NFSv4.1: Fix up replays of interrupted requests

If the previous request on a slot was interrupted before it was
processed by the server, then our slot sequence number may be out of whack,
and so we try the next operation using the old sequence number.

The problem with this, is that not all servers check to see that the
client is replaying the same operations as previously when they decide
to go to the replay cache, and so instead of the expected error of
NFS4ERR_SEQ_FALSE_RETRY, we get a replay of the old reply, which could
(if the operations match up) be mistaken by the client for a new reply.

To fix this, we attempt to send a COMPOUND containing only the SEQUENCE op
in order to resync our slot sequence number.

Cc: Olga Kornievskaia <[e-mail]>
[[e-mail]: fix an Oops]
Signed-off-by: Trond Myklebust <[e-mail]>
Signed-off-by: Anna Schumaker <[e-mail]>

fs/nfs/nfs4_fs.h

···
 extern void nfs_increment_lock_seqid(int status, struct nfs_seqid *seqid);
 extern void nfs_release_seqid(struct nfs_seqid *seqid);
 extern void nfs_free_seqid(struct nfs_seqid *seqid);
-extern int nfs4_setup_sequence(const struct nfs_client *client,
+extern int nfs4_setup_sequence(struct nfs_client *client,
 				struct nfs4_sequence_args *args,
 				struct nfs4_sequence_res *res,
 				struct rpc_task *task);

fs/nfs/nfs4proc.c

···
 			    struct nfs_open_context *ctx, struct nfs4_label *ilabel,
 			    struct nfs4_label *olabel);
 #ifdef CONFIG_NFS_V4_1
+static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp,
+		struct rpc_cred *cred,
+		struct nfs4_slot *slot,
+		bool is_privileged);
 static int nfs41_test_stateid(struct nfs_server *, nfs4_stateid *,
 		struct rpc_cred *);
 static int nfs41_free_stateid(struct nfs_server *, const nfs4_stateid *,
···
 
 #if defined(CONFIG_NFS_V4_1)
 
-static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
+static void nfs41_release_slot(struct nfs4_slot *slot)
 {
 	struct nfs4_session *session;
 	struct nfs4_slot_table *tbl;
-	struct nfs4_slot *slot = res->sr_slot;
 	bool send_new_highest_used_slotid = false;
 
+	if (!slot)
+		return;
 	tbl = slot->table;
 	session = tbl->session;
 
···
 		send_new_highest_used_slotid = false;
 out_unlock:
 	spin_unlock(&tbl->slot_tbl_lock);
-	res->sr_slot = NULL;
 	if (send_new_highest_used_slotid)
 		nfs41_notify_server(session->clp);
 	if (waitqueue_active(&tbl->slot_waitq))
 		wake_up_all(&tbl->slot_waitq);
+}
+
+static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
+{
+	nfs41_release_slot(res->sr_slot);
+	res->sr_slot = NULL;
 }
 
 static int nfs41_sequence_process(struct rpc_task *task,
···
 	/* Check the SEQUENCE operation status */
 	switch (res->sr_status) {
 	case 0:
-		/* If previous op on slot was interrupted and we reused
-		 * the seq# and got a reply from the cache, then retry
-		 */
-		if (task->tk_status == -EREMOTEIO && interrupted) {
-			++slot->seq_nr;
-			goto retry_nowait;
-		}
 		/* Update the slot's sequence and clientid lease timer */
 		slot->seq_done = 1;
 		clp = session->clp;
···
 		 * The slot id we used was probably retired. Try again
 		 * using a different slot id.
 		 */
+		if (slot->seq_nr < slot->table->target_highest_slotid)
+			goto session_recover;
 		goto retry_nowait;
 	case -NFS4ERR_SEQ_MISORDERED:
 		/*
 		 * Was the last operation on this sequence interrupted?
 		 * If so, retry after bumping the sequence number.
 		 */
-		if (interrupted) {
-			++slot->seq_nr;
-			goto retry_nowait;
-		}
+		if (interrupted)
+			goto retry_new_seq;
 		/*
 		 * Could this slot have been previously retired?
 		 * If so, then the server may be expecting seq_nr = 1!
···
 			slot->seq_nr = 1;
 			goto retry_nowait;
 		}
-		break;
+		goto session_recover;
 	case -NFS4ERR_SEQ_FALSE_RETRY:
-		++slot->seq_nr;
-		goto retry_nowait;
+		if (interrupted)
+			goto retry_new_seq;
+		goto session_recover;
 	default:
 		/* Just update the slot sequence no. */
 		slot->seq_done = 1;
···
 	dprintk("%s: Error %d free the slot \n", __func__, res->sr_status);
 out_noaction:
 	return ret;
+session_recover:
+	nfs4_schedule_session_recovery(session, res->sr_status);
+	goto retry_nowait;
+retry_new_seq:
+	++slot->seq_nr;
 retry_nowait:
 	if (rpc_restart_call_prepare(task)) {
 		nfs41_sequence_free_slot(res);
···
 	.rpc_call_done = nfs41_call_sync_done,
 };
 
+static void
+nfs4_sequence_process_interrupted(struct nfs_client *client,
+		struct nfs4_slot *slot, struct rpc_cred *cred)
+{
+	struct rpc_task *task;
+
+	task = _nfs41_proc_sequence(client, cred, slot, true);
+	if (!IS_ERR(task))
+		rpc_put_task_async(task);
+}
+
 #else	/* !CONFIG_NFS_V4_1 */
 
 static int nfs4_sequence_process(struct rpc_task *task, struct nfs4_sequence_res *res)
···
 }
 EXPORT_SYMBOL_GPL(nfs4_sequence_done);
 
