Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2388 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
new file mode 100644
index 000000000..3f7bf9f2d
--- /dev/null
+++ b/drivers/block/drbd/drbd_state.c
@@ -0,0 +1,2388 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+   drbd_state.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   Thanks to Carter Burden, Bart Grantham and Gennadiy Nerubayev
+   from Logicworks, Inc. for making SDP replication support possible.
+
+ */
+
+#include <linux/drbd_limits.h>
+#include "drbd_int.h"
+#include "drbd_protocol.h"
+#include "drbd_req.h"
+#include "drbd_state_change.h"
+
+struct after_state_chg_work {
+	struct drbd_work w;
+	struct drbd_device *device;
+	union drbd_state os;
+	union drbd_state ns;
+	enum chg_state_flags flags;
+	struct completion *done;
+	struct drbd_state_change *state_change;
+};
+
+enum sanitize_state_warnings {
+	NO_WARNING,
+	ABORTED_ONLINE_VERIFY,
+	ABORTED_RESYNC,
+	CONNECTION_LOST_NEGOTIATING,
+	IMPLICITLY_UPGRADED_DISK,
+	IMPLICITLY_UPGRADED_PDSK,
+};
+
+static void count_objects(struct drbd_resource *resource,
+			  unsigned int *n_devices,
+			  unsigned int *n_connections)
+{
+	struct drbd_device *device;
+	struct drbd_connection *connection;
+	int vnr;
+
+	*n_devices = 0;
+	*n_connections = 0;
+
+	idr_for_each_entry(&resource->devices, device, vnr)
+		(*n_devices)++;
+	for_each_connection(connection, resource)
+		(*n_connections)++;
+}
+
+static struct drbd_state_change *alloc_state_change(unsigned int n_devices, unsigned int n_connections, gfp_t gfp)
+{
+	struct drbd_state_change *state_change;
+	unsigned int size, n;
+
+	size = sizeof(struct drbd_state_change) +
+	       n_devices * sizeof(struct drbd_device_state_change) +
+	       n_connections * sizeof(struct drbd_connection_state_change) +
+	       n_devices * n_connections * sizeof(struct drbd_peer_device_state_change);
+	state_change = kmalloc(size, gfp);
+	if (!state_change)
+		return NULL;
+	state_change->n_devices = n_devices;
+	state_change->n_connections = n_connections;
+	state_change->devices = (void *)(state_change + 1);
+	state_change->connections = (void *)&state_change->devices[n_devices];
+	state_change->peer_devices = (void *)&state_change->connections[n_connections];
+	state_change->resource->resource = NULL;
+	for (n = 0; n < n_devices; n++)
+		state_change->devices[n].device = NULL;
+	for (n = 0; n < n_connections; n++)
+		state_change->connections[n].connection = NULL;
+	return state_change;
+}
+
+struct drbd_state_change *remember_old_state(struct drbd_resource *resource, gfp_t gfp)
+{
+	struct drbd_state_change *state_change;
+	struct drbd_device *device;
+	unsigned int n_devices;
+	struct drbd_connection *connection;
+	unsigned int n_connections;
+	int vnr;
+
+	struct drbd_device_state_change *device_state_change;
+	struct drbd_peer_device_state_change *peer_device_state_change;
+	struct drbd_connection_state_change *connection_state_change;
+
+	/* Caller holds req_lock spinlock.
+	 * No state, no device IDR, no connections lists can change. */
+	count_objects(resource, &n_devices, &n_connections);
+	state_change = alloc_state_change(n_devices, n_connections, gfp);
+	if (!state_change)
+		return NULL;
+
+	kref_get(&resource->kref);
+	state_change->resource->resource = resource;
+	state_change->resource->role[OLD] =
+		conn_highest_role(first_connection(resource));
+	state_change->resource->susp[OLD] = resource->susp;
+	state_change->resource->susp_nod[OLD] = resource->susp_nod;
+	state_change->resource->susp_fen[OLD] = resource->susp_fen;
+
+	connection_state_change = state_change->connections;
+	for_each_connection(connection, resource) {
+		kref_get(&connection->kref);
+		connection_state_change->connection = connection;
+		connection_state_change->cstate[OLD] =
+			connection->cstate;
+		connection_state_change->peer_role[OLD] =
+			conn_highest_peer(connection);
+		connection_state_change++;
+	}
+
+	device_state_change = state_change->devices;
+	peer_device_state_change = state_change->peer_devices;
+	idr_for_each_entry(&resource->devices, device, vnr) {
+		kref_get(&device->kref);
+		device_state_change->device = device;
+		device_state_change->disk_state[OLD] = device->state.disk;
+
+		/* The peer_devices for each device have to be enumerated in
+		   the order of the connections. We may not use for_each_peer_device() here. */
+		for_each_connection(connection, resource) {
+			struct drbd_peer_device *peer_device;
+
+			peer_device = conn_peer_device(connection, device->vnr);
+			peer_device_state_change->peer_device = peer_device;
+			peer_device_state_change->disk_state[OLD] =
+				device->state.pdsk;
+			peer_device_state_change->repl_state[OLD] =
+				max_t(enum drbd_conns,
+				      C_WF_REPORT_PARAMS, device->state.conn);
+			peer_device_state_change->resync_susp_user[OLD] =
+				device->state.user_isp;
+			peer_device_state_change->resync_susp_peer[OLD] =
+				device->state.peer_isp;
+			peer_device_state_change->resync_susp_dependency[OLD] =
+				device->state.aftr_isp;
+			peer_device_state_change++;
+		}
+		device_state_change++;
+	}
+
+	return state_change;
+}
+
+static void remember_new_state(struct drbd_state_change *state_change)
+{
+	struct drbd_resource_state_change *resource_state_change;
+	struct drbd_resource *resource;
+	unsigned int n;
+
+	if (!state_change)
+		return;
+
+	resource_state_change = &state_change->resource[0];
+	resource = resource_state_change->resource;
+
+	resource_state_change->role[NEW] =
+		conn_highest_role(first_connection(resource));
+	resource_state_change->susp[NEW] = resource->susp;
+	resource_state_change->susp_nod[NEW] = resource->susp_nod;
+	resource_state_change->susp_fen[NEW] = resource->susp_fen;
+
+	for (n = 0; n < state_change->n_devices; n++) {
+		struct drbd_device_state_change *device_state_change =
+			&state_change->devices[n];
+		struct drbd_device *device = device_state_change->device;
+
+		device_state_change->disk_state[NEW] = device->state.disk;
+	}
+
+	for (n = 0; n < state_change->n_connections; n++) {
+		struct drbd_connection_state_change *connection_state_change =
+			&state_change->connections[n];
+		struct drbd_connection *connection =
+			connection_state_change->connection;
+
+		connection_state_change->cstate[NEW] = connection->cstate;
+		connection_state_change->peer_role[NEW] =
+			conn_highest_peer(connection);
+	}
+
+	for (n = 0; n < state_change->n_devices * state_change->n_connections; n++) {
+		struct drbd_peer_device_state_change *peer_device_state_change =
+			&state_change->peer_devices[n];
+		struct drbd_device *device =
+			peer_device_state_change->peer_device->device;
+		union drbd_dev_state state = device->state;
+
+		peer_device_state_change->disk_state[NEW] = state.pdsk;
+		peer_device_state_change->repl_state[NEW] =
+			max_t(enum drbd_conns, C_WF_REPORT_PARAMS, state.conn);
+		peer_device_state_change->resync_susp_user[NEW] =
+			state.user_isp;
+		peer_device_state_change->resync_susp_peer[NEW] =
+			state.peer_isp;
+		peer_device_state_change->resync_susp_dependency[NEW] =
+			state.aftr_isp;
+	}
+}
+
+void copy_old_to_new_state_change(struct drbd_state_change *state_change)
+{
+	struct drbd_resource_state_change *resource_state_change = &state_change->resource[0];
+	unsigned int n_device, n_connection, n_peer_device, n_peer_devices;
+
+#define OLD_TO_NEW(x) \
+	(x[NEW] = x[OLD])
+
+	OLD_TO_NEW(resource_state_change->role);
+	OLD_TO_NEW(resource_state_change->susp);
+	OLD_TO_NEW(resource_state_change->susp_nod);
+	OLD_TO_NEW(resource_state_change->susp_fen);
+
+	for (n_connection = 0; n_connection < state_change->n_connections; n_connection++) {
+		struct drbd_connection_state_change *connection_state_change =
+				&state_change->connections[n_connection];
+
+		OLD_TO_NEW(connection_state_change->peer_role);
+		OLD_TO_NEW(connection_state_change->cstate);
+	}
+
+	for (n_device = 0; n_device < state_change->n_devices; n_device++) {
+		struct drbd_device_state_change *device_state_change =
+			&state_change->devices[n_device];
+
+		OLD_TO_NEW(device_state_change->disk_state);
+	}
+
+	n_peer_devices = state_change->n_devices * state_change->n_connections;
+	for (n_peer_device = 0; n_peer_device < n_peer_devices; n_peer_device++) {
+		struct drbd_peer_device_state_change *p =
+			&state_change->peer_devices[n_peer_device];
+
+		OLD_TO_NEW(p->disk_state);
+		OLD_TO_NEW(p->repl_state);
+		OLD_TO_NEW(p->resync_susp_user);
+		OLD_TO_NEW(p->resync_susp_peer);
+		OLD_TO_NEW(p->resync_susp_dependency);
+	}
+
+#undef OLD_TO_NEW
+}
+
+void forget_state_change(struct drbd_state_change *state_change)
+{
+	unsigned int n;
+
+	if (!state_change)
+		return;
+
+	if (state_change->resource->resource)
+		kref_put(&state_change->resource->resource->kref, drbd_destroy_resource);
+	for (n = 0; n < state_change->n_devices; n++) {
+		struct drbd_device *device = state_change->devices[n].device;
+
+		if (device)
+			kref_put(&device->kref, drbd_destroy_device);
+	}
+	for (n = 0; n < state_change->n_connections; n++) {
+		struct drbd_connection *connection =
+			state_change->connections[n].connection;
+
+		if (connection)
+			kref_put(&connection->kref, drbd_destroy_connection);
+	}
+	kfree(state_change);
+}
+
+static int w_after_state_ch(struct drbd_work *w, int unused);
+static void after_state_ch(struct drbd_device *device, union drbd_state os,
+			   union drbd_state ns, enum chg_state_flags flags,
+			   struct drbd_state_change *);
+static enum drbd_state_rv is_valid_state(struct drbd_device *, union drbd_state);
+static enum drbd_state_rv is_valid_soft_transition(union drbd_state, union drbd_state, struct drbd_connection *);
+static enum drbd_state_rv is_valid_transition(union drbd_state os, union drbd_state ns);
+static union drbd_state sanitize_state(struct drbd_device *device, union drbd_state os,
+				       union drbd_state ns, enum sanitize_state_warnings *warn);
+
+static inline bool is_susp(union drbd_state s)
+{
+        return s.susp || s.susp_nod || s.susp_fen;
+}
+
+bool conn_all_vols_unconf(struct drbd_connection *connection)
+{
+	struct drbd_peer_device *peer_device;
+	bool rv = true;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		if (device->state.disk != D_DISKLESS ||
+		    device->state.conn != C_STANDALONE ||
+		    device->state.role != R_SECONDARY) {
+			rv = false;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return rv;
+}
+
+/* Unfortunately the states where not correctly ordered, when
+   they where defined. therefore can not use max_t() here. */
+static enum drbd_role max_role(enum drbd_role role1, enum drbd_role role2)
+{
+	if (role1 == R_PRIMARY || role2 == R_PRIMARY)
+		return R_PRIMARY;
+	if (role1 == R_SECONDARY || role2 == R_SECONDARY)
+		return R_SECONDARY;
+	return R_UNKNOWN;
+}
+
+static enum drbd_role min_role(enum drbd_role role1, enum drbd_role role2)
+{
+	if (role1 == R_UNKNOWN || role2 == R_UNKNOWN)
+		return R_UNKNOWN;
+	if (role1 == R_SECONDARY || role2 == R_SECONDARY)
+		return R_SECONDARY;
+	return R_PRIMARY;
+}
+
+enum drbd_role conn_highest_role(struct drbd_connection *connection)
+{
+	enum drbd_role role = R_SECONDARY;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		role = max_role(role, device->state.role);
+	}
+	rcu_read_unlock();
+
+	return role;
+}
+
+enum drbd_role conn_highest_peer(struct drbd_connection *connection)
+{
+	enum drbd_role peer = R_UNKNOWN;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		peer = max_role(peer, device->state.peer);
+	}
+	rcu_read_unlock();
+
+	return peer;
+}
+
+enum drbd_disk_state conn_highest_disk(struct drbd_connection *connection)
+{
+	enum drbd_disk_state disk_state = D_DISKLESS;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		disk_state = max_t(enum drbd_disk_state, disk_state, device->state.disk);
+	}
+	rcu_read_unlock();
+
+	return disk_state;
+}
+
+enum drbd_disk_state conn_lowest_disk(struct drbd_connection *connection)
+{
+	enum drbd_disk_state disk_state = D_MASK;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		disk_state = min_t(enum drbd_disk_state, disk_state, device->state.disk);
+	}
+	rcu_read_unlock();
+
+	return disk_state;
+}
+
+enum drbd_disk_state conn_highest_pdsk(struct drbd_connection *connection)
+{
+	enum drbd_disk_state disk_state = D_DISKLESS;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		disk_state = max_t(enum drbd_disk_state, disk_state, device->state.pdsk);
+	}
+	rcu_read_unlock();
+
+	return disk_state;
+}
+
+enum drbd_conns conn_lowest_conn(struct drbd_connection *connection)
+{
+	enum drbd_conns conn = C_MASK;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		conn = min_t(enum drbd_conns, conn, device->state.conn);
+	}
+	rcu_read_unlock();
+
+	return conn;
+}
+
+static bool no_peer_wf_report_params(struct drbd_connection *connection)
+{
+	struct drbd_peer_device *peer_device;
+	int vnr;
+	bool rv = true;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
+		if (peer_device->device->state.conn == C_WF_REPORT_PARAMS) {
+			rv = false;
+			break;
+		}
+	rcu_read_unlock();
+
+	return rv;
+}
+
+static void wake_up_all_devices(struct drbd_connection *connection)
+{
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
+		wake_up(&peer_device->device->state_wait);
+	rcu_read_unlock();
+
+}
+
+
+/**
+ * cl_wide_st_chg() - true if the state change is a cluster wide one
+ * @device:	DRBD device.
