/*
   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.

   drbd is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   drbd is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with drbd; see the file COPYING.  If not, write to
   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/drbd_limits.h>
#include "drbd_int.h"
#include "drbd_req.h"

/* in drbd_main.c */
extern void tl_abort_disk_io(struct drbd_conf *mdev);

struct after_state_chg_work {
        struct drbd_work w;
        union drbd_state os;
        union drbd_state ns;
        enum chg_state_flags flags;
        struct completion *done;
};

enum sanitize_state_warnings {
        NO_WARNING,
        ABORTED_ONLINE_VERIFY,
        ABORTED_RESYNC,
        CONNECTION_LOST_NEGOTIATING,
        IMPLICITLY_UPGRADED_DISK,
        IMPLICITLY_UPGRADED_PDSK,
};

static int w_after_state_ch(struct drbd_work *w, int unused);
static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
                           union drbd_state ns, enum chg_state_flags flags);
static enum drbd_state_rv is_valid_state(struct drbd_conf *, union drbd_state);
static enum drbd_state_rv is_valid_soft_transition(union drbd_state, union drbd_state, struct drbd_tconn *);
static enum drbd_state_rv is_valid_transition(union drbd_state os, union drbd_state ns);
static union drbd_state sanitize_state(struct drbd_conf *mdev, 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_tconn *tconn)
{
        struct drbd_conf *mdev;
        bool rv = true;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr) {
                if (mdev->state.disk != D_DISKLESS ||
                    mdev->state.conn != C_STANDALONE ||
                    mdev->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_tconn *tconn)
{
        enum drbd_role role = R_UNKNOWN;
        struct drbd_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                role = max_role(role, mdev->state.role);
        rcu_read_unlock();

        return role;
}

enum drbd_role conn_highest_peer(struct drbd_tconn *tconn)
{
        enum drbd_role peer = R_UNKNOWN;
        struct drbd_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                peer = max_role(peer, mdev->state.peer);
        rcu_read_unlock();

        return peer;
}

enum drbd_disk_state conn_highest_disk(struct drbd_tconn *tconn)
{
        enum drbd_disk_state ds = D_DISKLESS;
        struct drbd_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                ds = max_t(enum drbd_disk_state, ds, mdev->state.disk);
        rcu_read_unlock();

        return ds;
}

enum drbd_disk_state conn_lowest_disk(struct drbd_tconn *tconn)
{
        enum drbd_disk_state ds = D_MASK;
        struct drbd_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                ds = min_t(enum drbd_disk_state, ds, mdev->state.disk);
        rcu_read_unlock();

        return ds;
}

enum drbd_disk_state conn_highest_pdsk(struct drbd_tconn *tconn)
{
        enum drbd_disk_state ds = D_DISKLESS;
        struct drbd_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                ds = max_t(enum drbd_disk_state, ds, mdev->state.pdsk);
        rcu_read_unlock();

        return ds;
}

enum drbd_conns conn_lowest_conn(struct drbd_tconn *tconn)
{
        enum drbd_conns conn = C_MASK;
        struct drbd_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                conn = min_t(enum drbd_conns, conn, mdev->state.conn);
        rcu_read_unlock();

        return conn;
}

static bool no_peer_wf_report_params(struct drbd_tconn *tconn)
{
        struct drbd_conf *mdev;
        int vnr;
        bool rv = true;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr)
                if (mdev->state.conn == C_WF_REPORT_PARAMS) {
                        rv = false;
                        break;
                }
        rcu_read_unlock();

        return rv;
}


/**
 * cl_wide_st_chg() - true if the state change is a cluster wide one
 * @mdev:       DRBD device.
 * @os:         old (current) state.
 * @ns:         new (wanted) state.
 */
static int cl_wide_st_chg(struct drbd_conf *mdev,
                          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_conf *mdev, 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(&mdev->tconn->req_lock, flags);
        ns = apply_mask_val(drbd_read_state(mdev), mask, val);
        rv = _drbd_set_state(mdev, ns, f, NULL);
        spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);

        return rv;
}

/**
 * drbd_force_state() - Impose a change which happens outside our control on our state
 * @mdev:       DRBD device.
 * @mask:       mask of state bits to change.
 * @val:        value of new state bits.
 */
void drbd_force_state(struct drbd_conf *mdev,
        union drbd_state mask, union drbd_state val)
{
        drbd_change_state(mdev, CS_HARD, mask, val);
}

