Merge branch 'work.whack-a-mole' of git://git.kernel.org/pub/scm/linux/kernel/git...

[mirror_ubuntu-bionic-kernel.git] / drivers / block / drbd / drbd_nl.c

/*
   drbd_nl.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>.

   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.

 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/drbd.h>
#include <linux/in.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/blkpg.h>
#include <linux/cpumask.h>
#include "drbd_int.h"
#include "drbd_protocol.h"
#include "drbd_req.h"
#include "drbd_state_change.h"
#include <asm/unaligned.h>
#include <linux/drbd_limits.h>
#include <linux/kthread.h>

#include <net/genetlink.h>

/* .doit */
// int drbd_adm_create_resource(struct sk_buff *skb, struct genl_info *info);
// int drbd_adm_delete_resource(struct sk_buff *skb, struct genl_info *info);

int drbd_adm_new_minor(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_del_minor(struct sk_buff *skb, struct genl_info *info);

int drbd_adm_new_resource(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_del_resource(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_down(struct sk_buff *skb, struct genl_info *info);

int drbd_adm_set_role(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_detach(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_connect(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_resize(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_start_ov(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_new_c_uuid(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_disconnect(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_pause_sync(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_resume_sync(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_suspend_io(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_resume_io(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_outdate(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_resource_opts(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_get_status(struct sk_buff *skb, struct genl_info *info);
int drbd_adm_get_timeout_type(struct sk_buff *skb, struct genl_info *info);
/* .dumpit */
int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb);
int drbd_adm_dump_resources(struct sk_buff *skb, struct netlink_callback *cb);
int drbd_adm_dump_devices(struct sk_buff *skb, struct netlink_callback *cb);
int drbd_adm_dump_devices_done(struct netlink_callback *cb);
int drbd_adm_dump_connections(struct sk_buff *skb, struct netlink_callback *cb);
int drbd_adm_dump_connections_done(struct netlink_callback *cb);
int drbd_adm_dump_peer_devices(struct sk_buff *skb, struct netlink_callback *cb);
int drbd_adm_dump_peer_devices_done(struct netlink_callback *cb);
int drbd_adm_get_initial_state(struct sk_buff *skb, struct netlink_callback *cb);

#include <linux/drbd_genl_api.h>
#include "drbd_nla.h"
#include <linux/genl_magic_func.h>

static atomic_t drbd_genl_seq = ATOMIC_INIT(2); /* two. */
static atomic_t notify_genl_seq = ATOMIC_INIT(2); /* two. */

DEFINE_MUTEX(notification_mutex);

/* used blkdev_get_by_path, to claim our meta data device(s) */
static char *drbd_m_holder = "Hands off! this is DRBD's meta data device.";

static void drbd_adm_send_reply(struct sk_buff *skb, struct genl_info *info)
{
        genlmsg_end(skb, genlmsg_data(nlmsg_data(nlmsg_hdr(skb))));
        if (genlmsg_reply(skb, info))
                pr_err("error sending genl reply\n");
}

/* Used on a fresh "drbd_adm_prepare"d reply_skb, this cannot fail: The only
 * reason it could fail was no space in skb, and there are 4k available. */
static int drbd_msg_put_info(struct sk_buff *skb, const char *info)
{
        struct nlattr *nla;
        int err = -EMSGSIZE;

        if (!info || !info[0])
                return 0;

        nla = nla_nest_start(skb, DRBD_NLA_CFG_REPLY);
        if (!nla)
                return err;

        err = nla_put_string(skb, T_info_text, info);
        if (err) {
                nla_nest_cancel(skb, nla);
                return err;
        } else
                nla_nest_end(skb, nla);
        return 0;
}

/* This would be a good candidate for a "pre_doit" hook,
 * and per-family private info->pointers.
 * But we need to stay compatible with older kernels.
 * If it returns successfully, adm_ctx members are valid.
 *
 * At this point, we still rely on the global genl_lock().
 * If we want to avoid that, and allow "genl_family.parallel_ops", we may need
 * to add additional synchronization against object destruction/modification.
 */
#define DRBD_ADM_NEED_MINOR     1
#define DRBD_ADM_NEED_RESOURCE  2
#define DRBD_ADM_NEED_CONNECTION 4
static int drbd_adm_prepare(struct drbd_config_context *adm_ctx,
        struct sk_buff *skb, struct genl_info *info, unsigned flags)
{
        struct drbd_genlmsghdr *d_in = info->userhdr;
        const u8 cmd = info->genlhdr->cmd;
        int err;

        memset(adm_ctx, 0, sizeof(*adm_ctx));

        /* genl_rcv_msg only checks for CAP_NET_ADMIN on "GENL_ADMIN_PERM" :( */
        if (cmd != DRBD_ADM_GET_STATUS && !capable(CAP_NET_ADMIN))
               return -EPERM;

        adm_ctx->reply_skb = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
        if (!adm_ctx->reply_skb) {
                err = -ENOMEM;
                goto fail;
        }

        adm_ctx->reply_dh = genlmsg_put_reply(adm_ctx->reply_skb,
                                        info, &drbd_genl_family, 0, cmd);
        /* put of a few bytes into a fresh skb of >= 4k will always succeed.
         * but anyways */
        if (!adm_ctx->reply_dh) {
                err = -ENOMEM;
                goto fail;
        }

        adm_ctx->reply_dh->minor = d_in->minor;
        adm_ctx->reply_dh->ret_code = NO_ERROR;

        adm_ctx->volume = VOLUME_UNSPECIFIED;
        if (info->attrs[DRBD_NLA_CFG_CONTEXT]) {
                struct nlattr *nla;
                /* parse and validate only */
                err = drbd_cfg_context_from_attrs(NULL, info);
                if (err)
                        goto fail;

                /* It was present, and valid,
                 * copy it over to the reply skb. */
                err = nla_put_nohdr(adm_ctx->reply_skb,
                                info->attrs[DRBD_NLA_CFG_CONTEXT]->nla_len,
                                info->attrs[DRBD_NLA_CFG_CONTEXT]);
                if (err)
                        goto fail;

                /* and assign stuff to the adm_ctx */
                nla = nested_attr_tb[__nla_type(T_ctx_volume)];
                if (nla)
                        adm_ctx->volume = nla_get_u32(nla);
                nla = nested_attr_tb[__nla_type(T_ctx_resource_name)];
                if (nla)
                        adm_ctx->resource_name = nla_data(nla);
                adm_ctx->my_addr = nested_attr_tb[__nla_type(T_ctx_my_addr)];
                adm_ctx->peer_addr = nested_attr_tb[__nla_type(T_ctx_peer_addr)];
                if ((adm_ctx->my_addr &&
                     nla_len(adm_ctx->my_addr) > sizeof(adm_ctx->connection->my_addr)) ||
                    (adm_ctx->peer_addr &&
                     nla_len(adm_ctx->peer_addr) > sizeof(adm_ctx->connection->peer_addr))) {
                        err = -EINVAL;
                        goto fail;
                }
        }

        adm_ctx->minor = d_in->minor;
        adm_ctx->device = minor_to_device(d_in->minor);

        /* We are protected by the global genl_lock().
         * But we may explicitly drop it/retake it in drbd_adm_set_role(),
         * so make sure this object stays around. */
        if (adm_ctx->device)
                kref_get(&adm_ctx->device->kref);

        if (adm_ctx->resource_name) {
                adm_ctx->resource = drbd_find_resource(adm_ctx->resource_name);
        }

        if (!adm_ctx->device && (flags & DRBD_ADM_NEED_MINOR)) {
                drbd_msg_put_info(adm_ctx->reply_skb, "unknown minor");
                return ERR_MINOR_INVALID;
        }
        if (!adm_ctx->resource && (flags & DRBD_ADM_NEED_RESOURCE)) {
                drbd_msg_put_info(adm_ctx->reply_skb, "unknown resource");
                if (adm_ctx->resource_name)
                        return ERR_RES_NOT_KNOWN;
                return ERR_INVALID_REQUEST;
        }

        if (flags & DRBD_ADM_NEED_CONNECTION) {
                if (adm_ctx->resource) {
                        drbd_msg_put_info(adm_ctx->reply_skb, "no resource name expected");
                        return ERR_INVALID_REQUEST;
                }
                if (adm_ctx->device) {
                        drbd_msg_put_info(adm_ctx->reply_skb, "no minor number expected");
                        return ERR_INVALID_REQUEST;
                }
                if (adm_ctx->my_addr && adm_ctx->peer_addr)
                        adm_ctx->connection = conn_get_by_addrs(nla_data(adm_ctx->my_addr),
                                                          nla_len(adm_ctx->my_addr),
                                                          nla_data(adm_ctx->peer_addr),
                                                          nla_len(adm_ctx->peer_addr));
                if (!adm_ctx->connection) {
                        drbd_msg_put_info(adm_ctx->reply_skb, "unknown connection");
                        return ERR_INVALID_REQUEST;
                }
        }

        /* some more paranoia, if the request was over-determined */
        if (adm_ctx->device && adm_ctx->resource &&
            adm_ctx->device->resource != adm_ctx->resource) {
                pr_warning("request: minor=%u, resource=%s; but that minor belongs to resource %s\n",
                                adm_ctx->minor, adm_ctx->resource->name,
                                adm_ctx->device->resource->name);
                drbd_msg_put_info(adm_ctx->reply_skb, "minor exists in different resource");
                return ERR_INVALID_REQUEST;
        }
        if (adm_ctx->device &&
            adm_ctx->volume != VOLUME_UNSPECIFIED &&
            adm_ctx->volume != adm_ctx->device->vnr) {
                pr_warning("request: minor=%u, volume=%u; but that minor is volume %u in %s\n",
                                adm_ctx->minor, adm_ctx->volume,
                                adm_ctx->device->vnr,
                                adm_ctx->device->resource->name);
                drbd_msg_put_info(adm_ctx->reply_skb, "minor exists as different volume");
                return ERR_INVALID_REQUEST;
        }

        /* still, provide adm_ctx->resource always, if possible. */
        if (!adm_ctx->resource) {
                adm_ctx->resource = adm_ctx->device ? adm_ctx->device->resource
                        : adm_ctx->connection ? adm_ctx->connection->resource : NULL;
                if (adm_ctx->resource)
                        kref_get(&adm_ctx->resource->kref);
        }

        return NO_ERROR;

fail:
        nlmsg_free(adm_ctx->reply_skb);
        adm_ctx->reply_skb = NULL;
        return err;
}

static int drbd_adm_finish(struct drbd_config_context *adm_ctx,
        struct genl_info *info, int retcode)
{
        if (adm_ctx->device) {
                kref_put(&adm_ctx->device->kref, drbd_destroy_device);
                adm_ctx->device = NULL;
        }
        if (adm_ctx->connection) {
                kref_put(&adm_ctx->connection->kref, &drbd_destroy_connection);
                adm_ctx->connection = NULL;
        }
        if (adm_ctx->resource) {
                kref_put(&adm_ctx->resource->kref, drbd_destroy_resource);
                adm_ctx->resource = NULL;
        }

        if (!adm_ctx->reply_skb)
                return -ENOMEM;

        adm_ctx->reply_dh->ret_code = retcode;
        drbd_adm_send_reply(adm_ctx->reply_skb, info);
        return 0;
}

static void setup_khelper_env(struct drbd_connection *connection, char **envp)
{
        char *afs;

        /* FIXME: A future version will not allow this case. */
        if (connection->my_addr_len == 0 || connection->peer_addr_len == 0)
                return;

        switch (((struct sockaddr *)&connection->peer_addr)->sa_family) {
        case AF_INET6:
                afs = "ipv6";
                snprintf(envp[4], 60, "DRBD_PEER_ADDRESS=%pI6",
                         &((struct sockaddr_in6 *)&connection->peer_addr)->sin6_addr);
                break;
        case AF_INET:
                afs = "ipv4";
                snprintf(envp[4], 60, "DRBD_PEER_ADDRESS=%pI4",
                         &((struct sockaddr_in *)&connection->peer_addr)->sin_addr);
                break;
        default:
                afs = "ssocks";
                snprintf(envp[4], 60, "DRBD_PEER_ADDRESS=%pI4",
                         &((struct sockaddr_in *)&connection->peer_addr)->sin_addr);
        }
        snprintf(envp[3], 20, "DRBD_PEER_AF=%s", afs);
}

int drbd_khelper(struct drbd_device *device, char *cmd)
{
        char *envp[] = { "HOME=/",
                        "TERM=linux",
                        "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
                         (char[20]) { }, /* address family */
                         (char[60]) { }, /* address */
                        NULL };
        char mb[14];
        char *argv[] = {drbd_usermode_helper, cmd, mb, NULL };
        struct drbd_connection *connection = first_peer_device(device)->connection;
        struct sib_info sib;
        int ret;

        if (current == connection->worker.task)
                set_bit(CALLBACK_PENDING, &connection->flags);

        snprintf(mb, 14, "minor-%d", device_to_minor(device));
        setup_khelper_env(connection, envp);

        /* The helper may take some time.
         * write out any unsynced meta data changes now */
        drbd_md_sync(device);

        drbd_info(device, "helper command: %s %s %s\n", drbd_usermode_helper, cmd, mb);
        sib.sib_reason = SIB_HELPER_PRE;
        sib.helper_name = cmd;
        drbd_bcast_event(device, &sib);
        notify_helper(NOTIFY_CALL, device, connection, cmd, 0);
        ret = call_usermodehelper(drbd_usermode_helper, argv, envp, UMH_WAIT_PROC);
        if (ret)
                drbd_warn(device, "helper command: %s %s %s exit code %u (0x%x)\n",
                                drbd_usermode_helper, cmd, mb,
                                (ret >> 8) & 0xff, ret);
        else
                drbd_info(device, "helper command: %s %s %s exit code %u (0x%x)\n",
                                drbd_usermode_helper, cmd, mb,
                                (ret >> 8) & 0xff, ret);
        sib.sib_reason = SIB_HELPER_POST;
        sib.helper_exit_code = ret;
        drbd_bcast_event(device, &sib);
        notify_helper(NOTIFY_RESPONSE, device, connection, cmd, ret);

        if (current == connection->worker.task)
                clear_bit(CALLBACK_PENDING, &connection->flags);

        if (ret < 0) /* Ignore any ERRNOs we got. */
                ret = 0;

        return ret;
}

enum drbd_peer_state conn_khelper(struct drbd_connection *connection, char *cmd)
{
        char *envp[] = { "HOME=/",
                        "TERM=linux",
                        "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
                         (char[20]) { }, /* address family */
                         (char[60]) { }, /* address */
                        NULL };
        char *resource_name = connection->resource->name;
        char *argv[] = {drbd_usermode_helper, cmd, resource_name, NULL };
        int ret;

        setup_khelper_env(connection, envp);
        conn_md_sync(connection);

        drbd_info(connection, "helper command: %s %s %s\n", drbd_usermode_helper, cmd, resource_name);
        /* TODO: conn_bcast_event() ?? */
        notify_helper(NOTIFY_CALL, NULL, connection, cmd, 0);

        ret = call_usermodehelper(drbd_usermode_helper, argv, envp, UMH_WAIT_PROC);
        if (ret)
                drbd_warn(connection, "helper command: %s %s %s exit code %u (0x%x)\n",
                          drbd_usermode_helper, cmd, resource_name,
                          (ret >> 8) & 0xff, ret);
        else
                drbd_info(connection, "helper command: %s %s %s exit code %u (0x%x)\n",
                          drbd_usermode_helper, cmd, resource_name,
                          (ret >> 8) & 0xff, ret);
        /* TODO: conn_bcast_event() ?? */
        notify_helper(NOTIFY_RESPONSE, NULL, connection, cmd, ret);

        if (ret < 0) /* Ignore any ERRNOs we got. */
                ret = 0;

        return ret;
}

static enum drbd_fencing_p highest_fencing_policy(struct drbd_connection *connection)
{
        enum drbd_fencing_p fp = FP_NOT_AVAIL;
        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;
                if (get_ldev_if_state(device, D_CONSISTENT)) {
                        struct disk_conf *disk_conf =
                                rcu_dereference(peer_device->device->ldev->disk_conf);
                        fp = max_t(enum drbd_fencing_p, fp, disk_conf->fencing);
                        put_ldev(device);
                }
        }
        rcu_read_unlock();

        return fp;
}

static bool resource_is_supended(struct drbd_resource *resource)
{
        return resource->susp || resource->susp_fen || resource->susp_nod;
}

bool conn_try_outdate_peer(struct drbd_connection *connection)
{
        struct drbd_resource * const resource = connection->resource;
        unsigned int connect_cnt;
        union drbd_state mask = { };
        union drbd_state val = { };
        enum drbd_fencing_p fp;
        char *ex_to_string;
        int r;

        spin_lock_irq(&resource->req_lock);
        if (connection->cstate >= C_WF_REPORT_PARAMS) {
                drbd_err(connection, "Expected cstate < C_WF_REPORT_PARAMS\n");
                spin_unlock_irq(&resource->req_lock);
                return false;
        }

        connect_cnt = connection->connect_cnt;
        spin_unlock_irq(&resource->req_lock);

        fp = highest_fencing_policy(connection);
        switch (fp) {
        case FP_NOT_AVAIL:
                drbd_warn(connection, "Not fencing peer, I'm not even Consistent myself.\n");
                spin_lock_irq(&resource->req_lock);
                if (connection->cstate < C_WF_REPORT_PARAMS) {
                        _conn_request_state(connection,
                                            (union drbd_state) { { .susp_fen = 1 } },
                                            (union drbd_state) { { .susp_fen = 0 } },
                                            CS_VERBOSE | CS_HARD | CS_DC_SUSP);
                        /* We are no longer suspended due to the fencing policy.
                         * We may still be suspended due to the on-no-data-accessible policy.
                         * If that was OND_IO_ERROR, fail pending requests. */
                        if (!resource_is_supended(resource))
                                _tl_restart(connection, CONNECTION_LOST_WHILE_PENDING);
                }
                /* Else: in case we raced with a connection handshake,
                 * let the handshake figure out if we maybe can RESEND,
                 * and do not resume/fail pending requests here.
                 * Worst case is we stay suspended for now, which may be
                 * resolved by either re-establishing the replication link, or
                 * the next link failure, or eventually the administrator.  */
                spin_unlock_irq(&resource->req_lock);
                return false;

        case FP_DONT_CARE:
                return true;
        default: ;
        }

        r = conn_khelper(connection, "fence-peer");

        switch ((r>>8) & 0xff) {
        case P_INCONSISTENT: /* peer is inconsistent */
                ex_to_string = "peer is inconsistent or worse";
                mask.pdsk = D_MASK;
                val.pdsk = D_INCONSISTENT;
                break;
        case P_OUTDATED: /* peer got outdated, or was already outdated */
                ex_to_string = "peer was fenced";
                mask.pdsk = D_MASK;
                val.pdsk = D_OUTDATED;
                break;
        case P_DOWN: /* peer was down */
                if (conn_highest_disk(connection) == D_UP_TO_DATE) {
                        /* we will(have) create(d) a new UUID anyways... */
                        ex_to_string = "peer is unreachable, assumed to be dead";
                        mask.pdsk = D_MASK;
                        val.pdsk = D_OUTDATED;
                } else {
                        ex_to_string = "peer unreachable, doing nothing since disk != UpToDate";
                }
                break;
        case P_PRIMARY: /* Peer is primary, voluntarily outdate myself.
                 * This is useful when an unconnected R_SECONDARY is asked to
                 * become R_PRIMARY, but finds the other peer being active. */
                ex_to_string = "peer is active";
                drbd_warn(connection, "Peer is primary, outdating myself.\n");
                mask.disk = D_MASK;
                val.disk = D_OUTDATED;
                break;
        case P_FENCING:
                /* THINK: do we need to handle this
                 * like case 4, or more like case 5? */
                if (fp != FP_STONITH)
                        drbd_err(connection, "fence-peer() = 7 && fencing != Stonith !!!\n");
                ex_to_string = "peer was stonithed";
                mask.pdsk = D_MASK;
                val.pdsk = D_OUTDATED;
                break;
        default:
                /* The script is broken ... */
                drbd_err(connection, "fence-peer helper broken, returned %d\n", (r>>8)&0xff);
                return false; /* Eventually leave IO frozen */
        }

        drbd_info(connection, "fence-peer helper returned %d (%s)\n",
                  (r>>8) & 0xff, ex_to_string);

