drbd: base completion and destruction of requests on ref counts

[mirror_ubuntu-zesty-kernel.git] / drivers / block / drbd / drbd_main.c

/*
   drbd.c

   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.

   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.

   Thanks to Carter Burden, Bart Grantham and Gennadiy Nerubayev
   from Logicworks, Inc. for making SDP replication support possible.

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

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

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

 */

#include <linux/module.h>
#include <linux/drbd.h>
#include <asm/uaccess.h>
#include <asm/types.h>
#include <net/sock.h>
#include <linux/ctype.h>
#include <linux/mutex.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/memcontrol.h>
#include <linux/mm_inline.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/reboot.h>
#include <linux/notifier.h>
#include <linux/kthread.h>

#define __KERNEL_SYSCALLS__
#include <linux/unistd.h>
#include <linux/vmalloc.h>

#include <linux/drbd_limits.h>
#include "drbd_int.h"
#include "drbd_req.h" /* only for _req_mod in tl_release and tl_clear */

#include "drbd_vli.h"

static DEFINE_MUTEX(drbd_main_mutex);
int drbdd_init(struct drbd_thread *);
int drbd_worker(struct drbd_thread *);
int drbd_asender(struct drbd_thread *);

int drbd_init(void);
static int drbd_open(struct block_device *bdev, fmode_t mode);
static int drbd_release(struct gendisk *gd, fmode_t mode);
static int w_md_sync(struct drbd_work *w, int unused);
static void md_sync_timer_fn(unsigned long data);
static int w_bitmap_io(struct drbd_work *w, int unused);
static int w_go_diskless(struct drbd_work *w, int unused);

MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
              "Lars Ellenberg <lars@linbit.com>");
MODULE_DESCRIPTION("drbd - Distributed Replicated Block Device v" REL_VERSION);
MODULE_VERSION(REL_VERSION);
MODULE_LICENSE("GPL");
MODULE_PARM_DESC(minor_count, "Approximate number of drbd devices ("
                 __stringify(DRBD_MINOR_COUNT_MIN) "-" __stringify(DRBD_MINOR_COUNT_MAX) ")");
MODULE_ALIAS_BLOCKDEV_MAJOR(DRBD_MAJOR);

#include <linux/moduleparam.h>
/* allow_open_on_secondary */
MODULE_PARM_DESC(allow_oos, "DONT USE!");
/* thanks to these macros, if compiled into the kernel (not-module),
 * this becomes the boot parameter drbd.minor_count */
module_param(minor_count, uint, 0444);
module_param(disable_sendpage, bool, 0644);
module_param(allow_oos, bool, 0);
module_param(proc_details, int, 0644);

#ifdef CONFIG_DRBD_FAULT_INJECTION
int enable_faults;
int fault_rate;
static int fault_count;
int fault_devs;
/* bitmap of enabled faults */
module_param(enable_faults, int, 0664);
/* fault rate % value - applies to all enabled faults */
module_param(fault_rate, int, 0664);
/* count of faults inserted */
module_param(fault_count, int, 0664);
/* bitmap of devices to insert faults on */
module_param(fault_devs, int, 0644);
#endif

/* module parameter, defined */
unsigned int minor_count = DRBD_MINOR_COUNT_DEF;
int disable_sendpage;
int allow_oos;
int proc_details;       /* Detail level in proc drbd*/

/* Module parameter for setting the user mode helper program
 * to run. Default is /sbin/drbdadm */
char usermode_helper[80] = "/sbin/drbdadm";

module_param_string(usermode_helper, usermode_helper, sizeof(usermode_helper), 0644);

/* in 2.6.x, our device mapping and config info contains our virtual gendisks
 * as member "struct gendisk *vdisk;"
 */
struct idr minors;
struct list_head drbd_tconns;  /* list of struct drbd_tconn */

struct kmem_cache *drbd_request_cache;
struct kmem_cache *drbd_ee_cache;       /* peer requests */
struct kmem_cache *drbd_bm_ext_cache;   /* bitmap extents */
struct kmem_cache *drbd_al_ext_cache;   /* activity log extents */
mempool_t *drbd_request_mempool;
mempool_t *drbd_ee_mempool;
mempool_t *drbd_md_io_page_pool;
struct bio_set *drbd_md_io_bio_set;

/* I do not use a standard mempool, because:
   1) I want to hand out the pre-allocated objects first.
   2) I want to be able to interrupt sleeping allocation with a signal.
   Note: This is a single linked list, the next pointer is the private
         member of struct page.
 */
struct page *drbd_pp_pool;
spinlock_t   drbd_pp_lock;
int          drbd_pp_vacant;
wait_queue_head_t drbd_pp_wait;

DEFINE_RATELIMIT_STATE(drbd_ratelimit_state, 5 * HZ, 5);

static const struct block_device_operations drbd_ops = {
        .owner =   THIS_MODULE,
        .open =    drbd_open,
        .release = drbd_release,
};

static void bio_destructor_drbd(struct bio *bio)
{
        bio_free(bio, drbd_md_io_bio_set);
}

struct bio *bio_alloc_drbd(gfp_t gfp_mask)
{
        struct bio *bio;

        if (!drbd_md_io_bio_set)
                return bio_alloc(gfp_mask, 1);

        bio = bio_alloc_bioset(gfp_mask, 1, drbd_md_io_bio_set);
        if (!bio)
                return NULL;
        bio->bi_destructor = bio_destructor_drbd;
        return bio;
}

#ifdef __CHECKER__
/* When checking with sparse, and this is an inline function, sparse will
   give tons of false positives. When this is a real functions sparse works.
 */
int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
{
        int io_allowed;

        atomic_inc(&mdev->local_cnt);
        io_allowed = (mdev->state.disk >= mins);
        if (!io_allowed) {
                if (atomic_dec_and_test(&mdev->local_cnt))
                        wake_up(&mdev->misc_wait);
        }
        return io_allowed;
}

#endif

/**
 * tl_release() - mark as BARRIER_ACKED all requests in the corresponding transfer log epoch
 * @tconn:      DRBD connection.
 * @barrier_nr: Expected identifier of the DRBD write barrier packet.
 * @set_size:   Expected number of requests before that barrier.
 *
 * In case the passed barrier_nr or set_size does not match the oldest
 * epoch of not yet barrier-acked requests, this function will cause a
 * termination of the connection.
 */
void tl_release(struct drbd_tconn *tconn, unsigned int barrier_nr,
                unsigned int set_size)
{
        struct drbd_request *r;
        struct drbd_request *req = NULL;
        int expect_epoch = 0;
        int expect_size = 0;

        spin_lock_irq(&tconn->req_lock);

        /* find latest not yet barrier-acked write request,
         * count writes in its epoch. */
        list_for_each_entry(r, &tconn->transfer_log, tl_requests) {
                const unsigned s = r->rq_state;
                if (!req) {
                        if (!(s & RQ_WRITE))
                                continue;
                        if (!(s & RQ_NET_MASK))
                                continue;
                        if (s & RQ_NET_DONE)
                                continue;
                        req = r;
                        expect_epoch = req->epoch;
                        expect_size ++;
                } else {
                        if (r->epoch != expect_epoch)
                                break;
                        if (!(s & RQ_WRITE))
                                continue;
                        /* if (s & RQ_DONE): not expected */
                        /* if (!(s & RQ_NET_MASK)): not expected */
                        expect_size++;
                }
        }

        /* first some paranoia code */
        if (req == NULL) {
                conn_err(tconn, "BAD! BarrierAck #%u received, but no epoch in tl!?\n",
                         barrier_nr);
                goto bail;
        }
        if (expect_epoch != barrier_nr) {
                conn_err(tconn, "BAD! BarrierAck #%u received, expected #%u!\n",
                         barrier_nr, expect_epoch);
                goto bail;
        }

        if (expect_size != set_size) {
                conn_err(tconn, "BAD! BarrierAck #%u received with n_writes=%u, expected n_writes=%u!\n",
                         barrier_nr, set_size, expect_size);
                goto bail;
        }

        /* Clean up list of requests processed during current epoch */
        list_for_each_entry_safe(req, r, &tconn->transfer_log, tl_requests) {
                if (req->epoch != expect_epoch)
                        break;
                _req_mod(req, BARRIER_ACKED);
        }
        spin_unlock_irq(&tconn->req_lock);

        return;

bail:
        spin_unlock_irq(&tconn->req_lock);
        conn_request_state(tconn, NS(conn, C_PROTOCOL_ERROR), CS_HARD);
}