static enum drbd_state_rv
_req_st_cond(struct drbd_conf *mdev, 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, &mdev->flags))
                return SS_CW_SUCCESS;

        if (test_and_clear_bit(CL_ST_CHG_FAIL, &mdev->flags))
                return SS_CW_FAILED_BY_PEER;

        spin_lock_irqsave(&mdev->tconn->req_lock, flags);
        os = drbd_read_state(mdev);
        ns = sanitize_state(mdev, 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(mdev, os, ns))
                rv = SS_CW_NO_NEED;
        if (rv == SS_UNKNOWN_ERROR) {
                rv = is_valid_state(mdev, ns);
                if (rv >= SS_SUCCESS) {
                        rv = is_valid_soft_transition(os, ns, mdev->tconn);
                        if (rv >= SS_SUCCESS)
                                rv = SS_UNKNOWN_ERROR; /* cont waiting, otherwise fail. */
                }
        }
        spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);

        return rv;
}

/**
 * drbd_req_state() - Perform an eventually cluster wide state change
 * @mdev:       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_conf *mdev, 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;

        init_completion(&done);

        if (f & CS_SERIALIZE)
                mutex_lock(mdev->state_mutex);

        spin_lock_irqsave(&mdev->tconn->req_lock, flags);
        os = drbd_read_state(mdev);
        ns = sanitize_state(mdev, apply_mask_val(os, mask, val), NULL);
        rv = is_valid_transition(os, ns);
        if (rv < SS_SUCCESS) {
                spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);
                goto abort;
        }

        if (cl_wide_st_chg(mdev, os, ns)) {
                rv = is_valid_state(mdev, ns);
                if (rv == SS_SUCCESS)
                        rv = is_valid_soft_transition(os, ns, mdev->tconn);
                spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);

                if (rv < SS_SUCCESS) {
                        if (f & CS_VERBOSE)
                                print_st_err(mdev, os, ns, rv);
                        goto abort;
                }

                if (drbd_send_state_req(mdev, mask, val)) {
                        rv = SS_CW_FAILED_BY_PEER;
                        if (f & CS_VERBOSE)
                                print_st_err(mdev, os, ns, rv);
                        goto abort;
                }

                wait_event(mdev->state_wait,
                        (rv = _req_st_cond(mdev, mask, val)));

                if (rv < SS_SUCCESS) {
                        if (f & CS_VERBOSE)
                                print_st_err(mdev, os, ns, rv);
                        goto abort;
                }
                spin_lock_irqsave(&mdev->tconn->req_lock, flags);
                ns = apply_mask_val(drbd_read_state(mdev), mask, val);
                rv = _drbd_set_state(mdev, ns, f, &done);
        } else {
                rv = _drbd_set_state(mdev, ns, f, &done);
        }

        spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);

        if (f & CS_WAIT_COMPLETE && rv == SS_SUCCESS) {
                D_ASSERT(current != mdev->tconn->worker.task);
                wait_for_completion(&done);
        }

abort:
        if (f & CS_SERIALIZE)
                mutex_unlock(mdev->state_mutex);

        return rv;
}

/**
 * _drbd_request_state() - Request a state change (with flags)
 * @mdev:       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_conf *mdev, union drbd_state mask,
                    union drbd_state val, enum chg_state_flags f)
{
        enum drbd_state_rv rv;

        wait_event(mdev->state_wait,
                   (rv = drbd_req_state(mdev, mask, val, f)) != SS_IN_TRANSIENT_STATE);

        return rv;
}

static void print_st(struct drbd_conf *mdev, char *name, union drbd_state ns)
{
        dev_err(DEV, " %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_conf *mdev, union drbd_state os,
                  union drbd_state ns, enum drbd_state_rv err)
{
        if (err == SS_IN_TRANSIENT_STATE)
                return;
        dev_err(DEV, "State change failed: %s\n", drbd_set_st_err_str(err));
        print_st(mdev, " state", os);
        print_st(mdev, "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_conf *mdev, 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)
                dev_info(DEV, "%s\n", pb);
}

static void conn_pr_state_change(struct drbd_tconn *tconn, 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)
                conn_info(tconn, "%s\n", pb);
}