        /* Not using
           conn_request_state(connection, mask, val, CS_VERBOSE);
           here, because we might were able to re-establish the connection in the
           meantime. */
        spin_lock_irq(&resource->req_lock);
        if (connection->cstate < C_WF_REPORT_PARAMS && !test_bit(STATE_SENT, &connection->flags)) {
                if (connection->connect_cnt != connect_cnt)
                        /* In case the connection was established and droped
                           while the fence-peer handler was running, ignore it */
                        drbd_info(connection, "Ignoring fence-peer exit code\n");
                else
                        _conn_request_state(connection, mask, val, CS_VERBOSE);
        }
        spin_unlock_irq(&resource->req_lock);

        return conn_highest_pdsk(connection) <= D_OUTDATED;
}

static int _try_outdate_peer_async(void *data)
{
        struct drbd_connection *connection = (struct drbd_connection *)data;

        conn_try_outdate_peer(connection);

        kref_put(&connection->kref, drbd_destroy_connection);
        return 0;
}

void conn_try_outdate_peer_async(struct drbd_connection *connection)
{
        struct task_struct *opa;

        kref_get(&connection->kref);
        /* We may just have force_sig()'ed this thread
         * to get it out of some blocking network function.
         * Clear signals; otherwise kthread_run(), which internally uses
         * wait_on_completion_killable(), will mistake our pending signal
         * for a new fatal signal and fail. */
        flush_signals(current);
        opa = kthread_run(_try_outdate_peer_async, connection, "drbd_async_h");
        if (IS_ERR(opa)) {
                drbd_err(connection, "out of mem, failed to invoke fence-peer helper\n");
                kref_put(&connection->kref, drbd_destroy_connection);
        }
}

enum drbd_state_rv
drbd_set_role(struct drbd_device *const device, enum drbd_role new_role, int force)
{
        struct drbd_peer_device *const peer_device = first_peer_device(device);
        struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
        const int max_tries = 4;
        enum drbd_state_rv rv = SS_UNKNOWN_ERROR;
        struct net_conf *nc;
        int try = 0;
        int forced = 0;
        union drbd_state mask, val;

        if (new_role == R_PRIMARY) {
                struct drbd_connection *connection;

                /* Detect dead peers as soon as possible.  */

                rcu_read_lock();
                for_each_connection(connection, device->resource)
                        request_ping(connection);
                rcu_read_unlock();
        }

        mutex_lock(device->state_mutex);

        mask.i = 0; mask.role = R_MASK;
        val.i  = 0; val.role  = new_role;

        while (try++ < max_tries) {
                rv = _drbd_request_state_holding_state_mutex(device, mask, val, CS_WAIT_COMPLETE);

                /* in case we first succeeded to outdate,
                 * but now suddenly could establish a connection */
                if (rv == SS_CW_FAILED_BY_PEER && mask.pdsk != 0) {
                        val.pdsk = 0;
                        mask.pdsk = 0;
                        continue;
                }

                if (rv == SS_NO_UP_TO_DATE_DISK && force &&
                    (device->state.disk < D_UP_TO_DATE &&
                     device->state.disk >= D_INCONSISTENT)) {
                        mask.disk = D_MASK;
                        val.disk  = D_UP_TO_DATE;
                        forced = 1;
                        continue;
                }

                if (rv == SS_NO_UP_TO_DATE_DISK &&
                    device->state.disk == D_CONSISTENT && mask.pdsk == 0) {
                        D_ASSERT(device, device->state.pdsk == D_UNKNOWN);

                        if (conn_try_outdate_peer(connection)) {
                                val.disk = D_UP_TO_DATE;
                                mask.disk = D_MASK;
                        }
                        continue;
                }

                if (rv == SS_NOTHING_TO_DO)
                        goto out;
                if (rv == SS_PRIMARY_NOP && mask.pdsk == 0) {
                        if (!conn_try_outdate_peer(connection) && force) {
                                drbd_warn(device, "Forced into split brain situation!\n");
                                mask.pdsk = D_MASK;
                                val.pdsk  = D_OUTDATED;

                        }
                        continue;
                }
                if (rv == SS_TWO_PRIMARIES) {
                        /* Maybe the peer is detected as dead very soon...
                           retry at most once more in this case. */
                        int timeo;
                        rcu_read_lock();
                        nc = rcu_dereference(connection->net_conf);
                        timeo = nc ? (nc->ping_timeo + 1) * HZ / 10 : 1;
                        rcu_read_unlock();
                        schedule_timeout_interruptible(timeo);
                        if (try < max_tries)
                                try = max_tries - 1;
                        continue;
                }
                if (rv < SS_SUCCESS) {
                        rv = _drbd_request_state(device, mask, val,
                                                CS_VERBOSE + CS_WAIT_COMPLETE);
                        if (rv < SS_SUCCESS)
                                goto out;
                }
                break;
        }

        if (rv < SS_SUCCESS)
                goto out;

        if (forced)
                drbd_warn(device, "Forced to consider local data as UpToDate!\n");

        /* Wait until nothing is on the fly :) */
        wait_event(device->misc_wait, atomic_read(&device->ap_pending_cnt) == 0);

        /* FIXME also wait for all pending P_BARRIER_ACK? */

        if (new_role == R_SECONDARY) {
                if (get_ldev(device)) {
                        device->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
                        put_ldev(device);
                }
        } else {
                mutex_lock(&device->resource->conf_update);
                nc = connection->net_conf;
                if (nc)
                        nc->discard_my_data = 0; /* without copy; single bit op is atomic */
                mutex_unlock(&device->resource->conf_update);

                if (get_ldev(device)) {
                        if (((device->state.conn < C_CONNECTED ||
                               device->state.pdsk <= D_FAILED)
                              && device->ldev->md.uuid[UI_BITMAP] == 0) || forced)
                                drbd_uuid_new_current(device);

                        device->ldev->md.uuid[UI_CURRENT] |=  (u64)1;
                        put_ldev(device);
                }
        }

        /* writeout of activity log covered areas of the bitmap
         * to stable storage done in after state change already */

        if (device->state.conn >= C_WF_REPORT_PARAMS) {
                /* if this was forced, we should consider sync */
                if (forced)
                        drbd_send_uuids(peer_device);
                drbd_send_current_state(peer_device);
        }

        drbd_md_sync(device);
        set_disk_ro(device->vdisk, new_role == R_SECONDARY);
        kobject_uevent(&disk_to_dev(device->vdisk)->kobj, KOBJ_CHANGE);
out:
        mutex_unlock(device->state_mutex);
        return rv;
}

static const char *from_attrs_err_to_txt(int err)
{
        return  err == -ENOMSG ? "required attribute missing" :
                err == -EOPNOTSUPP ? "unknown mandatory attribute" :
                err == -EEXIST ? "can not change invariant setting" :
                "invalid attribute value";
}

int drbd_adm_set_role(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct set_role_parms parms;
        int err;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        memset(&parms, 0, sizeof(parms));
        if (info->attrs[DRBD_NLA_SET_ROLE_PARMS]) {
                err = set_role_parms_from_attrs(&parms, info);
                if (err) {
                        retcode = ERR_MANDATORY_TAG;
                        drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                        goto out;
                }
        }
        genl_unlock();
        mutex_lock(&adm_ctx.resource->adm_mutex);

        if (info->genlhdr->cmd == DRBD_ADM_PRIMARY)
                retcode = drbd_set_role(adm_ctx.device, R_PRIMARY, parms.assume_uptodate);
        else
                retcode = drbd_set_role(adm_ctx.device, R_SECONDARY, 0);

        mutex_unlock(&adm_ctx.resource->adm_mutex);
        genl_lock();
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

/* Initializes the md.*_offset members, so we are able to find
 * the on disk meta data.
 *
 * We currently have two possible layouts:
 * external:
 *   |----------- md_size_sect ------------------|
 *   [ 4k superblock ][ activity log ][  Bitmap  ]
 *   | al_offset == 8 |
 *   | bm_offset = al_offset + X      |
 *  ==> bitmap sectors = md_size_sect - bm_offset
 *
 * internal:
 *            |----------- md_size_sect ------------------|
 * [data.....][  Bitmap  ][ activity log ][ 4k superblock ]
 *                        | al_offset < 0 |
 *            | bm_offset = al_offset - Y |
 *  ==> bitmap sectors = Y = al_offset - bm_offset
 *
 *  Activity log size used to be fixed 32kB,
 *  but is about to become configurable.
 */
static void drbd_md_set_sector_offsets(struct drbd_device *device,
                                       struct drbd_backing_dev *bdev)
{
        sector_t md_size_sect = 0;
        unsigned int al_size_sect = bdev->md.al_size_4k * 8;

        bdev->md.md_offset = drbd_md_ss(bdev);

        switch (bdev->md.meta_dev_idx) {
        default:
                /* v07 style fixed size indexed meta data */
                bdev->md.md_size_sect = MD_128MB_SECT;
                bdev->md.al_offset = MD_4kB_SECT;
                bdev->md.bm_offset = MD_4kB_SECT + al_size_sect;
                break;
        case DRBD_MD_INDEX_FLEX_EXT:
                /* just occupy the full device; unit: sectors */
                bdev->md.md_size_sect = drbd_get_capacity(bdev->md_bdev);
                bdev->md.al_offset = MD_4kB_SECT;
                bdev->md.bm_offset = MD_4kB_SECT + al_size_sect;
                break;
        case DRBD_MD_INDEX_INTERNAL:
        case DRBD_MD_INDEX_FLEX_INT:
                /* al size is still fixed */
                bdev->md.al_offset = -al_size_sect;
                /* we need (slightly less than) ~ this much bitmap sectors: */
                md_size_sect = drbd_get_capacity(bdev->backing_bdev);
                md_size_sect = ALIGN(md_size_sect, BM_SECT_PER_EXT);
                md_size_sect = BM_SECT_TO_EXT(md_size_sect);
                md_size_sect = ALIGN(md_size_sect, 8);

                /* plus the "drbd meta data super block",
                 * and the activity log; */
                md_size_sect += MD_4kB_SECT + al_size_sect;

                bdev->md.md_size_sect = md_size_sect;
                /* bitmap offset is adjusted by 'super' block size */
                bdev->md.bm_offset   = -md_size_sect + MD_4kB_SECT;
                break;
        }
}

/* input size is expected to be in KB */
char *ppsize(char *buf, unsigned long long size)
{
        /* Needs 9 bytes at max including trailing NUL:
         * -1ULL ==> "16384 EB" */
        static char units[] = { 'K', 'M', 'G', 'T', 'P', 'E' };
        int base = 0;
        while (size >= 10000 && base < sizeof(units)-1) {
                /* shift + round */
                size = (size >> 10) + !!(size & (1<<9));
                base++;
        }
        sprintf(buf, "%u %cB", (unsigned)size, units[base]);

        return buf;
}

/* there is still a theoretical deadlock when called from receiver
 * on an D_INCONSISTENT R_PRIMARY:
 *  remote READ does inc_ap_bio, receiver would need to receive answer
 *  packet from remote to dec_ap_bio again.
 *  receiver receive_sizes(), comes here,
 *  waits for ap_bio_cnt == 0. -> deadlock.
 * but this cannot happen, actually, because:
 *  R_PRIMARY D_INCONSISTENT, and peer's disk is unreachable
 *  (not connected, or bad/no disk on peer):
 *  see drbd_fail_request_early, ap_bio_cnt is zero.
 *  R_PRIMARY D_INCONSISTENT, and C_SYNC_TARGET:
 *  peer may not initiate a resize.
 */
/* Note these are not to be confused with
 * drbd_adm_suspend_io/drbd_adm_resume_io,
 * which are (sub) state changes triggered by admin (drbdsetup),
 * and can be long lived.
 * This changes an device->flag, is triggered by drbd internals,
 * and should be short-lived. */
/* It needs to be a counter, since multiple threads might
   independently suspend and resume IO. */
void drbd_suspend_io(struct drbd_device *device)
{
        atomic_inc(&device->suspend_cnt);
        if (drbd_suspended(device))
                return;
        wait_event(device->misc_wait, !atomic_read(&device->ap_bio_cnt));
}

void drbd_resume_io(struct drbd_device *device)
{
        if (atomic_dec_and_test(&device->suspend_cnt))
                wake_up(&device->misc_wait);
}

/**
 * drbd_determine_dev_size() -  Sets the right device size obeying all constraints
 * @device:     DRBD device.
 *
 * Returns 0 on success, negative return values indicate errors.
 * You should call drbd_md_sync() after calling this function.
 */
enum determine_dev_size
drbd_determine_dev_size(struct drbd_device *device, enum dds_flags flags, struct resize_parms *rs) __must_hold(local)
{
        struct md_offsets_and_sizes {
                u64 last_agreed_sect;
                u64 md_offset;
                s32 al_offset;
                s32 bm_offset;
                u32 md_size_sect;

                u32 al_stripes;
                u32 al_stripe_size_4k;
        } prev;
        sector_t u_size, size;
        struct drbd_md *md = &device->ldev->md;
        char ppb[10];
        void *buffer;

        int md_moved, la_size_changed;
        enum determine_dev_size rv = DS_UNCHANGED;

        /* We may change the on-disk offsets of our meta data below.  Lock out
         * anything that may cause meta data IO, to avoid acting on incomplete
         * layout changes or scribbling over meta data that is in the process
         * of being moved.
         *
         * Move is not exactly correct, btw, currently we have all our meta
         * data in core memory, to "move" it we just write it all out, there
         * are no reads. */
        drbd_suspend_io(device);
        buffer = drbd_md_get_buffer(device, __func__); /* Lock meta-data IO */
        if (!buffer) {
                drbd_resume_io(device);
                return DS_ERROR;
        }

        /* remember current offset and sizes */
        prev.last_agreed_sect = md->la_size_sect;
        prev.md_offset = md->md_offset;
        prev.al_offset = md->al_offset;
        prev.bm_offset = md->bm_offset;
        prev.md_size_sect = md->md_size_sect;
        prev.al_stripes = md->al_stripes;
        prev.al_stripe_size_4k = md->al_stripe_size_4k;

        if (rs) {
                /* rs is non NULL if we should change the AL layout only */
                md->al_stripes = rs->al_stripes;
                md->al_stripe_size_4k = rs->al_stripe_size / 4;
                md->al_size_4k = (u64)rs->al_stripes * rs->al_stripe_size / 4;
        }

        drbd_md_set_sector_offsets(device, device->ldev);

        rcu_read_lock();
        u_size = rcu_dereference(device->ldev->disk_conf)->disk_size;
        rcu_read_unlock();
        size = drbd_new_dev_size(device, device->ldev, u_size, flags & DDSF_FORCED);

        if (size < prev.last_agreed_sect) {
                if (rs && u_size == 0) {
                        /* Remove "rs &&" later. This check should always be active, but
                           right now the receiver expects the permissive behavior */
                        drbd_warn(device, "Implicit shrink not allowed. "
                                 "Use --size=%llus for explicit shrink.\n",
                                 (unsigned long long)size);
                        rv = DS_ERROR_SHRINK;
                }
                if (u_size > size)
                        rv = DS_ERROR_SPACE_MD;
                if (rv != DS_UNCHANGED)
                        goto err_out;
        }

        if (drbd_get_capacity(device->this_bdev) != size ||
            drbd_bm_capacity(device) != size) {
                int err;
                err = drbd_bm_resize(device, size, !(flags & DDSF_NO_RESYNC));
                if (unlikely(err)) {
                        /* currently there is only one error: ENOMEM! */
                        size = drbd_bm_capacity(device);
                        if (size == 0) {
                                drbd_err(device, "OUT OF MEMORY! "
                                    "Could not allocate bitmap!\n");
                        } else {
                                drbd_err(device, "BM resizing failed. "
                                    "Leaving size unchanged\n");
                        }
                        rv = DS_ERROR;
                }
                /* racy, see comments above. */
                drbd_set_my_capacity(device, size);
                md->la_size_sect = size;
                drbd_info(device, "size = %s (%llu KB)\n", ppsize(ppb, size>>1),
                     (unsigned long long)size>>1);
        }
        if (rv <= DS_ERROR)
                goto err_out;

        la_size_changed = (prev.last_agreed_sect != md->la_size_sect);

        md_moved = prev.md_offset    != md->md_offset
                || prev.md_size_sect != md->md_size_sect;

        if (la_size_changed || md_moved || rs) {
                u32 prev_flags;

                /* We do some synchronous IO below, which may take some time.
                 * Clear the timer, to avoid scary "timer expired!" messages,
                 * "Superblock" is written out at least twice below, anyways. */
                del_timer(&device->md_sync_timer);

                /* We won't change the "al-extents" setting, we just may need
                 * to move the on-disk location of the activity log ringbuffer.
                 * Lock for transaction is good enough, it may well be "dirty"
                 * or even "starving". */
                wait_event(device->al_wait, lc_try_lock_for_transaction(device->act_log));

                /* mark current on-disk bitmap and activity log as unreliable */
                prev_flags = md->flags;
                md->flags |= MDF_FULL_SYNC | MDF_AL_DISABLED;
                drbd_md_write(device, buffer);

                drbd_al_initialize(device, buffer);

                drbd_info(device, "Writing the whole bitmap, %s\n",
                         la_size_changed && md_moved ? "size changed and md moved" :
                         la_size_changed ? "size changed" : "md moved");
                /* next line implicitly does drbd_suspend_io()+drbd_resume_io() */
                drbd_bitmap_io(device, md_moved ? &drbd_bm_write_all : &drbd_bm_write,
                               "size changed", BM_LOCKED_MASK);

                /* on-disk bitmap and activity log is authoritative again
                 * (unless there was an IO error meanwhile...) */
                md->flags = prev_flags;
                drbd_md_write(device, buffer);

                if (rs)
                        drbd_info(device, "Changed AL layout to al-stripes = %d, al-stripe-size-kB = %d\n",
                                  md->al_stripes, md->al_stripe_size_4k * 4);
        }

        if (size > prev.last_agreed_sect)
                rv = prev.last_agreed_sect ? DS_GREW : DS_GREW_FROM_ZERO;
        if (size < prev.last_agreed_sect)
                rv = DS_SHRUNK;

        if (0) {
        err_out:
                /* restore previous offset and sizes */
                md->la_size_sect = prev.last_agreed_sect;
                md->md_offset = prev.md_offset;
                md->al_offset = prev.al_offset;
                md->bm_offset = prev.bm_offset;
                md->md_size_sect = prev.md_size_sect;
                md->al_stripes = prev.al_stripes;
                md->al_stripe_size_4k = prev.al_stripe_size_4k;
                md->al_size_4k = (u64)prev.al_stripes * prev.al_stripe_size_4k;
        }
        lc_unlock(device->act_log);
        wake_up(&device->al_wait);
        drbd_md_put_buffer(device);
        drbd_resume_io(device);

        return rv;
}

sector_t
drbd_new_dev_size(struct drbd_device *device, struct drbd_backing_dev *bdev,
                  sector_t u_size, int assume_peer_has_space)
{
        sector_t p_size = device->p_size;   /* partner's disk size. */
        sector_t la_size_sect = bdev->md.la_size_sect; /* last agreed size. */
        sector_t m_size; /* my size */
        sector_t size = 0;

        m_size = drbd_get_max_capacity(bdev);

        if (device->state.conn < C_CONNECTED && assume_peer_has_space) {
                drbd_warn(device, "Resize while not connected was forced by the user!\n");
                p_size = m_size;
        }

        if (p_size && m_size) {
                size = min_t(sector_t, p_size, m_size);
        } else {
                if (la_size_sect) {
                        size = la_size_sect;
                        if (m_size && m_size < size)
                                size = m_size;
                        if (p_size && p_size < size)
                                size = p_size;
                } else {
                        if (m_size)
                                size = m_size;
                        if (p_size)
                                size = p_size;
                }
        }

        if (size == 0)
                drbd_err(device, "Both nodes diskless!\n");

        if (u_size) {
                if (u_size > size)
                        drbd_err(device, "Requested disk size is too big (%lu > %lu)\n",
                            (unsigned long)u_size>>1, (unsigned long)size>>1);
                else
                        size = u_size;
        }

        return size;
}

/**
 * drbd_check_al_size() - Ensures that the AL is of the right size
 * @device:     DRBD device.
 *
 * Returns -EBUSY if current al lru is still used, -ENOMEM when allocation
 * failed, and 0 on success. You should call drbd_md_sync() after you called
 * this function.
 */
static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
{
        struct lru_cache *n, *t;
        struct lc_element *e;
        unsigned int in_use;
        int i;

        if (device->act_log &&
            device->act_log->nr_elements == dc->al_extents)
                return 0;

        in_use = 0;
        t = device->act_log;
        n = lc_create("act_log", drbd_al_ext_cache, AL_UPDATES_PER_TRANSACTION,
                dc->al_extents, sizeof(struct lc_element), 0);

        if (n == NULL) {
                drbd_err(device, "Cannot allocate act_log lru!\n");
                return -ENOMEM;
        }
        spin_lock_irq(&device->al_lock);
        if (t) {
                for (i = 0; i < t->nr_elements; i++) {
                        e = lc_element_by_index(t, i);
                        if (e->refcnt)
                                drbd_err(device, "refcnt(%d)==%d\n",
                                    e->lc_number, e->refcnt);
                        in_use += e->refcnt;
                }
        }
        if (!in_use)
                device->act_log = n;
        spin_unlock_irq(&device->al_lock);
        if (in_use) {
                drbd_err(device, "Activity log still in use!\n");
                lc_destroy(n);
                return -EBUSY;
        } else {
                lc_destroy(t);
        }
        drbd_md_mark_dirty(device); /* we changed device->act_log->nr_elemens */
        return 0;
}

