nfs4 write delegation status

["David V. Cloud" <david.v.cloud@gmail.com>]

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Hi all,
I was playing with nfs4 delegation, finding out that write delegations have
never been granted. I am using Benny Halevy's git tree with latest
pnfs-block-all branch. With rpcdebug,  I found out that the write-delegation
grant was rejected due to setlease failure with error code (-11, which is
-EAGAIN). I finally figured out that this failure was caused by the
following lines in generic_setlease function,

        if ((arg == F_WRLCK)
            && ((atomic_read(&dentry->d_count) > 1)
            || (atomic_read(&inode->i_count) > 1)))
            goto out;

In my nfsd, the i_count, and d_count turn out to be 2 (no conflicts actaully
exist in my test case), so write-delegations always failed. I did find some
similar posts on nfs4 related mail lists about this problem. One possible
hack by Ajay could be found at
http://osdir.com/ml/linux.nfsv4/2006-08/msg00063.html

I am curious whether there is any progress in awarding write delegation in
current linux nfs4 implementation (for example, any git branch with write
delegation enabled I can pull?) Or, is write-delegation feature available in
other systems like OpenSolaris?

Any suggestion if I would like to enable and test write delegation? I think
some changes are needed to the setlease interface, right?

Thanks,
David

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