/**
 * is_valid_state() - Returns an SS_ error code if ns is not valid
 * @mdev:       DRBD device.
 * @ns:         State to consider.
 */
static enum drbd_state_rv
is_valid_state(struct drbd_conf *mdev, 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(mdev)) {
                fp = rcu_dereference(mdev->ldev->disk_conf)->fencing;
                put_ldev(mdev);
        }

        nc = rcu_dereference(mdev->tconn->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(mdev->tconn) == R_PRIMARY)
                                rv = SS_O_VOL_PEER_PRI;
                }
        }

        if (rv <= 0)
                /* already found a reason to abort */;
        else if (ns.role == R_SECONDARY && mdev->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) &&
                  mdev->tconn->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;

        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).
 * @mdev:       DRBD device.
 * @ns:         new state.
 * @os:         old state.
 */
static enum drbd_state_rv
is_valid_soft_transition(union drbd_state os, union drbd_state ns, struct drbd_tconn *tconn)
{
        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;

        /* if (ns.conn == os.conn && ns.conn == C_WF_REPORT_PARAMS)
           rv = SS_IN_TRANSIENT_STATE; */

        /* While establishing a connection only allow cstate to change.
           Delay/refuse role changes, detach attach etc... */
        if (test_bit(STATE_SENT, &tconn->flags) &&
            !(os.conn == C_WF_REPORT_PARAMS ||
              (ns.conn == C_WF_REPORT_PARAMS && os.conn == C_WF_CONNECTION)))
                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_conf *mdev, 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)
                dev_warn(DEV, "%s\n", msg_table[warn]);
}

/**
 * sanitize_state() - Resolves implicitly necessary additional changes to a state transition
 * @mdev:       DRBD device.
 * @os:         old state.
 * @ns:         new state.
 * @warn_sync_abort:
 *
 * 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_conf *mdev, 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(mdev)) {
                rcu_read_lock();
                fp = rcu_dereference(mdev->ldev->disk_conf)->fencing;
                rcu_read_unlock();
                put_ldev(mdev);
        }

        /* 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(mdev, D_NEGOTIATING)) {
                if (mdev->ed_uuid == mdev->ldev->md.uuid[UI_CURRENT]) {
                        ns.disk = mdev->new_state_tmp.disk;
                        ns.pdsk = mdev->new_state_tmp.pdsk;
                } else {
                        if (warn)
                                *warn = CONNECTION_LOST_NEGOTIATING;
                        ns.disk = D_DISKLESS;
                        ns.pdsk = D_UNKNOWN;
                }
                put_ldev(mdev);
        }

        /* 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 stat 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))
                ns.susp_fen = 1; /* Suspend IO while fence-peer handler runs (peer lost) */

        if (mdev->tconn->res_opts.on_no_data == OND_SUSPEND_IO &&
            (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.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_conf *mdev)
{
        if (test_and_clear_bit(AL_SUSPENDED, &mdev->flags))
                dev_info(DEV, "Resumed AL updates\n");
}

/* helper for __drbd_set_state */
static void set_ov_position(struct drbd_conf *mdev, enum drbd_conns cs)
{
        if (mdev->tconn->agreed_pro_version < 90)
                mdev->ov_start_sector = 0;
        mdev->rs_total = drbd_bm_bits(mdev);
        mdev->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 */
                mdev->ov_start_sector = ~(sector_t)0;
        } else {
                unsigned long bit = BM_SECT_TO_BIT(mdev->ov_start_sector);
                if (bit >= mdev->rs_total) {
                        mdev->ov_start_sector =
                                BM_BIT_TO_SECT(mdev->rs_total - 1);
                        mdev->rs_total = 1;
                } else
                        mdev->rs_total -= bit;
                mdev->ov_position = mdev->ov_start_sector;
        }
        mdev->ov_left = mdev->rs_total;
}

/**
 * __drbd_set_state() - Set a new DRBD state
 * @mdev:       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, and global_state_lock. Do not call directly.
 */
enum drbd_state_rv
__drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
                 enum chg_state_flags flags, struct completion *done)
{
        union drbd_state os;
        enum drbd_state_rv rv = SS_SUCCESS;
        enum sanitize_state_warnings ssw;
        struct after_state_chg_work *ascw;
        bool did_remote, should_do_remote;

        os = drbd_read_state(mdev);

        ns = sanitize_state(mdev, 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(mdev, ns);
                if (rv < SS_SUCCESS) {
                        /* If the old state was illegal as well, then let
                           this happen...*/