static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
{
        q->limits.discard_granularity = granularity;
}

static unsigned int drbd_max_discard_sectors(struct drbd_connection *connection)
{
        /* when we introduced REQ_WRITE_SAME support, we also bumped
         * our maximum supported batch bio size used for discards. */
        if (connection->agreed_features & DRBD_FF_WSAME)
                return DRBD_MAX_BBIO_SECTORS;
        /* before, with DRBD <= 8.4.6, we only allowed up to one AL_EXTENT_SIZE. */
        return AL_EXTENT_SIZE >> 9;
}

static void decide_on_discard_support(struct drbd_device *device,
                        struct request_queue *q,
                        struct request_queue *b,
                        bool discard_zeroes_if_aligned)
{
        /* q = drbd device queue (device->rq_queue)
         * b = backing device queue (device->ldev->backing_bdev->bd_disk->queue),
         *     or NULL if diskless
         */
        struct drbd_connection *connection = first_peer_device(device)->connection;
        bool can_do = b ? blk_queue_discard(b) : true;

        if (can_do && connection->cstate >= C_CONNECTED && !(connection->agreed_features & DRBD_FF_TRIM)) {
                can_do = false;
                drbd_info(connection, "peer DRBD too old, does not support TRIM: disabling discards\n");
        }
        if (can_do) {
                /* We don't care for the granularity, really.
                 * Stacking limits below should fix it for the local
                 * device.  Whether or not it is a suitable granularity
                 * on the remote device is not our problem, really. If
                 * you care, you need to use devices with similar
                 * topology on all peers. */
                blk_queue_discard_granularity(q, 512);
                q->limits.max_discard_sectors = drbd_max_discard_sectors(connection);
                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
                q->limits.max_write_zeroes_sectors = drbd_max_discard_sectors(connection);
        } else {
                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
                blk_queue_discard_granularity(q, 0);
                q->limits.max_discard_sectors = 0;
                q->limits.max_write_zeroes_sectors = 0;
        }
}

static void fixup_discard_if_not_supported(struct request_queue *q)
{
        /* To avoid confusion, if this queue does not support discard, clear
         * max_discard_sectors, which is what lsblk -D reports to the user.
         * Older kernels got this wrong in "stack limits".
         * */
        if (!blk_queue_discard(q)) {
                blk_queue_max_discard_sectors(q, 0);
                blk_queue_discard_granularity(q, 0);
        }
}

static void decide_on_write_same_support(struct drbd_device *device,
                        struct request_queue *q,
                        struct request_queue *b, struct o_qlim *o,
                        bool disable_write_same)
{
        struct drbd_peer_device *peer_device = first_peer_device(device);
        struct drbd_connection *connection = peer_device->connection;
        bool can_do = b ? b->limits.max_write_same_sectors : true;

        if (can_do && disable_write_same) {
                can_do = false;
                drbd_info(peer_device, "WRITE_SAME disabled by config\n");
        }

        if (can_do && connection->cstate >= C_CONNECTED && !(connection->agreed_features & DRBD_FF_WSAME)) {
                can_do = false;
                drbd_info(peer_device, "peer does not support WRITE_SAME\n");
        }

        if (o) {
                /* logical block size; queue_logical_block_size(NULL) is 512 */
                unsigned int peer_lbs = be32_to_cpu(o->logical_block_size);
                unsigned int me_lbs_b = queue_logical_block_size(b);
                unsigned int me_lbs = queue_logical_block_size(q);

                if (me_lbs_b != me_lbs) {
                        drbd_warn(device,
                                "logical block size of local backend does not match (drbd:%u, backend:%u); was this a late attach?\n",
                                me_lbs, me_lbs_b);
                        /* rather disable write same than trigger some BUG_ON later in the scsi layer. */
                        can_do = false;
                }
                if (me_lbs_b != peer_lbs) {
                        drbd_warn(peer_device, "logical block sizes do not match (me:%u, peer:%u); this may cause problems.\n",
                                me_lbs, peer_lbs);
                        if (can_do) {
                                drbd_dbg(peer_device, "logical block size mismatch: WRITE_SAME disabled.\n");
                                can_do = false;
                        }
                        me_lbs = max(me_lbs, me_lbs_b);
                        /* We cannot change the logical block size of an in-use queue.
                         * We can only hope that access happens to be properly aligned.
                         * If not, the peer will likely produce an IO error, and detach. */
                        if (peer_lbs > me_lbs) {
                                if (device->state.role != R_PRIMARY) {
                                        blk_queue_logical_block_size(q, peer_lbs);
                                        drbd_warn(peer_device, "logical block size set to %u\n", peer_lbs);
                                } else {
                                        drbd_warn(peer_device,
                                                "current Primary must NOT adjust logical block size (%u -> %u); hope for the best.\n",
                                                me_lbs, peer_lbs);
                                }
                        }
                }
                if (can_do && !o->write_same_capable) {
                        /* If we introduce an open-coded write-same loop on the receiving side,
                         * the peer would present itself as "capable". */
                        drbd_dbg(peer_device, "WRITE_SAME disabled (peer device not capable)\n");
                        can_do = false;
                }
        }

        blk_queue_max_write_same_sectors(q, can_do ? DRBD_MAX_BBIO_SECTORS : 0);
}

static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
                                   unsigned int max_bio_size, struct o_qlim *o)
{
        struct request_queue * const q = device->rq_queue;
        unsigned int max_hw_sectors = max_bio_size >> 9;
        unsigned int max_segments = 0;
        struct request_queue *b = NULL;
        struct disk_conf *dc;
        bool discard_zeroes_if_aligned = true;
        bool disable_write_same = false;

        if (bdev) {
                b = bdev->backing_bdev->bd_disk->queue;

                max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
                rcu_read_lock();
                dc = rcu_dereference(device->ldev->disk_conf);
                max_segments = dc->max_bio_bvecs;
                discard_zeroes_if_aligned = dc->discard_zeroes_if_aligned;
                disable_write_same = dc->disable_write_same;
                rcu_read_unlock();

                blk_set_stacking_limits(&q->limits);
        }

        blk_queue_max_hw_sectors(q, max_hw_sectors);
        /* This is the workaround for "bio would need to, but cannot, be split" */
        blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
        blk_queue_segment_boundary(q, PAGE_SIZE-1);
        decide_on_discard_support(device, q, b, discard_zeroes_if_aligned);
        decide_on_write_same_support(device, q, b, o, disable_write_same);

        if (b) {
                blk_queue_stack_limits(q, b);

                if (q->backing_dev_info->ra_pages !=
                    b->backing_dev_info->ra_pages) {
                        drbd_info(device, "Adjusting my ra_pages to backing device's (%lu -> %lu)\n",
                                 q->backing_dev_info->ra_pages,
                                 b->backing_dev_info->ra_pages);
                        q->backing_dev_info->ra_pages =
                                                b->backing_dev_info->ra_pages;
                }
        }
        fixup_discard_if_not_supported(q);
}

void drbd_reconsider_queue_parameters(struct drbd_device *device, struct drbd_backing_dev *bdev, struct o_qlim *o)
{
        unsigned int now, new, local, peer;

        now = queue_max_hw_sectors(device->rq_queue) << 9;
        local = device->local_max_bio_size; /* Eventually last known value, from volatile memory */
        peer = device->peer_max_bio_size; /* Eventually last known value, from meta data */

        if (bdev) {
                local = queue_max_hw_sectors(bdev->backing_bdev->bd_disk->queue) << 9;
                device->local_max_bio_size = local;
        }
        local = min(local, DRBD_MAX_BIO_SIZE);

        /* We may ignore peer limits if the peer is modern enough.
           Because new from 8.3.8 onwards the peer can use multiple
           BIOs for a single peer_request */
        if (device->state.conn >= C_WF_REPORT_PARAMS) {
                if (first_peer_device(device)->connection->agreed_pro_version < 94)
                        peer = min(device->peer_max_bio_size, DRBD_MAX_SIZE_H80_PACKET);
                        /* Correct old drbd (up to 8.3.7) if it believes it can do more than 32KiB */
                else if (first_peer_device(device)->connection->agreed_pro_version == 94)
                        peer = DRBD_MAX_SIZE_H80_PACKET;
                else if (first_peer_device(device)->connection->agreed_pro_version < 100)
                        peer = DRBD_MAX_BIO_SIZE_P95;  /* drbd 8.3.8 onwards, before 8.4.0 */
                else
                        peer = DRBD_MAX_BIO_SIZE;

                /* We may later detach and re-attach on a disconnected Primary.
                 * Avoid this setting to jump back in that case.
                 * We want to store what we know the peer DRBD can handle,
                 * not what the peer IO backend can handle. */
                if (peer > device->peer_max_bio_size)
                        device->peer_max_bio_size = peer;
        }
        new = min(local, peer);

        if (device->state.role == R_PRIMARY && new < now)
                drbd_err(device, "ASSERT FAILED new < now; (%u < %u)\n", new, now);

        if (new != now)
                drbd_info(device, "max BIO size = %u\n", new);

        drbd_setup_queue_param(device, bdev, new, o);
}

/* Starts the worker thread */
static void conn_reconfig_start(struct drbd_connection *connection)
{
        drbd_thread_start(&connection->worker);
        drbd_flush_workqueue(&connection->sender_work);
}

/* if still unconfigured, stops worker again. */
static void conn_reconfig_done(struct drbd_connection *connection)
{
        bool stop_threads;
        spin_lock_irq(&connection->resource->req_lock);
        stop_threads = conn_all_vols_unconf(connection) &&
                connection->cstate == C_STANDALONE;
        spin_unlock_irq(&connection->resource->req_lock);
        if (stop_threads) {
                /* ack_receiver thread and ack_sender workqueue are implicitly
                 * stopped by receiver in conn_disconnect() */
                drbd_thread_stop(&connection->receiver);
                drbd_thread_stop(&connection->worker);
        }
}

/* Make sure IO is suspended before calling this function(). */
static void drbd_suspend_al(struct drbd_device *device)
{
        int s = 0;

        if (!lc_try_lock(device->act_log)) {
                drbd_warn(device, "Failed to lock al in drbd_suspend_al()\n");
                return;
        }

        drbd_al_shrink(device);
        spin_lock_irq(&device->resource->req_lock);
        if (device->state.conn < C_CONNECTED)
                s = !test_and_set_bit(AL_SUSPENDED, &device->flags);
        spin_unlock_irq(&device->resource->req_lock);
        lc_unlock(device->act_log);

        if (s)
                drbd_info(device, "Suspended AL updates\n");
}


static bool should_set_defaults(struct genl_info *info)
{
        unsigned flags = ((struct drbd_genlmsghdr*)info->userhdr)->flags;
        return 0 != (flags & DRBD_GENL_F_SET_DEFAULTS);
}

static unsigned int drbd_al_extents_max(struct drbd_backing_dev *bdev)
{
        /* This is limited by 16 bit "slot" numbers,
         * and by available on-disk context storage.
         *
         * Also (u16)~0 is special (denotes a "free" extent).
         *
         * One transaction occupies one 4kB on-disk block,
         * we have n such blocks in the on disk ring buffer,
         * the "current" transaction may fail (n-1),
         * and there is 919 slot numbers context information per transaction.
         *
         * 72 transaction blocks amounts to more than 2**16 context slots,
         * so cap there first.
         */
        const unsigned int max_al_nr = DRBD_AL_EXTENTS_MAX;
        const unsigned int sufficient_on_disk =
                (max_al_nr + AL_CONTEXT_PER_TRANSACTION -1)
                /AL_CONTEXT_PER_TRANSACTION;

        unsigned int al_size_4k = bdev->md.al_size_4k;

        if (al_size_4k > sufficient_on_disk)
                return max_al_nr;

        return (al_size_4k - 1) * AL_CONTEXT_PER_TRANSACTION;
}

static bool write_ordering_changed(struct disk_conf *a, struct disk_conf *b)
{
        return  a->disk_barrier != b->disk_barrier ||
                a->disk_flushes != b->disk_flushes ||
                a->disk_drain != b->disk_drain;
}

static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *disk_conf,
                               struct drbd_backing_dev *nbc)
{
        struct request_queue * const q = nbc->backing_bdev->bd_disk->queue;

        if (disk_conf->al_extents < DRBD_AL_EXTENTS_MIN)
                disk_conf->al_extents = DRBD_AL_EXTENTS_MIN;
        if (disk_conf->al_extents > drbd_al_extents_max(nbc))
                disk_conf->al_extents = drbd_al_extents_max(nbc);

        if (!blk_queue_discard(q)) {
                if (disk_conf->rs_discard_granularity) {
                        disk_conf->rs_discard_granularity = 0; /* disable feature */
                        drbd_info(device, "rs_discard_granularity feature disabled\n");
                }
        }

        if (disk_conf->rs_discard_granularity) {
                int orig_value = disk_conf->rs_discard_granularity;
                int remainder;

                if (q->limits.discard_granularity > disk_conf->rs_discard_granularity)
                        disk_conf->rs_discard_granularity = q->limits.discard_granularity;

                remainder = disk_conf->rs_discard_granularity % q->limits.discard_granularity;
                disk_conf->rs_discard_granularity += remainder;

                if (disk_conf->rs_discard_granularity > q->limits.max_discard_sectors << 9)
                        disk_conf->rs_discard_granularity = q->limits.max_discard_sectors << 9;

                if (disk_conf->rs_discard_granularity != orig_value)
                        drbd_info(device, "rs_discard_granularity changed to %d\n",
                                  disk_conf->rs_discard_granularity);
        }
}

int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        struct drbd_device *device;
        struct disk_conf *new_disk_conf, *old_disk_conf;
        struct fifo_buffer *old_plan = NULL, *new_plan = NULL;
        int err, fifo_size;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto finish;

        device = adm_ctx.device;
        mutex_lock(&adm_ctx.resource->adm_mutex);

        /* we also need a disk
         * to change the options on */
        if (!get_ldev(device)) {
                retcode = ERR_NO_DISK;
                goto out;
        }

        new_disk_conf = kmalloc(sizeof(struct disk_conf), GFP_KERNEL);
        if (!new_disk_conf) {
                retcode = ERR_NOMEM;
                goto fail;
        }

        mutex_lock(&device->resource->conf_update);
        old_disk_conf = device->ldev->disk_conf;
        *new_disk_conf = *old_disk_conf;
        if (should_set_defaults(info))
                set_disk_conf_defaults(new_disk_conf);

        err = disk_conf_from_attrs_for_change(new_disk_conf, info);
        if (err && err != -ENOMSG) {
                retcode = ERR_MANDATORY_TAG;
                drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                goto fail_unlock;
        }

        if (!expect(new_disk_conf->resync_rate >= 1))
                new_disk_conf->resync_rate = 1;

        sanitize_disk_conf(device, new_disk_conf, device->ldev);

        if (new_disk_conf->c_plan_ahead > DRBD_C_PLAN_AHEAD_MAX)
                new_disk_conf->c_plan_ahead = DRBD_C_PLAN_AHEAD_MAX;

        fifo_size = (new_disk_conf->c_plan_ahead * 10 * SLEEP_TIME) / HZ;
        if (fifo_size != device->rs_plan_s->size) {
                new_plan = fifo_alloc(fifo_size);
                if (!new_plan) {
                        drbd_err(device, "kmalloc of fifo_buffer failed");
                        retcode = ERR_NOMEM;
                        goto fail_unlock;
                }
        }

        drbd_suspend_io(device);
        wait_event(device->al_wait, lc_try_lock(device->act_log));
        drbd_al_shrink(device);
        err = drbd_check_al_size(device, new_disk_conf);
        lc_unlock(device->act_log);
        wake_up(&device->al_wait);
        drbd_resume_io(device);

        if (err) {
                retcode = ERR_NOMEM;
                goto fail_unlock;
        }

        lock_all_resources();
        retcode = drbd_resync_after_valid(device, new_disk_conf->resync_after);
        if (retcode == NO_ERROR) {
                rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
                drbd_resync_after_changed(device);
        }
        unlock_all_resources();

        if (retcode != NO_ERROR)
                goto fail_unlock;

        if (new_plan) {
                old_plan = device->rs_plan_s;
                rcu_assign_pointer(device->rs_plan_s, new_plan);
        }

        mutex_unlock(&device->resource->conf_update);

        if (new_disk_conf->al_updates)
                device->ldev->md.flags &= ~MDF_AL_DISABLED;
        else
                device->ldev->md.flags |= MDF_AL_DISABLED;

        if (new_disk_conf->md_flushes)
                clear_bit(MD_NO_FUA, &device->flags);
        else
                set_bit(MD_NO_FUA, &device->flags);

        if (write_ordering_changed(old_disk_conf, new_disk_conf))
                drbd_bump_write_ordering(device->resource, NULL, WO_BDEV_FLUSH);

        if (old_disk_conf->discard_zeroes_if_aligned != new_disk_conf->discard_zeroes_if_aligned
        ||  old_disk_conf->disable_write_same != new_disk_conf->disable_write_same)
                drbd_reconsider_queue_parameters(device, device->ldev, NULL);

        drbd_md_sync(device);

        if (device->state.conn >= C_CONNECTED) {
                struct drbd_peer_device *peer_device;

                for_each_peer_device(peer_device, device)
                        drbd_send_sync_param(peer_device);
        }

        synchronize_rcu();
        kfree(old_disk_conf);
        kfree(old_plan);
        mod_timer(&device->request_timer, jiffies + HZ);
        goto success;

fail_unlock:
        mutex_unlock(&device->resource->conf_update);
 fail:
        kfree(new_disk_conf);
        kfree(new_plan);
success:
        put_ldev(device);
 out:
        mutex_unlock(&adm_ctx.resource->adm_mutex);
 finish:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static struct block_device *open_backing_dev(struct drbd_device *device,
                const char *bdev_path, void *claim_ptr, bool do_bd_link)
{
        struct block_device *bdev;
        int err = 0;

        bdev = blkdev_get_by_path(bdev_path,
                                  FMODE_READ | FMODE_WRITE | FMODE_EXCL, claim_ptr);
        if (IS_ERR(bdev)) {
                drbd_err(device, "open(\"%s\") failed with %ld\n",
                                bdev_path, PTR_ERR(bdev));
                return bdev;
        }

        if (!do_bd_link)
                return bdev;

        err = bd_link_disk_holder(bdev, device->vdisk);
        if (err) {
                blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
                drbd_err(device, "bd_link_disk_holder(\"%s\", ...) failed with %d\n",
                                bdev_path, err);
                bdev = ERR_PTR(err);
        }
        return bdev;
}

static int open_backing_devices(struct drbd_device *device,
                struct disk_conf *new_disk_conf,
                struct drbd_backing_dev *nbc)
{
        struct block_device *bdev;

        bdev = open_backing_dev(device, new_disk_conf->backing_dev, device, true);
        if (IS_ERR(bdev))
                return ERR_OPEN_DISK;
        nbc->backing_bdev = bdev;

        /*
         * meta_dev_idx >= 0: external fixed size, possibly multiple
         * drbd sharing one meta device.  TODO in that case, paranoia
         * check that [md_bdev, meta_dev_idx] is not yet used by some
         * other drbd minor!  (if you use drbd.conf + drbdadm, that
         * should check it for you already; but if you don't, or
         * someone fooled it, we need to double check here)
         */
        bdev = open_backing_dev(device, new_disk_conf->meta_dev,
                /* claim ptr: device, if claimed exclusively; shared drbd_m_holder,
                 * if potentially shared with other drbd minors */
                        (new_disk_conf->meta_dev_idx < 0) ? (void*)device : (void*)drbd_m_holder,
                /* avoid double bd_claim_by_disk() for the same (source,target) tuple,
                 * as would happen with internal metadata. */
                        (new_disk_conf->meta_dev_idx != DRBD_MD_INDEX_FLEX_INT &&
                         new_disk_conf->meta_dev_idx != DRBD_MD_INDEX_INTERNAL));
        if (IS_ERR(bdev))
                return ERR_OPEN_MD_DISK;
        nbc->md_bdev = bdev;
        return NO_ERROR;
}

static void close_backing_dev(struct drbd_device *device, struct block_device *bdev,
        bool do_bd_unlink)
{
        if (!bdev)
                return;
        if (do_bd_unlink)
                bd_unlink_disk_holder(bdev, device->vdisk);
        blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
}

void drbd_backing_dev_free(struct drbd_device *device, struct drbd_backing_dev *ldev)
{
        if (ldev == NULL)
                return;

        close_backing_dev(device, ldev->md_bdev, ldev->md_bdev != ldev->backing_bdev);
        close_backing_dev(device, ldev->backing_bdev, true);

        kfree(ldev->disk_conf);
        kfree(ldev);
}

int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_device *device;
        struct drbd_peer_device *peer_device;
        struct drbd_connection *connection;
        int err;
        enum drbd_ret_code retcode;
        enum determine_dev_size dd;
        sector_t max_possible_sectors;
        sector_t min_md_device_sectors;
        struct drbd_backing_dev *nbc = NULL; /* new_backing_conf */
        struct disk_conf *new_disk_conf = NULL;
        struct lru_cache *resync_lru = NULL;
        struct fifo_buffer *new_plan = NULL;
        union drbd_state ns, os;
        enum drbd_state_rv rv;
        struct net_conf *nc;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto finish;

        device = adm_ctx.device;
        mutex_lock(&adm_ctx.resource->adm_mutex);
        peer_device = first_peer_device(device);
        connection = peer_device->connection;
        conn_reconfig_start(connection);