/**
 * _tl_restart() - Walks the transfer log, and applies an action to all requests
 * @mdev:       DRBD device.
 * @what:       The action/event to perform with all request objects
 *
 * @what might be one of CONNECTION_LOST_WHILE_PENDING, RESEND, FAIL_FROZEN_DISK_IO,
 * RESTART_FROZEN_DISK_IO.
 */
/* must hold resource->req_lock */
void _tl_restart(struct drbd_tconn *tconn, enum drbd_req_event what)
{
        struct drbd_request *req, *r;

        list_for_each_entry_safe(req, r, &tconn->transfer_log, tl_requests)
                _req_mod(req, what);
}

void tl_restart(struct drbd_tconn *tconn, enum drbd_req_event what)
{
        spin_lock_irq(&tconn->req_lock);
        _tl_restart(tconn, what);
        spin_unlock_irq(&tconn->req_lock);
}

/**
 * tl_clear() - Clears all requests and &struct drbd_tl_epoch objects out of the TL
 * @mdev:       DRBD device.
 *
 * This is called after the connection to the peer was lost. The storage covered
 * by the requests on the transfer gets marked as our of sync. Called from the
 * receiver thread and the worker thread.
 */
void tl_clear(struct drbd_tconn *tconn)
{
        tl_restart(tconn, CONNECTION_LOST_WHILE_PENDING);
}

/**
 * tl_abort_disk_io() - Abort disk I/O for all requests for a certain mdev in the TL
 * @mdev:       DRBD device.
 */
void tl_abort_disk_io(struct drbd_conf *mdev)
{
        struct drbd_tconn *tconn = mdev->tconn;
        struct drbd_request *req, *r;

        spin_lock_irq(&tconn->req_lock);
        list_for_each_entry_safe(req, r, &tconn->transfer_log, tl_requests) {
                if (!(req->rq_state & RQ_LOCAL_PENDING))
                        continue;
                if (req->w.mdev != mdev)
                        continue;
                _req_mod(req, ABORT_DISK_IO);
        }
        spin_unlock_irq(&tconn->req_lock);
}

static int drbd_thread_setup(void *arg)
{
        struct drbd_thread *thi = (struct drbd_thread *) arg;
        struct drbd_tconn *tconn = thi->tconn;
        unsigned long flags;
        int retval;

        snprintf(current->comm, sizeof(current->comm), "drbd_%c_%s",
                 thi->name[0], thi->tconn->name);

restart:
        retval = thi->function(thi);

        spin_lock_irqsave(&thi->t_lock, flags);

        /* if the receiver has been "EXITING", the last thing it did
         * was set the conn state to "StandAlone",
         * if now a re-connect request comes in, conn state goes C_UNCONNECTED,
         * and receiver thread will be "started".
         * drbd_thread_start needs to set "RESTARTING" in that case.
         * t_state check and assignment needs to be within the same spinlock,
         * so either thread_start sees EXITING, and can remap to RESTARTING,
         * or thread_start see NONE, and can proceed as normal.
         */

        if (thi->t_state == RESTARTING) {
                conn_info(tconn, "Restarting %s thread\n", thi->name);
                thi->t_state = RUNNING;
                spin_unlock_irqrestore(&thi->t_lock, flags);
                goto restart;
        }

        thi->task = NULL;
        thi->t_state = NONE;
        smp_mb();
        complete_all(&thi->stop);
        spin_unlock_irqrestore(&thi->t_lock, flags);

        conn_info(tconn, "Terminating %s\n", current->comm);

        /* Release mod reference taken when thread was started */

        kref_put(&tconn->kref, &conn_destroy);
        module_put(THIS_MODULE);
        return retval;
}

static void drbd_thread_init(struct drbd_tconn *tconn, struct drbd_thread *thi,
                             int (*func) (struct drbd_thread *), char *name)
{
        spin_lock_init(&thi->t_lock);
        thi->task    = NULL;
        thi->t_state = NONE;
        thi->function = func;
        thi->tconn = tconn;
        strncpy(thi->name, name, ARRAY_SIZE(thi->name));
}

int drbd_thread_start(struct drbd_thread *thi)
{
        struct drbd_tconn *tconn = thi->tconn;
        struct task_struct *nt;
        unsigned long flags;

        /* is used from state engine doing drbd_thread_stop_nowait,
         * while holding the req lock irqsave */
        spin_lock_irqsave(&thi->t_lock, flags);

        switch (thi->t_state) {
        case NONE:
                conn_info(tconn, "Starting %s thread (from %s [%d])\n",
                         thi->name, current->comm, current->pid);

                /* Get ref on module for thread - this is released when thread exits */
                if (!try_module_get(THIS_MODULE)) {
                        conn_err(tconn, "Failed to get module reference in drbd_thread_start\n");
                        spin_unlock_irqrestore(&thi->t_lock, flags);
                        return false;
                }

                kref_get(&thi->tconn->kref);

                init_completion(&thi->stop);
                thi->reset_cpu_mask = 1;
                thi->t_state = RUNNING;
                spin_unlock_irqrestore(&thi->t_lock, flags);
                flush_signals(current); /* otherw. may get -ERESTARTNOINTR */

                nt = kthread_create(drbd_thread_setup, (void *) thi,
                                    "drbd_%c_%s", thi->name[0], thi->tconn->name);

                if (IS_ERR(nt)) {
                        conn_err(tconn, "Couldn't start thread\n");

                        kref_put(&tconn->kref, &conn_destroy);
                        module_put(THIS_MODULE);
                        return false;
                }
                spin_lock_irqsave(&thi->t_lock, flags);
                thi->task = nt;
                thi->t_state = RUNNING;
                spin_unlock_irqrestore(&thi->t_lock, flags);
                wake_up_process(nt);
                break;
        case EXITING:
                thi->t_state = RESTARTING;
                conn_info(tconn, "Restarting %s thread (from %s [%d])\n",
                                thi->name, current->comm, current->pid);
                /* fall through */
        case RUNNING:
        case RESTARTING:
        default:
                spin_unlock_irqrestore(&thi->t_lock, flags);
                break;
        }

        return true;
}


void _drbd_thread_stop(struct drbd_thread *thi, int restart, int wait)
{
        unsigned long flags;

        enum drbd_thread_state ns = restart ? RESTARTING : EXITING;

        /* may be called from state engine, holding the req lock irqsave */
        spin_lock_irqsave(&thi->t_lock, flags);

        if (thi->t_state == NONE) {
                spin_unlock_irqrestore(&thi->t_lock, flags);
                if (restart)
                        drbd_thread_start(thi);
                return;
        }

        if (thi->t_state != ns) {
                if (thi->task == NULL) {
                        spin_unlock_irqrestore(&thi->t_lock, flags);
                        return;
                }

                thi->t_state = ns;
                smp_mb();
                init_completion(&thi->stop);
                if (thi->task != current)
                        force_sig(DRBD_SIGKILL, thi->task);
        }

        spin_unlock_irqrestore(&thi->t_lock, flags);

        if (wait)
                wait_for_completion(&thi->stop);
}

static struct drbd_thread *drbd_task_to_thread(struct drbd_tconn *tconn, struct task_struct *task)
{
        struct drbd_thread *thi =
                task == tconn->receiver.task ? &tconn->receiver :
                task == tconn->asender.task  ? &tconn->asender :
                task == tconn->worker.task   ? &tconn->worker : NULL;

        return thi;
}

char *drbd_task_to_thread_name(struct drbd_tconn *tconn, struct task_struct *task)
{
        struct drbd_thread *thi = drbd_task_to_thread(tconn, task);
        return thi ? thi->name : task->comm;
}

int conn_lowest_minor(struct drbd_tconn *tconn)
{
        struct drbd_conf *mdev;
        int vnr = 0, m;

        rcu_read_lock();
        mdev = idr_get_next(&tconn->volumes, &vnr);
        m = mdev ? mdev_to_minor(mdev) : -1;
        rcu_read_unlock();

        return m;
}

#ifdef CONFIG_SMP
/**
 * drbd_calc_cpu_mask() - Generate CPU masks, spread over all CPUs
 * @mdev:       DRBD device.
 *
 * Forces all threads of a device onto the same CPU. This is beneficial for
 * DRBD's performance. May be overwritten by user's configuration.
 */
void drbd_calc_cpu_mask(struct drbd_tconn *tconn)
{
        int ord, cpu;

        /* user override. */
        if (cpumask_weight(tconn->cpu_mask))
                return;

        ord = conn_lowest_minor(tconn) % cpumask_weight(cpu_online_mask);
        for_each_online_cpu(cpu) {
                if (ord-- == 0) {
                        cpumask_set_cpu(cpu, tconn->cpu_mask);
                        return;
                }
        }
        /* should not be reached */
        cpumask_setall(tconn->cpu_mask);
}

/**
 * drbd_thread_current_set_cpu() - modifies the cpu mask of the _current_ thread
 * @mdev:       DRBD device.
 * @thi:        drbd_thread object
 *
 * call in the "main loop" of _all_ threads, no need for any mutex, current won't die
 * prematurely.
 */
void drbd_thread_current_set_cpu(struct drbd_thread *thi)
{
        struct task_struct *p = current;

        if (!thi->reset_cpu_mask)
                return;
        thi->reset_cpu_mask = 0;
        set_cpus_allowed_ptr(p, thi->tconn->cpu_mask);
}
#endif