                        if (is_valid_state(mdev, os) == rv)
                                rv = is_valid_soft_transition(os, ns, mdev->tconn);
                } else
                        rv = is_valid_soft_transition(os, ns, mdev->tconn);
        }

        if (rv < SS_SUCCESS) {
                if (flags & CS_VERBOSE)
                        print_st_err(mdev, os, ns, rv);
                return rv;
        }

        print_sanitize_warnings(mdev, ssw);

        drbd_pr_state_change(mdev, 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(mdev->tconn, 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(&mdev->local_cnt);

        did_remote = drbd_should_do_remote(mdev->state);
        mdev->state.i = ns.i;
        should_do_remote = drbd_should_do_remote(mdev->state);
        mdev->tconn->susp = ns.susp;
        mdev->tconn->susp_nod = ns.susp_nod;

        mdev->tconn->susp_fen = ns.susp_fen;

        /* put replicated vs not-replicated requests in seperate epochs */
        if (did_remote != should_do_remote)
                start_new_tl_epoch(mdev->tconn);

        if (os.disk == D_ATTACHING && ns.disk >= D_NEGOTIATING)
                drbd_print_uuids(mdev, "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(mdev->tconn))
                clear_bit(STATE_SENT, &mdev->tconn->flags);

        wake_up(&mdev->misc_wait);
        wake_up(&mdev->state_wait);
        wake_up(&mdev->tconn->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) {
                mdev->ov_start_sector =
                        BM_BIT_TO_SECT(drbd_bm_bits(mdev) - mdev->ov_left);
                if (mdev->ov_left)
                        dev_info(DEV, "Online Verify reached sector %llu\n",
                                (unsigned long long)mdev->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)) {
                dev_info(DEV, "Syncer continues.\n");
                mdev->rs_paused += (long)jiffies
                                  -(long)mdev->rs_mark_time[mdev->rs_last_mark];
                if (ns.conn == C_SYNC_TARGET)
                        mod_timer(&mdev->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)) {
                dev_info(DEV, "Resync suspended\n");
                mdev->rs_mark_time[mdev->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(mdev, ns.conn);
                mdev->rs_start = now;
                mdev->rs_last_events = 0;
                mdev->rs_last_sect_ev = 0;
                mdev->ov_last_oos_size = 0;
                mdev->ov_last_oos_start = 0;

                for (i = 0; i < DRBD_SYNC_MARKS; i++) {
                        mdev->rs_mark_left[i] = mdev->ov_left;
                        mdev->rs_mark_time[i] = now;
                }

                drbd_rs_controller_reset(mdev);

                if (ns.conn == C_VERIFY_S) {
                        dev_info(DEV, "Starting Online Verify from sector %llu\n",
                                        (unsigned long long)mdev->ov_position);
                        mod_timer(&mdev->resync_timer, jiffies);
                }
        }

        if (get_ldev(mdev)) {
                u32 mdf = mdev->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, &mdev->flags))
                        mdf |= MDF_CRASHED_PRIMARY;
                if (mdev->state.role == R_PRIMARY ||
                    (mdev->state.pdsk < D_INCONSISTENT && mdev->state.peer == R_PRIMARY))
                        mdf |= MDF_PRIMARY_IND;
                if (mdev->state.conn > C_WF_REPORT_PARAMS)
                        mdf |= MDF_CONNECTED_IND;
                if (mdev->state.disk > D_INCONSISTENT)
                        mdf |= MDF_CONSISTENT;
                if (mdev->state.disk > D_OUTDATED)
                        mdf |= MDF_WAS_UP_TO_DATE;
                if (mdev->state.pdsk <= D_OUTDATED && mdev->state.pdsk >= D_INCONSISTENT)
                        mdf |= MDF_PEER_OUT_DATED;
                if (mdf != mdev->ldev->md.flags) {
                        mdev->ldev->md.flags = mdf;
                        drbd_md_mark_dirty(mdev);
                }
                if (os.disk < D_CONSISTENT && ns.disk >= D_CONSISTENT)
                        drbd_set_ed_uuid(mdev, mdev->ldev->md.uuid[UI_CURRENT]);
                put_ldev(mdev);
        }