        /* if you want to reconfigure, please tear down first */
        if (device->state.disk > D_DISKLESS) {
                retcode = ERR_DISK_CONFIGURED;
                goto fail;
        }
        /* It may just now have detached because of IO error.  Make sure
         * drbd_ldev_destroy is done already, we may end up here very fast,
         * e.g. if someone calls attach from the on-io-error handler,
         * to realize a "hot spare" feature (not that I'd recommend that) */
        wait_event(device->misc_wait, !test_bit(GOING_DISKLESS, &device->flags));

        /* make sure there is no leftover from previous force-detach attempts */
        clear_bit(FORCE_DETACH, &device->flags);
        clear_bit(WAS_IO_ERROR, &device->flags);
        clear_bit(WAS_READ_ERROR, &device->flags);

        /* and no leftover from previously aborted resync or verify, either */
        device->rs_total = 0;
        device->rs_failed = 0;
        atomic_set(&device->rs_pending_cnt, 0);

        /* allocation not in the IO path, drbdsetup context */
        nbc = kzalloc(sizeof(struct drbd_backing_dev), GFP_KERNEL);
        if (!nbc) {
                retcode = ERR_NOMEM;
                goto fail;
        }
        spin_lock_init(&nbc->md.uuid_lock);

        new_disk_conf = kzalloc(sizeof(struct disk_conf), GFP_KERNEL);
        if (!new_disk_conf) {
                retcode = ERR_NOMEM;
                goto fail;
        }
        nbc->disk_conf = new_disk_conf;

        set_disk_conf_defaults(new_disk_conf);
        err = disk_conf_from_attrs(new_disk_conf, info);
        if (err) {
                retcode = ERR_MANDATORY_TAG;
                drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                goto fail;
        }

        if (new_disk_conf->c_plan_ahead > DRBD_C_PLAN_AHEAD_MAX)
                new_disk_conf->c_plan_ahead = DRBD_C_PLAN_AHEAD_MAX;

        new_plan = fifo_alloc((new_disk_conf->c_plan_ahead * 10 * SLEEP_TIME) / HZ);
        if (!new_plan) {
                retcode = ERR_NOMEM;
                goto fail;
        }

        if (new_disk_conf->meta_dev_idx < DRBD_MD_INDEX_FLEX_INT) {
                retcode = ERR_MD_IDX_INVALID;
                goto fail;
        }

        rcu_read_lock();
        nc = rcu_dereference(connection->net_conf);
        if (nc) {
                if (new_disk_conf->fencing == FP_STONITH && nc->wire_protocol == DRBD_PROT_A) {
                        rcu_read_unlock();
                        retcode = ERR_STONITH_AND_PROT_A;
                        goto fail;
                }
        }
        rcu_read_unlock();

        retcode = open_backing_devices(device, new_disk_conf, nbc);
        if (retcode != NO_ERROR)
                goto fail;

        if ((nbc->backing_bdev == nbc->md_bdev) !=
            (new_disk_conf->meta_dev_idx == DRBD_MD_INDEX_INTERNAL ||
             new_disk_conf->meta_dev_idx == DRBD_MD_INDEX_FLEX_INT)) {
                retcode = ERR_MD_IDX_INVALID;
                goto fail;
        }

        resync_lru = lc_create("resync", drbd_bm_ext_cache,
                        1, 61, sizeof(struct bm_extent),
                        offsetof(struct bm_extent, lce));
        if (!resync_lru) {
                retcode = ERR_NOMEM;
                goto fail;
        }

        /* Read our meta data super block early.
         * This also sets other on-disk offsets. */
        retcode = drbd_md_read(device, nbc);
        if (retcode != NO_ERROR)
                goto fail;

        sanitize_disk_conf(device, new_disk_conf, nbc);

        if (drbd_get_max_capacity(nbc) < new_disk_conf->disk_size) {
                drbd_err(device, "max capacity %llu smaller than disk size %llu\n",
                        (unsigned long long) drbd_get_max_capacity(nbc),
                        (unsigned long long) new_disk_conf->disk_size);
                retcode = ERR_DISK_TOO_SMALL;
                goto fail;
        }

        if (new_disk_conf->meta_dev_idx < 0) {
                max_possible_sectors = DRBD_MAX_SECTORS_FLEX;
                /* at least one MB, otherwise it does not make sense */
                min_md_device_sectors = (2<<10);
        } else {
                max_possible_sectors = DRBD_MAX_SECTORS;
                min_md_device_sectors = MD_128MB_SECT * (new_disk_conf->meta_dev_idx + 1);
        }

        if (drbd_get_capacity(nbc->md_bdev) < min_md_device_sectors) {
                retcode = ERR_MD_DISK_TOO_SMALL;
                drbd_warn(device, "refusing attach: md-device too small, "
                     "at least %llu sectors needed for this meta-disk type\n",
                     (unsigned long long) min_md_device_sectors);
                goto fail;
        }

        /* Make sure the new disk is big enough
         * (we may currently be R_PRIMARY with no local disk...) */
        if (drbd_get_max_capacity(nbc) <
            drbd_get_capacity(device->this_bdev)) {
                retcode = ERR_DISK_TOO_SMALL;
                goto fail;
        }

        nbc->known_size = drbd_get_capacity(nbc->backing_bdev);

        if (nbc->known_size > max_possible_sectors) {
                drbd_warn(device, "==> truncating very big lower level device "
                        "to currently maximum possible %llu sectors <==\n",
                        (unsigned long long) max_possible_sectors);
                if (new_disk_conf->meta_dev_idx >= 0)
                        drbd_warn(device, "==>> using internal or flexible "
                                      "meta data may help <<==\n");
        }

        drbd_suspend_io(device);
        /* also wait for the last barrier ack. */
        /* FIXME see also https://daiquiri.linbit/cgi-bin/bugzilla/show_bug.cgi?id=171
         * We need a way to either ignore barrier acks for barriers sent before a device
         * was attached, or a way to wait for all pending barrier acks to come in.
         * As barriers are counted per resource,
         * we'd need to suspend io on all devices of a resource.
         */
        wait_event(device->misc_wait, !atomic_read(&device->ap_pending_cnt) || drbd_suspended(device));
        /* and for any other previously queued work */
        drbd_flush_workqueue(&connection->sender_work);

        rv = _drbd_request_state(device, NS(disk, D_ATTACHING), CS_VERBOSE);
        retcode = rv;  /* FIXME: Type mismatch. */
        drbd_resume_io(device);
        if (rv < SS_SUCCESS)
                goto fail;

        if (!get_ldev_if_state(device, D_ATTACHING))
                goto force_diskless;

        if (!device->bitmap) {
                if (drbd_bm_init(device)) {
                        retcode = ERR_NOMEM;
                        goto force_diskless_dec;
                }
        }

        if (device->state.conn < C_CONNECTED &&
            device->state.role == R_PRIMARY && device->ed_uuid &&
            (device->ed_uuid & ~((u64)1)) != (nbc->md.uuid[UI_CURRENT] & ~((u64)1))) {
                drbd_err(device, "Can only attach to data with current UUID=%016llX\n",
                    (unsigned long long)device->ed_uuid);
                retcode = ERR_DATA_NOT_CURRENT;
                goto force_diskless_dec;
        }

        /* Since we are diskless, fix the activity log first... */
        if (drbd_check_al_size(device, new_disk_conf)) {
                retcode = ERR_NOMEM;
                goto force_diskless_dec;
        }

        /* Prevent shrinking of consistent devices ! */
        if (drbd_md_test_flag(nbc, MDF_CONSISTENT) &&
            drbd_new_dev_size(device, nbc, nbc->disk_conf->disk_size, 0) < nbc->md.la_size_sect) {
                drbd_warn(device, "refusing to truncate a consistent device\n");
                retcode = ERR_DISK_TOO_SMALL;
                goto force_diskless_dec;
        }

        lock_all_resources();
        retcode = drbd_resync_after_valid(device, new_disk_conf->resync_after);
        if (retcode != NO_ERROR) {
                unlock_all_resources();
                goto force_diskless_dec;
        }

        /* Reset the "barriers don't work" bits here, then force meta data to
         * be written, to ensure we determine if barriers are supported. */
        if (new_disk_conf->md_flushes)
                clear_bit(MD_NO_FUA, &device->flags);
        else
                set_bit(MD_NO_FUA, &device->flags);

        /* Point of no return reached.
         * Devices and memory are no longer released by error cleanup below.
         * now device takes over responsibility, and the state engine should
         * clean it up somewhere.  */
        D_ASSERT(device, device->ldev == NULL);
        device->ldev = nbc;
        device->resync = resync_lru;
        device->rs_plan_s = new_plan;
        nbc = NULL;
        resync_lru = NULL;
        new_disk_conf = NULL;
        new_plan = NULL;

        drbd_resync_after_changed(device);
        drbd_bump_write_ordering(device->resource, device->ldev, WO_BDEV_FLUSH);
        unlock_all_resources();

        if (drbd_md_test_flag(device->ldev, MDF_CRASHED_PRIMARY))
                set_bit(CRASHED_PRIMARY, &device->flags);
        else
                clear_bit(CRASHED_PRIMARY, &device->flags);

        if (drbd_md_test_flag(device->ldev, MDF_PRIMARY_IND) &&
            !(device->state.role == R_PRIMARY && device->resource->susp_nod))
                set_bit(CRASHED_PRIMARY, &device->flags);

        device->send_cnt = 0;
        device->recv_cnt = 0;
        device->read_cnt = 0;
        device->writ_cnt = 0;

        drbd_reconsider_queue_parameters(device, device->ldev, NULL);

        /* If I am currently not R_PRIMARY,
         * but meta data primary indicator is set,
         * I just now recover from a hard crash,
         * and have been R_PRIMARY before that crash.
         *
         * Now, if I had no connection before that crash
         * (have been degraded R_PRIMARY), chances are that
         * I won't find my peer now either.
         *
         * In that case, and _only_ in that case,
         * we use the degr-wfc-timeout instead of the default,
         * so we can automatically recover from a crash of a
         * degraded but active "cluster" after a certain timeout.
         */
        clear_bit(USE_DEGR_WFC_T, &device->flags);
        if (device->state.role != R_PRIMARY &&
             drbd_md_test_flag(device->ldev, MDF_PRIMARY_IND) &&
            !drbd_md_test_flag(device->ldev, MDF_CONNECTED_IND))
                set_bit(USE_DEGR_WFC_T, &device->flags);

        dd = drbd_determine_dev_size(device, 0, NULL);
        if (dd <= DS_ERROR) {
                retcode = ERR_NOMEM_BITMAP;
                goto force_diskless_dec;
        } else if (dd == DS_GREW)
                set_bit(RESYNC_AFTER_NEG, &device->flags);

        if (drbd_md_test_flag(device->ldev, MDF_FULL_SYNC) ||
            (test_bit(CRASHED_PRIMARY, &device->flags) &&
             drbd_md_test_flag(device->ldev, MDF_AL_DISABLED))) {
                drbd_info(device, "Assuming that all blocks are out of sync "
                     "(aka FullSync)\n");
                if (drbd_bitmap_io(device, &drbd_bmio_set_n_write,
                        "set_n_write from attaching", BM_LOCKED_MASK)) {
                        retcode = ERR_IO_MD_DISK;
                        goto force_diskless_dec;
                }
        } else {
                if (drbd_bitmap_io(device, &drbd_bm_read,
                        "read from attaching", BM_LOCKED_MASK)) {
                        retcode = ERR_IO_MD_DISK;
                        goto force_diskless_dec;
                }
        }

        if (_drbd_bm_total_weight(device) == drbd_bm_bits(device))
                drbd_suspend_al(device); /* IO is still suspended here... */

        spin_lock_irq(&device->resource->req_lock);
        os = drbd_read_state(device);
        ns = os;
        /* If MDF_CONSISTENT is not set go into inconsistent state,
           otherwise investigate MDF_WasUpToDate...
           If MDF_WAS_UP_TO_DATE is not set go into D_OUTDATED disk state,
           otherwise into D_CONSISTENT state.
        */
        if (drbd_md_test_flag(device->ldev, MDF_CONSISTENT)) {
                if (drbd_md_test_flag(device->ldev, MDF_WAS_UP_TO_DATE))
                        ns.disk = D_CONSISTENT;
                else
                        ns.disk = D_OUTDATED;
        } else {
                ns.disk = D_INCONSISTENT;
        }

        if (drbd_md_test_flag(device->ldev, MDF_PEER_OUT_DATED))
                ns.pdsk = D_OUTDATED;

        rcu_read_lock();
        if (ns.disk == D_CONSISTENT &&
            (ns.pdsk == D_OUTDATED || rcu_dereference(device->ldev->disk_conf)->fencing == FP_DONT_CARE))
                ns.disk = D_UP_TO_DATE;

        /* All tests on MDF_PRIMARY_IND, MDF_CONNECTED_IND,
           MDF_CONSISTENT and MDF_WAS_UP_TO_DATE must happen before
           this point, because drbd_request_state() modifies these
           flags. */

        if (rcu_dereference(device->ldev->disk_conf)->al_updates)
                device->ldev->md.flags &= ~MDF_AL_DISABLED;
        else
                device->ldev->md.flags |= MDF_AL_DISABLED;

        rcu_read_unlock();

        /* In case we are C_CONNECTED postpone any decision on the new disk
           state after the negotiation phase. */
        if (device->state.conn == C_CONNECTED) {
                device->new_state_tmp.i = ns.i;
                ns.i = os.i;
                ns.disk = D_NEGOTIATING;

                /* We expect to receive up-to-date UUIDs soon.
                   To avoid a race in receive_state, free p_uuid while
                   holding req_lock. I.e. atomic with the state change */
                kfree(device->p_uuid);
                device->p_uuid = NULL;
        }

        rv = _drbd_set_state(device, ns, CS_VERBOSE, NULL);
        spin_unlock_irq(&device->resource->req_lock);

        if (rv < SS_SUCCESS)
                goto force_diskless_dec;

        mod_timer(&device->request_timer, jiffies + HZ);

        if (device->state.role == R_PRIMARY)
                device->ldev->md.uuid[UI_CURRENT] |=  (u64)1;
        else
                device->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;

        drbd_md_mark_dirty(device);
        drbd_md_sync(device);

        kobject_uevent(&disk_to_dev(device->vdisk)->kobj, KOBJ_CHANGE);
        put_ldev(device);
        conn_reconfig_done(connection);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;

 force_diskless_dec:
        put_ldev(device);
 force_diskless:
        drbd_force_state(device, NS(disk, D_DISKLESS));
        drbd_md_sync(device);
 fail:
        conn_reconfig_done(connection);
        if (nbc) {
                close_backing_dev(device, nbc->md_bdev, nbc->md_bdev != nbc->backing_bdev);
                close_backing_dev(device, nbc->backing_bdev, true);
                kfree(nbc);
        }
        kfree(new_disk_conf);
        lc_destroy(resync_lru);
        kfree(new_plan);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
 finish:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static int adm_detach(struct drbd_device *device, int force)
{
        if (force) {
                set_bit(FORCE_DETACH, &device->flags);
                drbd_force_state(device, NS(disk, D_FAILED));
                return SS_SUCCESS;
        }

        return drbd_request_detach_interruptible(device);
}

/* Detaching the disk is a process in multiple stages.  First we need to lock
 * out application IO, in-flight IO, IO stuck in drbd_al_begin_io.
 * Then we transition to D_DISKLESS, and wait for put_ldev() to return all
 * internal references as well.
 * Only then we have finally detached. */
int drbd_adm_detach(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        struct detach_parms parms = { };
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        if (info->attrs[DRBD_NLA_DETACH_PARMS]) {
                err = detach_parms_from_attrs(&parms, info);
                if (err) {
                        retcode = ERR_MANDATORY_TAG;
                        drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                        goto out;
                }
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);
        retcode = adm_detach(adm_ctx.device, parms.force_detach);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static bool conn_resync_running(struct drbd_connection *connection)
{
        struct drbd_peer_device *peer_device;
        bool rv = false;
        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.conn == C_SYNC_SOURCE ||
                    device->state.conn == C_SYNC_TARGET ||
                    device->state.conn == C_PAUSED_SYNC_S ||
                    device->state.conn == C_PAUSED_SYNC_T) {
                        rv = true;
                        break;
                }
        }
        rcu_read_unlock();

        return rv;
}

static bool conn_ov_running(struct drbd_connection *connection)
{
        struct drbd_peer_device *peer_device;
        bool rv = false;
        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.conn == C_VERIFY_S ||
                    device->state.conn == C_VERIFY_T) {
                        rv = true;
                        break;
                }
        }
        rcu_read_unlock();

        return rv;
}

static enum drbd_ret_code
_check_net_options(struct drbd_connection *connection, struct net_conf *old_net_conf, struct net_conf *new_net_conf)
{
        struct drbd_peer_device *peer_device;
        int i;

        if (old_net_conf && connection->cstate == C_WF_REPORT_PARAMS && connection->agreed_pro_version < 100) {
                if (new_net_conf->wire_protocol != old_net_conf->wire_protocol)
                        return ERR_NEED_APV_100;

                if (new_net_conf->two_primaries != old_net_conf->two_primaries)
                        return ERR_NEED_APV_100;

                if (strcmp(new_net_conf->integrity_alg, old_net_conf->integrity_alg))
                        return ERR_NEED_APV_100;
        }

        if (!new_net_conf->two_primaries &&
            conn_highest_role(connection) == R_PRIMARY &&
            conn_highest_peer(connection) == R_PRIMARY)
                return ERR_NEED_ALLOW_TWO_PRI;

        if (new_net_conf->two_primaries &&
            (new_net_conf->wire_protocol != DRBD_PROT_C))
                return ERR_NOT_PROTO_C;

        idr_for_each_entry(&connection->peer_devices, peer_device, i) {
                struct drbd_device *device = peer_device->device;
                if (get_ldev(device)) {
                        enum drbd_fencing_p fp = rcu_dereference(device->ldev->disk_conf)->fencing;
                        put_ldev(device);
                        if (new_net_conf->wire_protocol == DRBD_PROT_A && fp == FP_STONITH)
                                return ERR_STONITH_AND_PROT_A;
                }
                if (device->state.role == R_PRIMARY && new_net_conf->discard_my_data)
                        return ERR_DISCARD_IMPOSSIBLE;
        }

        if (new_net_conf->on_congestion != OC_BLOCK && new_net_conf->wire_protocol != DRBD_PROT_A)
                return ERR_CONG_NOT_PROTO_A;

        return NO_ERROR;
}

static enum drbd_ret_code
check_net_options(struct drbd_connection *connection, struct net_conf *new_net_conf)
{
        enum drbd_ret_code rv;
        struct drbd_peer_device *peer_device;
        int i;

        rcu_read_lock();
        rv = _check_net_options(connection, rcu_dereference(connection->net_conf), new_net_conf);
        rcu_read_unlock();

        /* connection->peer_devices protected by genl_lock() here */
        idr_for_each_entry(&connection->peer_devices, peer_device, i) {
                struct drbd_device *device = peer_device->device;
                if (!device->bitmap) {
                        if (drbd_bm_init(device))
                                return ERR_NOMEM;
                }
        }

        return rv;
}

struct crypto {
        struct crypto_ahash *verify_tfm;
        struct crypto_ahash *csums_tfm;
        struct crypto_shash *cram_hmac_tfm;
        struct crypto_ahash *integrity_tfm;
};

static int
alloc_shash(struct crypto_shash **tfm, char *tfm_name, int err_alg)
{
        if (!tfm_name[0])
                return NO_ERROR;

        *tfm = crypto_alloc_shash(tfm_name, 0, 0);
        if (IS_ERR(*tfm)) {
                *tfm = NULL;
                return err_alg;
        }

        return NO_ERROR;
}

static int
alloc_ahash(struct crypto_ahash **tfm, char *tfm_name, int err_alg)
{
        if (!tfm_name[0])
                return NO_ERROR;

