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    SubjectRe: [PATCH] Define a UNIQUE value for AS_UNEVICTABLE flag
    On Thu, 2009-04-02 at 09:53 -0700, Andrew Morton wrote:
    > On Thu, 02 Apr 2009 12:47:15 -0400 Lee Schermerhorn <> wrote:
    > > [PATCH] Define UNIQUE value of AS_UNEVICTABLE
    > >
    > > Needed in 2.6.28, 2.6.29, ...
    > >
    > > A new "address_space flag"--AS_MM_ALL_LOCKS--was defined to use the next
    > > available AS flag while the Unevictable LRU was under development. The
    > > Unevictable LRU was using the same flag and "no one" noticed. Current
    > > mainline, since 2.6.28, has same value for two symbolic flag names.
    > argh.
    > What are the user-observable effects of the bug, and why didn't anyone
    > notice it until now?

    Well, AS_MM_ALL_LOCKS seems to be used for mmu notifiers. So, I expect
    I've never enabled it. However, I think that if it got set, all of the
    pages in all of the vmas that had it set will appear to be unevictable.
    This would only matter if/when one tried to reclaim/evict them. The
    pages would probably get stranded on the unevictable lru [until freed]
    in that case as there would be no scan to rescue them when
    AS_MM_ALL_LOCKS is cleared.

    Not sure about the other way around: flag set as AS_UNEVICTABLE and
    code examining AS_MM_ALL_LOCKS sees it...

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      Last update: 2009-04-02 20:11    [W:0.024 / U:8.908 seconds]
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