        /* 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, &mdev->flags);

        /* Receiver should clean up itself */
        if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
                drbd_thread_stop_nowait(&mdev->tconn->receiver);

        /* Now the receiver finished cleaning up itself, it should die */
        if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
                drbd_thread_stop_nowait(&mdev->tconn->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(&mdev->tconn->receiver);

        /* Resume AL writing if we get a connection */
        if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)
                drbd_resume_al(mdev);

        /* 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)
                mdev->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->w.mdev = mdev;
                ascw->done = done;
                drbd_queue_work(&mdev->tconn->sender_work, &ascw->w);
        } else {
                dev_err(DEV, "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_conf *mdev = w->mdev;

        after_state_ch(mdev, ascw->os, ascw->ns, ascw->flags);
        if (ascw->flags & CS_WAIT_COMPLETE) {
                D_ASSERT(ascw->done != NULL);
                complete(ascw->done);
        }
        kfree(ascw);

        return 0;
}

static void abw_start_sync(struct drbd_conf *mdev, int rv)
{
        if (rv) {
                dev_err(DEV, "Writing the bitmap failed not starting resync.\n");
                _drbd_request_state(mdev, NS(conn, C_CONNECTED), CS_VERBOSE);
                return;
        }

        switch (mdev->state.conn) {
        case C_STARTING_SYNC_T:
                _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
                break;
        case C_STARTING_SYNC_S:
                drbd_start_resync(mdev, C_SYNC_SOURCE);
                break;
        }
}

int drbd_bitmap_io_from_worker(struct drbd_conf *mdev,
                int (*io_fn)(struct drbd_conf *),
                char *why, enum bm_flag flags)
{
        int rv;

        D_ASSERT(current == mdev->tconn->worker.task);

        /* open coded non-blocking drbd_suspend_io(mdev); */
        set_bit(SUSPEND_IO, &mdev->flags);

        drbd_bm_lock(mdev, why, flags);
        rv = io_fn(mdev);
        drbd_bm_unlock(mdev);

        drbd_resume_io(mdev);

        return rv;
}

/**
 * after_state_ch() - Perform after state change actions that may sleep
 * @mdev:       DRBD device.
 * @os:         old state.
 * @ns:         new state.
 * @flags:      Flags
 */
static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
                           union drbd_state ns, enum chg_state_flags flags)
{
        struct sib_info sib;

        sib.sib_reason = SIB_STATE_CHANGE;
        sib.os = os;
        sib.ns = ns;

        if (os.conn != C_CONNECTED && ns.conn == C_CONNECTED) {
                clear_bit(CRASHED_PRIMARY, &mdev->flags);
                if (mdev->p_uuid)
                        mdev->p_uuid[UI_FLAGS] &= ~((u64)2);
        }

        /* Inform userspace about the change... */
        drbd_bcast_event(mdev, &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(mdev, "pri-on-incon-degr");

        /* Here we have the actions that are performed after a
           state change. This function might sleep */

        if (ns.susp_nod) {
                struct drbd_tconn *tconn = mdev->tconn;
                enum drbd_req_event what = NOTHING;

                spin_lock_irq(&tconn->req_lock);
                if (os.conn < C_CONNECTED && conn_lowest_conn(tconn) >= C_CONNECTED)
                        what = RESEND;

                if ((os.disk == D_ATTACHING || os.disk == D_NEGOTIATING) &&
                    conn_lowest_disk(tconn) > D_NEGOTIATING)
                        what = RESTART_FROZEN_DISK_IO;

                if (tconn->susp_nod && what != NOTHING) {
                        _tl_restart(tconn, what);
                        _conn_request_state(tconn,
                                            (union drbd_state) { { .susp_nod = 1 } },
                                            (union drbd_state) { { .susp_nod = 0 } },
                                            CS_VERBOSE);
                }
                spin_unlock_irq(&tconn->req_lock);
        }

        if (ns.susp_fen) {
                struct drbd_tconn *tconn = mdev->tconn;

                spin_lock_irq(&tconn->req_lock);
                if (tconn->susp_fen && conn_lowest_conn(tconn) >= C_CONNECTED) {
                        /* case2: The connection was established again: */
                        struct drbd_conf *odev;
                        int vnr;