        *tfm = crypto_alloc_ahash(tfm_name, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(*tfm)) {
                *tfm = NULL;
                return err_alg;
        }

        return NO_ERROR;
}

static enum drbd_ret_code
alloc_crypto(struct crypto *crypto, struct net_conf *new_net_conf)
{
        char hmac_name[CRYPTO_MAX_ALG_NAME];
        enum drbd_ret_code rv;

        rv = alloc_ahash(&crypto->csums_tfm, new_net_conf->csums_alg,
                         ERR_CSUMS_ALG);
        if (rv != NO_ERROR)
                return rv;
        rv = alloc_ahash(&crypto->verify_tfm, new_net_conf->verify_alg,
                         ERR_VERIFY_ALG);
        if (rv != NO_ERROR)
                return rv;
        rv = alloc_ahash(&crypto->integrity_tfm, new_net_conf->integrity_alg,
                         ERR_INTEGRITY_ALG);
        if (rv != NO_ERROR)
                return rv;
        if (new_net_conf->cram_hmac_alg[0] != 0) {
                snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
                         new_net_conf->cram_hmac_alg);

                rv = alloc_shash(&crypto->cram_hmac_tfm, hmac_name,
                                 ERR_AUTH_ALG);
        }

        return rv;
}

static void free_crypto(struct crypto *crypto)
{
        crypto_free_shash(crypto->cram_hmac_tfm);
        crypto_free_ahash(crypto->integrity_tfm);
        crypto_free_ahash(crypto->csums_tfm);
        crypto_free_ahash(crypto->verify_tfm);
}

int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        struct drbd_connection *connection;
        struct net_conf *old_net_conf, *new_net_conf = NULL;
        int err;
        int ovr; /* online verify running */
        int rsr; /* re-sync running */
        struct crypto crypto = { };

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_CONNECTION);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto finish;

        connection = adm_ctx.connection;
        mutex_lock(&adm_ctx.resource->adm_mutex);

        new_net_conf = kzalloc(sizeof(struct net_conf), GFP_KERNEL);
        if (!new_net_conf) {
                retcode = ERR_NOMEM;
                goto out;
        }

        conn_reconfig_start(connection);

        mutex_lock(&connection->data.mutex);
        mutex_lock(&connection->resource->conf_update);
        old_net_conf = connection->net_conf;

        if (!old_net_conf) {
                drbd_msg_put_info(adm_ctx.reply_skb, "net conf missing, try connect");
                retcode = ERR_INVALID_REQUEST;
                goto fail;
        }

        *new_net_conf = *old_net_conf;
        if (should_set_defaults(info))
                set_net_conf_defaults(new_net_conf);

        err = net_conf_from_attrs_for_change(new_net_conf, info);
        if (err && err != -ENOMSG) {
                retcode = ERR_MANDATORY_TAG;
                drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                goto fail;
        }

        retcode = check_net_options(connection, new_net_conf);
        if (retcode != NO_ERROR)
                goto fail;

        /* re-sync running */
        rsr = conn_resync_running(connection);
        if (rsr && strcmp(new_net_conf->csums_alg, old_net_conf->csums_alg)) {
                retcode = ERR_CSUMS_RESYNC_RUNNING;
                goto fail;
        }

        /* online verify running */
        ovr = conn_ov_running(connection);
        if (ovr && strcmp(new_net_conf->verify_alg, old_net_conf->verify_alg)) {
                retcode = ERR_VERIFY_RUNNING;
                goto fail;
        }

        retcode = alloc_crypto(&crypto, new_net_conf);
        if (retcode != NO_ERROR)
                goto fail;

        rcu_assign_pointer(connection->net_conf, new_net_conf);

        if (!rsr) {
                crypto_free_ahash(connection->csums_tfm);
                connection->csums_tfm = crypto.csums_tfm;
                crypto.csums_tfm = NULL;
        }
        if (!ovr) {
                crypto_free_ahash(connection->verify_tfm);
                connection->verify_tfm = crypto.verify_tfm;
                crypto.verify_tfm = NULL;
        }

        crypto_free_ahash(connection->integrity_tfm);
        connection->integrity_tfm = crypto.integrity_tfm;
        if (connection->cstate >= C_WF_REPORT_PARAMS && connection->agreed_pro_version >= 100)
                /* Do this without trying to take connection->data.mutex again.  */
                __drbd_send_protocol(connection, P_PROTOCOL_UPDATE);

        crypto_free_shash(connection->cram_hmac_tfm);
        connection->cram_hmac_tfm = crypto.cram_hmac_tfm;

        mutex_unlock(&connection->resource->conf_update);
        mutex_unlock(&connection->data.mutex);
        synchronize_rcu();
        kfree(old_net_conf);

        if (connection->cstate >= C_WF_REPORT_PARAMS) {
                struct drbd_peer_device *peer_device;
                int vnr;

                idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
                        drbd_send_sync_param(peer_device);
        }

        goto done;

 fail:
        mutex_unlock(&connection->resource->conf_update);
        mutex_unlock(&connection->data.mutex);
        free_crypto(&crypto);
        kfree(new_net_conf);
 done:
        conn_reconfig_done(connection);
 out:
        mutex_unlock(&adm_ctx.resource->adm_mutex);
 finish:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static void connection_to_info(struct connection_info *info,
                               struct drbd_connection *connection)
{
        info->conn_connection_state = connection->cstate;
        info->conn_role = conn_highest_peer(connection);
}

static void peer_device_to_info(struct peer_device_info *info,
                                struct drbd_peer_device *peer_device)
{
        struct drbd_device *device = peer_device->device;

        info->peer_repl_state =
                max_t(enum drbd_conns, C_WF_REPORT_PARAMS, device->state.conn);
        info->peer_disk_state = device->state.pdsk;
        info->peer_resync_susp_user = device->state.user_isp;
        info->peer_resync_susp_peer = device->state.peer_isp;
        info->peer_resync_susp_dependency = device->state.aftr_isp;
}

int drbd_adm_connect(struct sk_buff *skb, struct genl_info *info)
{
        struct connection_info connection_info;
        enum drbd_notification_type flags;
        unsigned int peer_devices = 0;
        struct drbd_config_context adm_ctx;
        struct drbd_peer_device *peer_device;
        struct net_conf *old_net_conf, *new_net_conf = NULL;
        struct crypto crypto = { };
        struct drbd_resource *resource;
        struct drbd_connection *connection;
        enum drbd_ret_code retcode;
        int i;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_RESOURCE);

        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;
        if (!(adm_ctx.my_addr && adm_ctx.peer_addr)) {
                drbd_msg_put_info(adm_ctx.reply_skb, "connection endpoint(s) missing");
                retcode = ERR_INVALID_REQUEST;
                goto out;
        }

        /* No need for _rcu here. All reconfiguration is
         * strictly serialized on genl_lock(). We are protected against
         * concurrent reconfiguration/addition/deletion */
        for_each_resource(resource, &drbd_resources) {
                for_each_connection(connection, resource) {
                        if (nla_len(adm_ctx.my_addr) == connection->my_addr_len &&
                            !memcmp(nla_data(adm_ctx.my_addr), &connection->my_addr,
                                    connection->my_addr_len)) {
                                retcode = ERR_LOCAL_ADDR;
                                goto out;
                        }

                        if (nla_len(adm_ctx.peer_addr) == connection->peer_addr_len &&
                            !memcmp(nla_data(adm_ctx.peer_addr), &connection->peer_addr,
                                    connection->peer_addr_len)) {
                                retcode = ERR_PEER_ADDR;
                                goto out;
                        }
                }
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);
        connection = first_connection(adm_ctx.resource);
        conn_reconfig_start(connection);

        if (connection->cstate > C_STANDALONE) {
                retcode = ERR_NET_CONFIGURED;
                goto fail;
        }

        /* allocation not in the IO path, drbdsetup / netlink process context */
        new_net_conf = kzalloc(sizeof(*new_net_conf), GFP_KERNEL);
        if (!new_net_conf) {
                retcode = ERR_NOMEM;
                goto fail;
        }

        set_net_conf_defaults(new_net_conf);

        err = net_conf_from_attrs(new_net_conf, info);
        if (err && err != -ENOMSG) {
                retcode = ERR_MANDATORY_TAG;
                drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                goto fail;
        }

        retcode = check_net_options(connection, new_net_conf);
        if (retcode != NO_ERROR)
                goto fail;

        retcode = alloc_crypto(&crypto, new_net_conf);
        if (retcode != NO_ERROR)
                goto fail;

        ((char *)new_net_conf->shared_secret)[SHARED_SECRET_MAX-1] = 0;

        drbd_flush_workqueue(&connection->sender_work);

        mutex_lock(&adm_ctx.resource->conf_update);
        old_net_conf = connection->net_conf;
        if (old_net_conf) {
                retcode = ERR_NET_CONFIGURED;
                mutex_unlock(&adm_ctx.resource->conf_update);
                goto fail;
        }
        rcu_assign_pointer(connection->net_conf, new_net_conf);

        conn_free_crypto(connection);
        connection->cram_hmac_tfm = crypto.cram_hmac_tfm;
        connection->integrity_tfm = crypto.integrity_tfm;
        connection->csums_tfm = crypto.csums_tfm;
        connection->verify_tfm = crypto.verify_tfm;

        connection->my_addr_len = nla_len(adm_ctx.my_addr);
        memcpy(&connection->my_addr, nla_data(adm_ctx.my_addr), connection->my_addr_len);
        connection->peer_addr_len = nla_len(adm_ctx.peer_addr);
        memcpy(&connection->peer_addr, nla_data(adm_ctx.peer_addr), connection->peer_addr_len);

        idr_for_each_entry(&connection->peer_devices, peer_device, i) {
                peer_devices++;
        }

        connection_to_info(&connection_info, connection);
        flags = (peer_devices--) ? NOTIFY_CONTINUES : 0;
        mutex_lock(&notification_mutex);
        notify_connection_state(NULL, 0, connection, &connection_info, NOTIFY_CREATE | flags);
        idr_for_each_entry(&connection->peer_devices, peer_device, i) {
                struct peer_device_info peer_device_info;

                peer_device_to_info(&peer_device_info, peer_device);
                flags = (peer_devices--) ? NOTIFY_CONTINUES : 0;
                notify_peer_device_state(NULL, 0, peer_device, &peer_device_info, NOTIFY_CREATE | flags);
        }
        mutex_unlock(&notification_mutex);
        mutex_unlock(&adm_ctx.resource->conf_update);

        rcu_read_lock();
        idr_for_each_entry(&connection->peer_devices, peer_device, i) {
                struct drbd_device *device = peer_device->device;
                device->send_cnt = 0;
                device->recv_cnt = 0;
        }
        rcu_read_unlock();

        retcode = conn_request_state(connection, NS(conn, C_UNCONNECTED), CS_VERBOSE);

        conn_reconfig_done(connection);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;

fail:
        free_crypto(&crypto);
        kfree(new_net_conf);

        conn_reconfig_done(connection);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static enum drbd_state_rv conn_try_disconnect(struct drbd_connection *connection, bool force)
{
        enum drbd_state_rv rv;

        rv = conn_request_state(connection, NS(conn, C_DISCONNECTING),
                        force ? CS_HARD : 0);

        switch (rv) {
        case SS_NOTHING_TO_DO:
                break;
        case SS_ALREADY_STANDALONE:
                return SS_SUCCESS;
        case SS_PRIMARY_NOP:
                /* Our state checking code wants to see the peer outdated. */
                rv = conn_request_state(connection, NS2(conn, C_DISCONNECTING, pdsk, D_OUTDATED), 0);

                if (rv == SS_OUTDATE_WO_CONN) /* lost connection before graceful disconnect succeeded */
                        rv = conn_request_state(connection, NS(conn, C_DISCONNECTING), CS_VERBOSE);

                break;
        case SS_CW_FAILED_BY_PEER:
                /* The peer probably wants to see us outdated. */
                rv = conn_request_state(connection, NS2(conn, C_DISCONNECTING,
                                                        disk, D_OUTDATED), 0);
                if (rv == SS_IS_DISKLESS || rv == SS_LOWER_THAN_OUTDATED) {
                        rv = conn_request_state(connection, NS(conn, C_DISCONNECTING),
                                        CS_HARD);
                }
                break;
        default:;
                /* no special handling necessary */
        }

        if (rv >= SS_SUCCESS) {
                enum drbd_state_rv rv2;
                /* No one else can reconfigure the network while I am here.
                 * The state handling only uses drbd_thread_stop_nowait(),
                 * we want to really wait here until the receiver is no more.
                 */
                drbd_thread_stop(&connection->receiver);

                /* Race breaker.  This additional state change request may be
                 * necessary, if this was a forced disconnect during a receiver
                 * restart.  We may have "killed" the receiver thread just
                 * after drbd_receiver() returned.  Typically, we should be
                 * C_STANDALONE already, now, and this becomes a no-op.
                 */
                rv2 = conn_request_state(connection, NS(conn, C_STANDALONE),
                                CS_VERBOSE | CS_HARD);
                if (rv2 < SS_SUCCESS)
                        drbd_err(connection,
                                "unexpected rv2=%d in conn_try_disconnect()\n",
                                rv2);
                /* Unlike in DRBD 9, the state engine has generated
                 * NOTIFY_DESTROY events before clearing connection->net_conf. */
        }
        return rv;
}

int drbd_adm_disconnect(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct disconnect_parms parms;
        struct drbd_connection *connection;
        enum drbd_state_rv rv;
        enum drbd_ret_code retcode;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_CONNECTION);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto fail;

        connection = adm_ctx.connection;
        memset(&parms, 0, sizeof(parms));
        if (info->attrs[DRBD_NLA_DISCONNECT_PARMS]) {
                err = disconnect_parms_from_attrs(&parms, info);
                if (err) {
                        retcode = ERR_MANDATORY_TAG;
                        drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                        goto fail;
                }
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);
        rv = conn_try_disconnect(connection, parms.force_disconnect);
        if (rv < SS_SUCCESS)
                retcode = rv;  /* FIXME: Type mismatch. */
        else
                retcode = NO_ERROR;
        mutex_unlock(&adm_ctx.resource->adm_mutex);
 fail:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

void resync_after_online_grow(struct drbd_device *device)
{
        int iass; /* I am sync source */

        drbd_info(device, "Resync of new storage after online grow\n");
        if (device->state.role != device->state.peer)
                iass = (device->state.role == R_PRIMARY);
        else
                iass = test_bit(RESOLVE_CONFLICTS, &first_peer_device(device)->connection->flags);

        if (iass)
                drbd_start_resync(device, C_SYNC_SOURCE);
        else
                _drbd_request_state(device, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE + CS_SERIALIZE);
}

int drbd_adm_resize(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct disk_conf *old_disk_conf, *new_disk_conf = NULL;
        struct resize_parms rs;
        struct drbd_device *device;
        enum drbd_ret_code retcode;
        enum determine_dev_size dd;
        bool change_al_layout = false;
        enum dds_flags ddsf;
        sector_t u_size;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto finish;

        mutex_lock(&adm_ctx.resource->adm_mutex);
        device = adm_ctx.device;
        if (!get_ldev(device)) {
                retcode = ERR_NO_DISK;
                goto fail;
        }

        memset(&rs, 0, sizeof(struct resize_parms));
        rs.al_stripes = device->ldev->md.al_stripes;
        rs.al_stripe_size = device->ldev->md.al_stripe_size_4k * 4;
        if (info->attrs[DRBD_NLA_RESIZE_PARMS]) {
                err = resize_parms_from_attrs(&rs, info);
                if (err) {
                        retcode = ERR_MANDATORY_TAG;
                        drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                        goto fail_ldev;
                }
        }

        if (device->state.conn > C_CONNECTED) {
                retcode = ERR_RESIZE_RESYNC;
                goto fail_ldev;
        }

        if (device->state.role == R_SECONDARY &&
            device->state.peer == R_SECONDARY) {
                retcode = ERR_NO_PRIMARY;
                goto fail_ldev;
        }

        if (rs.no_resync && first_peer_device(device)->connection->agreed_pro_version < 93) {
                retcode = ERR_NEED_APV_93;
                goto fail_ldev;
        }

        rcu_read_lock();
        u_size = rcu_dereference(device->ldev->disk_conf)->disk_size;
        rcu_read_unlock();
        if (u_size != (sector_t)rs.resize_size) {
                new_disk_conf = kmalloc(sizeof(struct disk_conf), GFP_KERNEL);
                if (!new_disk_conf) {
                        retcode = ERR_NOMEM;
                        goto fail_ldev;
                }
        }

        if (device->ldev->md.al_stripes != rs.al_stripes ||
            device->ldev->md.al_stripe_size_4k != rs.al_stripe_size / 4) {
                u32 al_size_k = rs.al_stripes * rs.al_stripe_size;

                if (al_size_k > (16 * 1024 * 1024)) {
                        retcode = ERR_MD_LAYOUT_TOO_BIG;
                        goto fail_ldev;
                }

                if (al_size_k < MD_32kB_SECT/2) {
                        retcode = ERR_MD_LAYOUT_TOO_SMALL;
                        goto fail_ldev;
                }

                if (device->state.conn != C_CONNECTED && !rs.resize_force) {
                        retcode = ERR_MD_LAYOUT_CONNECTED;
                        goto fail_ldev;
                }

                change_al_layout = true;
        }

        if (device->ldev->known_size != drbd_get_capacity(device->ldev->backing_bdev))
                device->ldev->known_size = drbd_get_capacity(device->ldev->backing_bdev);

        if (new_disk_conf) {
                mutex_lock(&device->resource->conf_update);
                old_disk_conf = device->ldev->disk_conf;
                *new_disk_conf = *old_disk_conf;
                new_disk_conf->disk_size = (sector_t)rs.resize_size;
                rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
                mutex_unlock(&device->resource->conf_update);
                synchronize_rcu();
                kfree(old_disk_conf);
                new_disk_conf = NULL;
        }

        ddsf = (rs.resize_force ? DDSF_FORCED : 0) | (rs.no_resync ? DDSF_NO_RESYNC : 0);
        dd = drbd_determine_dev_size(device, ddsf, change_al_layout ? &rs : NULL);
        drbd_md_sync(device);
        put_ldev(device);
        if (dd == DS_ERROR) {
                retcode = ERR_NOMEM_BITMAP;
                goto fail;
        } else if (dd == DS_ERROR_SPACE_MD) {
                retcode = ERR_MD_LAYOUT_NO_FIT;
                goto fail;
        } else if (dd == DS_ERROR_SHRINK) {
                retcode = ERR_IMPLICIT_SHRINK;
                goto fail;
        }

        if (device->state.conn == C_CONNECTED) {
                if (dd == DS_GREW)
                        set_bit(RESIZE_PENDING, &device->flags);

                drbd_send_uuids(first_peer_device(device));
                drbd_send_sizes(first_peer_device(device), 1, ddsf);
        }

 fail:
        mutex_unlock(&adm_ctx.resource->adm_mutex);
 finish:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;

 fail_ldev:
        put_ldev(device);
        kfree(new_disk_conf);
        goto fail;
}

int drbd_adm_resource_opts(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        struct res_opts res_opts;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_RESOURCE);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto fail;

        res_opts = adm_ctx.resource->res_opts;
        if (should_set_defaults(info))
                set_res_opts_defaults(&res_opts);

        err = res_opts_from_attrs(&res_opts, info);
        if (err && err != -ENOMSG) {
                retcode = ERR_MANDATORY_TAG;
                drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                goto fail;
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);
        err = set_resource_options(adm_ctx.resource, &res_opts);
        if (err) {
                retcode = ERR_INVALID_REQUEST;
                if (err == -ENOMEM)
                        retcode = ERR_NOMEM;
        }
        mutex_unlock(&adm_ctx.resource->adm_mutex);

fail:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_device *device;
        int retcode; /* enum drbd_ret_code rsp. enum drbd_state_rv */

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        device = adm_ctx.device;
        if (!get_ldev(device)) {
                retcode = ERR_NO_DISK;
                goto out;
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);

        /* If there is still bitmap IO pending, probably because of a previous
         * resync just being finished, wait for it before requesting a new resync.
         * Also wait for it's after_state_ch(). */
        drbd_suspend_io(device);
        wait_event(device->misc_wait, !test_bit(BITMAP_IO, &device->flags));
        drbd_flush_workqueue(&first_peer_device(device)->connection->sender_work);

        /* If we happen to be C_STANDALONE R_SECONDARY, just change to
         * D_INCONSISTENT, and set all bits in the bitmap.  Otherwise,
         * try to start a resync handshake as sync target for full sync.
         */
        if (device->state.conn == C_STANDALONE && device->state.role == R_SECONDARY) {
                retcode = drbd_request_state(device, NS(disk, D_INCONSISTENT));
                if (retcode >= SS_SUCCESS) {
                        if (drbd_bitmap_io(device, &drbd_bmio_set_n_write,
                                "set_n_write from invalidate", BM_LOCKED_MASK))
                                retcode = ERR_IO_MD_DISK;
                }
        } else
                retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_T));
        drbd_resume_io(device);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
        put_ldev(device);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static int drbd_adm_simple_request_state(struct sk_buff *skb, struct genl_info *info,
                union drbd_state mask, union drbd_state val)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        mutex_lock(&adm_ctx.resource->adm_mutex);
        retcode = drbd_request_state(adm_ctx.device, mask, val);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static int drbd_bmio_set_susp_al(struct drbd_device *device) __must_hold(local)
{
        int rv;

        rv = drbd_bmio_set_n_write(device);
        drbd_suspend_al(device);
        return rv;
}

int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        int retcode; /* drbd_ret_code, drbd_state_rv */
        struct drbd_device *device;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        device = adm_ctx.device;
        if (!get_ldev(device)) {
                retcode = ERR_NO_DISK;
                goto out;
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);

