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    SubjectRe: [PATCH v2] SUNRPC: skip dead but not buried clients on PipeFS events
    On Wed, 2012-04-25 at 13:30 -0400, J. Bruce Fields wrote:
    > On Fri, Apr 20, 2012 at 06:11:02PM +0400, Stanislav Kinsbursky wrote:
    > > v2: atomic_inc_return() was replaced by atomic_inc_not_zero().
    > >
    > > These clients can't be safely dereferenced if their counter in 0.
    > I'm pretty confused by how these notifiers work....
    > rpc_release_client decrements cl_count to zero temporarily, to have it
    > immediately re-incremented by rpc_free_auth.
    > So if we're called concurrently with rpc_release_client then it's sort
    > of random whether someone gets this callback.
    > Is that a problem?

    Not really. If we re-increment the client->cl_count in rpc_free_auth()
    then it would be so that we can send off a bunch of NULL rpc calls to
    destroy existing RPCSEC_GSS contexts. We shouldn't need to do any more
    upcalls in pipefs.

    If we care, we could simply move the call to rpc_unregister_client()
    into rpc_free_auth() so that the pipefs notifier doesn't see us, or we
    could set a flag to have it ignore us.

    > Also, is this an existing bug? (In which case Trond should take it
    > now.)

    Trond Myklebust
    Linux NFS client maintainer


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