                        rcu_read_lock();
                        idr_for_each_entry(&tconn->volumes, odev, vnr)
                                clear_bit(NEW_CUR_UUID, &odev->flags);
                        rcu_read_unlock();
                        _tl_restart(tconn, RESEND);
                        _conn_request_state(tconn,
                                            (union drbd_state) { { .susp_fen = 1 } },
                                            (union drbd_state) { { .susp_fen = 0 } },
                                            CS_VERBOSE);
                }
                spin_unlock_irq(&tconn->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) &&
            mdev->tconn->agreed_pro_version >= 96 && get_ldev(mdev)) {
                drbd_gen_and_send_sync_uuid(mdev);
                put_ldev(mdev);
        }

        /* 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. */
                mdev->rs_total = 0;
                mdev->rs_failed = 0;
                atomic_set(&mdev->rs_pending_cnt, 0);
                drbd_rs_cancel_all(mdev);

                drbd_send_uuids(mdev);
                drbd_send_state(mdev, 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 &&
            mdev->state.conn == C_WF_BITMAP_S)
                drbd_queue_bitmap_io(mdev, &drbd_send_bitmap, NULL,
                                "send_bitmap (WFBitMapS)",
                                BM_LOCKED_TEST_ALLOWED);

        /* Lost contact to peer's copy of the data */
        if ((os.pdsk >= D_INCONSISTENT &&
             os.pdsk != D_UNKNOWN &&
             os.pdsk != D_OUTDATED)
        &&  (ns.pdsk < D_INCONSISTENT ||
             ns.pdsk == D_UNKNOWN ||
             ns.pdsk == D_OUTDATED)) {
                if (get_ldev(mdev)) {
                        if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
                            mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
                                if (drbd_suspended(mdev)) {
                                        set_bit(NEW_CUR_UUID, &mdev->flags);
                                } else {
                                        drbd_uuid_new_current(mdev);
                                        drbd_send_uuids(mdev);
                                }
                        }
                        put_ldev(mdev);
                }
        }

        if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
                if (os.peer == R_SECONDARY && ns.peer == R_PRIMARY &&
                    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
                        drbd_uuid_new_current(mdev);
                        drbd_send_uuids(mdev);
                }
                /* 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(mdev, &drbd_bm_write,
                                "demote diskless peer", BM_LOCKED_SET_ALLOWED);
                put_ldev(mdev);
        }

        /* 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 &&
                mdev->state.conn <= C_CONNECTED && get_ldev(mdev)) {
                /* 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(mdev, &drbd_bm_write,
                                "demote", BM_LOCKED_TEST_ALLOWED);
                put_ldev(mdev);
        }

        /* Last part of the attaching process ... */
        if (ns.conn >= C_CONNECTED &&
            os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
                drbd_send_sizes(mdev, 0, 0);  /* to start sync... */
                drbd_send_uuids(mdev);
                drbd_send_state(mdev, 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(mdev, 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(mdev);

        /* 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(mdev, ns);

        if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
                drbd_send_state(mdev, 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(mdev,
                        &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 (mdev->ldev) {
                        rcu_read_lock();
                        eh = rcu_dereference(mdev->ldev->disk_conf)->on_io_error;
                        rcu_read_unlock();

                        was_io_error = test_and_clear_bit(WAS_IO_ERROR, &mdev->flags);

                        if (was_io_error && eh == EP_CALL_HELPER)
                                drbd_khelper(mdev, "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, &mdev->flags))
                                tl_abort_disk_io(mdev);

                        /* 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 (mdev->state.disk != D_FAILED)
                                dev_err(DEV,
                                        "ASSERT FAILED: disk is %s during detach\n",
                                        drbd_disk_str(mdev->state.disk));

                        if (ns.conn >= C_CONNECTED)
                                drbd_send_state(mdev, ns);

                        drbd_rs_cancel_all(mdev);

                        /* 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(mdev);
                }
                put_ldev(mdev);
        }

        /* 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 (mdev->state.disk != D_DISKLESS)
                        dev_err(DEV,
                                "ASSERT FAILED: disk is %s while going diskless\n",
                                drbd_disk_str(mdev->state.disk));

                if (ns.conn >= C_CONNECTED)
                        drbd_send_state(mdev, ns);
                /* corresponding get_ldev in __drbd_set_state
                 * this may finally trigger drbd_ldev_destroy. */
                put_ldev(mdev);
        }