        /* If there is still bitmap IO pending, probably because of a previous
         * resync just being finished, wait for it before requesting a new resync.
         * Also wait for it's after_state_ch(). */
        drbd_suspend_io(device);
        wait_event(device->misc_wait, !test_bit(BITMAP_IO, &device->flags));
        drbd_flush_workqueue(&first_peer_device(device)->connection->sender_work);

        /* If we happen to be C_STANDALONE R_PRIMARY, just set all bits
         * in the bitmap.  Otherwise, try to start a resync handshake
         * as sync source for full sync.
         */
        if (device->state.conn == C_STANDALONE && device->state.role == R_PRIMARY) {
                /* The peer will get a resync upon connect anyways. Just make that
                   into a full resync. */
                retcode = drbd_request_state(device, NS(pdsk, D_INCONSISTENT));
                if (retcode >= SS_SUCCESS) {
                        if (drbd_bitmap_io(device, &drbd_bmio_set_susp_al,
                                "set_n_write from invalidate_peer",
                                BM_LOCKED_SET_ALLOWED))
                                retcode = ERR_IO_MD_DISK;
                }
        } else
                retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_S));
        drbd_resume_io(device);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
        put_ldev(device);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_pause_sync(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        mutex_lock(&adm_ctx.resource->adm_mutex);
        if (drbd_request_state(adm_ctx.device, NS(user_isp, 1)) == SS_NOTHING_TO_DO)
                retcode = ERR_PAUSE_IS_SET;
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_resume_sync(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        union drbd_dev_state s;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        mutex_lock(&adm_ctx.resource->adm_mutex);
        if (drbd_request_state(adm_ctx.device, NS(user_isp, 0)) == SS_NOTHING_TO_DO) {
                s = adm_ctx.device->state;
                if (s.conn == C_PAUSED_SYNC_S || s.conn == C_PAUSED_SYNC_T) {
                        retcode = s.aftr_isp ? ERR_PIC_AFTER_DEP :
                                  s.peer_isp ? ERR_PIC_PEER_DEP : ERR_PAUSE_IS_CLEAR;
                } else {
                        retcode = ERR_PAUSE_IS_CLEAR;
                }
        }
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_suspend_io(struct sk_buff *skb, struct genl_info *info)
{
        return drbd_adm_simple_request_state(skb, info, NS(susp, 1));
}

int drbd_adm_resume_io(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_device *device;
        int retcode; /* enum drbd_ret_code rsp. enum drbd_state_rv */

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        mutex_lock(&adm_ctx.resource->adm_mutex);
        device = adm_ctx.device;
        if (test_bit(NEW_CUR_UUID, &device->flags)) {
                if (get_ldev_if_state(device, D_ATTACHING)) {
                        drbd_uuid_new_current(device);
                        put_ldev(device);
                } else {
                        /* This is effectively a multi-stage "forced down".
                         * The NEW_CUR_UUID bit is supposedly only set, if we
                         * lost the replication connection, and are configured
                         * to freeze IO and wait for some fence-peer handler.
                         * So we still don't have a replication connection.
                         * And now we don't have a local disk either.  After
                         * resume, we will fail all pending and new IO, because
                         * we don't have any data anymore.  Which means we will
                         * eventually be able to terminate all users of this
                         * device, and then take it down.  By bumping the
                         * "effective" data uuid, we make sure that you really
                         * need to tear down before you reconfigure, we will
                         * the refuse to re-connect or re-attach (because no
                         * matching real data uuid exists).
                         */
                        u64 val;
                        get_random_bytes(&val, sizeof(u64));
                        drbd_set_ed_uuid(device, val);
                        drbd_warn(device, "Resumed without access to data; please tear down before attempting to re-configure.\n");
                }
                clear_bit(NEW_CUR_UUID, &device->flags);
        }
        drbd_suspend_io(device);
        retcode = drbd_request_state(device, NS3(susp, 0, susp_nod, 0, susp_fen, 0));
        if (retcode == SS_SUCCESS) {
                if (device->state.conn < C_CONNECTED)
                        tl_clear(first_peer_device(device)->connection);
                if (device->state.disk == D_DISKLESS || device->state.disk == D_FAILED)
                        tl_restart(first_peer_device(device)->connection, FAIL_FROZEN_DISK_IO);
        }
        drbd_resume_io(device);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_outdate(struct sk_buff *skb, struct genl_info *info)
{
        return drbd_adm_simple_request_state(skb, info, NS(disk, D_OUTDATED));
}

static int nla_put_drbd_cfg_context(struct sk_buff *skb,
                                    struct drbd_resource *resource,
                                    struct drbd_connection *connection,
                                    struct drbd_device *device)
{
        struct nlattr *nla;
        nla = nla_nest_start(skb, DRBD_NLA_CFG_CONTEXT);
        if (!nla)
                goto nla_put_failure;
        if (device &&
            nla_put_u32(skb, T_ctx_volume, device->vnr))
                goto nla_put_failure;
        if (nla_put_string(skb, T_ctx_resource_name, resource->name))
                goto nla_put_failure;
        if (connection) {
                if (connection->my_addr_len &&
                    nla_put(skb, T_ctx_my_addr, connection->my_addr_len, &connection->my_addr))
                        goto nla_put_failure;
                if (connection->peer_addr_len &&
                    nla_put(skb, T_ctx_peer_addr, connection->peer_addr_len, &connection->peer_addr))
                        goto nla_put_failure;
        }
        nla_nest_end(skb, nla);
        return 0;

nla_put_failure:
        if (nla)
                nla_nest_cancel(skb, nla);
        return -EMSGSIZE;
}

/*
 * The generic netlink dump callbacks are called outside the genl_lock(), so
 * they cannot use the simple attribute parsing code which uses global
 * attribute tables.
 */
static struct nlattr *find_cfg_context_attr(const struct nlmsghdr *nlh, int attr)
{
        const unsigned hdrlen = GENL_HDRLEN + GENL_MAGIC_FAMILY_HDRSZ;
        const int maxtype = ARRAY_SIZE(drbd_cfg_context_nl_policy) - 1;
        struct nlattr *nla;

        nla = nla_find(nlmsg_attrdata(nlh, hdrlen), nlmsg_attrlen(nlh, hdrlen),
                       DRBD_NLA_CFG_CONTEXT);
        if (!nla)
                return NULL;
        return drbd_nla_find_nested(maxtype, nla, __nla_type(attr));
}

static void resource_to_info(struct resource_info *, struct drbd_resource *);

int drbd_adm_dump_resources(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct drbd_genlmsghdr *dh;
        struct drbd_resource *resource;
        struct resource_info resource_info;
        struct resource_statistics resource_statistics;
        int err;

        rcu_read_lock();
        if (cb->args[0]) {
                for_each_resource_rcu(resource, &drbd_resources)
                        if (resource == (struct drbd_resource *)cb->args[0])
                                goto found_resource;
                err = 0;  /* resource was probably deleted */
                goto out;
        }
        resource = list_entry(&drbd_resources,
                              struct drbd_resource, resources);

found_resource:
        list_for_each_entry_continue_rcu(resource, &drbd_resources, resources) {
                goto put_result;
        }
        err = 0;
        goto out;

put_result:
        dh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
                        cb->nlh->nlmsg_seq, &drbd_genl_family,
                        NLM_F_MULTI, DRBD_ADM_GET_RESOURCES);
        err = -ENOMEM;
        if (!dh)
                goto out;
        dh->minor = -1U;
        dh->ret_code = NO_ERROR;
        err = nla_put_drbd_cfg_context(skb, resource, NULL, NULL);
        if (err)
                goto out;
        err = res_opts_to_skb(skb, &resource->res_opts, !capable(CAP_SYS_ADMIN));
        if (err)
                goto out;
        resource_to_info(&resource_info, resource);
        err = resource_info_to_skb(skb, &resource_info, !capable(CAP_SYS_ADMIN));
        if (err)
                goto out;
        resource_statistics.res_stat_write_ordering = resource->write_ordering;
        err = resource_statistics_to_skb(skb, &resource_statistics, !capable(CAP_SYS_ADMIN));
        if (err)
                goto out;
        cb->args[0] = (long)resource;
        genlmsg_end(skb, dh);
        err = 0;

out:
        rcu_read_unlock();
        if (err)
                return err;
        return skb->len;
}

static void device_to_statistics(struct device_statistics *s,
                                 struct drbd_device *device)
{
        memset(s, 0, sizeof(*s));
        s->dev_upper_blocked = !may_inc_ap_bio(device);
        if (get_ldev(device)) {
                struct drbd_md *md = &device->ldev->md;
                u64 *history_uuids = (u64 *)s->history_uuids;
                struct request_queue *q;
                int n;

                spin_lock_irq(&md->uuid_lock);
                s->dev_current_uuid = md->uuid[UI_CURRENT];
                BUILD_BUG_ON(sizeof(s->history_uuids) < UI_HISTORY_END - UI_HISTORY_START + 1);
                for (n = 0; n < UI_HISTORY_END - UI_HISTORY_START + 1; n++)
                        history_uuids[n] = md->uuid[UI_HISTORY_START + n];
                for (; n < HISTORY_UUIDS; n++)
                        history_uuids[n] = 0;
                s->history_uuids_len = HISTORY_UUIDS;
                spin_unlock_irq(&md->uuid_lock);

                s->dev_disk_flags = md->flags;
                q = bdev_get_queue(device->ldev->backing_bdev);
                s->dev_lower_blocked =
                        bdi_congested(q->backing_dev_info,
                                      (1 << WB_async_congested) |
                                      (1 << WB_sync_congested));
                put_ldev(device);
        }
        s->dev_size = drbd_get_capacity(device->this_bdev);
        s->dev_read = device->read_cnt;
        s->dev_write = device->writ_cnt;
        s->dev_al_writes = device->al_writ_cnt;
        s->dev_bm_writes = device->bm_writ_cnt;
        s->dev_upper_pending = atomic_read(&device->ap_bio_cnt);
        s->dev_lower_pending = atomic_read(&device->local_cnt);
        s->dev_al_suspended = test_bit(AL_SUSPENDED, &device->flags);
        s->dev_exposed_data_uuid = device->ed_uuid;
}

static int put_resource_in_arg0(struct netlink_callback *cb, int holder_nr)
{
        if (cb->args[0]) {
                struct drbd_resource *resource =
                        (struct drbd_resource *)cb->args[0];
                kref_put(&resource->kref, drbd_destroy_resource);
        }

        return 0;
}

int drbd_adm_dump_devices_done(struct netlink_callback *cb) {
        return put_resource_in_arg0(cb, 7);
}

static void device_to_info(struct device_info *, struct drbd_device *);

int drbd_adm_dump_devices(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct nlattr *resource_filter;
        struct drbd_resource *resource;
        struct drbd_device *uninitialized_var(device);
        int minor, err, retcode;
        struct drbd_genlmsghdr *dh;
        struct device_info device_info;
        struct device_statistics device_statistics;
        struct idr *idr_to_search;

        resource = (struct drbd_resource *)cb->args[0];
        if (!cb->args[0] && !cb->args[1]) {
                resource_filter = find_cfg_context_attr(cb->nlh, T_ctx_resource_name);
                if (resource_filter) {
                        retcode = ERR_RES_NOT_KNOWN;
                        resource = drbd_find_resource(nla_data(resource_filter));
                        if (!resource)
                                goto put_result;
                        cb->args[0] = (long)resource;
                }
        }

        rcu_read_lock();
        minor = cb->args[1];
        idr_to_search = resource ? &resource->devices : &drbd_devices;
        device = idr_get_next(idr_to_search, &minor);
        if (!device) {
                err = 0;
                goto out;
        }
        idr_for_each_entry_continue(idr_to_search, device, minor) {
                retcode = NO_ERROR;
                goto put_result;  /* only one iteration */
        }
        err = 0;
        goto out;  /* no more devices */

put_result:
        dh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
                        cb->nlh->nlmsg_seq, &drbd_genl_family,
                        NLM_F_MULTI, DRBD_ADM_GET_DEVICES);
        err = -ENOMEM;
        if (!dh)
                goto out;
        dh->ret_code = retcode;
        dh->minor = -1U;
        if (retcode == NO_ERROR) {
                dh->minor = device->minor;
                err = nla_put_drbd_cfg_context(skb, device->resource, NULL, device);
                if (err)
                        goto out;
                if (get_ldev(device)) {
                        struct disk_conf *disk_conf =
                                rcu_dereference(device->ldev->disk_conf);

                        err = disk_conf_to_skb(skb, disk_conf, !capable(CAP_SYS_ADMIN));
                        put_ldev(device);
                        if (err)
                                goto out;
                }
                device_to_info(&device_info, device);
                err = device_info_to_skb(skb, &device_info, !capable(CAP_SYS_ADMIN));
                if (err)
                        goto out;

                device_to_statistics(&device_statistics, device);
                err = device_statistics_to_skb(skb, &device_statistics, !capable(CAP_SYS_ADMIN));
                if (err)
                        goto out;
                cb->args[1] = minor + 1;
        }
        genlmsg_end(skb, dh);
        err = 0;

out:
        rcu_read_unlock();
        if (err)
                return err;
        return skb->len;
}

int drbd_adm_dump_connections_done(struct netlink_callback *cb)
{
        return put_resource_in_arg0(cb, 6);
}

enum { SINGLE_RESOURCE, ITERATE_RESOURCES };

int drbd_adm_dump_connections(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct nlattr *resource_filter;
        struct drbd_resource *resource = NULL, *next_resource;
        struct drbd_connection *uninitialized_var(connection);
        int err = 0, retcode;
        struct drbd_genlmsghdr *dh;
        struct connection_info connection_info;
        struct connection_statistics connection_statistics;

        rcu_read_lock();
        resource = (struct drbd_resource *)cb->args[0];
        if (!cb->args[0]) {
                resource_filter = find_cfg_context_attr(cb->nlh, T_ctx_resource_name);
                if (resource_filter) {
                        retcode = ERR_RES_NOT_KNOWN;
                        resource = drbd_find_resource(nla_data(resource_filter));
                        if (!resource)
                                goto put_result;
                        cb->args[0] = (long)resource;
                        cb->args[1] = SINGLE_RESOURCE;
                }
        }
        if (!resource) {
                if (list_empty(&drbd_resources))
                        goto out;
                resource = list_first_entry(&drbd_resources, struct drbd_resource, resources);
                kref_get(&resource->kref);
                cb->args[0] = (long)resource;
                cb->args[1] = ITERATE_RESOURCES;
        }

    next_resource:
        rcu_read_unlock();
        mutex_lock(&resource->conf_update);
        rcu_read_lock();
        if (cb->args[2]) {
                for_each_connection_rcu(connection, resource)
                        if (connection == (struct drbd_connection *)cb->args[2])
                                goto found_connection;
                /* connection was probably deleted */
                goto no_more_connections;
        }
        connection = list_entry(&resource->connections, struct drbd_connection, connections);

found_connection:
        list_for_each_entry_continue_rcu(connection, &resource->connections, connections) {
                if (!has_net_conf(connection))
                        continue;
                retcode = NO_ERROR;
                goto put_result;  /* only one iteration */
        }

no_more_connections:
        if (cb->args[1] == ITERATE_RESOURCES) {
                for_each_resource_rcu(next_resource, &drbd_resources) {
                        if (next_resource == resource)
                                goto found_resource;
                }
                /* resource was probably deleted */
        }
        goto out;

found_resource:
        list_for_each_entry_continue_rcu(next_resource, &drbd_resources, resources) {
                mutex_unlock(&resource->conf_update);
                kref_put(&resource->kref, drbd_destroy_resource);
                resource = next_resource;
                kref_get(&resource->kref);
                cb->args[0] = (long)resource;
                cb->args[2] = 0;
                goto next_resource;
        }
        goto out;  /* no more resources */

put_result:
        dh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
                        cb->nlh->nlmsg_seq, &drbd_genl_family,
                        NLM_F_MULTI, DRBD_ADM_GET_CONNECTIONS);
        err = -ENOMEM;
        if (!dh)
                goto out;
        dh->ret_code = retcode;
        dh->minor = -1U;
        if (retcode == NO_ERROR) {
                struct net_conf *net_conf;

                err = nla_put_drbd_cfg_context(skb, resource, connection, NULL);
                if (err)
                        goto out;
                net_conf = rcu_dereference(connection->net_conf);
                if (net_conf) {
                        err = net_conf_to_skb(skb, net_conf, !capable(CAP_SYS_ADMIN));
                        if (err)
                                goto out;
                }
                connection_to_info(&connection_info, connection);
                err = connection_info_to_skb(skb, &connection_info, !capable(CAP_SYS_ADMIN));
                if (err)
                        goto out;
                connection_statistics.conn_congested = test_bit(NET_CONGESTED, &connection->flags);
                err = connection_statistics_to_skb(skb, &connection_statistics, !capable(CAP_SYS_ADMIN));
                if (err)
                        goto out;
                cb->args[2] = (long)connection;
        }
        genlmsg_end(skb, dh);
        err = 0;

out:
        rcu_read_unlock();
        if (resource)
                mutex_unlock(&resource->conf_update);
        if (err)
                return err;
        return skb->len;
}

enum mdf_peer_flag {
        MDF_PEER_CONNECTED =    1 << 0,
        MDF_PEER_OUTDATED =     1 << 1,
        MDF_PEER_FENCING =      1 << 2,
        MDF_PEER_FULL_SYNC =    1 << 3,
};

static void peer_device_to_statistics(struct peer_device_statistics *s,
                                      struct drbd_peer_device *peer_device)
{
        struct drbd_device *device = peer_device->device;

        memset(s, 0, sizeof(*s));
        s->peer_dev_received = device->recv_cnt;
        s->peer_dev_sent = device->send_cnt;
        s->peer_dev_pending = atomic_read(&device->ap_pending_cnt) +
                              atomic_read(&device->rs_pending_cnt);
        s->peer_dev_unacked = atomic_read(&device->unacked_cnt);
        s->peer_dev_out_of_sync = drbd_bm_total_weight(device) << (BM_BLOCK_SHIFT - 9);
        s->peer_dev_resync_failed = device->rs_failed << (BM_BLOCK_SHIFT - 9);
        if (get_ldev(device)) {
                struct drbd_md *md = &device->ldev->md;

                spin_lock_irq(&md->uuid_lock);
                s->peer_dev_bitmap_uuid = md->uuid[UI_BITMAP];
                spin_unlock_irq(&md->uuid_lock);
                s->peer_dev_flags =
                        (drbd_md_test_flag(device->ldev, MDF_CONNECTED_IND) ?
                                MDF_PEER_CONNECTED : 0) +
                        (drbd_md_test_flag(device->ldev, MDF_CONSISTENT) &&
                         !drbd_md_test_flag(device->ldev, MDF_WAS_UP_TO_DATE) ?
                                MDF_PEER_OUTDATED : 0) +
                        /* FIXME: MDF_PEER_FENCING? */
                        (drbd_md_test_flag(device->ldev, MDF_FULL_SYNC) ?
                                MDF_PEER_FULL_SYNC : 0);
                put_ldev(device);
        }
}

int drbd_adm_dump_peer_devices_done(struct netlink_callback *cb)
{
        return put_resource_in_arg0(cb, 9);
}

int drbd_adm_dump_peer_devices(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct nlattr *resource_filter;
        struct drbd_resource *resource;
        struct drbd_device *uninitialized_var(device);
        struct drbd_peer_device *peer_device = NULL;
        int minor, err, retcode;
        struct drbd_genlmsghdr *dh;
        struct idr *idr_to_search;

        resource = (struct drbd_resource *)cb->args[0];
        if (!cb->args[0] && !cb->args[1]) {
                resource_filter = find_cfg_context_attr(cb->nlh, T_ctx_resource_name);
                if (resource_filter) {
                        retcode = ERR_RES_NOT_KNOWN;
                        resource = drbd_find_resource(nla_data(resource_filter));
                        if (!resource)
                                goto put_result;
                }
                cb->args[0] = (long)resource;
        }

        rcu_read_lock();
        minor = cb->args[1];
        idr_to_search = resource ? &resource->devices : &drbd_devices;
        device = idr_find(idr_to_search, minor);
        if (!device) {
next_device:
                minor++;
                cb->args[2] = 0;
                device = idr_get_next(idr_to_search, &minor);
                if (!device) {
                        err = 0;
                        goto out;
                }
        }
        if (cb->args[2]) {
                for_each_peer_device(peer_device, device)
                        if (peer_device == (struct drbd_peer_device *)cb->args[2])
                                goto found_peer_device;
                /* peer device was probably deleted */
                goto next_device;
        }
        /* Make peer_device point to the list head (not the first entry). */
        peer_device = list_entry(&device->peer_devices, struct drbd_peer_device, peer_devices);

found_peer_device:
        list_for_each_entry_continue_rcu(peer_device, &device->peer_devices, peer_devices) {
                if (!has_net_conf(peer_device->connection))
                        continue;
                retcode = NO_ERROR;
                goto put_result;  /* only one iteration */
        }
        goto next_device;

put_result:
        dh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
                        cb->nlh->nlmsg_seq, &drbd_genl_family,
                        NLM_F_MULTI, DRBD_ADM_GET_PEER_DEVICES);
        err = -ENOMEM;
        if (!dh)
                goto out;
        dh->ret_code = retcode;
        dh->minor = -1U;
        if (retcode == NO_ERROR) {
                struct peer_device_info peer_device_info;
                struct peer_device_statistics peer_device_statistics;

                dh->minor = minor;
                err = nla_put_drbd_cfg_context(skb, device->resource, peer_device->connection, device);
                if (err)
                        goto out;
                peer_device_to_info(&peer_device_info, peer_device);
                err = peer_device_info_to_skb(skb, &peer_device_info, !capable(CAP_SYS_ADMIN));
                if (err)
                        goto out;
                peer_device_to_statistics(&peer_device_statistics, peer_device);
                err = peer_device_statistics_to_skb(skb, &peer_device_statistics, !capable(CAP_SYS_ADMIN));
                if (err)
                        goto out;
                cb->args[1] = minor;
                cb->args[2] = (long)peer_device;
        }
        genlmsg_end(skb, dh);
        err = 0;

out:
        rcu_read_unlock();
        if (err)
                return err;
        return skb->len;
}
/*
 * Return the connection of @resource if @resource has exactly one connection.
 */
static struct drbd_connection *the_only_connection(struct drbd_resource *resource)
{
        struct list_head *connections = &resource->connections;

        if (list_empty(connections) || connections->next->next != connections)
                return NULL;
        return list_first_entry(&resource->connections, struct drbd_connection, connections);
}

static int nla_put_status_info(struct sk_buff *skb, struct drbd_device *device,
                const struct sib_info *sib)
{
        struct drbd_resource *resource = device->resource;
        struct state_info *si = NULL; /* for sizeof(si->member); */
        struct nlattr *nla;
        int got_ldev;
        int err = 0;
        int exclude_sensitive;

