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    SubjectRe: find_get_swapcache_page() question
    On Tue, 28 Aug 2001, Rik van Riel wrote:
    > On Tue, 28 Aug 2001, Hugh Dickins wrote:
    >
    > > if (!PageSwapCache(found))
    > > BUG();
    > > if (found->mapping != &swapper_space)
    > > BUG();
    > > are not safe, since there may a concurrent remove_from_swap_cache(),
    > > either from try_to_unuse() or from Rik's new vm_swap_full() deletion.
    > > Those tests would be safe if the page were locked, but it's not.
    >
    > vm_swap_full() is called with the page locked,
    > remove_from_swap_cache() also seems to want the
    > page locked...

    Certainly (I seem to recall composing a comment to that effect
    recently :-)! Sorry for being unclear, I meant that those tests
    in lookup_swap_cache() are made without the page being locked
    by lookup_swap_cache() or its caller (and I'm not proposing
    that the page should be locked, but the unsafe tests removed).

    Hugh

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