/**
 * drbd_header_size  -  size of a packet header
 *
 * The header size is a multiple of 8, so any payload following the header is
 * word aligned on 64-bit architectures.  (The bitmap send and receive code
 * relies on this.)
 */
unsigned int drbd_header_size(struct drbd_tconn *tconn)
{
        if (tconn->agreed_pro_version >= 100) {
                BUILD_BUG_ON(!IS_ALIGNED(sizeof(struct p_header100), 8));
                return sizeof(struct p_header100);
        } else {
                BUILD_BUG_ON(sizeof(struct p_header80) !=
                             sizeof(struct p_header95));
                BUILD_BUG_ON(!IS_ALIGNED(sizeof(struct p_header80), 8));
                return sizeof(struct p_header80);
        }
}

static unsigned int prepare_header80(struct p_header80 *h, enum drbd_packet cmd, int size)
{
        h->magic   = cpu_to_be32(DRBD_MAGIC);
        h->command = cpu_to_be16(cmd);
        h->length  = cpu_to_be16(size);
        return sizeof(struct p_header80);
}

static unsigned int prepare_header95(struct p_header95 *h, enum drbd_packet cmd, int size)
{
        h->magic   = cpu_to_be16(DRBD_MAGIC_BIG);
        h->command = cpu_to_be16(cmd);
        h->length = cpu_to_be32(size);
        return sizeof(struct p_header95);
}

static unsigned int prepare_header100(struct p_header100 *h, enum drbd_packet cmd,
                                      int size, int vnr)
{
        h->magic = cpu_to_be32(DRBD_MAGIC_100);
        h->volume = cpu_to_be16(vnr);
        h->command = cpu_to_be16(cmd);
        h->length = cpu_to_be32(size);
        h->pad = 0;
        return sizeof(struct p_header100);
}

static unsigned int prepare_header(struct drbd_tconn *tconn, int vnr,
                                   void *buffer, enum drbd_packet cmd, int size)
{
        if (tconn->agreed_pro_version >= 100)
                return prepare_header100(buffer, cmd, size, vnr);
        else if (tconn->agreed_pro_version >= 95 &&
                 size > DRBD_MAX_SIZE_H80_PACKET)
                return prepare_header95(buffer, cmd, size);
        else
                return prepare_header80(buffer, cmd, size);
}

static void *__conn_prepare_command(struct drbd_tconn *tconn,
                                    struct drbd_socket *sock)
{
        if (!sock->socket)
                return NULL;
        return sock->sbuf + drbd_header_size(tconn);
}

void *conn_prepare_command(struct drbd_tconn *tconn, struct drbd_socket *sock)
{
        void *p;

        mutex_lock(&sock->mutex);
        p = __conn_prepare_command(tconn, sock);
        if (!p)
                mutex_unlock(&sock->mutex);

        return p;
}

void *drbd_prepare_command(struct drbd_conf *mdev, struct drbd_socket *sock)
{
        return conn_prepare_command(mdev->tconn, sock);
}

static int __send_command(struct drbd_tconn *tconn, int vnr,
                          struct drbd_socket *sock, enum drbd_packet cmd,
                          unsigned int header_size, void *data,
                          unsigned int size)
{
        int msg_flags;
        int err;

        /*
         * Called with @data == NULL and the size of the data blocks in @size
         * for commands that send data blocks.  For those commands, omit the
         * MSG_MORE flag: this will increase the likelihood that data blocks
         * which are page aligned on the sender will end up page aligned on the
         * receiver.
         */
        msg_flags = data ? MSG_MORE : 0;

        header_size += prepare_header(tconn, vnr, sock->sbuf, cmd,
                                      header_size + size);
        err = drbd_send_all(tconn, sock->socket, sock->sbuf, header_size,
                            msg_flags);
        if (data && !err)
                err = drbd_send_all(tconn, sock->socket, data, size, 0);
        return err;
}

static int __conn_send_command(struct drbd_tconn *tconn, struct drbd_socket *sock,
                               enum drbd_packet cmd, unsigned int header_size,
                               void *data, unsigned int size)
{
        return __send_command(tconn, 0, sock, cmd, header_size, data, size);
}

int conn_send_command(struct drbd_tconn *tconn, struct drbd_socket *sock,
                      enum drbd_packet cmd, unsigned int header_size,
                      void *data, unsigned int size)
{
        int err;

        err = __conn_send_command(tconn, sock, cmd, header_size, data, size);
        mutex_unlock(&sock->mutex);
        return err;
}

int drbd_send_command(struct drbd_conf *mdev, struct drbd_socket *sock,
                      enum drbd_packet cmd, unsigned int header_size,
                      void *data, unsigned int size)
{
        int err;

        err = __send_command(mdev->tconn, mdev->vnr, sock, cmd, header_size,
                             data, size);
        mutex_unlock(&sock->mutex);
        return err;
}

int drbd_send_ping(struct drbd_tconn *tconn)
{
        struct drbd_socket *sock;

        sock = &tconn->meta;
        if (!conn_prepare_command(tconn, sock))
                return -EIO;
        return conn_send_command(tconn, sock, P_PING, 0, NULL, 0);
}

int drbd_send_ping_ack(struct drbd_tconn *tconn)
{
        struct drbd_socket *sock;

        sock = &tconn->meta;
        if (!conn_prepare_command(tconn, sock))
                return -EIO;
        return conn_send_command(tconn, sock, P_PING_ACK, 0, NULL, 0);
}

int drbd_send_sync_param(struct drbd_conf *mdev)
{
        struct drbd_socket *sock;
        struct p_rs_param_95 *p;
        int size;
        const int apv = mdev->tconn->agreed_pro_version;
        enum drbd_packet cmd;
        struct net_conf *nc;
        struct disk_conf *dc;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;

        rcu_read_lock();
        nc = rcu_dereference(mdev->tconn->net_conf);

        size = apv <= 87 ? sizeof(struct p_rs_param)
                : apv == 88 ? sizeof(struct p_rs_param)
                        + strlen(nc->verify_alg) + 1
                : apv <= 94 ? sizeof(struct p_rs_param_89)
                : /* apv >= 95 */ sizeof(struct p_rs_param_95);

        cmd = apv >= 89 ? P_SYNC_PARAM89 : P_SYNC_PARAM;

        /* initialize verify_alg and csums_alg */
        memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);

        if (get_ldev(mdev)) {
                dc = rcu_dereference(mdev->ldev->disk_conf);
                p->resync_rate = cpu_to_be32(dc->resync_rate);
                p->c_plan_ahead = cpu_to_be32(dc->c_plan_ahead);
                p->c_delay_target = cpu_to_be32(dc->c_delay_target);
                p->c_fill_target = cpu_to_be32(dc->c_fill_target);
                p->c_max_rate = cpu_to_be32(dc->c_max_rate);
                put_ldev(mdev);
        } else {
                p->resync_rate = cpu_to_be32(DRBD_RESYNC_RATE_DEF);
                p->c_plan_ahead = cpu_to_be32(DRBD_C_PLAN_AHEAD_DEF);
                p->c_delay_target = cpu_to_be32(DRBD_C_DELAY_TARGET_DEF);
                p->c_fill_target = cpu_to_be32(DRBD_C_FILL_TARGET_DEF);
                p->c_max_rate = cpu_to_be32(DRBD_C_MAX_RATE_DEF);
        }

        if (apv >= 88)
                strcpy(p->verify_alg, nc->verify_alg);
        if (apv >= 89)
                strcpy(p->csums_alg, nc->csums_alg);
        rcu_read_unlock();

        return drbd_send_command(mdev, sock, cmd, size, NULL, 0);
}

int __drbd_send_protocol(struct drbd_tconn *tconn, enum drbd_packet cmd)
{
        struct drbd_socket *sock;
        struct p_protocol *p;
        struct net_conf *nc;
        int size, cf;

        sock = &tconn->data;
        p = __conn_prepare_command(tconn, sock);
        if (!p)
                return -EIO;

        rcu_read_lock();
        nc = rcu_dereference(tconn->net_conf);

        if (nc->tentative && tconn->agreed_pro_version < 92) {
                rcu_read_unlock();
                mutex_unlock(&sock->mutex);
                conn_err(tconn, "--dry-run is not supported by peer");
                return -EOPNOTSUPP;
        }

        size = sizeof(*p);
        if (tconn->agreed_pro_version >= 87)
                size += strlen(nc->integrity_alg) + 1;

