Messages in this thread | | | Subject | Re: [PATCH 3/3] nfs: use ->mmap_prepare() to avoid an AB-BA deadlock | From | Peter Zijlstra <> | Date | Wed, 14 Nov 2007 22:31:45 +0100 |
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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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