nfs: enforce FIFO ordering of operations trying to acquire slot

Signed-off-by: Alexandros Batsakis <batsakis@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 18 insertions, 4 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index acd698baf8eb..02513da9a016 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -346,8 +346,12 @@ nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
  */
 static void nfs41_check_drain_session_complete(struct nfs4_session *ses)
 {
+        struct rpc_task *task;
+
         if (!test_bit(NFS4CLNT_SESSION_DRAINING, &ses->clp->cl_state)) {
-                rpc_wake_up_next(&ses->fc_slot_table.slot_tbl_waitq);
+                task = rpc_wake_up_next(&ses->fc_slot_table.slot_tbl_waitq);
+                if (task)
+                        rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
                 return;
         }
 
@@ -483,6 +487,14 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
                 return -EAGAIN;
         }
 
+        if (!rpc_queue_empty(&tbl->slot_tbl_waitq) &&
+            !rpc_task_has_priority(task, RPC_PRIORITY_PRIVILEGED)) {
+                rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL);
+                spin_unlock(&tbl->slot_tbl_lock);
+                dprintk("%s enforce FIFO order\n", __func__);
+                return -EAGAIN;
+        }
+
         slotid = nfs4_find_slot(tbl);
         if (slotid == NFS4_MAX_SLOT_TABLE) {
                 rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL);
@@ -492,6 +504,7 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
         }
         spin_unlock(&tbl->slot_tbl_lock);
 
+        rpc_task_set_priority(task, RPC_PRIORITY_NORMAL);
         slot = tbl->slots + slotid;
         args->sa_session = session;
         args->sa_slotid = slotid;
@@ -4401,11 +4414,12 @@ static void nfs4_get_lease_time_prepare(struct rpc_task *task,
                         (struct nfs4_get_lease_time_data *)calldata;
 
         dprintk("--> %s\n", __func__);
+        rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
         /* just setup sequence, do not trigger session recovery
            since we're invoked within one */
         ret = nfs41_setup_sequence(data->clp->cl_session,
-                                        &data->args->la_seq_args,
-                                        &data->res->lr_seq_res, 0, task);
+                                   &data->args->la_seq_args,
+                                   &data->res->lr_seq_res, 0, task);
 
         BUG_ON(ret == -EAGAIN);
         rpc_call_start(task);
@@ -4625,7 +4639,7 @@ struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
         tbl = &session->fc_slot_table;
         tbl->highest_used_slotid = -1;
         spin_lock_init(&tbl->slot_tbl_lock);
-        rpc_init_wait_queue(&tbl->slot_tbl_waitq, "ForeChannel Slot table");
+        rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, "ForeChannel Slot table");
 
         tbl = &session->bc_slot_table;
         tbl->highest_used_slotid = -1;