+static void
+nfs4_sequence_process_interrupted(struct nfs_client *client,
+		struct nfs4_slot *slot, struct rpc_cred *cred)
+{
+	WARN_ON_ONCE(1);
+	slot->interrupted = 0;
+}
+
 #endif	/* !CONFIG_NFS_V4_1 */
 
-int nfs4_setup_sequence(const struct nfs_client *client,
+static
+void nfs4_sequence_attach_slot(struct nfs4_sequence_args *args,
+		struct nfs4_sequence_res *res,
+		struct nfs4_slot *slot)
+{
+	if (!slot)
+		return;
+	slot->privileged = args->sa_privileged ? 1 : 0;
+	args->sa_slot = slot;
+
+	res->sr_slot = slot;
+	res->sr_timestamp = jiffies;
+	res->sr_status_flags = 0;
+	res->sr_status = 1;
+
+}
+
+int nfs4_setup_sequence(struct nfs_client *client,
 			struct nfs4_sequence_args *args,
 			struct nfs4_sequence_res *res,
 			struct rpc_task *task)
···
 		task->tk_timeout = 0;
 	}
 
-	spin_lock(&tbl->slot_tbl_lock);
-	/* The state manager will wait until the slot table is empty */
-	if (nfs4_slot_tbl_draining(tbl) && !args->sa_privileged)
-		goto out_sleep;
+	for (;;) {
+		spin_lock(&tbl->slot_tbl_lock);
+		/* The state manager will wait until the slot table is empty */
+		if (nfs4_slot_tbl_draining(tbl) && !args->sa_privileged)
+			goto out_sleep;
 
-	slot = nfs4_alloc_slot(tbl);
-	if (IS_ERR(slot)) {
-		/* Try again in 1/4 second */
-		if (slot == ERR_PTR(-ENOMEM))
-			task->tk_timeout = HZ >> 2;
-		goto out_sleep;
+		slot = nfs4_alloc_slot(tbl);
+		if (IS_ERR(slot)) {
+			/* Try again in 1/4 second */
+			if (slot == ERR_PTR(-ENOMEM))
+				task->tk_timeout = HZ >> 2;
+			goto out_sleep;
+		}
+		spin_unlock(&tbl->slot_tbl_lock);
+
+		if (likely(!slot->interrupted))
+			break;
+		nfs4_sequence_process_interrupted(client,
+				slot, task->tk_msg.rpc_cred);
 	}
-	spin_unlock(&tbl->slot_tbl_lock);
 
-	slot->privileged = args->sa_privileged ? 1 : 0;
-	args->sa_slot = slot;
-
-	res->sr_slot = slot;
-	if (session) {
-		res->sr_timestamp = jiffies;
-		res->sr_status_flags = 0;
-		res->sr_status = 1;
-	}
+	nfs4_sequence_attach_slot(args, res, slot);
 
 	trace_nfs4_setup_sequence(session, args);
 out_start:
···
 
 static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp,
 		struct rpc_cred *cred,
+		struct nfs4_slot *slot,
 		bool is_privileged)
 {
 	struct nfs4_sequence_data *calldata;
···
 		.callback_ops = &nfs41_sequence_ops,
 		.flags = RPC_TASK_ASYNC | RPC_TASK_TIMEOUT,
 	};
+	struct rpc_task *ret;
 
+	ret = ERR_PTR(-EIO);
 	if (!atomic_inc_not_zero(&clp->cl_count))
-		return ERR_PTR(-EIO);
+		goto out_err;
+
+	ret = ERR_PTR(-ENOMEM);
 	calldata = kzalloc(sizeof(*calldata), GFP_NOFS);
-	if (calldata == NULL) {
-		nfs_put_client(clp);
-		return ERR_PTR(-ENOMEM);
-	}
+	if (calldata == NULL)
+		goto out_put_clp;
 	nfs4_init_sequence(&calldata->args, &calldata->res, 0);
+	nfs4_sequence_attach_slot(&calldata->args, &calldata->res, slot);
 	if (is_privileged)
 		nfs4_set_sequence_privileged(&calldata->args);
 	msg.rpc_argp = &calldata->args;
···
 	calldata->clp = clp;
 	task_setup_data.callback_data = calldata;
 
-	return rpc_run_task(&task_setup_data);
+	ret = rpc_run_task(&task_setup_data);
+	if (IS_ERR(ret))
+		goto out_err;
+	return ret;
+out_put_clp:
+	nfs_put_client(clp);
+out_err:
+	nfs41_release_slot(slot);
+	return ret;
 }
 
 static int nfs41_proc_async_sequence(struct nfs_client *clp, struct rpc_cred *cred, unsigned renew_flags)
···
 
 	if ((renew_flags & NFS4_RENEW_TIMEOUT) == 0)
 		return -EAGAIN;
-	task = _nfs41_proc_sequence(clp, cred, false);
+	task = _nfs41_proc_sequence(clp, cred, NULL, false);
 	if (IS_ERR(task))
 		ret = PTR_ERR(task);
 	else
···
 	struct rpc_task *task;
 	int ret;
 
-	task = _nfs41_proc_sequence(clp, cred, true);
+	task = _nfs41_proc_sequence(clp, cred, NULL, true);
 	if (IS_ERR(task)) {
 		ret = PTR_ERR(task);
 		goto out;