        /* If sib != NULL, this is drbd_bcast_event, which anyone can listen
         * to.  So we better exclude_sensitive information.
         *
         * If sib == NULL, this is drbd_adm_get_status, executed synchronously
         * in the context of the requesting user process. Exclude sensitive
         * information, unless current has superuser.
         *
         * NOTE: for drbd_adm_get_status_all(), this is a netlink dump, and
         * relies on the current implementation of netlink_dump(), which
         * executes the dump callback successively from netlink_recvmsg(),
         * always in the context of the receiving process */
        exclude_sensitive = sib || !capable(CAP_SYS_ADMIN);

        got_ldev = get_ldev(device);

        /* We need to add connection name and volume number information still.
         * Minor number is in drbd_genlmsghdr. */
        if (nla_put_drbd_cfg_context(skb, resource, the_only_connection(resource), device))
                goto nla_put_failure;

        if (res_opts_to_skb(skb, &device->resource->res_opts, exclude_sensitive))
                goto nla_put_failure;

        rcu_read_lock();
        if (got_ldev) {
                struct disk_conf *disk_conf;

                disk_conf = rcu_dereference(device->ldev->disk_conf);
                err = disk_conf_to_skb(skb, disk_conf, exclude_sensitive);
        }
        if (!err) {
                struct net_conf *nc;

                nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
                if (nc)
                        err = net_conf_to_skb(skb, nc, exclude_sensitive);
        }
        rcu_read_unlock();
        if (err)
                goto nla_put_failure;

        nla = nla_nest_start(skb, DRBD_NLA_STATE_INFO);
        if (!nla)
                goto nla_put_failure;
        if (nla_put_u32(skb, T_sib_reason, sib ? sib->sib_reason : SIB_GET_STATUS_REPLY) ||
            nla_put_u32(skb, T_current_state, device->state.i) ||
            nla_put_u64_0pad(skb, T_ed_uuid, device->ed_uuid) ||
            nla_put_u64_0pad(skb, T_capacity,
                             drbd_get_capacity(device->this_bdev)) ||
            nla_put_u64_0pad(skb, T_send_cnt, device->send_cnt) ||
            nla_put_u64_0pad(skb, T_recv_cnt, device->recv_cnt) ||
            nla_put_u64_0pad(skb, T_read_cnt, device->read_cnt) ||
            nla_put_u64_0pad(skb, T_writ_cnt, device->writ_cnt) ||
            nla_put_u64_0pad(skb, T_al_writ_cnt, device->al_writ_cnt) ||
            nla_put_u64_0pad(skb, T_bm_writ_cnt, device->bm_writ_cnt) ||
            nla_put_u32(skb, T_ap_bio_cnt, atomic_read(&device->ap_bio_cnt)) ||
            nla_put_u32(skb, T_ap_pending_cnt, atomic_read(&device->ap_pending_cnt)) ||
            nla_put_u32(skb, T_rs_pending_cnt, atomic_read(&device->rs_pending_cnt)))
                goto nla_put_failure;

        if (got_ldev) {
                int err;

                spin_lock_irq(&device->ldev->md.uuid_lock);
                err = nla_put(skb, T_uuids, sizeof(si->uuids), device->ldev->md.uuid);
                spin_unlock_irq(&device->ldev->md.uuid_lock);

                if (err)
                        goto nla_put_failure;

                if (nla_put_u32(skb, T_disk_flags, device->ldev->md.flags) ||
                    nla_put_u64_0pad(skb, T_bits_total, drbd_bm_bits(device)) ||
                    nla_put_u64_0pad(skb, T_bits_oos,
                                     drbd_bm_total_weight(device)))
                        goto nla_put_failure;
                if (C_SYNC_SOURCE <= device->state.conn &&
                    C_PAUSED_SYNC_T >= device->state.conn) {
                        if (nla_put_u64_0pad(skb, T_bits_rs_total,
                                             device->rs_total) ||
                            nla_put_u64_0pad(skb, T_bits_rs_failed,
                                             device->rs_failed))
                                goto nla_put_failure;
                }
        }

        if (sib) {
                switch(sib->sib_reason) {
                case SIB_SYNC_PROGRESS:
                case SIB_GET_STATUS_REPLY:
                        break;
                case SIB_STATE_CHANGE:
                        if (nla_put_u32(skb, T_prev_state, sib->os.i) ||
                            nla_put_u32(skb, T_new_state, sib->ns.i))
                                goto nla_put_failure;
                        break;
                case SIB_HELPER_POST:
                        if (nla_put_u32(skb, T_helper_exit_code,
                                        sib->helper_exit_code))
                                goto nla_put_failure;
                        /* fall through */
                case SIB_HELPER_PRE:
                        if (nla_put_string(skb, T_helper, sib->helper_name))
                                goto nla_put_failure;
                        break;
                }
        }
        nla_nest_end(skb, nla);

        if (0)
nla_put_failure:
                err = -EMSGSIZE;
        if (got_ldev)
                put_ldev(device);
        return err;
}

int drbd_adm_get_status(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        err = nla_put_status_info(adm_ctx.reply_skb, adm_ctx.device, NULL);
        if (err) {
                nlmsg_free(adm_ctx.reply_skb);
                return err;
        }
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static int get_one_status(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct drbd_device *device;
        struct drbd_genlmsghdr *dh;
        struct drbd_resource *pos = (struct drbd_resource *)cb->args[0];
        struct drbd_resource *resource = NULL;
        struct drbd_resource *tmp;
        unsigned volume = cb->args[1];

        /* Open coded, deferred, iteration:
         * for_each_resource_safe(resource, tmp, &drbd_resources) {
         *      connection = "first connection of resource or undefined";
         *      idr_for_each_entry(&resource->devices, device, i) {
         *        ...
         *      }
         * }
         * where resource is cb->args[0];
         * and i is cb->args[1];
         *
         * cb->args[2] indicates if we shall loop over all resources,
         * or just dump all volumes of a single resource.
         *
         * This may miss entries inserted after this dump started,
         * or entries deleted before they are reached.
         *
         * We need to make sure the device won't disappear while
         * we are looking at it, and revalidate our iterators
         * on each iteration.
         */

        /* synchronize with conn_create()/drbd_destroy_connection() */
        rcu_read_lock();
        /* revalidate iterator position */
        for_each_resource_rcu(tmp, &drbd_resources) {
                if (pos == NULL) {
                        /* first iteration */
                        pos = tmp;
                        resource = pos;
                        break;
                }
                if (tmp == pos) {
                        resource = pos;
                        break;
                }
        }
        if (resource) {
next_resource:
                device = idr_get_next(&resource->devices, &volume);
                if (!device) {
                        /* No more volumes to dump on this resource.
                         * Advance resource iterator. */
                        pos = list_entry_rcu(resource->resources.next,
                                             struct drbd_resource, resources);
                        /* Did we dump any volume of this resource yet? */
                        if (volume != 0) {
                                /* If we reached the end of the list,
                                 * or only a single resource dump was requested,
                                 * we are done. */
                                if (&pos->resources == &drbd_resources || cb->args[2])
                                        goto out;
                                volume = 0;
                                resource = pos;
                                goto next_resource;
                        }
                }

                dh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
                                cb->nlh->nlmsg_seq, &drbd_genl_family,
                                NLM_F_MULTI, DRBD_ADM_GET_STATUS);
                if (!dh)
                        goto out;

                if (!device) {
                        /* This is a connection without a single volume.
                         * Suprisingly enough, it may have a network
                         * configuration. */
                        struct drbd_connection *connection;

                        dh->minor = -1U;
                        dh->ret_code = NO_ERROR;
                        connection = the_only_connection(resource);
                        if (nla_put_drbd_cfg_context(skb, resource, connection, NULL))
                                goto cancel;
                        if (connection) {
                                struct net_conf *nc;

                                nc = rcu_dereference(connection->net_conf);
                                if (nc && net_conf_to_skb(skb, nc, 1) != 0)
                                        goto cancel;
                        }
                        goto done;
                }

                D_ASSERT(device, device->vnr == volume);
                D_ASSERT(device, device->resource == resource);

                dh->minor = device_to_minor(device);
                dh->ret_code = NO_ERROR;

                if (nla_put_status_info(skb, device, NULL)) {
cancel:
                        genlmsg_cancel(skb, dh);
                        goto out;
                }
done:
                genlmsg_end(skb, dh);
        }

out:
        rcu_read_unlock();
        /* where to start the next iteration */
        cb->args[0] = (long)pos;
        cb->args[1] = (pos == resource) ? volume + 1 : 0;

        /* No more resources/volumes/minors found results in an empty skb.
         * Which will terminate the dump. */
        return skb->len;
}

/*
 * Request status of all resources, or of all volumes within a single resource.
 *
 * This is a dump, as the answer may not fit in a single reply skb otherwise.
 * Which means we cannot use the family->attrbuf or other such members, because
 * dump is NOT protected by the genl_lock().  During dump, we only have access
 * to the incoming skb, and need to opencode "parsing" of the nlattr payload.
 *
 * Once things are setup properly, we call into get_one_status().
 */
int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
{
        const unsigned hdrlen = GENL_HDRLEN + GENL_MAGIC_FAMILY_HDRSZ;
        struct nlattr *nla;
        const char *resource_name;
        struct drbd_resource *resource;
        int maxtype;

        /* Is this a followup call? */
        if (cb->args[0]) {
                /* ... of a single resource dump,
                 * and the resource iterator has been advanced already? */
                if (cb->args[2] && cb->args[2] != cb->args[0])
                        return 0; /* DONE. */
                goto dump;
        }

        /* First call (from netlink_dump_start).  We need to figure out
         * which resource(s) the user wants us to dump. */
        nla = nla_find(nlmsg_attrdata(cb->nlh, hdrlen),
                        nlmsg_attrlen(cb->nlh, hdrlen),
                        DRBD_NLA_CFG_CONTEXT);

        /* No explicit context given.  Dump all. */
        if (!nla)
                goto dump;
        maxtype = ARRAY_SIZE(drbd_cfg_context_nl_policy) - 1;
        nla = drbd_nla_find_nested(maxtype, nla, __nla_type(T_ctx_resource_name));
        if (IS_ERR(nla))
                return PTR_ERR(nla);
        /* context given, but no name present? */
        if (!nla)
                return -EINVAL;
        resource_name = nla_data(nla);
        if (!*resource_name)
                return -ENODEV;
        resource = drbd_find_resource(resource_name);
        if (!resource)
                return -ENODEV;

        kref_put(&resource->kref, drbd_destroy_resource); /* get_one_status() revalidates the resource */

        /* prime iterators, and set "filter" mode mark:
         * only dump this connection. */
        cb->args[0] = (long)resource;
        /* cb->args[1] = 0; passed in this way. */
        cb->args[2] = (long)resource;

dump:
        return get_one_status(skb, cb);
}

int drbd_adm_get_timeout_type(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        struct timeout_parms tp;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        tp.timeout_type =
                adm_ctx.device->state.pdsk == D_OUTDATED ? UT_PEER_OUTDATED :
                test_bit(USE_DEGR_WFC_T, &adm_ctx.device->flags) ? UT_DEGRADED :
                UT_DEFAULT;

        err = timeout_parms_to_priv_skb(adm_ctx.reply_skb, &tp);
        if (err) {
                nlmsg_free(adm_ctx.reply_skb);
                return err;
        }
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_start_ov(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_device *device;
        enum drbd_ret_code retcode;
        struct start_ov_parms parms;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        device = adm_ctx.device;

        /* resume from last known position, if possible */
        parms.ov_start_sector = device->ov_start_sector;
        parms.ov_stop_sector = ULLONG_MAX;
        if (info->attrs[DRBD_NLA_START_OV_PARMS]) {
                int err = start_ov_parms_from_attrs(&parms, info);
                if (err) {
                        retcode = ERR_MANDATORY_TAG;
                        drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                        goto out;
                }
        }
        mutex_lock(&adm_ctx.resource->adm_mutex);

        /* w_make_ov_request expects position to be aligned */
        device->ov_start_sector = parms.ov_start_sector & ~(BM_SECT_PER_BIT-1);
        device->ov_stop_sector = parms.ov_stop_sector;

        /* If there is still bitmap IO pending, e.g. previous resync or verify
         * just being finished, wait for it before requesting a new resync. */
        drbd_suspend_io(device);
        wait_event(device->misc_wait, !test_bit(BITMAP_IO, &device->flags));
        retcode = drbd_request_state(device, NS(conn, C_VERIFY_S));
        drbd_resume_io(device);

        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}


int drbd_adm_new_c_uuid(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_device *device;
        enum drbd_ret_code retcode;
        int skip_initial_sync = 0;
        int err;
        struct new_c_uuid_parms args;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out_nolock;

        device = adm_ctx.device;
        memset(&args, 0, sizeof(args));
        if (info->attrs[DRBD_NLA_NEW_C_UUID_PARMS]) {
                err = new_c_uuid_parms_from_attrs(&args, info);
                if (err) {
                        retcode = ERR_MANDATORY_TAG;
                        drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                        goto out_nolock;
                }
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);
        mutex_lock(device->state_mutex); /* Protects us against serialized state changes. */

        if (!get_ldev(device)) {
                retcode = ERR_NO_DISK;
                goto out;
        }

        /* this is "skip initial sync", assume to be clean */
        if (device->state.conn == C_CONNECTED &&
            first_peer_device(device)->connection->agreed_pro_version >= 90 &&
            device->ldev->md.uuid[UI_CURRENT] == UUID_JUST_CREATED && args.clear_bm) {
                drbd_info(device, "Preparing to skip initial sync\n");
                skip_initial_sync = 1;
        } else if (device->state.conn != C_STANDALONE) {
                retcode = ERR_CONNECTED;
                goto out_dec;
        }

        drbd_uuid_set(device, UI_BITMAP, 0); /* Rotate UI_BITMAP to History 1, etc... */
        drbd_uuid_new_current(device); /* New current, previous to UI_BITMAP */

        if (args.clear_bm) {
                err = drbd_bitmap_io(device, &drbd_bmio_clear_n_write,
                        "clear_n_write from new_c_uuid", BM_LOCKED_MASK);
                if (err) {
                        drbd_err(device, "Writing bitmap failed with %d\n", err);
                        retcode = ERR_IO_MD_DISK;
                }
                if (skip_initial_sync) {
                        drbd_send_uuids_skip_initial_sync(first_peer_device(device));
                        _drbd_uuid_set(device, UI_BITMAP, 0);
                        drbd_print_uuids(device, "cleared bitmap UUID");
                        spin_lock_irq(&device->resource->req_lock);
                        _drbd_set_state(_NS2(device, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
                                        CS_VERBOSE, NULL);
                        spin_unlock_irq(&device->resource->req_lock);
                }
        }

        drbd_md_sync(device);
out_dec:
        put_ldev(device);
out:
        mutex_unlock(device->state_mutex);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out_nolock:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static enum drbd_ret_code
drbd_check_resource_name(struct drbd_config_context *adm_ctx)
{
        const char *name = adm_ctx->resource_name;
        if (!name || !name[0]) {
                drbd_msg_put_info(adm_ctx->reply_skb, "resource name missing");
                return ERR_MANDATORY_TAG;
        }
        /* if we want to use these in sysfs/configfs/debugfs some day,
         * we must not allow slashes */
        if (strchr(name, '/')) {
                drbd_msg_put_info(adm_ctx->reply_skb, "invalid resource name");
                return ERR_INVALID_REQUEST;
        }
        return NO_ERROR;
}

static void resource_to_info(struct resource_info *info,
                             struct drbd_resource *resource)
{
        info->res_role = conn_highest_role(first_connection(resource));
        info->res_susp = resource->susp;
        info->res_susp_nod = resource->susp_nod;
        info->res_susp_fen = resource->susp_fen;
}

int drbd_adm_new_resource(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_connection *connection;
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;
        struct res_opts res_opts;
        int err;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, 0);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        set_res_opts_defaults(&res_opts);
        err = res_opts_from_attrs(&res_opts, info);
        if (err && err != -ENOMSG) {
                retcode = ERR_MANDATORY_TAG;
                drbd_msg_put_info(adm_ctx.reply_skb, from_attrs_err_to_txt(err));
                goto out;
        }

        retcode = drbd_check_resource_name(&adm_ctx);
        if (retcode != NO_ERROR)
                goto out;

        if (adm_ctx.resource) {
                if (info->nlhdr->nlmsg_flags & NLM_F_EXCL) {
                        retcode = ERR_INVALID_REQUEST;
                        drbd_msg_put_info(adm_ctx.reply_skb, "resource exists");
                }
                /* else: still NO_ERROR */
                goto out;
        }

        /* not yet safe for genl_family.parallel_ops */
        mutex_lock(&resources_mutex);
        connection = conn_create(adm_ctx.resource_name, &res_opts);
        mutex_unlock(&resources_mutex);

        if (connection) {
                struct resource_info resource_info;

                mutex_lock(&notification_mutex);
                resource_to_info(&resource_info, connection->resource);
                notify_resource_state(NULL, 0, connection->resource,
                                      &resource_info, NOTIFY_CREATE);
                mutex_unlock(&notification_mutex);
        } else
                retcode = ERR_NOMEM;

out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static void device_to_info(struct device_info *info,
                           struct drbd_device *device)
{
        info->dev_disk_state = device->state.disk;
}


int drbd_adm_new_minor(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_genlmsghdr *dh = info->userhdr;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_RESOURCE);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        if (dh->minor > MINORMASK) {
                drbd_msg_put_info(adm_ctx.reply_skb, "requested minor out of range");
                retcode = ERR_INVALID_REQUEST;
                goto out;
        }
        if (adm_ctx.volume > DRBD_VOLUME_MAX) {
                drbd_msg_put_info(adm_ctx.reply_skb, "requested volume id out of range");
                retcode = ERR_INVALID_REQUEST;
                goto out;
        }