        p->protocol      = cpu_to_be32(nc->wire_protocol);
        p->after_sb_0p   = cpu_to_be32(nc->after_sb_0p);
        p->after_sb_1p   = cpu_to_be32(nc->after_sb_1p);
        p->after_sb_2p   = cpu_to_be32(nc->after_sb_2p);
        p->two_primaries = cpu_to_be32(nc->two_primaries);
        cf = 0;
        if (nc->discard_my_data)
                cf |= CF_DISCARD_MY_DATA;
        if (nc->tentative)
                cf |= CF_DRY_RUN;
        p->conn_flags    = cpu_to_be32(cf);

        if (tconn->agreed_pro_version >= 87)
                strcpy(p->integrity_alg, nc->integrity_alg);
        rcu_read_unlock();

        return __conn_send_command(tconn, sock, cmd, size, NULL, 0);
}

int drbd_send_protocol(struct drbd_tconn *tconn)
{
        int err;

        mutex_lock(&tconn->data.mutex);
        err = __drbd_send_protocol(tconn, P_PROTOCOL);
        mutex_unlock(&tconn->data.mutex);

        return err;
}

int _drbd_send_uuids(struct drbd_conf *mdev, u64 uuid_flags)
{
        struct drbd_socket *sock;
        struct p_uuids *p;
        int i;

        if (!get_ldev_if_state(mdev, D_NEGOTIATING))
                return 0;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p) {
                put_ldev(mdev);
                return -EIO;
        }
        for (i = UI_CURRENT; i < UI_SIZE; i++)
                p->uuid[i] = mdev->ldev ? cpu_to_be64(mdev->ldev->md.uuid[i]) : 0;

        mdev->comm_bm_set = drbd_bm_total_weight(mdev);
        p->uuid[UI_SIZE] = cpu_to_be64(mdev->comm_bm_set);
        rcu_read_lock();
        uuid_flags |= rcu_dereference(mdev->tconn->net_conf)->discard_my_data ? 1 : 0;
        rcu_read_unlock();
        uuid_flags |= test_bit(CRASHED_PRIMARY, &mdev->flags) ? 2 : 0;
        uuid_flags |= mdev->new_state_tmp.disk == D_INCONSISTENT ? 4 : 0;
        p->uuid[UI_FLAGS] = cpu_to_be64(uuid_flags);

        put_ldev(mdev);
        return drbd_send_command(mdev, sock, P_UUIDS, sizeof(*p), NULL, 0);
}

int drbd_send_uuids(struct drbd_conf *mdev)
{
        return _drbd_send_uuids(mdev, 0);
}

int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev)
{
        return _drbd_send_uuids(mdev, 8);
}

void drbd_print_uuids(struct drbd_conf *mdev, const char *text)
{
        if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
                u64 *uuid = mdev->ldev->md.uuid;
                dev_info(DEV, "%s %016llX:%016llX:%016llX:%016llX\n",
                     text,
                     (unsigned long long)uuid[UI_CURRENT],
                     (unsigned long long)uuid[UI_BITMAP],
                     (unsigned long long)uuid[UI_HISTORY_START],
                     (unsigned long long)uuid[UI_HISTORY_END]);
                put_ldev(mdev);
        } else {
                dev_info(DEV, "%s effective data uuid: %016llX\n",
                                text,
                                (unsigned long long)mdev->ed_uuid);
        }
}

void drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev)
{
        struct drbd_socket *sock;
        struct p_rs_uuid *p;
        u64 uuid;

        D_ASSERT(mdev->state.disk == D_UP_TO_DATE);

        uuid = mdev->ldev->md.uuid[UI_BITMAP];
        if (uuid && uuid != UUID_JUST_CREATED)
                uuid = uuid + UUID_NEW_BM_OFFSET;
        else
                get_random_bytes(&uuid, sizeof(u64));
        drbd_uuid_set(mdev, UI_BITMAP, uuid);
        drbd_print_uuids(mdev, "updated sync UUID");
        drbd_md_sync(mdev);

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (p) {
                p->uuid = cpu_to_be64(uuid);
                drbd_send_command(mdev, sock, P_SYNC_UUID, sizeof(*p), NULL, 0);
        }
}

int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags)
{
        struct drbd_socket *sock;
        struct p_sizes *p;
        sector_t d_size, u_size;
        int q_order_type, max_bio_size;

        if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
                D_ASSERT(mdev->ldev->backing_bdev);
                d_size = drbd_get_max_capacity(mdev->ldev);
                rcu_read_lock();
                u_size = rcu_dereference(mdev->ldev->disk_conf)->disk_size;
                rcu_read_unlock();
                q_order_type = drbd_queue_order_type(mdev);
                max_bio_size = queue_max_hw_sectors(mdev->ldev->backing_bdev->bd_disk->queue) << 9;
                max_bio_size = min_t(int, max_bio_size, DRBD_MAX_BIO_SIZE);
                put_ldev(mdev);
        } else {
                d_size = 0;
                u_size = 0;
                q_order_type = QUEUE_ORDERED_NONE;
                max_bio_size = DRBD_MAX_BIO_SIZE; /* ... multiple BIOs per peer_request */
        }

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;

        if (mdev->tconn->agreed_pro_version <= 94)
                max_bio_size = min_t(int, max_bio_size, DRBD_MAX_SIZE_H80_PACKET);
        else if (mdev->tconn->agreed_pro_version < 100)
                max_bio_size = min_t(int, max_bio_size, DRBD_MAX_BIO_SIZE_P95);

        p->d_size = cpu_to_be64(d_size);
        p->u_size = cpu_to_be64(u_size);
        p->c_size = cpu_to_be64(trigger_reply ? 0 : drbd_get_capacity(mdev->this_bdev));
        p->max_bio_size = cpu_to_be32(max_bio_size);
        p->queue_order_type = cpu_to_be16(q_order_type);
        p->dds_flags = cpu_to_be16(flags);
        return drbd_send_command(mdev, sock, P_SIZES, sizeof(*p), NULL, 0);
}

/**
 * drbd_send_current_state() - Sends the drbd state to the peer
 * @mdev:       DRBD device.
 */
int drbd_send_current_state(struct drbd_conf *mdev)
{
        struct drbd_socket *sock;
        struct p_state *p;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->state = cpu_to_be32(mdev->state.i); /* Within the send mutex */
        return drbd_send_command(mdev, sock, P_STATE, sizeof(*p), NULL, 0);
}

/**
 * drbd_send_state() - After a state change, sends the new state to the peer
 * @mdev:      DRBD device.
 * @state:     the state to send, not necessarily the current state.
 *
 * Each state change queues an "after_state_ch" work, which will eventually
 * send the resulting new state to the peer. If more state changes happen
 * between queuing and processing of the after_state_ch work, we still
 * want to send each intermediary state in the order it occurred.
 */
int drbd_send_state(struct drbd_conf *mdev, union drbd_state state)
{
        struct drbd_socket *sock;
        struct p_state *p;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->state = cpu_to_be32(state.i); /* Within the send mutex */
        return drbd_send_command(mdev, sock, P_STATE, sizeof(*p), NULL, 0);
}

int drbd_send_state_req(struct drbd_conf *mdev, union drbd_state mask, union drbd_state val)
{
        struct drbd_socket *sock;
        struct p_req_state *p;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->mask = cpu_to_be32(mask.i);
        p->val = cpu_to_be32(val.i);
        return drbd_send_command(mdev, sock, P_STATE_CHG_REQ, sizeof(*p), NULL, 0);
}

int conn_send_state_req(struct drbd_tconn *tconn, union drbd_state mask, union drbd_state val)
{
        enum drbd_packet cmd;
        struct drbd_socket *sock;
        struct p_req_state *p;

        cmd = tconn->agreed_pro_version < 100 ? P_STATE_CHG_REQ : P_CONN_ST_CHG_REQ;
        sock = &tconn->data;
        p = conn_prepare_command(tconn, sock);
        if (!p)
                return -EIO;
        p->mask = cpu_to_be32(mask.i);
        p->val = cpu_to_be32(val.i);
        return conn_send_command(tconn, sock, cmd, sizeof(*p), NULL, 0);
}

void drbd_send_sr_reply(struct drbd_conf *mdev, enum drbd_state_rv retcode)
{
        struct drbd_socket *sock;
        struct p_req_state_reply *p;

        sock = &mdev->tconn->meta;
        p = drbd_prepare_command(mdev, sock);
        if (p) {
                p->retcode = cpu_to_be32(retcode);
                drbd_send_command(mdev, sock, P_STATE_CHG_REPLY, sizeof(*p), NULL, 0);
        }
}

void conn_send_sr_reply(struct drbd_tconn *tconn, enum drbd_state_rv retcode)
{
        struct drbd_socket *sock;
        struct p_req_state_reply *p;
        enum drbd_packet cmd = tconn->agreed_pro_version < 100 ? P_STATE_CHG_REPLY : P_CONN_ST_CHG_REPLY;

        sock = &tconn->meta;
        p = conn_prepare_command(tconn, sock);
        if (p) {
                p->retcode = cpu_to_be32(retcode);
                conn_send_command(tconn, sock, cmd, sizeof(*p), NULL, 0);
        }
}

static void dcbp_set_code(struct p_compressed_bm *p, enum drbd_bitmap_code code)
{
        BUG_ON(code & ~0xf);
        p->encoding = (p->encoding & ~0xf) | code;
}

static void dcbp_set_start(struct p_compressed_bm *p, int set)
{
        p->encoding = (p->encoding & ~0x80) | (set ? 0x80 : 0);
}

static void dcbp_set_pad_bits(struct p_compressed_bm *p, int n)
{
        BUG_ON(n & ~0x7);
        p->encoding = (p->encoding & (~0x7 << 4)) | (n << 4);
}

int fill_bitmap_rle_bits(struct drbd_conf *mdev,
                         struct p_compressed_bm *p,
                         unsigned int size,
                         struct bm_xfer_ctx *c)
{
        struct bitstream bs;
        unsigned long plain_bits;
        unsigned long tmp;
        unsigned long rl;
        unsigned len;
        unsigned toggle;
        int bits, use_rle;