        /* 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(mdev, ns);

        /* Disks got bigger while they were detached */
        if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
            test_and_clear_bit(RESYNC_AFTER_NEG, &mdev->flags)) {
                if (ns.conn == C_CONNECTED)
                        resync_after_online_grow(mdev);
        }

        /* 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(mdev);

        /* 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(mdev, 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(mdev))
                drbd_send_state(mdev, ns);

        /* This triggers bitmap writeout of potentially still unwritten pages
         * if the resync finished cleanly, or aborted because of peer disk
         * failure, or because of connection loss.
         * 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 && ns.conn <= C_CONNECTED && get_ldev(mdev)) {
                drbd_queue_bitmap_io(mdev, &drbd_bm_write_copy_pages, NULL,
                        "write from resync_finished", BM_LOCKED_CHANGE_ALLOWED);
                put_ldev(mdev);
        }

        if (ns.disk == D_DISKLESS &&
            ns.conn == C_STANDALONE &&
            ns.role == R_SECONDARY) {
                if (os.aftr_isp != ns.aftr_isp)
                        resume_next_sg(mdev);
        }

        drbd_md_sync(mdev);
}

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 mdevs */
        enum chg_state_flags flags;
};

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_tconn *tconn = w->tconn;
        enum drbd_conns oc = acscw->oc;
        union drbd_state ns_max = acscw->ns_max;
        struct drbd_conf *mdev;
        int vnr;

        kfree(acscw);

        /* Upon network configuration, we need to start the receiver */
        if (oc == C_STANDALONE && ns_max.conn == C_UNCONNECTED)
                drbd_thread_start(&tconn->receiver);

        if (oc == C_DISCONNECTING && ns_max.conn == C_STANDALONE) {
                struct net_conf *old_conf;

                mutex_lock(&tconn->conf_update);
                old_conf = tconn->net_conf;
                tconn->my_addr_len = 0;
                tconn->peer_addr_len = 0;
                rcu_assign_pointer(tconn->net_conf, NULL);
                conn_free_crypto(tconn);
                mutex_unlock(&tconn->conf_update);

                synchronize_rcu();
                kfree(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(&tconn->volumes, mdev, vnr) {
                                if (test_bit(NEW_CUR_UUID, &mdev->flags)) {
                                        drbd_uuid_new_current(mdev);
                                        clear_bit(NEW_CUR_UUID, &mdev->flags);
                                }
                        }
                        rcu_read_unlock();
                        spin_lock_irq(&tconn->req_lock);
                        _tl_restart(tconn, CONNECTION_LOST_WHILE_PENDING);
                        _conn_request_state(tconn,
                                            (union drbd_state) { { .susp_fen = 1 } },
                                            (union drbd_state) { { .susp_fen = 0 } },
                                            CS_VERBOSE);
                        spin_unlock_irq(&tconn->req_lock);
                }
        }
        kref_put(&tconn->kref, &conn_destroy);

        conn_md_sync(tconn);

        return 0;
}

void conn_old_common_state(struct drbd_tconn *tconn, union drbd_state *pcs, enum chg_state_flags *pf)
{
        enum chg_state_flags flags = ~0;
        struct drbd_conf *mdev;
        int vnr, first_vol = 1;
        union drbd_dev_state os, cs = {
                { .role = R_SECONDARY,
                  .peer = R_UNKNOWN,
                  .conn = tconn->cstate,
                  .disk = D_DISKLESS,
                  .pdsk = D_UNKNOWN,
                } };

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr) {
                os = mdev->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_tconn *tconn, 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_conf *mdev;
        int vnr;

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr) {
                os = drbd_read_state(mdev);
                ns = sanitize_state(mdev, 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)
                        break;

                if (!(flags & CS_HARD)) {
                        rv = is_valid_state(mdev, ns);
                        if (rv < SS_SUCCESS) {
                                if (is_valid_state(mdev, os) == rv)
                                        rv = is_valid_soft_transition(os, ns, tconn);
                        } else
                                rv = is_valid_soft_transition(os, ns, tconn);
                }
                if (rv < SS_SUCCESS)
                        break;
        }
        rcu_read_unlock();

        if (rv < SS_SUCCESS && flags & CS_VERBOSE)
                print_st_err(mdev, os, ns, rv);