+ * @os:		old (current) state.
+ * @ns:		new (wanted) state.
+ */
+static int cl_wide_st_chg(struct drbd_device *device,
+			  union drbd_state os, union drbd_state ns)
+{
+	return (os.conn >= C_CONNECTED && ns.conn >= C_CONNECTED &&
+		 ((os.role != R_PRIMARY && ns.role == R_PRIMARY) ||
+		  (os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+		  (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S) ||
+		  (os.disk != D_FAILED && ns.disk == D_FAILED))) ||
+		(os.conn >= C_CONNECTED && ns.conn == C_DISCONNECTING) ||
+		(os.conn == C_CONNECTED && ns.conn == C_VERIFY_S) ||
+		(os.conn == C_CONNECTED && ns.conn == C_WF_REPORT_PARAMS);
+}
+
+static union drbd_state
+apply_mask_val(union drbd_state os, union drbd_state mask, union drbd_state val)
+{
+	union drbd_state ns;
+	ns.i = (os.i & ~mask.i) | val.i;
+	return ns;
+}
+
+enum drbd_state_rv
+drbd_change_state(struct drbd_device *device, enum chg_state_flags f,
+		  union drbd_state mask, union drbd_state val)
+{
+	unsigned long flags;
+	union drbd_state ns;
+	enum drbd_state_rv rv;
+
+	spin_lock_irqsave(&device->resource->req_lock, flags);
+	ns = apply_mask_val(drbd_read_state(device), mask, val);
+	rv = _drbd_set_state(device, ns, f, NULL);
+	spin_unlock_irqrestore(&device->resource->req_lock, flags);
+
+	return rv;
+}
+
+/**
+ * drbd_force_state() - Impose a change which happens outside our control on our state
+ * @device:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ */
+void drbd_force_state(struct drbd_device *device,
+	union drbd_state mask, union drbd_state val)
+{
+	drbd_change_state(device, CS_HARD, mask, val);
+}
+
+static enum drbd_state_rv
+_req_st_cond(struct drbd_device *device, union drbd_state mask,
+	     union drbd_state val)
+{
+	union drbd_state os, ns;
+	unsigned long flags;
+	enum drbd_state_rv rv;
+
+	if (test_and_clear_bit(CL_ST_CHG_SUCCESS, &device->flags))
+		return SS_CW_SUCCESS;
+
+	if (test_and_clear_bit(CL_ST_CHG_FAIL, &device->flags))
+		return SS_CW_FAILED_BY_PEER;
+
+	spin_lock_irqsave(&device->resource->req_lock, flags);
+	os = drbd_read_state(device);
+	ns = sanitize_state(device, os, apply_mask_val(os, mask, val), NULL);
+	rv = is_valid_transition(os, ns);
+	if (rv >= SS_SUCCESS)
+		rv = SS_UNKNOWN_ERROR;  /* cont waiting, otherwise fail. */
+
+	if (!cl_wide_st_chg(device, os, ns))
+		rv = SS_CW_NO_NEED;
+	if (rv == SS_UNKNOWN_ERROR) {
+		rv = is_valid_state(device, ns);
+		if (rv >= SS_SUCCESS) {
+			rv = is_valid_soft_transition(os, ns, first_peer_device(device)->connection);
+			if (rv >= SS_SUCCESS)
+				rv = SS_UNKNOWN_ERROR; /* cont waiting, otherwise fail. */
+		}
+	}
+	spin_unlock_irqrestore(&device->resource->req_lock, flags);
+
+	return rv;
+}
+
+/**
+ * drbd_req_state() - Perform an eventually cluster wide state change
+ * @device:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ * @f:		flags
+ *
+ * Should not be called directly, use drbd_request_state() or
+ * _drbd_request_state().
+ */
+static enum drbd_state_rv
+drbd_req_state(struct drbd_device *device, union drbd_state mask,
+	       union drbd_state val, enum chg_state_flags f)
+{
+	struct completion done;
+	unsigned long flags;
+	union drbd_state os, ns;
+	enum drbd_state_rv rv;
+	void *buffer = NULL;
+
+	init_completion(&done);
+
+	if (f & CS_SERIALIZE)
+		mutex_lock(device->state_mutex);
+	if (f & CS_INHIBIT_MD_IO)
+		buffer = drbd_md_get_buffer(device, __func__);
+
+	spin_lock_irqsave(&device->resource->req_lock, flags);
+	os = drbd_read_state(device);
+	ns = sanitize_state(device, os, apply_mask_val(os, mask, val), NULL);
+	rv = is_valid_transition(os, ns);
+	if (rv < SS_SUCCESS) {
+		spin_unlock_irqrestore(&device->resource->req_lock, flags);
+		goto abort;
+	}
+
+	if (cl_wide_st_chg(device, os, ns)) {
+		rv = is_valid_state(device, ns);
+		if (rv == SS_SUCCESS)
+			rv = is_valid_soft_transition(os, ns, first_peer_device(device)->connection);
+		spin_unlock_irqrestore(&device->resource->req_lock, flags);
+
+		if (rv < SS_SUCCESS) {
+			if (f & CS_VERBOSE)
+				print_st_err(device, os, ns, rv);
+			goto abort;
+		}
+
+		if (drbd_send_state_req(first_peer_device(device), mask, val)) {
+			rv = SS_CW_FAILED_BY_PEER;
+			if (f & CS_VERBOSE)
+				print_st_err(device, os, ns, rv);
+			goto abort;
+		}
+
+		wait_event(device->state_wait,
+			(rv = _req_st_cond(device, mask, val)));
+
+		if (rv < SS_SUCCESS) {
+			if (f & CS_VERBOSE)
+				print_st_err(device, os, ns, rv);
+			goto abort;
+		}
+		spin_lock_irqsave(&device->resource->req_lock, flags);
+		ns = apply_mask_val(drbd_read_state(device), mask, val);
+		rv = _drbd_set_state(device, ns, f, &done);
+	} else {
+		rv = _drbd_set_state(device, ns, f, &done);
+	}
+
+	spin_unlock_irqrestore(&device->resource->req_lock, flags);
+
+	if (f & CS_WAIT_COMPLETE && rv == SS_SUCCESS) {
+		D_ASSERT(device, current != first_peer_device(device)->connection->worker.task);
+		wait_for_completion(&done);
+	}
+
+abort:
+	if (buffer)
+		drbd_md_put_buffer(device);
+	if (f & CS_SERIALIZE)
+		mutex_unlock(device->state_mutex);
+
+	return rv;
+}
+
+/**
+ * _drbd_request_state() - Request a state change (with flags)
+ * @device:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ * @f:		flags
+ *
+ * Cousin of drbd_request_state(), useful with the CS_WAIT_COMPLETE
+ * flag, or when logging of failed state change requests is not desired.
+ */
+enum drbd_state_rv
+_drbd_request_state(struct drbd_device *device, union drbd_state mask,
+		    union drbd_state val, enum chg_state_flags f)
+{
+	enum drbd_state_rv rv;
+
+	wait_event(device->state_wait,
+		   (rv = drbd_req_state(device, mask, val, f)) != SS_IN_TRANSIENT_STATE);
+
+	return rv;
+}
+
+/*
+ * We grab drbd_md_get_buffer(), because we don't want to "fail" the disk while
+ * there is IO in-flight: the transition into D_FAILED for detach purposes
+ * may get misinterpreted as actual IO error in a confused endio function.
+ *
+ * We wrap it all into wait_event(), to retry in case the drbd_req_state()
+ * returns SS_IN_TRANSIENT_STATE.
+ *
+ * To avoid potential deadlock with e.g. the receiver thread trying to grab
+ * drbd_md_get_buffer() while trying to get out of the "transient state", we
+ * need to grab and release the meta data buffer inside of that wait_event loop.