        /* may we use this feature? */
        rcu_read_lock();
        use_rle = rcu_dereference(mdev->tconn->net_conf)->use_rle;
        rcu_read_unlock();
        if (!use_rle || mdev->tconn->agreed_pro_version < 90)
                return 0;

        if (c->bit_offset >= c->bm_bits)
                return 0; /* nothing to do. */

        /* use at most thus many bytes */
        bitstream_init(&bs, p->code, size, 0);
        memset(p->code, 0, size);
        /* plain bits covered in this code string */
        plain_bits = 0;

        /* p->encoding & 0x80 stores whether the first run length is set.
         * bit offset is implicit.
         * start with toggle == 2 to be able to tell the first iteration */
        toggle = 2;

        /* see how much plain bits we can stuff into one packet
         * using RLE and VLI. */
        do {
                tmp = (toggle == 0) ? _drbd_bm_find_next_zero(mdev, c->bit_offset)
                                    : _drbd_bm_find_next(mdev, c->bit_offset);
                if (tmp == -1UL)
                        tmp = c->bm_bits;
                rl = tmp - c->bit_offset;

                if (toggle == 2) { /* first iteration */
                        if (rl == 0) {
                                /* the first checked bit was set,
                                 * store start value, */
                                dcbp_set_start(p, 1);
                                /* but skip encoding of zero run length */
                                toggle = !toggle;
                                continue;
                        }
                        dcbp_set_start(p, 0);
                }

                /* paranoia: catch zero runlength.
                 * can only happen if bitmap is modified while we scan it. */
                if (rl == 0) {
                        dev_err(DEV, "unexpected zero runlength while encoding bitmap "
                            "t:%u bo:%lu\n", toggle, c->bit_offset);
                        return -1;
                }

                bits = vli_encode_bits(&bs, rl);
                if (bits == -ENOBUFS) /* buffer full */
                        break;
                if (bits <= 0) {
                        dev_err(DEV, "error while encoding bitmap: %d\n", bits);
                        return 0;
                }

                toggle = !toggle;
                plain_bits += rl;
                c->bit_offset = tmp;
        } while (c->bit_offset < c->bm_bits);

        len = bs.cur.b - p->code + !!bs.cur.bit;

        if (plain_bits < (len << 3)) {
                /* incompressible with this method.
                 * we need to rewind both word and bit position. */
                c->bit_offset -= plain_bits;
                bm_xfer_ctx_bit_to_word_offset(c);
                c->bit_offset = c->word_offset * BITS_PER_LONG;
                return 0;
        }

        /* RLE + VLI was able to compress it just fine.
         * update c->word_offset. */
        bm_xfer_ctx_bit_to_word_offset(c);

        /* store pad_bits */
        dcbp_set_pad_bits(p, (8 - bs.cur.bit) & 0x7);

        return len;
}

/**
 * send_bitmap_rle_or_plain
 *
 * Return 0 when done, 1 when another iteration is needed, and a negative error
 * code upon failure.
 */
static int
send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
{
        struct drbd_socket *sock = &mdev->tconn->data;
        unsigned int header_size = drbd_header_size(mdev->tconn);
        struct p_compressed_bm *p = sock->sbuf + header_size;
        int len, err;

        len = fill_bitmap_rle_bits(mdev, p,
                        DRBD_SOCKET_BUFFER_SIZE - header_size - sizeof(*p), c);
        if (len < 0)
                return -EIO;

        if (len) {
                dcbp_set_code(p, RLE_VLI_Bits);
                err = __send_command(mdev->tconn, mdev->vnr, sock,
                                     P_COMPRESSED_BITMAP, sizeof(*p) + len,
                                     NULL, 0);
                c->packets[0]++;
                c->bytes[0] += header_size + sizeof(*p) + len;

                if (c->bit_offset >= c->bm_bits)
                        len = 0; /* DONE */
        } else {
                /* was not compressible.
                 * send a buffer full of plain text bits instead. */
                unsigned int data_size;
                unsigned long num_words;
                unsigned long *p = sock->sbuf + header_size;

                data_size = DRBD_SOCKET_BUFFER_SIZE - header_size;
                num_words = min_t(size_t, data_size / sizeof(*p),
                                  c->bm_words - c->word_offset);
                len = num_words * sizeof(*p);
                if (len)
                        drbd_bm_get_lel(mdev, c->word_offset, num_words, p);
                err = __send_command(mdev->tconn, mdev->vnr, sock, P_BITMAP, len, NULL, 0);
                c->word_offset += num_words;
                c->bit_offset = c->word_offset * BITS_PER_LONG;

                c->packets[1]++;
                c->bytes[1] += header_size + len;

                if (c->bit_offset > c->bm_bits)
                        c->bit_offset = c->bm_bits;
        }
        if (!err) {
                if (len == 0) {
                        INFO_bm_xfer_stats(mdev, "send", c);
                        return 0;
                } else
                        return 1;
        }
        return -EIO;
}

/* See the comment at receive_bitmap() */
static int _drbd_send_bitmap(struct drbd_conf *mdev)
{
        struct bm_xfer_ctx c;
        int err;

        if (!expect(mdev->bitmap))
                return false;

        if (get_ldev(mdev)) {
                if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
                        dev_info(DEV, "Writing the whole bitmap, MDF_FullSync was set.\n");
                        drbd_bm_set_all(mdev);
                        if (drbd_bm_write(mdev)) {
                                /* write_bm did fail! Leave full sync flag set in Meta P_DATA
                                 * but otherwise process as per normal - need to tell other
                                 * side that a full resync is required! */
                                dev_err(DEV, "Failed to write bitmap to disk!\n");
                        } else {
                                drbd_md_clear_flag(mdev, MDF_FULL_SYNC);
                                drbd_md_sync(mdev);
                        }
                }
                put_ldev(mdev);
        }

        c = (struct bm_xfer_ctx) {
                .bm_bits = drbd_bm_bits(mdev),
                .bm_words = drbd_bm_words(mdev),
        };

        do {
                err = send_bitmap_rle_or_plain(mdev, &c);
        } while (err > 0);

        return err == 0;
}

int drbd_send_bitmap(struct drbd_conf *mdev)
{
        struct drbd_socket *sock = &mdev->tconn->data;
        int err = -1;

        mutex_lock(&sock->mutex);
        if (sock->socket)
                err = !_drbd_send_bitmap(mdev);
        mutex_unlock(&sock->mutex);
        return err;
}

void drbd_send_b_ack(struct drbd_tconn *tconn, u32 barrier_nr, u32 set_size)
{
        struct drbd_socket *sock;
        struct p_barrier_ack *p;

        if (tconn->cstate < C_WF_REPORT_PARAMS)
                return;

        sock = &tconn->meta;
        p = conn_prepare_command(tconn, sock);
        if (!p)
                return;
        p->barrier = barrier_nr;
        p->set_size = cpu_to_be32(set_size);
        conn_send_command(tconn, sock, P_BARRIER_ACK, sizeof(*p), NULL, 0);
}

/**
 * _drbd_send_ack() - Sends an ack packet
 * @mdev:       DRBD device.
 * @cmd:        Packet command code.
 * @sector:     sector, needs to be in big endian byte order
 * @blksize:    size in byte, needs to be in big endian byte order
 * @block_id:   Id, big endian byte order
 */
static int _drbd_send_ack(struct drbd_conf *mdev, enum drbd_packet cmd,
                          u64 sector, u32 blksize, u64 block_id)
{
        struct drbd_socket *sock;
        struct p_block_ack *p;

        if (mdev->state.conn < C_CONNECTED)
                return -EIO;

        sock = &mdev->tconn->meta;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->sector = sector;
        p->block_id = block_id;
        p->blksize = blksize;
        p->seq_num = cpu_to_be32(atomic_inc_return(&mdev->packet_seq));
        return drbd_send_command(mdev, sock, cmd, sizeof(*p), NULL, 0);
}