        return rv;
}

void
conn_set_state(struct drbd_tconn *tconn, 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_conf *mdev;
        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 (tconn->cstate != C_WF_REPORT_PARAMS && val.conn == C_WF_REPORT_PARAMS)
                        tconn->last_reconnect_jif = jiffies;

                tconn->cstate = val.conn;
        }

        rcu_read_lock();
        idr_for_each_entry(&tconn->volumes, mdev, vnr) {
                number_of_volumes++;
                os = drbd_read_state(mdev);
                ns = apply_mask_val(os, mask, val);
                ns = sanitize_state(mdev, ns, NULL);

                if (flags & CS_IGN_OUTD_FAIL && ns.disk == D_OUTDATED && os.disk < D_OUTDATED)
                        ns.disk = os.disk;

                rv = __drbd_set_state(mdev, ns, flags, NULL);
                if (rv < SS_SUCCESS)
                        BUG();

                ns.i = mdev->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 = tconn->susp;
        ns_min.susp_nod = ns_max.susp_nod = tconn->susp_nod;
        ns_min.susp_fen = ns_max.susp_fen = tconn->susp_fen;

        *pns_min = ns_min;
        *pns_max = ns_max;
}

static enum drbd_state_rv
_conn_rq_cond(struct drbd_tconn *tconn, union drbd_state mask, union drbd_state val)
{
        enum drbd_state_rv rv;

        if (test_and_clear_bit(CONN_WD_ST_CHG_OKAY, &tconn->flags))
                return SS_CW_SUCCESS;

        if (test_and_clear_bit(CONN_WD_ST_CHG_FAIL, &tconn->flags))
                return SS_CW_FAILED_BY_PEER;

        rv = conn_is_valid_transition(tconn, mask, val, 0);
        if (rv == SS_SUCCESS && tconn->cstate == C_WF_REPORT_PARAMS)
                rv = SS_UNKNOWN_ERROR; /* continue waiting */

        return rv;
}

enum drbd_state_rv
_conn_request_state(struct drbd_tconn *tconn, 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 = tconn->cstate;
        union drbd_state ns_max, ns_min, os;
        bool have_mutex = false;

        if (mask.conn) {
                rv = is_valid_conn_transition(oc, val.conn);
                if (rv < SS_SUCCESS)
                        goto abort;
        }

        rv = conn_is_valid_transition(tconn, 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(&tconn->req_lock);
                mutex_lock(&tconn->cstate_mutex);
                have_mutex = true;

                set_bit(CONN_WD_ST_CHG_REQ, &tconn->flags);
                if (conn_send_state_req(tconn, mask, val)) {
                        /* sending failed. */
                        clear_bit(CONN_WD_ST_CHG_REQ, &tconn->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, &tconn->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(&tconn->req_lock);
                wait_event_lock_irq(tconn->ping_wait,
                                (rv = _conn_rq_cond(tconn, mask, val)),
                                tconn->req_lock);
                clear_bit(CONN_WD_ST_CHG_REQ, &tconn->flags);
                if (rv < SS_SUCCESS)
                        goto abort;
        }

        conn_old_common_state(tconn, &os, &flags);
        flags |= CS_DC_SUSP;
        conn_set_state(tconn, mask, val, &ns_min, &ns_max, flags);
        conn_pr_state_change(tconn, os, ns_max, flags);

        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(&tconn->kref);
                acscw->w.tconn = tconn;
                drbd_queue_work(&tconn->sender_work, &acscw->w);
        } else {
                conn_err(tconn, "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(&tconn->req_lock);
 abort_unlocked:
                mutex_unlock(&tconn->cstate_mutex);
                spin_lock_irq(&tconn->req_lock);
        }
        if (rv < SS_SUCCESS && flags & CS_VERBOSE) {
                conn_err(tconn, "State change failed: %s\n", drbd_set_st_err_str(rv));
                conn_err(tconn, " mask = 0x%x val = 0x%x\n", mask.i, val.i);
                conn_err(tconn, " 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_tconn *tconn, union drbd_state mask, union drbd_state val,
                   enum chg_state_flags flags)
{
        enum drbd_state_rv rv;

        spin_lock_irq(&tconn->req_lock);
        rv = _conn_request_state(tconn, mask, val, flags);
        spin_unlock_irq(&tconn->req_lock);

        return rv;
}