+ */
+static enum drbd_state_rv
+request_detach(struct drbd_device *device)
+{
+	return drbd_req_state(device, NS(disk, D_FAILED),
+			CS_VERBOSE | CS_ORDERED | CS_INHIBIT_MD_IO);
+}
+
+int drbd_request_detach_interruptible(struct drbd_device *device)
+{
+	int ret, rv;
+
+	drbd_suspend_io(device); /* so no-one is stuck in drbd_al_begin_io */
+	wait_event_interruptible(device->state_wait,
+		(rv = request_detach(device)) != SS_IN_TRANSIENT_STATE);
+	drbd_resume_io(device);
+
+	ret = wait_event_interruptible(device->misc_wait,
+			device->state.disk != D_FAILED);
+
+	if (rv == SS_IS_DISKLESS)
+		rv = SS_NOTHING_TO_DO;
+	if (ret)
+		rv = ERR_INTR;
+
+	return rv;
+}
+
+enum drbd_state_rv
+_drbd_request_state_holding_state_mutex(struct drbd_device *device, union drbd_state mask,
+		    union drbd_state val, enum chg_state_flags f)
+{
+	enum drbd_state_rv rv;
+
+	BUG_ON(f & CS_SERIALIZE);
+
+	wait_event_cmd(device->state_wait,
+		       (rv = drbd_req_state(device, mask, val, f)) != SS_IN_TRANSIENT_STATE,
+		       mutex_unlock(device->state_mutex),
+		       mutex_lock(device->state_mutex));
+
+	return rv;
+}
+
+static void print_st(struct drbd_device *device, const char *name, union drbd_state ns)
+{
+	drbd_err(device, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c%c%c }\n",
+	    name,
+	    drbd_conn_str(ns.conn),
+	    drbd_role_str(ns.role),
+	    drbd_role_str(ns.peer),
+	    drbd_disk_str(ns.disk),
+	    drbd_disk_str(ns.pdsk),
+	    is_susp(ns) ? 's' : 'r',
+	    ns.aftr_isp ? 'a' : '-',
+	    ns.peer_isp ? 'p' : '-',
+	    ns.user_isp ? 'u' : '-',
+	    ns.susp_fen ? 'F' : '-',
+	    ns.susp_nod ? 'N' : '-'
+	    );
+}
+
+void print_st_err(struct drbd_device *device, union drbd_state os,
+	          union drbd_state ns, enum drbd_state_rv err)
+{
+	if (err == SS_IN_TRANSIENT_STATE)
+		return;
+	drbd_err(device, "State change failed: %s\n", drbd_set_st_err_str(err));
+	print_st(device, " state", os);
+	print_st(device, "wanted", ns);
+}
+
+static long print_state_change(char *pb, union drbd_state os, union drbd_state ns,
+			       enum chg_state_flags flags)
+{
+	char *pbp;
+	pbp = pb;
+	*pbp = 0;
+
+	if (ns.role != os.role && flags & CS_DC_ROLE)
+		pbp += sprintf(pbp, "role( %s -> %s ) ",
+			       drbd_role_str(os.role),
+			       drbd_role_str(ns.role));
+	if (ns.peer != os.peer && flags & CS_DC_PEER)
+		pbp += sprintf(pbp, "peer( %s -> %s ) ",
+			       drbd_role_str(os.peer),
+			       drbd_role_str(ns.peer));
+	if (ns.conn != os.conn && flags & CS_DC_CONN)
+		pbp += sprintf(pbp, "conn( %s -> %s ) ",
+			       drbd_conn_str(os.conn),
+			       drbd_conn_str(ns.conn));
+	if (ns.disk != os.disk && flags & CS_DC_DISK)
+		pbp += sprintf(pbp, "disk( %s -> %s ) ",
+			       drbd_disk_str(os.disk),
+			       drbd_disk_str(ns.disk));
+	if (ns.pdsk != os.pdsk && flags & CS_DC_PDSK)
+		pbp += sprintf(pbp, "pdsk( %s -> %s ) ",
+			       drbd_disk_str(os.pdsk),
+			       drbd_disk_str(ns.pdsk));
+
+	return pbp - pb;
+}
+
+static void drbd_pr_state_change(struct drbd_device *device, union drbd_state os, union drbd_state ns,
+				 enum chg_state_flags flags)
+{
+	char pb[300];
+	char *pbp = pb;
+
+	pbp += print_state_change(pbp, os, ns, flags ^ CS_DC_MASK);
+
+	if (ns.aftr_isp != os.aftr_isp)
+		pbp += sprintf(pbp, "aftr_isp( %d -> %d ) ",
+			       os.aftr_isp,
+			       ns.aftr_isp);
+	if (ns.peer_isp != os.peer_isp)
+		pbp += sprintf(pbp, "peer_isp( %d -> %d ) ",
+			       os.peer_isp,
+			       ns.peer_isp);
+	if (ns.user_isp != os.user_isp)
+		pbp += sprintf(pbp, "user_isp( %d -> %d ) ",
+			       os.user_isp,
+			       ns.user_isp);
+
+	if (pbp != pb)
+		drbd_info(device, "%s\n", pb);
+}
+
+static void conn_pr_state_change(struct drbd_connection *connection, union drbd_state os, union drbd_state ns,
+				 enum chg_state_flags flags)
+{
+	char pb[300];
+	char *pbp = pb;
+
+	pbp += print_state_change(pbp, os, ns, flags);
+
+	if (is_susp(ns) != is_susp(os) && flags & CS_DC_SUSP)
+		pbp += sprintf(pbp, "susp( %d -> %d ) ",
+			       is_susp(os),
+			       is_susp(ns));
+
+	if (pbp != pb)
+		drbd_info(connection, "%s\n", pb);
+}
+
+
+/**
+ * is_valid_state() - Returns an SS_ error code if ns is not valid
+ * @device:	DRBD device.
+ * @ns:		State to consider.
+ */
+static enum drbd_state_rv
+is_valid_state(struct drbd_device *device, union drbd_state ns)
+{
+	/* See drbd_state_sw_errors in drbd_strings.c */
+
+	enum drbd_fencing_p fp;
+	enum drbd_state_rv rv = SS_SUCCESS;
+	struct net_conf *nc;
+
+	rcu_read_lock();
+	fp = FP_DONT_CARE;
+	if (get_ldev(device)) {
+		fp = rcu_dereference(device->ldev->disk_conf)->fencing;
+		put_ldev(device);
+	}
+
+	nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+	if (nc) {
+		if (!nc->two_primaries && ns.role == R_PRIMARY) {
+			if (ns.peer == R_PRIMARY)
+				rv = SS_TWO_PRIMARIES;
+			else if (conn_highest_peer(first_peer_device(device)->connection) == R_PRIMARY)
+				rv = SS_O_VOL_PEER_PRI;
+		}
+	}
+
+	if (rv <= 0)
+		goto out; /* already found a reason to abort */
+	else if (ns.role == R_SECONDARY && device->open_cnt)
+		rv = SS_DEVICE_IN_USE;
+
+	else if (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.disk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if (fp >= FP_RESOURCE &&
+		 ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk >= D_UNKNOWN)
+		rv = SS_PRIMARY_NOP;
+
+	else if (ns.role == R_PRIMARY && ns.disk <= D_INCONSISTENT && ns.pdsk <= D_INCONSISTENT)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.disk < D_INCONSISTENT)
+		rv = SS_NO_LOCAL_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.pdsk < D_INCONSISTENT)
+		rv = SS_NO_REMOTE_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if ((ns.conn == C_CONNECTED ||
+		  ns.conn == C_WF_BITMAP_S ||
+		  ns.conn == C_SYNC_SOURCE ||
+		  ns.conn == C_PAUSED_SYNC_S) &&
+		  ns.disk == D_OUTDATED)
+		rv = SS_CONNECTED_OUTDATES;
+
+	else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+		 (nc->verify_alg[0] == 0))
+		rv = SS_NO_VERIFY_ALG;
+
+	else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+		  first_peer_device(device)->connection->agreed_pro_version < 88)
+		rv = SS_NOT_SUPPORTED;
+
+	else if (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if ((ns.conn == C_STARTING_SYNC_S || ns.conn == C_STARTING_SYNC_T) &&
+                 ns.pdsk == D_UNKNOWN)
+		rv = SS_NEED_CONNECTION;
+
+	else if (ns.conn >= C_CONNECTED && ns.pdsk == D_UNKNOWN)
+		rv = SS_CONNECTED_OUTDATES;
+
+out:
+	rcu_read_unlock();
+
+	return rv;
+}
+
+/**
+ * is_valid_soft_transition() - Returns an SS_ error code if the state transition is not possible
+ * This function limits state transitions that may be declined by DRBD. I.e.
+ * user requests (aka soft transitions).
+ * @os:		old state.
+ * @ns:		new state.
+ * @connection:  DRBD connection.
+ */
+static enum drbd_state_rv
+is_valid_soft_transition(union drbd_state os, union drbd_state ns, struct drbd_connection *connection)
+{
+	enum drbd_state_rv rv = SS_SUCCESS;
+
+	if ((ns.conn == C_STARTING_SYNC_T || ns.conn == C_STARTING_SYNC_S) &&
+	    os.conn > C_CONNECTED)
+		rv = SS_RESYNC_RUNNING;
+
+	if (ns.conn == C_DISCONNECTING && os.conn == C_STANDALONE)
+		rv = SS_ALREADY_STANDALONE;
+
+	if (ns.disk > D_ATTACHING && os.disk == D_DISKLESS)
+		rv = SS_IS_DISKLESS;
+
+	if (ns.conn == C_WF_CONNECTION && os.conn < C_UNCONNECTED)
+		rv = SS_NO_NET_CONFIG;
+
+	if (ns.disk == D_OUTDATED && os.disk < D_OUTDATED && os.disk != D_ATTACHING)
+		rv = SS_LOWER_THAN_OUTDATED;
+
+	if (ns.conn == C_DISCONNECTING && os.conn == C_UNCONNECTED)
+		rv = SS_IN_TRANSIENT_STATE;
+
+	/* While establishing a connection only allow cstate to change.
+	   Delay/refuse role changes, detach attach etc... (they do not touch cstate) */
+	if (test_bit(STATE_SENT, &connection->flags) &&
+	    !((ns.conn == C_WF_REPORT_PARAMS && os.conn == C_WF_CONNECTION) ||
+	      (ns.conn >= C_CONNECTED && os.conn == C_WF_REPORT_PARAMS)))
+		rv = SS_IN_TRANSIENT_STATE;
+
+	/* Do not promote during resync handshake triggered by "force primary".
+	 * This is a hack. It should really be rejected by the peer during the
+	 * cluster wide state change request. */
+	if (os.role != R_PRIMARY && ns.role == R_PRIMARY
+		&& ns.pdsk == D_UP_TO_DATE
+		&& ns.disk != D_UP_TO_DATE && ns.disk != D_DISKLESS
+		&& (ns.conn <= C_WF_SYNC_UUID || ns.conn != os.conn))
+			rv = SS_IN_TRANSIENT_STATE;
+
+	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) && os.conn < C_CONNECTED)
+		rv = SS_NEED_CONNECTION;
+
+	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+	    ns.conn != os.conn && os.conn > C_CONNECTED)
+		rv = SS_RESYNC_RUNNING;
+
+	if ((ns.conn == C_STARTING_SYNC_S || ns.conn == C_STARTING_SYNC_T) &&
+	    os.conn < C_CONNECTED)
+		rv = SS_NEED_CONNECTION;
+
+	if ((ns.conn == C_SYNC_TARGET || ns.conn == C_SYNC_SOURCE)
+	    && os.conn < C_WF_REPORT_PARAMS)
+		rv = SS_NEED_CONNECTION; /* No NetworkFailure -> SyncTarget etc... */
+
+	if (ns.conn == C_DISCONNECTING && ns.pdsk == D_OUTDATED &&
+	    os.conn < C_CONNECTED && os.pdsk > D_OUTDATED)
+		rv = SS_OUTDATE_WO_CONN;
+
+	return rv;
+}
+
+static enum drbd_state_rv
+is_valid_conn_transition(enum drbd_conns oc, enum drbd_conns nc)
+{
+	/* no change -> nothing to do, at least for the connection part */
+	if (oc == nc)
+		return SS_NOTHING_TO_DO;
+
+	/* disconnect of an unconfigured connection does not make sense */
+	if (oc == C_STANDALONE && nc == C_DISCONNECTING)
+		return SS_ALREADY_STANDALONE;
+
+	/* from C_STANDALONE, we start with C_UNCONNECTED */
+	if (oc == C_STANDALONE && nc != C_UNCONNECTED)
+		return SS_NEED_CONNECTION;
+
+	/* When establishing a connection we need to go through WF_REPORT_PARAMS!