/* dp->sector and dp->block_id already/still in network byte order,
 * data_size is payload size according to dp->head,
 * and may need to be corrected for digest size. */
void drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packet cmd,
                      struct p_data *dp, int data_size)
{
        if (mdev->tconn->peer_integrity_tfm)
                data_size -= crypto_hash_digestsize(mdev->tconn->peer_integrity_tfm);
        _drbd_send_ack(mdev, cmd, dp->sector, cpu_to_be32(data_size),
                       dp->block_id);
}

void drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packet cmd,
                      struct p_block_req *rp)
{
        _drbd_send_ack(mdev, cmd, rp->sector, rp->blksize, rp->block_id);
}

/**
 * drbd_send_ack() - Sends an ack packet
 * @mdev:       DRBD device
 * @cmd:        packet command code
 * @peer_req:   peer request
 */
int drbd_send_ack(struct drbd_conf *mdev, enum drbd_packet cmd,
                  struct drbd_peer_request *peer_req)
{
        return _drbd_send_ack(mdev, cmd,
                              cpu_to_be64(peer_req->i.sector),
                              cpu_to_be32(peer_req->i.size),
                              peer_req->block_id);
}

/* This function misuses the block_id field to signal if the blocks
 * are is sync or not. */
int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packet cmd,
                     sector_t sector, int blksize, u64 block_id)
{
        return _drbd_send_ack(mdev, cmd,
                              cpu_to_be64(sector),
                              cpu_to_be32(blksize),
                              cpu_to_be64(block_id));
}

int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
                       sector_t sector, int size, u64 block_id)
{
        struct drbd_socket *sock;
        struct p_block_req *p;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->sector = cpu_to_be64(sector);
        p->block_id = block_id;
        p->blksize = cpu_to_be32(size);
        return drbd_send_command(mdev, sock, cmd, sizeof(*p), NULL, 0);
}

int drbd_send_drequest_csum(struct drbd_conf *mdev, sector_t sector, int size,
                            void *digest, int digest_size, enum drbd_packet cmd)
{
        struct drbd_socket *sock;
        struct p_block_req *p;

        /* FIXME: Put the digest into the preallocated socket buffer.  */

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->sector = cpu_to_be64(sector);
        p->block_id = ID_SYNCER /* unused */;
        p->blksize = cpu_to_be32(size);
        return drbd_send_command(mdev, sock, cmd, sizeof(*p),
                                 digest, digest_size);
}

int drbd_send_ov_request(struct drbd_conf *mdev, sector_t sector, int size)
{
        struct drbd_socket *sock;
        struct p_block_req *p;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->sector = cpu_to_be64(sector);
        p->block_id = ID_SYNCER /* unused */;
        p->blksize = cpu_to_be32(size);
        return drbd_send_command(mdev, sock, P_OV_REQUEST, sizeof(*p), NULL, 0);
}

/* called on sndtimeo
 * returns false if we should retry,
 * true if we think connection is dead
 */
static int we_should_drop_the_connection(struct drbd_tconn *tconn, struct socket *sock)
{
        int drop_it;
        /* long elapsed = (long)(jiffies - mdev->last_received); */

        drop_it =   tconn->meta.socket == sock
                || !tconn->asender.task
                || get_t_state(&tconn->asender) != RUNNING
                || tconn->cstate < C_WF_REPORT_PARAMS;

        if (drop_it)
                return true;

        drop_it = !--tconn->ko_count;
        if (!drop_it) {
                conn_err(tconn, "[%s/%d] sock_sendmsg time expired, ko = %u\n",
                         current->comm, current->pid, tconn->ko_count);
                request_ping(tconn);
        }

        return drop_it; /* && (mdev->state == R_PRIMARY) */;
}

static void drbd_update_congested(struct drbd_tconn *tconn)
{
        struct sock *sk = tconn->data.socket->sk;
        if (sk->sk_wmem_queued > sk->sk_sndbuf * 4 / 5)
                set_bit(NET_CONGESTED, &tconn->flags);
}

/* The idea of sendpage seems to be to put some kind of reference
 * to the page into the skb, and to hand it over to the NIC. In
 * this process get_page() gets called.
 *
 * As soon as the page was really sent over the network put_page()
 * gets called by some part of the network layer. [ NIC driver? ]
 *
 * [ get_page() / put_page() increment/decrement the count. If count
 *   reaches 0 the page will be freed. ]
 *
 * This works nicely with pages from FSs.
 * But this means that in protocol A we might signal IO completion too early!
 *
 * In order not to corrupt data during a resync we must make sure
 * that we do not reuse our own buffer pages (EEs) to early, therefore
 * we have the net_ee list.
 *
 * XFS seems to have problems, still, it submits pages with page_count == 0!
 * As a workaround, we disable sendpage on pages
 * with page_count == 0 or PageSlab.
 */
static int _drbd_no_send_page(struct drbd_conf *mdev, struct page *page,
                              int offset, size_t size, unsigned msg_flags)
{
        struct socket *socket;
        void *addr;
        int err;

        socket = mdev->tconn->data.socket;
        addr = kmap(page) + offset;
        err = drbd_send_all(mdev->tconn, socket, addr, size, msg_flags);
        kunmap(page);
        if (!err)
                mdev->send_cnt += size >> 9;
        return err;
}

static int _drbd_send_page(struct drbd_conf *mdev, struct page *page,
                    int offset, size_t size, unsigned msg_flags)
{
        struct socket *socket = mdev->tconn->data.socket;
        mm_segment_t oldfs = get_fs();
        int len = size;
        int err = -EIO;

        /* e.g. XFS meta- & log-data is in slab pages, which have a
         * page_count of 0 and/or have PageSlab() set.
         * we cannot use send_page for those, as that does get_page();
         * put_page(); and would cause either a VM_BUG directly, or
         * __page_cache_release a page that would actually still be referenced
         * by someone, leading to some obscure delayed Oops somewhere else. */
        if (disable_sendpage || (page_count(page) < 1) || PageSlab(page))
                return _drbd_no_send_page(mdev, page, offset, size, msg_flags);

        msg_flags |= MSG_NOSIGNAL;
        drbd_update_congested(mdev->tconn);
        set_fs(KERNEL_DS);
        do {
                int sent;

                sent = socket->ops->sendpage(socket, page, offset, len, msg_flags);
                if (sent <= 0) {
                        if (sent == -EAGAIN) {
                                if (we_should_drop_the_connection(mdev->tconn, socket))
                                        break;
                                continue;
                        }
                        dev_warn(DEV, "%s: size=%d len=%d sent=%d\n",
                             __func__, (int)size, len, sent);
                        if (sent < 0)
                                err = sent;
                        break;
                }
                len    -= sent;
                offset += sent;
        } while (len > 0 /* THINK && mdev->cstate >= C_CONNECTED*/);
        set_fs(oldfs);
        clear_bit(NET_CONGESTED, &mdev->tconn->flags);

        if (len == 0) {
                err = 0;
                mdev->send_cnt += size >> 9;
        }
        return err;
}

static int _drbd_send_bio(struct drbd_conf *mdev, struct bio *bio)
{
        struct bio_vec *bvec;
        int i;
        /* hint all but last page with MSG_MORE */
        bio_for_each_segment(bvec, bio, i) {
                int err;

                err = _drbd_no_send_page(mdev, bvec->bv_page,
                                         bvec->bv_offset, bvec->bv_len,
                                         i == bio->bi_vcnt - 1 ? 0 : MSG_MORE);
                if (err)
                        return err;
        }
        return 0;
}

static int _drbd_send_zc_bio(struct drbd_conf *mdev, struct bio *bio)
{
        struct bio_vec *bvec;
        int i;
        /* hint all but last page with MSG_MORE */
        bio_for_each_segment(bvec, bio, i) {
                int err;

                err = _drbd_send_page(mdev, bvec->bv_page,
                                      bvec->bv_offset, bvec->bv_len,
                                      i == bio->bi_vcnt - 1 ? 0 : MSG_MORE);
                if (err)
                        return err;
        }
        return 0;
}

static int _drbd_send_zc_ee(struct drbd_conf *mdev,
                            struct drbd_peer_request *peer_req)
{
        struct page *page = peer_req->pages;
        unsigned len = peer_req->i.size;
        int err;

        /* hint all but last page with MSG_MORE */
        page_chain_for_each(page) {
                unsigned l = min_t(unsigned, len, PAGE_SIZE);

                err = _drbd_send_page(mdev, page, 0, l,
                                      page_chain_next(page) ? MSG_MORE : 0);
                if (err)
                        return err;
                len -= l;
        }
        return 0;
}

static u32 bio_flags_to_wire(struct drbd_conf *mdev, unsigned long bi_rw)
{
        if (mdev->tconn->agreed_pro_version >= 95)
                return  (bi_rw & REQ_SYNC ? DP_RW_SYNC : 0) |
                        (bi_rw & REQ_FUA ? DP_FUA : 0) |
                        (bi_rw & REQ_FLUSH ? DP_FLUSH : 0) |
                        (bi_rw & REQ_DISCARD ? DP_DISCARD : 0);
        else
                return bi_rw & REQ_SYNC ? DP_RW_SYNC : 0;
}