        /* drbd_adm_prepare made sure already
         * that first_peer_device(device)->connection and device->vnr match the request. */
        if (adm_ctx.device) {
                if (info->nlhdr->nlmsg_flags & NLM_F_EXCL)
                        retcode = ERR_MINOR_OR_VOLUME_EXISTS;
                /* else: still NO_ERROR */
                goto out;
        }

        mutex_lock(&adm_ctx.resource->adm_mutex);
        retcode = drbd_create_device(&adm_ctx, dh->minor);
        if (retcode == NO_ERROR) {
                struct drbd_device *device;
                struct drbd_peer_device *peer_device;
                struct device_info info;
                unsigned int peer_devices = 0;
                enum drbd_notification_type flags;

                device = minor_to_device(dh->minor);
                for_each_peer_device(peer_device, device) {
                        if (!has_net_conf(peer_device->connection))
                                continue;
                        peer_devices++;
                }

                device_to_info(&info, device);
                mutex_lock(&notification_mutex);
                flags = (peer_devices--) ? NOTIFY_CONTINUES : 0;
                notify_device_state(NULL, 0, device, &info, NOTIFY_CREATE | flags);
                for_each_peer_device(peer_device, device) {
                        struct peer_device_info peer_device_info;

                        if (!has_net_conf(peer_device->connection))
                                continue;
                        peer_device_to_info(&peer_device_info, peer_device);
                        flags = (peer_devices--) ? NOTIFY_CONTINUES : 0;
                        notify_peer_device_state(NULL, 0, peer_device, &peer_device_info,
                                                 NOTIFY_CREATE | flags);
                }
                mutex_unlock(&notification_mutex);
        }
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static enum drbd_ret_code adm_del_minor(struct drbd_device *device)
{
        struct drbd_peer_device *peer_device;

        if (device->state.disk == D_DISKLESS &&
            /* no need to be device->state.conn == C_STANDALONE &&
             * we may want to delete a minor from a live replication group.
             */
            device->state.role == R_SECONDARY) {
                struct drbd_connection *connection =
                        first_connection(device->resource);

                _drbd_request_state(device, NS(conn, C_WF_REPORT_PARAMS),
                                    CS_VERBOSE + CS_WAIT_COMPLETE);

                /* If the state engine hasn't stopped the sender thread yet, we
                 * need to flush the sender work queue before generating the
                 * DESTROY events here. */
                if (get_t_state(&connection->worker) == RUNNING)
                        drbd_flush_workqueue(&connection->sender_work);

                mutex_lock(&notification_mutex);
                for_each_peer_device(peer_device, device) {
                        if (!has_net_conf(peer_device->connection))
                                continue;
                        notify_peer_device_state(NULL, 0, peer_device, NULL,
                                                 NOTIFY_DESTROY | NOTIFY_CONTINUES);
                }
                notify_device_state(NULL, 0, device, NULL, NOTIFY_DESTROY);
                mutex_unlock(&notification_mutex);

                drbd_delete_device(device);
                return NO_ERROR;
        } else
                return ERR_MINOR_CONFIGURED;
}

int drbd_adm_del_minor(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_MINOR);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto out;

        mutex_lock(&adm_ctx.resource->adm_mutex);
        retcode = adm_del_minor(adm_ctx.device);
        mutex_unlock(&adm_ctx.resource->adm_mutex);
out:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

static int adm_del_resource(struct drbd_resource *resource)
{
        struct drbd_connection *connection;

        for_each_connection(connection, resource) {
                if (connection->cstate > C_STANDALONE)
                        return ERR_NET_CONFIGURED;
        }
        if (!idr_is_empty(&resource->devices))
                return ERR_RES_IN_USE;

        /* The state engine has stopped the sender thread, so we don't
         * need to flush the sender work queue before generating the
         * DESTROY event here. */
        mutex_lock(&notification_mutex);
        notify_resource_state(NULL, 0, resource, NULL, NOTIFY_DESTROY);
        mutex_unlock(&notification_mutex);

        mutex_lock(&resources_mutex);
        list_del_rcu(&resource->resources);
        mutex_unlock(&resources_mutex);
        /* Make sure all threads have actually stopped: state handling only
         * does drbd_thread_stop_nowait(). */
        list_for_each_entry(connection, &resource->connections, connections)
                drbd_thread_stop(&connection->worker);
        synchronize_rcu();
        drbd_free_resource(resource);
        return NO_ERROR;
}

int drbd_adm_down(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_resource *resource;
        struct drbd_connection *connection;
        struct drbd_device *device;
        int retcode; /* enum drbd_ret_code rsp. enum drbd_state_rv */
        unsigned i;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_RESOURCE);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto finish;

        resource = adm_ctx.resource;
        mutex_lock(&resource->adm_mutex);
        /* demote */
        for_each_connection(connection, resource) {
                struct drbd_peer_device *peer_device;

                idr_for_each_entry(&connection->peer_devices, peer_device, i) {
                        retcode = drbd_set_role(peer_device->device, R_SECONDARY, 0);
                        if (retcode < SS_SUCCESS) {
                                drbd_msg_put_info(adm_ctx.reply_skb, "failed to demote");
                                goto out;
                        }
                }

                retcode = conn_try_disconnect(connection, 0);
                if (retcode < SS_SUCCESS) {
                        drbd_msg_put_info(adm_ctx.reply_skb, "failed to disconnect");
                        goto out;
                }
        }

        /* detach */
        idr_for_each_entry(&resource->devices, device, i) {
                retcode = adm_detach(device, 0);
                if (retcode < SS_SUCCESS || retcode > NO_ERROR) {
                        drbd_msg_put_info(adm_ctx.reply_skb, "failed to detach");
                        goto out;
                }
        }

        /* delete volumes */
        idr_for_each_entry(&resource->devices, device, i) {
                retcode = adm_del_minor(device);
                if (retcode != NO_ERROR) {
                        /* "can not happen" */
                        drbd_msg_put_info(adm_ctx.reply_skb, "failed to delete volume");
                        goto out;
                }
        }

        retcode = adm_del_resource(resource);
out:
        mutex_unlock(&resource->adm_mutex);
finish:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

int drbd_adm_del_resource(struct sk_buff *skb, struct genl_info *info)
{
        struct drbd_config_context adm_ctx;
        struct drbd_resource *resource;
        enum drbd_ret_code retcode;

        retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_RESOURCE);
        if (!adm_ctx.reply_skb)
                return retcode;
        if (retcode != NO_ERROR)
                goto finish;
        resource = adm_ctx.resource;

        mutex_lock(&resource->adm_mutex);
        retcode = adm_del_resource(resource);
        mutex_unlock(&resource->adm_mutex);
finish:
        drbd_adm_finish(&adm_ctx, info, retcode);
        return 0;
}

void drbd_bcast_event(struct drbd_device *device, const struct sib_info *sib)
{
        struct sk_buff *msg;
        struct drbd_genlmsghdr *d_out;
        unsigned seq;
        int err = -ENOMEM;

        seq = atomic_inc_return(&drbd_genl_seq);
        msg = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
        if (!msg)
                goto failed;

        err = -EMSGSIZE;
        d_out = genlmsg_put(msg, 0, seq, &drbd_genl_family, 0, DRBD_EVENT);
        if (!d_out) /* cannot happen, but anyways. */
                goto nla_put_failure;
        d_out->minor = device_to_minor(device);
        d_out->ret_code = NO_ERROR;

        if (nla_put_status_info(msg, device, sib))
                goto nla_put_failure;
        genlmsg_end(msg, d_out);
        err = drbd_genl_multicast_events(msg, GFP_NOWAIT);
        /* msg has been consumed or freed in netlink_broadcast() */
        if (err && err != -ESRCH)
                goto failed;

        return;

nla_put_failure:
        nlmsg_free(msg);
failed:
        drbd_err(device, "Error %d while broadcasting event. "
                        "Event seq:%u sib_reason:%u\n",
                        err, seq, sib->sib_reason);
}

static int nla_put_notification_header(struct sk_buff *msg,
                                       enum drbd_notification_type type)
{
        struct drbd_notification_header nh = {
                .nh_type = type,
        };

        return drbd_notification_header_to_skb(msg, &nh, true);
}

void notify_resource_state(struct sk_buff *skb,
                           unsigned int seq,
                           struct drbd_resource *resource,
                           struct resource_info *resource_info,
                           enum drbd_notification_type type)
{
        struct resource_statistics resource_statistics;
        struct drbd_genlmsghdr *dh;
        bool multicast = false;
        int err;

        if (!skb) {
                seq = atomic_inc_return(&notify_genl_seq);
                skb = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
                err = -ENOMEM;
                if (!skb)
                        goto failed;
                multicast = true;
        }

        err = -EMSGSIZE;
        dh = genlmsg_put(skb, 0, seq, &drbd_genl_family, 0, DRBD_RESOURCE_STATE);
        if (!dh)
                goto nla_put_failure;
        dh->minor = -1U;
        dh->ret_code = NO_ERROR;
        if (nla_put_drbd_cfg_context(skb, resource, NULL, NULL) ||
            nla_put_notification_header(skb, type) ||
            ((type & ~NOTIFY_FLAGS) != NOTIFY_DESTROY &&
             resource_info_to_skb(skb, resource_info, true)))
                goto nla_put_failure;
        resource_statistics.res_stat_write_ordering = resource->write_ordering;
        err = resource_statistics_to_skb(skb, &resource_statistics, !capable(CAP_SYS_ADMIN));
        if (err)
                goto nla_put_failure;
        genlmsg_end(skb, dh);
        if (multicast) {
                err = drbd_genl_multicast_events(skb, GFP_NOWAIT);
                /* skb has been consumed or freed in netlink_broadcast() */
                if (err && err != -ESRCH)
                        goto failed;
        }
        return;

nla_put_failure:
        nlmsg_free(skb);
failed:
        drbd_err(resource, "Error %d while broadcasting event. Event seq:%u\n",
                        err, seq);
}

void notify_device_state(struct sk_buff *skb,
                         unsigned int seq,
                         struct drbd_device *device,
                         struct device_info *device_info,
                         enum drbd_notification_type type)
{
        struct device_statistics device_statistics;
        struct drbd_genlmsghdr *dh;
        bool multicast = false;
        int err;

        if (!skb) {
                seq = atomic_inc_return(&notify_genl_seq);
                skb = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
                err = -ENOMEM;
                if (!skb)
                        goto failed;
                multicast = true;
        }

        err = -EMSGSIZE;
        dh = genlmsg_put(skb, 0, seq, &drbd_genl_family, 0, DRBD_DEVICE_STATE);
        if (!dh)
                goto nla_put_failure;
        dh->minor = device->minor;
        dh->ret_code = NO_ERROR;
        if (nla_put_drbd_cfg_context(skb, device->resource, NULL, device) ||
            nla_put_notification_header(skb, type) ||
            ((type & ~NOTIFY_FLAGS) != NOTIFY_DESTROY &&
             device_info_to_skb(skb, device_info, true)))
                goto nla_put_failure;
        device_to_statistics(&device_statistics, device);
        device_statistics_to_skb(skb, &device_statistics, !capable(CAP_SYS_ADMIN));
        genlmsg_end(skb, dh);
        if (multicast) {
                err = drbd_genl_multicast_events(skb, GFP_NOWAIT);
                /* skb has been consumed or freed in netlink_broadcast() */
                if (err && err != -ESRCH)
                        goto failed;
        }
        return;

nla_put_failure:
        nlmsg_free(skb);
failed:
        drbd_err(device, "Error %d while broadcasting event. Event seq:%u\n",
                 err, seq);
}

void notify_connection_state(struct sk_buff *skb,
                             unsigned int seq,
                             struct drbd_connection *connection,
                             struct connection_info *connection_info,
                             enum drbd_notification_type type)
{
        struct connection_statistics connection_statistics;
        struct drbd_genlmsghdr *dh;
        bool multicast = false;
        int err;

        if (!skb) {
                seq = atomic_inc_return(&notify_genl_seq);
                skb = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
                err = -ENOMEM;
                if (!skb)
                        goto failed;
                multicast = true;
        }

        err = -EMSGSIZE;
        dh = genlmsg_put(skb, 0, seq, &drbd_genl_family, 0, DRBD_CONNECTION_STATE);
        if (!dh)
                goto nla_put_failure;
        dh->minor = -1U;
        dh->ret_code = NO_ERROR;
        if (nla_put_drbd_cfg_context(skb, connection->resource, connection, NULL) ||
            nla_put_notification_header(skb, type) ||
            ((type & ~NOTIFY_FLAGS) != NOTIFY_DESTROY &&
             connection_info_to_skb(skb, connection_info, true)))
                goto nla_put_failure;
        connection_statistics.conn_congested = test_bit(NET_CONGESTED, &connection->flags);
        connection_statistics_to_skb(skb, &connection_statistics, !capable(CAP_SYS_ADMIN));
        genlmsg_end(skb, dh);
        if (multicast) {
                err = drbd_genl_multicast_events(skb, GFP_NOWAIT);
                /* skb has been consumed or freed in netlink_broadcast() */
                if (err && err != -ESRCH)
                        goto failed;
        }
        return;

nla_put_failure:
        nlmsg_free(skb);
failed:
        drbd_err(connection, "Error %d while broadcasting event. Event seq:%u\n",
                 err, seq);
}

void notify_peer_device_state(struct sk_buff *skb,
                              unsigned int seq,
                              struct drbd_peer_device *peer_device,
                              struct peer_device_info *peer_device_info,
                              enum drbd_notification_type type)
{
        struct peer_device_statistics peer_device_statistics;
        struct drbd_resource *resource = peer_device->device->resource;
        struct drbd_genlmsghdr *dh;
        bool multicast = false;
        int err;

        if (!skb) {
                seq = atomic_inc_return(&notify_genl_seq);
                skb = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
                err = -ENOMEM;
                if (!skb)
                        goto failed;
                multicast = true;
        }

        err = -EMSGSIZE;
        dh = genlmsg_put(skb, 0, seq, &drbd_genl_family, 0, DRBD_PEER_DEVICE_STATE);
        if (!dh)
                goto nla_put_failure;
        dh->minor = -1U;
        dh->ret_code = NO_ERROR;
        if (nla_put_drbd_cfg_context(skb, resource, peer_device->connection, peer_device->device) ||
            nla_put_notification_header(skb, type) ||
            ((type & ~NOTIFY_FLAGS) != NOTIFY_DESTROY &&
             peer_device_info_to_skb(skb, peer_device_info, true)))
                goto nla_put_failure;
        peer_device_to_statistics(&peer_device_statistics, peer_device);
        peer_device_statistics_to_skb(skb, &peer_device_statistics, !capable(CAP_SYS_ADMIN));
        genlmsg_end(skb, dh);
        if (multicast) {
                err = drbd_genl_multicast_events(skb, GFP_NOWAIT);
                /* skb has been consumed or freed in netlink_broadcast() */
                if (err && err != -ESRCH)
                        goto failed;
        }
        return;

nla_put_failure:
        nlmsg_free(skb);
failed:
        drbd_err(peer_device, "Error %d while broadcasting event. Event seq:%u\n",
                 err, seq);
}

void notify_helper(enum drbd_notification_type type,
                   struct drbd_device *device, struct drbd_connection *connection,
                   const char *name, int status)
{
        struct drbd_resource *resource = device ? device->resource : connection->resource;
        struct drbd_helper_info helper_info;
        unsigned int seq = atomic_inc_return(&notify_genl_seq);
        struct sk_buff *skb = NULL;
        struct drbd_genlmsghdr *dh;
        int err;

        strlcpy(helper_info.helper_name, name, sizeof(helper_info.helper_name));
        helper_info.helper_name_len = min(strlen(name), sizeof(helper_info.helper_name));
        helper_info.helper_status = status;

        skb = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
        err = -ENOMEM;
        if (!skb)
                goto fail;

        err = -EMSGSIZE;
        dh = genlmsg_put(skb, 0, seq, &drbd_genl_family, 0, DRBD_HELPER);
        if (!dh)
                goto fail;
        dh->minor = device ? device->minor : -1;
        dh->ret_code = NO_ERROR;
        mutex_lock(&notification_mutex);
        if (nla_put_drbd_cfg_context(skb, resource, connection, device) ||
            nla_put_notification_header(skb, type) ||
            drbd_helper_info_to_skb(skb, &helper_info, true))
                goto unlock_fail;
        genlmsg_end(skb, dh);
        err = drbd_genl_multicast_events(skb, GFP_NOWAIT);
        skb = NULL;
        /* skb has been consumed or freed in netlink_broadcast() */
        if (err && err != -ESRCH)
                goto unlock_fail;
        mutex_unlock(&notification_mutex);
        return;

unlock_fail:
        mutex_unlock(&notification_mutex);
fail:
        nlmsg_free(skb);
        drbd_err(resource, "Error %d while broadcasting event. Event seq:%u\n",
                 err, seq);
}

static void notify_initial_state_done(struct sk_buff *skb, unsigned int seq)
{
        struct drbd_genlmsghdr *dh;
        int err;

        err = -EMSGSIZE;
        dh = genlmsg_put(skb, 0, seq, &drbd_genl_family, 0, DRBD_INITIAL_STATE_DONE);
        if (!dh)
                goto nla_put_failure;
        dh->minor = -1U;
        dh->ret_code = NO_ERROR;
        if (nla_put_notification_header(skb, NOTIFY_EXISTS))
                goto nla_put_failure;
        genlmsg_end(skb, dh);
        return;

nla_put_failure:
        nlmsg_free(skb);
        pr_err("Error %d sending event. Event seq:%u\n", err, seq);
}

static void free_state_changes(struct list_head *list)
{
        while (!list_empty(list)) {
                struct drbd_state_change *state_change =
                        list_first_entry(list, struct drbd_state_change, list);
                list_del(&state_change->list);
                forget_state_change(state_change);
        }
}

static unsigned int notifications_for_state_change(struct drbd_state_change *state_change)
{
        return 1 +
               state_change->n_connections +
               state_change->n_devices +
               state_change->n_devices * state_change->n_connections;
}

static int get_initial_state(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct drbd_state_change *state_change = (struct drbd_state_change *)cb->args[0];
        unsigned int seq = cb->args[2];
        unsigned int n;
        enum drbd_notification_type flags = 0;

        /* There is no need for taking notification_mutex here: it doesn't
           matter if the initial state events mix with later state chage
           events; we can always tell the events apart by the NOTIFY_EXISTS
           flag. */

        cb->args[5]--;
        if (cb->args[5] == 1) {
                notify_initial_state_done(skb, seq);
                goto out;
        }
        n = cb->args[4]++;
        if (cb->args[4] < cb->args[3])
                flags |= NOTIFY_CONTINUES;
        if (n < 1) {
                notify_resource_state_change(skb, seq, state_change->resource,
                                             NOTIFY_EXISTS | flags);
                goto next;
        }
        n--;
        if (n < state_change->n_connections) {
                notify_connection_state_change(skb, seq, &state_change->connections[n],
                                               NOTIFY_EXISTS | flags);
                goto next;
        }
        n -= state_change->n_connections;
        if (n < state_change->n_devices) {
                notify_device_state_change(skb, seq, &state_change->devices[n],
                                           NOTIFY_EXISTS | flags);
                goto next;
        }
        n -= state_change->n_devices;
        if (n < state_change->n_devices * state_change->n_connections) {
                notify_peer_device_state_change(skb, seq, &state_change->peer_devices[n],
                                                NOTIFY_EXISTS | flags);
                goto next;
        }

next:
        if (cb->args[4] == cb->args[3]) {
                struct drbd_state_change *next_state_change =
                        list_entry(state_change->list.next,
                                   struct drbd_state_change, list);
                cb->args[0] = (long)next_state_change;
                cb->args[3] = notifications_for_state_change(next_state_change);
                cb->args[4] = 0;
        }
out:
        return skb->len;
}

int drbd_adm_get_initial_state(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct drbd_resource *resource;
        LIST_HEAD(head);

        if (cb->args[5] >= 1) {
                if (cb->args[5] > 1)
                        return get_initial_state(skb, cb);
                if (cb->args[0]) {
                        struct drbd_state_change *state_change =
                                (struct drbd_state_change *)cb->args[0];

                        /* connect list to head */
                        list_add(&head, &state_change->list);
                        free_state_changes(&head);
                }
                return 0;
        }

        cb->args[5] = 2;  /* number of iterations */
        mutex_lock(&resources_mutex);
        for_each_resource(resource, &drbd_resources) {
                struct drbd_state_change *state_change;

                state_change = remember_old_state(resource, GFP_KERNEL);
                if (!state_change) {
                        if (!list_empty(&head))
                                free_state_changes(&head);
                        mutex_unlock(&resources_mutex);
                        return -ENOMEM;
                }
                copy_old_to_new_state_change(state_change);
                list_add_tail(&state_change->list, &head);
                cb->args[5] += notifications_for_state_change(state_change);
        }
        mutex_unlock(&resources_mutex);

        if (!list_empty(&head)) {
                struct drbd_state_change *state_change =
                        list_entry(head.next, struct drbd_state_change, list);
                cb->args[0] = (long)state_change;
                cb->args[3] = notifications_for_state_change(state_change);
                list_del(&head);  /* detach list from head */
        }

        cb->args[2] = cb->nlh->nlmsg_seq;
        return get_initial_state(skb, cb);
}