+	   Necessary to do the right thing upon invalidate-remote on a disconnected resource */
+	if (oc < C_WF_REPORT_PARAMS && nc >= C_CONNECTED)
+		return SS_NEED_CONNECTION;
+
+	/* After a network error only C_UNCONNECTED or C_DISCONNECTING may follow. */
+	if (oc >= C_TIMEOUT && oc <= C_TEAR_DOWN && nc != C_UNCONNECTED && nc != C_DISCONNECTING)
+		return SS_IN_TRANSIENT_STATE;
+
+	/* After C_DISCONNECTING only C_STANDALONE may follow */
+	if (oc == C_DISCONNECTING && nc != C_STANDALONE)
+		return SS_IN_TRANSIENT_STATE;
+
+	return SS_SUCCESS;
+}
+
+
+/**
+ * is_valid_transition() - Returns an SS_ error code if the state transition is not possible
+ * This limits hard state transitions. Hard state transitions are facts there are
+ * imposed on DRBD by the environment. E.g. disk broke or network broke down.
+ * But those hard state transitions are still not allowed to do everything.
+ * @ns:		new state.
+ * @os:		old state.
+ */
+static enum drbd_state_rv
+is_valid_transition(union drbd_state os, union drbd_state ns)
+{
+	enum drbd_state_rv rv;
+
+	rv = is_valid_conn_transition(os.conn, ns.conn);
+
+	/* we cannot fail (again) if we already detached */
+	if (ns.disk == D_FAILED && os.disk == D_DISKLESS)
+		rv = SS_IS_DISKLESS;
+
+	return rv;
+}
+
+static void print_sanitize_warnings(struct drbd_device *device, enum sanitize_state_warnings warn)
+{
+	static const char *msg_table[] = {
+		[NO_WARNING] = "",
+		[ABORTED_ONLINE_VERIFY] = "Online-verify aborted.",
+		[ABORTED_RESYNC] = "Resync aborted.",
+		[CONNECTION_LOST_NEGOTIATING] = "Connection lost while negotiating, no data!",
+		[IMPLICITLY_UPGRADED_DISK] = "Implicitly upgraded disk",
+		[IMPLICITLY_UPGRADED_PDSK] = "Implicitly upgraded pdsk",
+	};
+
+	if (warn != NO_WARNING)
+		drbd_warn(device, "%s\n", msg_table[warn]);
+}
+
+/**
+ * sanitize_state() - Resolves implicitly necessary additional changes to a state transition
+ * @device:	DRBD device.
+ * @os:		old state.
+ * @ns:		new state.
+ * @warn:	placeholder for returned state warning.
+ *
+ * When we loose connection, we have to set the state of the peers disk (pdsk)
+ * to D_UNKNOWN. This rule and many more along those lines are in this function.
+ */
+static union drbd_state sanitize_state(struct drbd_device *device, union drbd_state os,
+				       union drbd_state ns, enum sanitize_state_warnings *warn)
+{
+	enum drbd_fencing_p fp;
+	enum drbd_disk_state disk_min, disk_max, pdsk_min, pdsk_max;
+
+	if (warn)
+		*warn = NO_WARNING;
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(device)) {
+		rcu_read_lock();
+		fp = rcu_dereference(device->ldev->disk_conf)->fencing;
+		rcu_read_unlock();
+		put_ldev(device);
+	}
+
+	/* Implications from connection to peer and peer_isp */
+	if (ns.conn < C_CONNECTED) {
+		ns.peer_isp = 0;
+		ns.peer = R_UNKNOWN;
+		if (ns.pdsk > D_UNKNOWN || ns.pdsk < D_INCONSISTENT)
+			ns.pdsk = D_UNKNOWN;
+	}
+
+	/* Clear the aftr_isp when becoming unconfigured */
+	if (ns.conn == C_STANDALONE && ns.disk == D_DISKLESS && ns.role == R_SECONDARY)
+		ns.aftr_isp = 0;
+
+	/* An implication of the disk states onto the connection state */
+	/* Abort resync if a disk fails/detaches */
+	if (ns.conn > C_CONNECTED && (ns.disk <= D_FAILED || ns.pdsk <= D_FAILED)) {
+		if (warn)
+			*warn = ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T ?
+				ABORTED_ONLINE_VERIFY : ABORTED_RESYNC;
+		ns.conn = C_CONNECTED;
+	}
+
+	/* Connection breaks down before we finished "Negotiating" */
+	if (ns.conn < C_CONNECTED && ns.disk == D_NEGOTIATING &&
+	    get_ldev_if_state(device, D_NEGOTIATING)) {
+		if (device->ed_uuid == device->ldev->md.uuid[UI_CURRENT]) {
+			ns.disk = device->new_state_tmp.disk;
+			ns.pdsk = device->new_state_tmp.pdsk;
+		} else {
+			if (warn)
+				*warn = CONNECTION_LOST_NEGOTIATING;
+			ns.disk = D_DISKLESS;
+			ns.pdsk = D_UNKNOWN;
+		}
+		put_ldev(device);
+	}
+
+	/* D_CONSISTENT and D_OUTDATED vanish when we get connected */
+	if (ns.conn >= C_CONNECTED && ns.conn < C_AHEAD) {
+		if (ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED)
+			ns.disk = D_UP_TO_DATE;
+		if (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)
+			ns.pdsk = D_UP_TO_DATE;
+	}
+
+	/* Implications of the connection state on the disk states */
+	disk_min = D_DISKLESS;
+	disk_max = D_UP_TO_DATE;
+	pdsk_min = D_INCONSISTENT;
+	pdsk_max = D_UNKNOWN;
+	switch ((enum drbd_conns)ns.conn) {
+	case C_WF_BITMAP_T:
+	case C_PAUSED_SYNC_T:
+	case C_STARTING_SYNC_T:
+	case C_WF_SYNC_UUID:
+	case C_BEHIND:
+		disk_min = D_INCONSISTENT;
+		disk_max = D_OUTDATED;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_VERIFY_S:
+	case C_VERIFY_T:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_CONNECTED:
+		disk_min = D_DISKLESS;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_DISKLESS;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_WF_BITMAP_S:
+	case C_PAUSED_SYNC_S:
+	case C_STARTING_SYNC_S:
+	case C_AHEAD:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_INCONSISTENT;
+		pdsk_max = D_CONSISTENT; /* D_OUTDATED would be nice. But explicit outdate necessary*/
+		break;
+	case C_SYNC_TARGET:
+		disk_min = D_INCONSISTENT;
+		disk_max = D_INCONSISTENT;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_SYNC_SOURCE:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_INCONSISTENT;
+		pdsk_max = D_INCONSISTENT;
+		break;
+	case C_STANDALONE:
+	case C_DISCONNECTING:
+	case C_UNCONNECTED:
+	case C_TIMEOUT:
+	case C_BROKEN_PIPE:
+	case C_NETWORK_FAILURE:
+	case C_PROTOCOL_ERROR:
+	case C_TEAR_DOWN:
+	case C_WF_CONNECTION:
+	case C_WF_REPORT_PARAMS:
+	case C_MASK:
+		break;
+	}
+	if (ns.disk > disk_max)
+		ns.disk = disk_max;
+
+	if (ns.disk < disk_min) {
+		if (warn)
+			*warn = IMPLICITLY_UPGRADED_DISK;
+		ns.disk = disk_min;
+	}
+	if (ns.pdsk > pdsk_max)
+		ns.pdsk = pdsk_max;
+
+	if (ns.pdsk < pdsk_min) {
+		if (warn)
+			*warn = IMPLICITLY_UPGRADED_PDSK;
+		ns.pdsk = pdsk_min;
+	}
+
+	if (fp == FP_STONITH &&
+	    (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk > D_OUTDATED) &&
+	    !(os.role == R_PRIMARY && os.conn < C_CONNECTED && os.pdsk > D_OUTDATED))
+		ns.susp_fen = 1; /* Suspend IO while fence-peer handler runs (peer lost) */
+
+	if (device->resource->res_opts.on_no_data == OND_SUSPEND_IO &&
+	    (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE) &&
+	    !(os.role == R_PRIMARY && os.disk < D_UP_TO_DATE && os.pdsk < D_UP_TO_DATE))
+		ns.susp_nod = 1; /* Suspend IO while no data available (no accessible data available) */
+
+	if (ns.aftr_isp || ns.peer_isp || ns.user_isp) {
+		if (ns.conn == C_SYNC_SOURCE)
+			ns.conn = C_PAUSED_SYNC_S;
+		if (ns.conn == C_SYNC_TARGET)
+			ns.conn = C_PAUSED_SYNC_T;
+	} else {
+		if (ns.conn == C_PAUSED_SYNC_S)
+			ns.conn = C_SYNC_SOURCE;
+		if (ns.conn == C_PAUSED_SYNC_T)
+			ns.conn = C_SYNC_TARGET;
+	}
+
+	return ns;
+}
+
+void drbd_resume_al(struct drbd_device *device)
+{
+	if (test_and_clear_bit(AL_SUSPENDED, &device->flags))
+		drbd_info(device, "Resumed AL updates\n");
+}
+
+/* helper for _drbd_set_state */
+static void set_ov_position(struct drbd_device *device, enum drbd_conns cs)
+{
+	if (first_peer_device(device)->connection->agreed_pro_version < 90)
+		device->ov_start_sector = 0;
+	device->rs_total = drbd_bm_bits(device);
+	device->ov_position = 0;
+	if (cs == C_VERIFY_T) {
+		/* starting online verify from an arbitrary position
+		 * does not fit well into the existing protocol.
+		 * on C_VERIFY_T, we initialize ov_left and friends
+		 * implicitly in receive_DataRequest once the
+		 * first P_OV_REQUEST is received */
+		device->ov_start_sector = ~(sector_t)0;
+	} else {
+		unsigned long bit = BM_SECT_TO_BIT(device->ov_start_sector);
+		if (bit >= device->rs_total) {
+			device->ov_start_sector =
+				BM_BIT_TO_SECT(device->rs_total - 1);
+			device->rs_total = 1;
+		} else
+			device->rs_total -= bit;
+		device->ov_position = device->ov_start_sector;
+	}
+	device->ov_left = device->rs_total;
+}
+
+/**
+ * _drbd_set_state() - Set a new DRBD state
+ * @device:	DRBD device.
+ * @ns:		new state.
+ * @flags:	Flags
+ * @done:	Optional completion, that will get completed after the after_state_ch() finished
+ *
+ * Caller needs to hold req_lock. Do not call directly.