/* Used to send write requests
 * R_PRIMARY -> Peer    (P_DATA)
 */
int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
{
        struct drbd_socket *sock;
        struct p_data *p;
        unsigned int dp_flags = 0;
        int dgs;
        int err;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        dgs = mdev->tconn->integrity_tfm ? crypto_hash_digestsize(mdev->tconn->integrity_tfm) : 0;

        if (!p)
                return -EIO;
        p->sector = cpu_to_be64(req->i.sector);
        p->block_id = (unsigned long)req;
        p->seq_num = cpu_to_be32(atomic_inc_return(&mdev->packet_seq));
        dp_flags = bio_flags_to_wire(mdev, req->master_bio->bi_rw);
        if (mdev->state.conn >= C_SYNC_SOURCE &&
            mdev->state.conn <= C_PAUSED_SYNC_T)
                dp_flags |= DP_MAY_SET_IN_SYNC;
        if (mdev->tconn->agreed_pro_version >= 100) {
                if (req->rq_state & RQ_EXP_RECEIVE_ACK)
                        dp_flags |= DP_SEND_RECEIVE_ACK;
                if (req->rq_state & RQ_EXP_WRITE_ACK)
                        dp_flags |= DP_SEND_WRITE_ACK;
        }
        p->dp_flags = cpu_to_be32(dp_flags);
        if (dgs)
                drbd_csum_bio(mdev, mdev->tconn->integrity_tfm, req->master_bio, p + 1);
        err = __send_command(mdev->tconn, mdev->vnr, sock, P_DATA, sizeof(*p) + dgs, NULL, req->i.size);
        if (!err) {
                /* For protocol A, we have to memcpy the payload into
                 * socket buffers, as we may complete right away
                 * as soon as we handed it over to tcp, at which point the data
                 * pages may become invalid.
                 *
                 * For data-integrity enabled, we copy it as well, so we can be
                 * sure that even if the bio pages may still be modified, it
                 * won't change the data on the wire, thus if the digest checks
                 * out ok after sending on this side, but does not fit on the
                 * receiving side, we sure have detected corruption elsewhere.
                 */
                if (!(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK)) || dgs)
                        err = _drbd_send_bio(mdev, req->master_bio);
                else
                        err = _drbd_send_zc_bio(mdev, req->master_bio);

                /* double check digest, sometimes buffers have been modified in flight. */
                if (dgs > 0 && dgs <= 64) {
                        /* 64 byte, 512 bit, is the largest digest size
                         * currently supported in kernel crypto. */
                        unsigned char digest[64];
                        drbd_csum_bio(mdev, mdev->tconn->integrity_tfm, req->master_bio, digest);
                        if (memcmp(p + 1, digest, dgs)) {
                                dev_warn(DEV,
                                        "Digest mismatch, buffer modified by upper layers during write: %llus +%u\n",
                                        (unsigned long long)req->i.sector, req->i.size);
                        }
                } /* else if (dgs > 64) {
                     ... Be noisy about digest too large ...
                } */
        }
        mutex_unlock(&sock->mutex);  /* locked by drbd_prepare_command() */

        return err;
}

/* answer packet, used to send data back for read requests:
 *  Peer       -> (diskless) R_PRIMARY   (P_DATA_REPLY)
 *  C_SYNC_SOURCE -> C_SYNC_TARGET         (P_RS_DATA_REPLY)
 */
int drbd_send_block(struct drbd_conf *mdev, enum drbd_packet cmd,
                    struct drbd_peer_request *peer_req)
{
        struct drbd_socket *sock;
        struct p_data *p;
        int err;
        int dgs;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);

        dgs = mdev->tconn->integrity_tfm ? crypto_hash_digestsize(mdev->tconn->integrity_tfm) : 0;

        if (!p)
                return -EIO;
        p->sector = cpu_to_be64(peer_req->i.sector);
        p->block_id = peer_req->block_id;
        p->seq_num = 0;  /* unused */
        p->dp_flags = 0;
        if (dgs)
                drbd_csum_ee(mdev, mdev->tconn->integrity_tfm, peer_req, p + 1);
        err = __send_command(mdev->tconn, mdev->vnr, sock, cmd, sizeof(*p) + dgs, NULL, peer_req->i.size);
        if (!err)
                err = _drbd_send_zc_ee(mdev, peer_req);
        mutex_unlock(&sock->mutex);  /* locked by drbd_prepare_command() */

        return err;
}

int drbd_send_out_of_sync(struct drbd_conf *mdev, struct drbd_request *req)
{
        struct drbd_socket *sock;
        struct p_block_desc *p;

        sock = &mdev->tconn->data;
        p = drbd_prepare_command(mdev, sock);
        if (!p)
                return -EIO;
        p->sector = cpu_to_be64(req->i.sector);
        p->blksize = cpu_to_be32(req->i.size);
        return drbd_send_command(mdev, sock, P_OUT_OF_SYNC, sizeof(*p), NULL, 0);
}

/*
  drbd_send distinguishes two cases:

  Packets sent via the data socket "sock"
  and packets sent via the meta data socket "msock"

                    sock                      msock
  -----------------+-------------------------+------------------------------
  timeout           conf.timeout / 2          conf.timeout / 2
  timeout action    send a ping via msock     Abort communication
                                              and close all sockets
*/

/*
 * you must have down()ed the appropriate [m]sock_mutex elsewhere!
 */
int drbd_send(struct drbd_tconn *tconn, struct socket *sock,
              void *buf, size_t size, unsigned msg_flags)
{
        struct kvec iov;
        struct msghdr msg;
        int rv, sent = 0;

        if (!sock)
                return -EBADR;

        /* THINK  if (signal_pending) return ... ? */

        iov.iov_base = buf;
        iov.iov_len  = size;

        msg.msg_name       = NULL;
        msg.msg_namelen    = 0;
        msg.msg_control    = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags      = msg_flags | MSG_NOSIGNAL;

        if (sock == tconn->data.socket) {
                rcu_read_lock();
                tconn->ko_count = rcu_dereference(tconn->net_conf)->ko_count;
                rcu_read_unlock();
                drbd_update_congested(tconn);
        }
        do {
                /* STRANGE
                 * tcp_sendmsg does _not_ use its size parameter at all ?
                 *
                 * -EAGAIN on timeout, -EINTR on signal.
                 */
/* THINK
 * do we need to block DRBD_SIG if sock == &meta.socket ??
 * otherwise wake_asender() might interrupt some send_*Ack !
 */
                rv = kernel_sendmsg(sock, &msg, &iov, 1, size);
                if (rv == -EAGAIN) {
                        if (we_should_drop_the_connection(tconn, sock))
                                break;
                        else
                                continue;
                }
                if (rv == -EINTR) {
                        flush_signals(current);
                        rv = 0;
                }
                if (rv < 0)
                        break;
                sent += rv;
                iov.iov_base += rv;
                iov.iov_len  -= rv;
        } while (sent < size);

        if (sock == tconn->data.socket)
                clear_bit(NET_CONGESTED, &tconn->flags);

        if (rv <= 0) {
                if (rv != -EAGAIN) {
                        conn_err(tconn, "%s_sendmsg returned %d\n",
                                 sock == tconn->meta.socket ? "msock" : "sock",
                                 rv);
                        conn_request_state(tconn, NS(conn, C_BROKEN_PIPE), CS_HARD);
                } else
                        conn_request_state(tconn, NS(conn, C_TIMEOUT), CS_HARD);
        }

        return sent;
}

/**
 * drbd_send_all  -  Send an entire buffer
 *
 * Returns 0 upon success and a negative error value otherwise.
 */
int drbd_send_all(struct drbd_tconn *tconn, struct socket *sock, void *buffer,
                  size_t size, unsigned msg_flags)
{
        int err;

        err = drbd_send(tconn, sock, buffer, size, msg_flags);
        if (err < 0)
                return err;
        if (err != size)
                return -EIO;
        return 0;
}

static int drbd_open(struct block_device *bdev, fmode_t mode)
{
        struct drbd_conf *mdev = bdev->bd_disk->private_data;
        unsigned long flags;
        int rv = 0;

        mutex_lock(&drbd_main_mutex);
        spin_lock_irqsave(&mdev->tconn->req_lock, flags);
        /* to have a stable mdev->state.role
         * and no race with updating open_cnt */

