nfs41: nfs41: fix state manager deadlock in session reset

If the session is reset during state recovery, the state manager thread can
sleep on the slot_tbl_waitq causing a deadlock.

Add a completion framework to the session.  Have the state manager thread set
a new session state (NFS4CLNT_SESSION_DRAINING) and wait for the session slot
table to drain.

Signal the state manager thread in nfs41_sequence_free_slot when the
NFS4CLNT_SESSION_DRAINING bit is set and the session is drained.

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

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index f56f6be5e314..3c1433598b60 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1181,8 +1181,23 @@ static void nfs4_session_recovery_handle_error(struct nfs_client *clp, int err)
 
 static int nfs4_reset_session(struct nfs_client *clp)
 {
+        struct nfs4_session *ses = clp->cl_session;
+        struct nfs4_slot_table *tbl = &ses->fc_slot_table;
         int status;
 
+        INIT_COMPLETION(ses->complete);
+        spin_lock(&tbl->slot_tbl_lock);
+        if (tbl->highest_used_slotid != -1) {
+                set_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state);
+                spin_unlock(&tbl->slot_tbl_lock);
+                status = wait_for_completion_interruptible(&ses->complete);
+                clear_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state);
+                if (status) /* -ERESTARTSYS */
+                        goto out;
+        } else {
+                spin_unlock(&tbl->slot_tbl_lock);
+        }
+
         status = nfs4_proc_destroy_session(clp->cl_session);
         if (status && status != -NFS4ERR_BADSESSION &&
             status != -NFS4ERR_DEADSESSION) {