+ */
+enum drbd_state_rv
+_drbd_set_state(struct drbd_device *device, union drbd_state ns,
+	        enum chg_state_flags flags, struct completion *done)
+{
+	struct drbd_peer_device *peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	union drbd_state os;
+	enum drbd_state_rv rv = SS_SUCCESS;
+	enum sanitize_state_warnings ssw;
+	struct after_state_chg_work *ascw;
+	struct drbd_state_change *state_change;
+
+	os = drbd_read_state(device);
+
+	ns = sanitize_state(device, os, ns, &ssw);
+	if (ns.i == os.i)
+		return SS_NOTHING_TO_DO;
+
+	rv = is_valid_transition(os, ns);
+	if (rv < SS_SUCCESS)
+		return rv;
+
+	if (!(flags & CS_HARD)) {
+		/*  pre-state-change checks ; only look at ns  */
+		/* See drbd_state_sw_errors in drbd_strings.c */
+
+		rv = is_valid_state(device, ns);
+		if (rv < SS_SUCCESS) {
+			/* If the old state was illegal as well, then let
+			   this happen...*/
+
+			if (is_valid_state(device, os) == rv)
+				rv = is_valid_soft_transition(os, ns, connection);
+		} else
+			rv = is_valid_soft_transition(os, ns, connection);
+	}
+
+	if (rv < SS_SUCCESS) {
+		if (flags & CS_VERBOSE)
+			print_st_err(device, os, ns, rv);
+		return rv;
+	}
+
+	print_sanitize_warnings(device, ssw);
+
+	drbd_pr_state_change(device, os, ns, flags);
+
+	/* Display changes to the susp* flags that where caused by the call to
+	   sanitize_state(). Only display it here if we where not called from
+	   _conn_request_state() */
+	if (!(flags & CS_DC_SUSP))
+		conn_pr_state_change(connection, os, ns,
+				     (flags & ~CS_DC_MASK) | CS_DC_SUSP);
+
+	/* if we are going -> D_FAILED or D_DISKLESS, grab one extra reference
+	 * on the ldev here, to be sure the transition -> D_DISKLESS resp.
+	 * drbd_ldev_destroy() won't happen before our corresponding
+	 * after_state_ch works run, where we put_ldev again. */
+	if ((os.disk != D_FAILED && ns.disk == D_FAILED) ||
+	    (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))
+		atomic_inc(&device->local_cnt);
+
+	if (!is_sync_state(os.conn) && is_sync_state(ns.conn))
+		clear_bit(RS_DONE, &device->flags);
+
+	/* FIXME: Have any flags been set earlier in this function already? */
+	state_change = remember_old_state(device->resource, GFP_ATOMIC);
+
+	/* changes to local_cnt and device flags should be visible before
+	 * changes to state, which again should be visible before anything else
+	 * depending on that change happens. */
+	smp_wmb();
+	device->state.i = ns.i;
+	device->resource->susp = ns.susp;
+	device->resource->susp_nod = ns.susp_nod;
+	device->resource->susp_fen = ns.susp_fen;
+	smp_wmb();
+
+	remember_new_state(state_change);
+
+	/* put replicated vs not-replicated requests in seperate epochs */
+	if (drbd_should_do_remote((union drbd_dev_state)os.i) !=
+	    drbd_should_do_remote((union drbd_dev_state)ns.i))
+		start_new_tl_epoch(connection);
+
+	if (os.disk == D_ATTACHING && ns.disk >= D_NEGOTIATING)
+		drbd_print_uuids(device, "attached to UUIDs");
+
+	/* Wake up role changes, that were delayed because of connection establishing */
+	if (os.conn == C_WF_REPORT_PARAMS && ns.conn != C_WF_REPORT_PARAMS &&
+	    no_peer_wf_report_params(connection)) {
+		clear_bit(STATE_SENT, &connection->flags);
+		wake_up_all_devices(connection);
+	}
+
+	wake_up(&device->misc_wait);
+	wake_up(&device->state_wait);
+	wake_up(&connection->ping_wait);
+
+	/* Aborted verify run, or we reached the stop sector.
+	 * Log the last position, unless end-of-device. */
+	if ((os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) &&
+	    ns.conn <= C_CONNECTED) {
+		device->ov_start_sector =
+			BM_BIT_TO_SECT(drbd_bm_bits(device) - device->ov_left);
+		if (device->ov_left)
+			drbd_info(device, "Online Verify reached sector %llu\n",
+				(unsigned long long)device->ov_start_sector);
+	}
+
+	if ((os.conn == C_PAUSED_SYNC_T || os.conn == C_PAUSED_SYNC_S) &&
+	    (ns.conn == C_SYNC_TARGET  || ns.conn == C_SYNC_SOURCE)) {
+		drbd_info(device, "Syncer continues.\n");
+		device->rs_paused += (long)jiffies
+				  -(long)device->rs_mark_time[device->rs_last_mark];
+		if (ns.conn == C_SYNC_TARGET)
+			mod_timer(&device->resync_timer, jiffies);
+	}
+
+	if ((os.conn == C_SYNC_TARGET  || os.conn == C_SYNC_SOURCE) &&
+	    (ns.conn == C_PAUSED_SYNC_T || ns.conn == C_PAUSED_SYNC_S)) {
+		drbd_info(device, "Resync suspended\n");
+		device->rs_mark_time[device->rs_last_mark] = jiffies;
+	}
+
+	if (os.conn == C_CONNECTED &&
+	    (ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T)) {
+		unsigned long now = jiffies;
+		int i;
+
+		set_ov_position(device, ns.conn);
+		device->rs_start = now;
+		device->rs_last_sect_ev = 0;
+		device->ov_last_oos_size = 0;
+		device->ov_last_oos_start = 0;
+
+		for (i = 0; i < DRBD_SYNC_MARKS; i++) {
+			device->rs_mark_left[i] = device->ov_left;
+			device->rs_mark_time[i] = now;
+		}
+
+		drbd_rs_controller_reset(device);
+
+		if (ns.conn == C_VERIFY_S) {
+			drbd_info(device, "Starting Online Verify from sector %llu\n",
+					(unsigned long long)device->ov_position);
+			mod_timer(&device->resync_timer, jiffies);
+		}
+	}
+
+	if (get_ldev(device)) {
+		u32 mdf = device->ldev->md.flags & ~(MDF_CONSISTENT|MDF_PRIMARY_IND|
+						 MDF_CONNECTED_IND|MDF_WAS_UP_TO_DATE|
+						 MDF_PEER_OUT_DATED|MDF_CRASHED_PRIMARY);
+
+		mdf &= ~MDF_AL_CLEAN;
+		if (test_bit(CRASHED_PRIMARY, &device->flags))
+			mdf |= MDF_CRASHED_PRIMARY;
+		if (device->state.role == R_PRIMARY ||
+		    (device->state.pdsk < D_INCONSISTENT && device->state.peer == R_PRIMARY))
+			mdf |= MDF_PRIMARY_IND;
+		if (device->state.conn > C_WF_REPORT_PARAMS)
+			mdf |= MDF_CONNECTED_IND;
+		if (device->state.disk > D_INCONSISTENT)
+			mdf |= MDF_CONSISTENT;
+		if (device->state.disk > D_OUTDATED)
+			mdf |= MDF_WAS_UP_TO_DATE;
+		if (device->state.pdsk <= D_OUTDATED && device->state.pdsk >= D_INCONSISTENT)
+			mdf |= MDF_PEER_OUT_DATED;
+		if (mdf != device->ldev->md.flags) {
+			device->ldev->md.flags = mdf;
+			drbd_md_mark_dirty(device);
+		}
+		if (os.disk < D_CONSISTENT && ns.disk >= D_CONSISTENT)
+			drbd_set_ed_uuid(device, device->ldev->md.uuid[UI_CURRENT]);
+		put_ldev(device);
+	}
+
+	/* Peer was forced D_UP_TO_DATE & R_PRIMARY, consider to resync */
+	if (os.disk == D_INCONSISTENT && os.pdsk == D_INCONSISTENT &&
+	    os.peer == R_SECONDARY && ns.peer == R_PRIMARY)
+		set_bit(CONSIDER_RESYNC, &device->flags);
+
+	/* Receiver should clean up itself */
+	if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
+		drbd_thread_stop_nowait(&connection->receiver);
+
+	/* Now the receiver finished cleaning up itself, it should die */
+	if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
+		drbd_thread_stop_nowait(&connection->receiver);
+
+	/* Upon network failure, we need to restart the receiver. */
+	if (os.conn > C_WF_CONNECTION &&
+	    ns.conn <= C_TEAR_DOWN && ns.conn >= C_TIMEOUT)
+		drbd_thread_restart_nowait(&connection->receiver);
+
+	/* Resume AL writing if we get a connection */
+	if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED) {
+		drbd_resume_al(device);
+		connection->connect_cnt++;
+	}
+
+	/* remember last attach time so request_timer_fn() won't
+	 * kill newly established sessions while we are still trying to thaw
+	 * previously frozen IO */
+	if ((os.disk == D_ATTACHING || os.disk == D_NEGOTIATING) &&
+	    ns.disk > D_NEGOTIATING)
+		device->last_reattach_jif = jiffies;
+
+	ascw = kmalloc(sizeof(*ascw), GFP_ATOMIC);
+	if (ascw) {
+		ascw->os = os;
+		ascw->ns = ns;
+		ascw->flags = flags;
+		ascw->w.cb = w_after_state_ch;
+		ascw->device = device;
+		ascw->done = done;
+		ascw->state_change = state_change;
+		drbd_queue_work(&connection->sender_work,
+				&ascw->w);
+	} else {
+		drbd_err(device, "Could not kmalloc an ascw\n");
+	}
+
+	return rv;
+}
+
+static int w_after_state_ch(struct drbd_work *w, int unused)
+{
+	struct after_state_chg_work *ascw =
+		container_of(w, struct after_state_chg_work, w);
+	struct drbd_device *device = ascw->device;
+
+	after_state_ch(device, ascw->os, ascw->ns, ascw->flags, ascw->state_change);
+	forget_state_change(ascw->state_change);
+	if (ascw->flags & CS_WAIT_COMPLETE)
+		complete(ascw->done);
+	kfree(ascw);
+
+	return 0;
+}
+
+static void abw_start_sync(struct drbd_device *device, int rv)
+{
+	if (rv) {
+		drbd_err(device, "Writing the bitmap failed not starting resync.\n");
+		_drbd_request_state(device, NS(conn, C_CONNECTED), CS_VERBOSE);
+		return;
+	}
+
+	switch (device->state.conn) {
+	case C_STARTING_SYNC_T:
+		_drbd_request_state(device, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+		break;
+	case C_STARTING_SYNC_S:
+		drbd_start_resync(device, C_SYNC_SOURCE);
+		break;
+	}
+}
+
+int drbd_bitmap_io_from_worker(struct drbd_device *device,
+		int (*io_fn)(struct drbd_device *),
+		char *why, enum bm_flag flags)
+{
+	int rv;
+
+	D_ASSERT(device, current == first_peer_device(device)->connection->worker.task);
+
+	/* open coded non-blocking drbd_suspend_io(device); */
+	atomic_inc(&device->suspend_cnt);
+
+	drbd_bm_lock(device, why, flags);
+	rv = io_fn(device);
+	drbd_bm_unlock(device);
+
+	drbd_resume_io(device);
+
+	return rv;
+}
+
