NFS add session back channel draining

Currently session draining only drains the fore channel.
The back channel processing must also be drained.

Use the back channel highest_slot_used to indicate that a callback is being
processed by the callback thread.  Move the session complete to be per channel.

When the session is draininig, wait for any current back channel processing
to complete and stop all new back channel processing by returning NFS4ERR_DELAY
to the back channel client.

Drain the back channel, then the fore channel.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index b70e46da16fc..c1bead2f3e04 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -253,6 +253,12 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
         if (clp == NULL)
                 goto out;
 
+        /* state manager is resetting the session */
+        if (test_bit(NFS4_SESSION_DRAINING, &clp->cl_session->session_state)) {
+                status = NFS4ERR_DELAY;
+                goto out;
+        }
+
         status = validate_seqid(&clp->cl_session->bc_slot_table, args);
         if (status)
                 goto out;
@@ -273,6 +279,7 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
         res->csr_slotid = args->csa_slotid;
         res->csr_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
         res->csr_target_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
+        nfs4_cb_take_slot(clp);
         cps->clp = clp; /* put in nfs4_callback_compound */
 
 out: