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    SubjectRe: [PATCH 3/3] nfs: use ->mmap_prepare() to avoid an AB-BA deadlock

    On Wed, 2007-11-14 at 22:22 +0100, Nick Piggin wrote:
    > On Wed, Nov 14, 2007 at 09:01:39PM +0100, Peter Zijlstra wrote:
    > > Normal locking order is:
    > >
    > > i_mutex
    > > mmap_sem
    > >
    > > However NFS's ->mmap hook, which is called under mmap_sem, can take i_mutex.
    > > Avoid this potential deadlock by doing the work that requires i_mutex from
    > > the new ->mmap_prepare().
    > >
    > > [ Is this sufficient, or does it introduce a race? ]
    > Seems like an OK patchset in my opinion. I don't know much about NFS
    > unfortunately, but I wonder what prevents the condition fixed by
    > nfs_revalidate_mapping from happening again while the mmap is active...?

    As the changelog might have suggested, I'm not overly sure of the nfs
    requirements myself. I think it just does a best effort at getting the
    pages coherent with other clients, and then hopes for the best.

    I'll let Trond enlighten us further before I make an utter fool of
    myself :-)

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      Last update: 2007-11-14 22:35    [W:0.020 / U:4.512 seconds]
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