+int notify_resource_state_change(struct sk_buff *skb,
+				  unsigned int seq,
+				  struct drbd_resource_state_change *resource_state_change,
+				  enum drbd_notification_type type)
+{
+	struct drbd_resource *resource = resource_state_change->resource;
+	struct resource_info resource_info = {
+		.res_role = resource_state_change->role[NEW],
+		.res_susp = resource_state_change->susp[NEW],
+		.res_susp_nod = resource_state_change->susp_nod[NEW],
+		.res_susp_fen = resource_state_change->susp_fen[NEW],
+	};
+
+	return notify_resource_state(skb, seq, resource, &resource_info, type);
+}
+
+int notify_connection_state_change(struct sk_buff *skb,
+				    unsigned int seq,
+				    struct drbd_connection_state_change *connection_state_change,
+				    enum drbd_notification_type type)
+{
+	struct drbd_connection *connection = connection_state_change->connection;
+	struct connection_info connection_info = {
+		.conn_connection_state = connection_state_change->cstate[NEW],
+		.conn_role = connection_state_change->peer_role[NEW],
+	};
+
+	return notify_connection_state(skb, seq, connection, &connection_info, type);
+}
+
+int notify_device_state_change(struct sk_buff *skb,
+				unsigned int seq,
+				struct drbd_device_state_change *device_state_change,
+				enum drbd_notification_type type)
+{
+	struct drbd_device *device = device_state_change->device;
+	struct device_info device_info = {
+		.dev_disk_state = device_state_change->disk_state[NEW],
+	};
+
+	return notify_device_state(skb, seq, device, &device_info, type);
+}
+
+int notify_peer_device_state_change(struct sk_buff *skb,
+				     unsigned int seq,
+				     struct drbd_peer_device_state_change *p,
+				     enum drbd_notification_type type)
+{
+	struct drbd_peer_device *peer_device = p->peer_device;
+	struct peer_device_info peer_device_info = {
+		.peer_repl_state = p->repl_state[NEW],
+		.peer_disk_state = p->disk_state[NEW],
+		.peer_resync_susp_user = p->resync_susp_user[NEW],
+		.peer_resync_susp_peer = p->resync_susp_peer[NEW],
+		.peer_resync_susp_dependency = p->resync_susp_dependency[NEW],
+	};
+
+	return notify_peer_device_state(skb, seq, peer_device, &peer_device_info, type);
+}
+
+static void broadcast_state_change(struct drbd_state_change *state_change)
+{
+	struct drbd_resource_state_change *resource_state_change = &state_change->resource[0];
+	bool resource_state_has_changed;
+	unsigned int n_device, n_connection, n_peer_device, n_peer_devices;
+	int (*last_func)(struct sk_buff *, unsigned int, void *,
+			  enum drbd_notification_type) = NULL;
+	void *last_arg = NULL;
+
+#define HAS_CHANGED(state) ((state)[OLD] != (state)[NEW])
+#define FINAL_STATE_CHANGE(type) \
+	({ if (last_func) \
+		last_func(NULL, 0, last_arg, type); \
+	})
+#define REMEMBER_STATE_CHANGE(func, arg, type) \
+	({ FINAL_STATE_CHANGE(type | NOTIFY_CONTINUES); \
+	   last_func = (typeof(last_func))func; \
+	   last_arg = arg; \
+	 })
+
+	mutex_lock(&notification_mutex);
+
+	resource_state_has_changed =
+	    HAS_CHANGED(resource_state_change->role) ||
+	    HAS_CHANGED(resource_state_change->susp) ||
+	    HAS_CHANGED(resource_state_change->susp_nod) ||
+	    HAS_CHANGED(resource_state_change->susp_fen);
+
+	if (resource_state_has_changed)
+		REMEMBER_STATE_CHANGE(notify_resource_state_change,
+				      resource_state_change, NOTIFY_CHANGE);
+
+	for (n_connection = 0; n_connection < state_change->n_connections; n_connection++) {
+		struct drbd_connection_state_change *connection_state_change =
+				&state_change->connections[n_connection];
+
+		if (HAS_CHANGED(connection_state_change->peer_role) ||
+		    HAS_CHANGED(connection_state_change->cstate))
+			REMEMBER_STATE_CHANGE(notify_connection_state_change,
+					      connection_state_change, NOTIFY_CHANGE);
+	}
+
+	for (n_device = 0; n_device < state_change->n_devices; n_device++) {
+		struct drbd_device_state_change *device_state_change =
+			&state_change->devices[n_device];
+
+		if (HAS_CHANGED(device_state_change->disk_state))
+			REMEMBER_STATE_CHANGE(notify_device_state_change,
+					      device_state_change, NOTIFY_CHANGE);
+	}
+
+	n_peer_devices = state_change->n_devices * state_change->n_connections;
+	for (n_peer_device = 0; n_peer_device < n_peer_devices; n_peer_device++) {
+		struct drbd_peer_device_state_change *p =
+			&state_change->peer_devices[n_peer_device];
+
+		if (HAS_CHANGED(p->disk_state) ||
+		    HAS_CHANGED(p->repl_state) ||
+		    HAS_CHANGED(p->resync_susp_user) ||
+		    HAS_CHANGED(p->resync_susp_peer) ||
+		    HAS_CHANGED(p->resync_susp_dependency))
+			REMEMBER_STATE_CHANGE(notify_peer_device_state_change,
+					      p, NOTIFY_CHANGE);
+	}
+
+	FINAL_STATE_CHANGE(NOTIFY_CHANGE);
+	mutex_unlock(&notification_mutex);
+
+#undef HAS_CHANGED
+#undef FINAL_STATE_CHANGE
+#undef REMEMBER_STATE_CHANGE
+}
+
+/* takes old and new peer disk state */
+static bool lost_contact_to_peer_data(enum drbd_disk_state os, enum drbd_disk_state ns)
+{
+	if ((os >= D_INCONSISTENT && os != D_UNKNOWN && os != D_OUTDATED)
+	&&  (ns < D_INCONSISTENT || ns == D_UNKNOWN || ns == D_OUTDATED))
+		return true;
+
+	/* Scenario, starting with normal operation
+	 * Connected Primary/Secondary UpToDate/UpToDate
+	 * NetworkFailure Primary/Unknown UpToDate/DUnknown (frozen)
+	 * ...
+	 * Connected Primary/Secondary UpToDate/Diskless (resumed; needs to bump uuid!)
+	 */
+	if (os == D_UNKNOWN
+	&&  (ns == D_DISKLESS || ns == D_FAILED || ns == D_OUTDATED))
+		return true;
+
+	return false;
+}
+
+/**
+ * after_state_ch() - Perform after state change actions that may sleep
+ * @device:	DRBD device.
+ * @os:		old state.
+ * @ns:		new state.
+ * @flags:	Flags
+ * @state_change: state change to broadcast
+ */
+static void after_state_ch(struct drbd_device *device, union drbd_state os,
+			   union drbd_state ns, enum chg_state_flags flags,
+			   struct drbd_state_change *state_change)
+{
+	struct drbd_resource *resource = device->resource;
+	struct drbd_peer_device *peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	struct sib_info sib;
+
+	broadcast_state_change(state_change);
+
+	sib.sib_reason = SIB_STATE_CHANGE;
+	sib.os = os;
+	sib.ns = ns;
+
+	if ((os.disk != D_UP_TO_DATE || os.pdsk != D_UP_TO_DATE)
+	&&  (ns.disk == D_UP_TO_DATE && ns.pdsk == D_UP_TO_DATE)) {
+		clear_bit(CRASHED_PRIMARY, &device->flags);
+		if (device->p_uuid)
+			device->p_uuid[UI_FLAGS] &= ~((u64)2);
+	}
+
+	/* Inform userspace about the change... */
+	drbd_bcast_event(device, &sib);
+
+	if (!(os.role == R_PRIMARY && os.disk < D_UP_TO_DATE && os.pdsk < D_UP_TO_DATE) &&
+	    (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE))
+		drbd_khelper(device, "pri-on-incon-degr");
+
+	/* Here we have the actions that are performed after a
+	   state change. This function might sleep */
+
+	if (ns.susp_nod) {
+		enum drbd_req_event what = NOTHING;
+
+		spin_lock_irq(&device->resource->req_lock);
+		if (os.conn < C_CONNECTED && conn_lowest_conn(connection) >= C_CONNECTED)
+			what = RESEND;
+
+		if ((os.disk == D_ATTACHING || os.disk == D_NEGOTIATING) &&
+		    conn_lowest_disk(connection) == D_UP_TO_DATE)
+			what = RESTART_FROZEN_DISK_IO;
+
+		if (resource->susp_nod && what != NOTHING) {
+			_tl_restart(connection, what);
+			_conn_request_state(connection,
+					    (union drbd_state) { { .susp_nod = 1 } },
+					    (union drbd_state) { { .susp_nod = 0 } },
+					    CS_VERBOSE);
+		}
+		spin_unlock_irq(&device->resource->req_lock);
+	}
+
+	if (ns.susp_fen) {
+		spin_lock_irq(&device->resource->req_lock);
+		if (resource->susp_fen && conn_lowest_conn(connection) >= C_CONNECTED) {
+			/* case2: The connection was established again: */
+			struct drbd_peer_device *peer_device;
+			int vnr;
+
+			rcu_read_lock();
+			idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
+				clear_bit(NEW_CUR_UUID, &peer_device->device->flags);
+			rcu_read_unlock();
+
+			/* We should actively create a new uuid, _before_
+			 * we resume/resent, if the peer is diskless
+			 * (recovery from a multiple error scenario).
+			 * Currently, this happens with a slight delay
+			 * below when checking lost_contact_to_peer_data() ...
+			 */
+			_tl_restart(connection, RESEND);
+			_conn_request_state(connection,
+					    (union drbd_state) { { .susp_fen = 1 } },
+					    (union drbd_state) { { .susp_fen = 0 } },
+					    CS_VERBOSE);
+		}
+		spin_unlock_irq(&device->resource->req_lock);
+	}
+
+	/* Became sync source.  With protocol >= 96, we still need to send out
+	 * the sync uuid now. Need to do that before any drbd_send_state, or
+	 * the other side may go "paused sync" before receiving the sync uuids,
+	 * which is unexpected. */
+	if ((os.conn != C_SYNC_SOURCE && os.conn != C_PAUSED_SYNC_S) &&
+	    (ns.conn == C_SYNC_SOURCE || ns.conn == C_PAUSED_SYNC_S) &&
+	    connection->agreed_pro_version >= 96 && get_ldev(device)) {
+		drbd_gen_and_send_sync_uuid(peer_device);
+		put_ldev(device);
+	}
+
+	/* Do not change the order of the if above and the two below... */
+	if (os.pdsk == D_DISKLESS &&
+	    ns.pdsk > D_DISKLESS && ns.pdsk != D_UNKNOWN) {      /* attach on the peer */
+		/* we probably will start a resync soon.
