_DUMP.
>
> get_dump_page() doesn't even want a ZERO_PAGE: an error suits fine.
>
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>

Acked-by: Rik van Riel <riel@redhat.com>

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