+		 * make sure those things are properly reset. */
+		device->rs_total = 0;
+		device->rs_failed = 0;
+		atomic_set(&device->rs_pending_cnt, 0);
+		drbd_rs_cancel_all(device);
+
+		drbd_send_uuids(peer_device);
+		drbd_send_state(peer_device, ns);
+	}
+	/* No point in queuing send_bitmap if we don't have a connection
+	 * anymore, so check also the _current_ state, not only the new state
+	 * at the time this work was queued. */
+	if (os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S &&
+	    device->state.conn == C_WF_BITMAP_S)
+		drbd_queue_bitmap_io(device, &drbd_send_bitmap, NULL,
+				"send_bitmap (WFBitMapS)",
+				BM_LOCKED_TEST_ALLOWED);
+
+	/* Lost contact to peer's copy of the data */
+	if (lost_contact_to_peer_data(os.pdsk, ns.pdsk)) {
+		if (get_ldev(device)) {
+			if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
+			    device->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
+				if (drbd_suspended(device)) {
+					set_bit(NEW_CUR_UUID, &device->flags);
+				} else {
+					drbd_uuid_new_current(device);
+					drbd_send_uuids(peer_device);
+				}
+			}
+			put_ldev(device);
+		}
+	}
+
+	if (ns.pdsk < D_INCONSISTENT && get_ldev(device)) {
+		if (os.peer != R_PRIMARY && ns.peer == R_PRIMARY &&
+		    device->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
+			drbd_uuid_new_current(device);
+			drbd_send_uuids(peer_device);
+		}
+		/* D_DISKLESS Peer becomes secondary */
+		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
+			/* We may still be Primary ourselves.
+			 * No harm done if the bitmap still changes,
+			 * redirtied pages will follow later. */
+			drbd_bitmap_io_from_worker(device, &drbd_bm_write,
+				"demote diskless peer", BM_LOCKED_SET_ALLOWED);
+		put_ldev(device);
+	}
+
+	/* Write out all changed bits on demote.
+	 * Though, no need to da that just yet
+	 * if there is a resync going on still */
+	if (os.role == R_PRIMARY && ns.role == R_SECONDARY &&
+		device->state.conn <= C_CONNECTED && get_ldev(device)) {
+		/* No changes to the bitmap expected this time, so assert that,
+		 * even though no harm was done if it did change. */
+		drbd_bitmap_io_from_worker(device, &drbd_bm_write,
+				"demote", BM_LOCKED_TEST_ALLOWED);
+		put_ldev(device);
+	}
+
+	/* Last part of the attaching process ... */
+	if (ns.conn >= C_CONNECTED &&
+	    os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
+		drbd_send_sizes(peer_device, 0, 0);  /* to start sync... */
+		drbd_send_uuids(peer_device);
+		drbd_send_state(peer_device, ns);
+	}
+
+	/* We want to pause/continue resync, tell peer. */
+	if (ns.conn >= C_CONNECTED &&
+	     ((os.aftr_isp != ns.aftr_isp) ||
+	      (os.user_isp != ns.user_isp)))
+		drbd_send_state(peer_device, ns);
+
+	/* In case one of the isp bits got set, suspend other devices. */
+	if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
+	    (ns.aftr_isp || ns.peer_isp || ns.user_isp))
+		suspend_other_sg(device);
+
+	/* Make sure the peer gets informed about eventual state
+	   changes (ISP bits) while we were in WFReportParams. */
+	if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
+		drbd_send_state(peer_device, ns);
+
+	if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
+		drbd_send_state(peer_device, ns);
+
+	/* We are in the progress to start a full sync... */
+	if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+	    (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S))
+		/* no other bitmap changes expected during this phase */
+		drbd_queue_bitmap_io(device,
+			&drbd_bmio_set_n_write, &abw_start_sync,
+			"set_n_write from StartingSync", BM_LOCKED_TEST_ALLOWED);
+
+	/* first half of local IO error, failure to attach,
+	 * or administrative detach */
+	if (os.disk != D_FAILED && ns.disk == D_FAILED) {
+		enum drbd_io_error_p eh = EP_PASS_ON;
+		int was_io_error = 0;
+		/* corresponding get_ldev was in _drbd_set_state, to serialize
+		 * our cleanup here with the transition to D_DISKLESS.
+		 * But is is still not save to dreference ldev here, since
+		 * we might come from an failed Attach before ldev was set. */
+		if (device->ldev) {
+			rcu_read_lock();
+			eh = rcu_dereference(device->ldev->disk_conf)->on_io_error;
+			rcu_read_unlock();
+
+			was_io_error = test_and_clear_bit(WAS_IO_ERROR, &device->flags);
+
+			/* Intentionally call this handler first, before drbd_send_state().
+			 * See: 2932204 drbd: call local-io-error handler early
+			 * People may chose to hard-reset the box from this handler.
+			 * It is useful if this looks like a "regular node crash". */
+			if (was_io_error && eh == EP_CALL_HELPER)
+				drbd_khelper(device, "local-io-error");
+
+			/* Immediately allow completion of all application IO,
+			 * that waits for completion from the local disk,
+			 * if this was a force-detach due to disk_timeout
+			 * or administrator request (drbdsetup detach --force).
+			 * Do NOT abort otherwise.
+			 * Aborting local requests may cause serious problems,
+			 * if requests are completed to upper layers already,
+			 * and then later the already submitted local bio completes.
+			 * This can cause DMA into former bio pages that meanwhile
+			 * have been re-used for other things.
+			 * So aborting local requests may cause crashes,
+			 * or even worse, silent data corruption.
+			 */
+			if (test_and_clear_bit(FORCE_DETACH, &device->flags))
+				tl_abort_disk_io(device);
+
+			/* current state still has to be D_FAILED,
+			 * there is only one way out: to D_DISKLESS,
+			 * and that may only happen after our put_ldev below. */
+			if (device->state.disk != D_FAILED)
+				drbd_err(device,
+					"ASSERT FAILED: disk is %s during detach\n",
+					drbd_disk_str(device->state.disk));
+
+			if (ns.conn >= C_CONNECTED)
+				drbd_send_state(peer_device, ns);
+
+			drbd_rs_cancel_all(device);
+
+			/* In case we want to get something to stable storage still,
+			 * this may be the last chance.
+			 * Following put_ldev may transition to D_DISKLESS. */
+			drbd_md_sync(device);
+		}
+		put_ldev(device);
+	}
+
+	/* second half of local IO error, failure to attach,
+	 * or administrative detach,
+	 * after local_cnt references have reached zero again */
+	if (os.disk != D_DISKLESS && ns.disk == D_DISKLESS) {
+		/* We must still be diskless,
+		 * re-attach has to be serialized with this! */
+		if (device->state.disk != D_DISKLESS)
+			drbd_err(device,
+				 "ASSERT FAILED: disk is %s while going diskless\n",
+				 drbd_disk_str(device->state.disk));
+
+		if (ns.conn >= C_CONNECTED)
+			drbd_send_state(peer_device, ns);
+		/* corresponding get_ldev in __drbd_set_state
+		 * this may finally trigger drbd_ldev_destroy. */
+		put_ldev(device);
+	}
+
+	/* Notify peer that I had a local IO error, and did not detached.. */
+	if (os.disk == D_UP_TO_DATE && ns.disk == D_INCONSISTENT && ns.conn >= C_CONNECTED)
+		drbd_send_state(peer_device, ns);
+
+	/* Disks got bigger while they were detached */
+	if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
+	    test_and_clear_bit(RESYNC_AFTER_NEG, &device->flags)) {
+		if (ns.conn == C_CONNECTED)
+			resync_after_online_grow(device);
+	}
+
+	/* A resync finished or aborted, wake paused devices... */
+	if ((os.conn > C_CONNECTED && ns.conn <= C_CONNECTED) ||
+	    (os.peer_isp && !ns.peer_isp) ||
+	    (os.user_isp && !ns.user_isp))
+		resume_next_sg(device);
+
+	/* sync target done with resync.  Explicitly notify peer, even though
+	 * it should (at least for non-empty resyncs) already know itself. */
+	if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
+		drbd_send_state(peer_device, ns);
+
+	/* Verify finished, or reached stop sector.  Peer did not know about
+	 * the stop sector, and we may even have changed the stop sector during
+	 * verify to interrupt/stop early.  Send the new state. */
+	if (os.conn == C_VERIFY_S && ns.conn == C_CONNECTED
+	&& verify_can_do_stop_sector(device))
+		drbd_send_state(peer_device, ns);
+
+	/* This triggers bitmap writeout of potentially still unwritten pages
+	 * if the resync finished cleanly, or aborted because of peer disk
+	 * failure, or on transition from resync back to AHEAD/BEHIND.
+	 *
+	 * Connection loss is handled in drbd_disconnected() by the receiver.
+	 *
+	 * For resync aborted because of local disk failure, we cannot do
+	 * any bitmap writeout anymore.
+	 *
+	 * No harm done if some bits change during this phase.
+	 */
+	if ((os.conn > C_CONNECTED && os.conn < C_AHEAD) &&
+	    (ns.conn == C_CONNECTED || ns.conn >= C_AHEAD) && get_ldev(device)) {
+		drbd_queue_bitmap_io(device, &drbd_bm_write_copy_pages, NULL,
+			"write from resync_finished", BM_LOCKED_CHANGE_ALLOWED);
+		put_ldev(device);
+	}
+
+	if (ns.disk == D_DISKLESS &&
+	    ns.conn == C_STANDALONE &&
+	    ns.role == R_SECONDARY) {
+		if (os.aftr_isp != ns.aftr_isp)
+			resume_next_sg(device);
+	}
+
+	drbd_md_sync(device);
+}
+
+struct after_conn_state_chg_work {
+	struct drbd_work w;
+	enum drbd_conns oc;
+	union drbd_state ns_min;
+	union drbd_state ns_max; /* new, max state, over all devices */
+	enum chg_state_flags flags;
+	struct drbd_connection *connection;
+	struct drbd_state_change *state_change;
+};
+
+static int w_after_conn_state_ch(struct drbd_work *w, int unused)
+{
+	struct after_conn_state_chg_work *acscw =
+		container_of(w, struct after_conn_state_chg_work, w);
+	struct drbd_connection *connection = acscw->connection;
+	enum drbd_conns oc = acscw->oc;
+	union drbd_state ns_max = acscw->ns_max;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	broadcast_state_change(acscw->state_change);
+	forget_state_change(acscw->state_change);
+	kfree(acscw);
+
+	/* Upon network configuration, we need to start the receiver */
+	if (oc == C_STANDALONE && ns_max.conn == C_UNCONNECTED)
+		drbd_thread_start(&connection->receiver);
+
+	if (oc == C_DISCONNECTING && ns_max.conn == C_STANDALONE) {
+		struct net_conf *old_conf;
+
+		mutex_lock(&notification_mutex);
+		idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
+			notify_peer_device_state(NULL, 0, peer_device, NULL,
+						 NOTIFY_DESTROY | NOTIFY_CONTINUES);
+		notify_connection_state(NULL, 0, connection, NULL, NOTIFY_DESTROY);
+		mutex_unlock(&notification_mutex);
+
+		mutex_lock(&connection->resource->conf_update);
+		old_conf = connection->net_conf;
+		connection->my_addr_len = 0;
+		connection->peer_addr_len = 0;
+		RCU_INIT_POINTER(connection->net_conf, NULL);
+		conn_free_crypto(connection);
+		mutex_unlock(&connection->resource->conf_update);
+
+		kvfree_rcu(old_conf);
+	}
+
+	if (ns_max.susp_fen) {
+		/* case1: The outdate peer handler is successful: */
+		if (ns_max.pdsk <= D_OUTDATED) {
+			rcu_read_lock();
+			idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+				struct drbd_device *device = peer_device->device;
+				if (test_bit(NEW_CUR_UUID, &device->flags)) {
+					drbd_uuid_new_current(device);
+					clear_bit(NEW_CUR_UUID, &device->flags);
+				}
+			}
+			rcu_read_unlock();
+			spin_lock_irq(&connection->resource->req_lock);
+			_tl_restart(connection, CONNECTION_LOST_WHILE_PENDING);
+			_conn_request_state(connection,
+					    (union drbd_state) { { .susp_fen = 1 } },
+					    (union drbd_state) { { .susp_fen = 0 } },
+					    CS_VERBOSE);
+			spin_unlock_irq(&connection->resource->req_lock);
+		}
+	}
+	conn_md_sync(connection);
+	kref_put(&connection->kref, drbd_destroy_connection);
+
+	return 0;
+}
+
+static void conn_old_common_state(struct drbd_connection *connection, union drbd_state *pcs, enum chg_state_flags *pf)
+{
+	enum chg_state_flags flags = ~0;
+	struct drbd_peer_device *peer_device;
+	int vnr, first_vol = 1;
+	union drbd_dev_state os, cs = {
+		{ .role = R_SECONDARY,
+		  .peer = R_UNKNOWN,
+		  .conn = connection->cstate,
+		  .disk = D_DISKLESS,
+		  .pdsk = D_UNKNOWN,
+		} };
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		os = device->state;
+
+		if (first_vol) {
+			cs = os;
+			first_vol = 0;
+			continue;
+		}
+
+		if (cs.role != os.role)
+			flags &= ~CS_DC_ROLE;
+
+		if (cs.peer != os.peer)
+			flags &= ~CS_DC_PEER;
+
+		if (cs.conn != os.conn)
+			flags &= ~CS_DC_CONN;
+
+		if (cs.disk != os.disk)
+			flags &= ~CS_DC_DISK;
+
+		if (cs.pdsk != os.pdsk)
+			flags &= ~CS_DC_PDSK;
+	}
+	rcu_read_unlock();
+
+	*pf |= CS_DC_MASK;
+	*pf &= flags;
+	(*pcs).i = cs.i;
+}
+
+static enum drbd_state_rv
+conn_is_valid_transition(struct drbd_connection *connection, union drbd_state mask, union drbd_state val,
+			 enum chg_state_flags flags)
+{
+	enum drbd_state_rv rv = SS_SUCCESS;
+	union drbd_state ns, os;
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		os = drbd_read_state(device);
+		ns = sanitize_state(device, os, apply_mask_val(os, mask, val), NULL);
+
+		if (flags & CS_IGN_OUTD_FAIL && ns.disk == D_OUTDATED && os.disk < D_OUTDATED)
+			ns.disk = os.disk;
+
+		if (ns.i == os.i)
+			continue;
+
+		rv = is_valid_transition(os, ns);
+
+		if (rv >= SS_SUCCESS && !(flags & CS_HARD)) {
+			rv = is_valid_state(device, ns);
+			if (rv < SS_SUCCESS) {
+				if (is_valid_state(device, os) == rv)
+					rv = is_valid_soft_transition(os, ns, connection);
+			} else
+				rv = is_valid_soft_transition(os, ns, connection);
+		}
+
+		if (rv < SS_SUCCESS) {
+			if (flags & CS_VERBOSE)
+				print_st_err(device, os, ns, rv);
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return rv;
+}
+
+static void
+conn_set_state(struct drbd_connection *connection, union drbd_state mask, union drbd_state val,
+	       union drbd_state *pns_min, union drbd_state *pns_max, enum chg_state_flags flags)
+{
+	union drbd_state ns, os, ns_max = { };
+	union drbd_state ns_min = {
+		{ .role = R_MASK,
+		  .peer = R_MASK,
+		  .conn = val.conn,
+		  .disk = D_MASK,
+		  .pdsk = D_MASK
+		} };
+	struct drbd_peer_device *peer_device;
+	enum drbd_state_rv rv;
+	int vnr, number_of_volumes = 0;
+
+	if (mask.conn == C_MASK) {
+		/* remember last connect time so request_timer_fn() won't
+		 * kill newly established sessions while we are still trying to thaw
+		 * previously frozen IO */
+		if (connection->cstate != C_WF_REPORT_PARAMS && val.conn == C_WF_REPORT_PARAMS)
+			connection->last_reconnect_jif = jiffies;
+
+		connection->cstate = val.conn;
+	}
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		number_of_volumes++;
+		os = drbd_read_state(device);
+		ns = apply_mask_val(os, mask, val);
+		ns = sanitize_state(device, os, ns, NULL);
+
+		if (flags & CS_IGN_OUTD_FAIL && ns.disk == D_OUTDATED && os.disk < D_OUTDATED)
+			ns.disk = os.disk;
+
+		rv = _drbd_set_state(device, ns, flags, NULL);
+		BUG_ON(rv < SS_SUCCESS);
+		ns.i = device->state.i;
+		ns_max.role = max_role(ns.role, ns_max.role);
+		ns_max.peer = max_role(ns.peer, ns_max.peer);
+		ns_max.conn = max_t(enum drbd_conns, ns.conn, ns_max.conn);
+		ns_max.disk = max_t(enum drbd_disk_state, ns.disk, ns_max.disk);
+		ns_max.pdsk = max_t(enum drbd_disk_state, ns.pdsk, ns_max.pdsk);
+
+		ns_min.role = min_role(ns.role, ns_min.role);
+		ns_min.peer = min_role(ns.peer, ns_min.peer);
+		ns_min.conn = min_t(enum drbd_conns, ns.conn, ns_min.conn);
+		ns_min.disk = min_t(enum drbd_disk_state, ns.disk, ns_min.disk);
+		ns_min.pdsk = min_t(enum drbd_disk_state, ns.pdsk, ns_min.pdsk);
+	}
+	rcu_read_unlock();
+
+	if (number_of_volumes == 0) {
+		ns_min = ns_max = (union drbd_state) { {
+				.role = R_SECONDARY,
+				.peer = R_UNKNOWN,
+				.conn = val.conn,
+				.disk = D_DISKLESS,
+				.pdsk = D_UNKNOWN
+			} };
+	}
+
+	ns_min.susp = ns_max.susp = connection->resource->susp;
+	ns_min.susp_nod = ns_max.susp_nod = connection->resource->susp_nod;
+	ns_min.susp_fen = ns_max.susp_fen = connection->resource->susp_fen;
+
+	*pns_min = ns_min;
+	*pns_max = ns_max;
+}
+
+static enum drbd_state_rv
+_conn_rq_cond(struct drbd_connection *connection, union drbd_state mask, union drbd_state val)
+{
+	enum drbd_state_rv err, rv = SS_UNKNOWN_ERROR; /* continue waiting */;
+
+	if (test_and_clear_bit(CONN_WD_ST_CHG_OKAY, &connection->flags))
+		rv = SS_CW_SUCCESS;
+
+	if (test_and_clear_bit(CONN_WD_ST_CHG_FAIL, &connection->flags))
+		rv = SS_CW_FAILED_BY_PEER;
+
+	err = conn_is_valid_transition(connection, mask, val, 0);
+	if (err == SS_SUCCESS && connection->cstate == C_WF_REPORT_PARAMS)
+		return rv;
+
+	return err;
+}
+
+enum drbd_state_rv
+_conn_request_state(struct drbd_connection *connection, union drbd_state mask, union drbd_state val,
+		    enum chg_state_flags flags)
+{
+	enum drbd_state_rv rv = SS_SUCCESS;
+	struct after_conn_state_chg_work *acscw;
+	enum drbd_conns oc = connection->cstate;
+	union drbd_state ns_max, ns_min, os;
+	bool have_mutex = false;
+	struct drbd_state_change *state_change;
+
+	if (mask.conn) {
+		rv = is_valid_conn_transition(oc, val.conn);
+		if (rv < SS_SUCCESS)
+			goto abort;
+	}
+
+	rv = conn_is_valid_transition(connection, mask, val, flags);
+	if (rv < SS_SUCCESS)
+		goto abort;
+
+	if (oc == C_WF_REPORT_PARAMS && val.conn == C_DISCONNECTING &&
+	    !(flags & (CS_LOCAL_ONLY | CS_HARD))) {
+
+		/* This will be a cluster-wide state change.
+		 * Need to give up the spinlock, grab the mutex,
+		 * then send the state change request, ... */
+		spin_unlock_irq(&connection->resource->req_lock);
+		mutex_lock(&connection->cstate_mutex);
+		have_mutex = true;
+
+		set_bit(CONN_WD_ST_CHG_REQ, &connection->flags);
+		if (conn_send_state_req(connection, mask, val)) {
+			/* sending failed. */
+			clear_bit(CONN_WD_ST_CHG_REQ, &connection->flags);
+			rv = SS_CW_FAILED_BY_PEER;
+			/* need to re-aquire the spin lock, though */
+			goto abort_unlocked;
+		}
+
+		if (val.conn == C_DISCONNECTING)
+			set_bit(DISCONNECT_SENT, &connection->flags);
+
+		/* ... and re-aquire the spinlock.
+		 * If _conn_rq_cond() returned >= SS_SUCCESS, we must call
+		 * conn_set_state() within the same spinlock. */
+		spin_lock_irq(&connection->resource->req_lock);
+		wait_event_lock_irq(connection->ping_wait,
+				(rv = _conn_rq_cond(connection, mask, val)),
+				connection->resource->req_lock);
+		clear_bit(CONN_WD_ST_CHG_REQ, &connection->flags);
+		if (rv < SS_SUCCESS)
+			goto abort;
+	}
+
+	state_change = remember_old_state(connection->resource, GFP_ATOMIC);
+	conn_old_common_state(connection, &os, &flags);
+	flags |= CS_DC_SUSP;
+	conn_set_state(connection, mask, val, &ns_min, &ns_max, flags);
+	conn_pr_state_change(connection, os, ns_max, flags);
+	remember_new_state(state_change);
+
+	acscw = kmalloc(sizeof(*acscw), GFP_ATOMIC);
+	if (acscw) {
+		acscw->oc = os.conn;
+		acscw->ns_min = ns_min;
+		acscw->ns_max = ns_max;
+		acscw->flags = flags;
+		acscw->w.cb = w_after_conn_state_ch;
+		kref_get(&connection->kref);
+		acscw->connection = connection;
+		acscw->state_change = state_change;
+		drbd_queue_work(&connection->sender_work, &acscw->w);
+	} else {
+		drbd_err(connection, "Could not kmalloc an acscw\n");
+	}
+
+ abort:
+	if (have_mutex) {
+		/* mutex_unlock() "... must not be used in interrupt context.",
+		 * so give up the spinlock, then re-aquire it */
+		spin_unlock_irq(&connection->resource->req_lock);
+ abort_unlocked:
+		mutex_unlock(&connection->cstate_mutex);
+		spin_lock_irq(&connection->resource->req_lock);
+	}
+	if (rv < SS_SUCCESS && flags & CS_VERBOSE) {
+		drbd_err(connection, "State change failed: %s\n", drbd_set_st_err_str(rv));
+		drbd_err(connection, " mask = 0x%x val = 0x%x\n", mask.i, val.i);
+		drbd_err(connection, " old_conn:%s wanted_conn:%s\n", drbd_conn_str(oc), drbd_conn_str(val.conn));
+	}
+	return rv;
+}
+
+enum drbd_state_rv
+conn_request_state(struct drbd_connection *connection, union drbd_state mask, union drbd_state val,
+		   enum chg_state_flags flags)
+{
+	enum drbd_state_rv rv;
+
+	spin_lock_irq(&connection->resource->req_lock);
+	rv = _conn_request_state(connection, mask, val, flags);
+	spin_unlock_irq(&connection->resource->req_lock);
+
+	return rv;
+}