        if (mdev->state.role != R_PRIMARY) {
                if (mode & FMODE_WRITE)
                        rv = -EROFS;
                else if (!allow_oos)
                        rv = -EMEDIUMTYPE;
        }

        if (!rv)
                mdev->open_cnt++;
        spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);
        mutex_unlock(&drbd_main_mutex);

        return rv;
}

static int drbd_release(struct gendisk *gd, fmode_t mode)
{
        struct drbd_conf *mdev = gd->private_data;
        mutex_lock(&drbd_main_mutex);
        mdev->open_cnt--;
        mutex_unlock(&drbd_main_mutex);
        return 0;
}

static void drbd_set_defaults(struct drbd_conf *mdev)
{
        /* Beware! The actual layout differs
         * between big endian and little endian */
        mdev->state = (union drbd_dev_state) {
                { .role = R_SECONDARY,
                  .peer = R_UNKNOWN,
                  .conn = C_STANDALONE,
                  .disk = D_DISKLESS,
                  .pdsk = D_UNKNOWN,
                } };
}

void drbd_init_set_defaults(struct drbd_conf *mdev)
{
        /* the memset(,0,) did most of this.
         * note: only assignments, no allocation in here */

        drbd_set_defaults(mdev);

        atomic_set(&mdev->ap_bio_cnt, 0);
        atomic_set(&mdev->ap_pending_cnt, 0);
        atomic_set(&mdev->rs_pending_cnt, 0);
        atomic_set(&mdev->unacked_cnt, 0);
        atomic_set(&mdev->local_cnt, 0);
        atomic_set(&mdev->pp_in_use_by_net, 0);
        atomic_set(&mdev->rs_sect_in, 0);
        atomic_set(&mdev->rs_sect_ev, 0);
        atomic_set(&mdev->ap_in_flight, 0);
        atomic_set(&mdev->md_io_in_use, 0);

        mutex_init(&mdev->own_state_mutex);
        mdev->state_mutex = &mdev->own_state_mutex;

        spin_lock_init(&mdev->al_lock);
        spin_lock_init(&mdev->peer_seq_lock);

        INIT_LIST_HEAD(&mdev->active_ee);
        INIT_LIST_HEAD(&mdev->sync_ee);
        INIT_LIST_HEAD(&mdev->done_ee);
        INIT_LIST_HEAD(&mdev->read_ee);
        INIT_LIST_HEAD(&mdev->net_ee);
        INIT_LIST_HEAD(&mdev->resync_reads);
        INIT_LIST_HEAD(&mdev->resync_work.list);
        INIT_LIST_HEAD(&mdev->unplug_work.list);
        INIT_LIST_HEAD(&mdev->go_diskless.list);
        INIT_LIST_HEAD(&mdev->md_sync_work.list);
        INIT_LIST_HEAD(&mdev->start_resync_work.list);
        INIT_LIST_HEAD(&mdev->bm_io_work.w.list);

        mdev->resync_work.cb  = w_resync_timer;
        mdev->unplug_work.cb  = w_send_write_hint;
        mdev->go_diskless.cb  = w_go_diskless;
        mdev->md_sync_work.cb = w_md_sync;
        mdev->bm_io_work.w.cb = w_bitmap_io;
        mdev->start_resync_work.cb = w_start_resync;

        mdev->resync_work.mdev  = mdev;
        mdev->unplug_work.mdev  = mdev;
        mdev->go_diskless.mdev  = mdev;
        mdev->md_sync_work.mdev = mdev;
        mdev->bm_io_work.w.mdev = mdev;
        mdev->start_resync_work.mdev = mdev;

        init_timer(&mdev->resync_timer);
        init_timer(&mdev->md_sync_timer);
        init_timer(&mdev->start_resync_timer);
        init_timer(&mdev->request_timer);
        mdev->resync_timer.function = resync_timer_fn;
        mdev->resync_timer.data = (unsigned long) mdev;
        mdev->md_sync_timer.function = md_sync_timer_fn;
        mdev->md_sync_timer.data = (unsigned long) mdev;
        mdev->start_resync_timer.function = start_resync_timer_fn;
        mdev->start_resync_timer.data = (unsigned long) mdev;
        mdev->request_timer.function = request_timer_fn;
        mdev->request_timer.data = (unsigned long) mdev;

        init_waitqueue_head(&mdev->misc_wait);
        init_waitqueue_head(&mdev->state_wait);
        init_waitqueue_head(&mdev->ee_wait);
        init_waitqueue_head(&mdev->al_wait);
        init_waitqueue_head(&mdev->seq_wait);

        mdev->resync_wenr = LC_FREE;
        mdev->peer_max_bio_size = DRBD_MAX_BIO_SIZE_SAFE;
        mdev->local_max_bio_size = DRBD_MAX_BIO_SIZE_SAFE;
}

void drbd_mdev_cleanup(struct drbd_conf *mdev)
{
        int i;
        if (mdev->tconn->receiver.t_state != NONE)
                dev_err(DEV, "ASSERT FAILED: receiver t_state == %d expected 0.\n",
                                mdev->tconn->receiver.t_state);

        mdev->al_writ_cnt  =
        mdev->bm_writ_cnt  =
        mdev->read_cnt     =
        mdev->recv_cnt     =
        mdev->send_cnt     =
        mdev->writ_cnt     =
        mdev->p_size       =
        mdev->rs_start     =
        mdev->rs_total     =
        mdev->rs_failed    = 0;
        mdev->rs_last_events = 0;
        mdev->rs_last_sect_ev = 0;
        for (i = 0; i < DRBD_SYNC_MARKS; i++) {
                mdev->rs_mark_left[i] = 0;
                mdev->rs_mark_time[i] = 0;
        }
        D_ASSERT(mdev->tconn->net_conf == NULL);

        drbd_set_my_capacity(mdev, 0);
        if (mdev->bitmap) {
                /* maybe never allocated. */
                drbd_bm_resize(mdev, 0, 1);
                drbd_bm_cleanup(mdev);
        }

        drbd_free_bc(mdev->ldev);
        mdev->ldev = NULL;

        clear_bit(AL_SUSPENDED, &mdev->flags);

        D_ASSERT(list_empty(&mdev->active_ee));
        D_ASSERT(list_empty(&mdev->sync_ee));
        D_ASSERT(list_empty(&mdev->done_ee));
        D_ASSERT(list_empty(&mdev->read_ee));
        D_ASSERT(list_empty(&mdev->net_ee));
        D_ASSERT(list_empty(&mdev->resync_reads));
        D_ASSERT(list_empty(&mdev->tconn->sender_work.q));
        D_ASSERT(list_empty(&mdev->resync_work.list));
        D_ASSERT(list_empty(&mdev->unplug_work.list));
        D_ASSERT(list_empty(&mdev->go_diskless.list));

        drbd_set_defaults(mdev);
}


static void drbd_destroy_mempools(void)
{
        struct page *page;

        while (drbd_pp_pool) {
                page = drbd_pp_pool;
                drbd_pp_pool = (struct page *)page_private(page);
                __free_page(page);
                drbd_pp_vacant--;
        }

        /* D_ASSERT(atomic_read(&drbd_pp_vacant)==0); */

        if (drbd_md_io_bio_set)
                bioset_free(drbd_md_io_bio_set);
        if (drbd_md_io_page_pool)
                mempool_destroy(drbd_md_io_page_pool);
        if (drbd_ee_mempool)
                mempool_destroy(drbd_ee_mempool);
        if (drbd_request_mempool)
                mempool_destroy(drbd_request_mempool);
        if (drbd_ee_cache)
                kmem_cache_destroy(drbd_ee_cache);
        if (drbd_request_cache)
                kmem_cache_destroy(drbd_request_cache);
        if (drbd_bm_ext_cache)
                kmem_cache_destroy(drbd_bm_ext_cache);
        if (drbd_al_ext_cache)
                kmem_cache_destroy(drbd_al_ext_cache);

        drbd_md_io_bio_set   = NULL;
        drbd_md_io_page_pool = NULL;
        drbd_ee_mempool      = NULL;
        drbd_request_mempool = NULL;
        drbd_ee_cache        = NULL;
        drbd_request_cache   = NULL;
        drbd_bm_ext_cache    = NULL;
        drbd_al_ext_cache    = NULL;

        return;
}

static int drbd_create_mempools(void)
{
        struct page *page;
        const int number = (DRBD_MAX_BIO_SIZE/PAGE_SIZE) * minor_count;
        int i;

        /* prepare our caches and mempools */
        drbd_request_mempool = NULL;
        drbd_ee_cache        = NULL;
        drbd_request_cache   = NULL;
        drbd_bm_ext_cache    = NULL;
        drbd_al_ext_cache    = NULL;
        drbd_pp_pool         = NULL;
        drbd_md_io_page_pool = NULL;
        drbd_md_io_bio_set   = NULL;

        /* caches */
        drbd_request_cache = kmem_cache_create(
                "drbd_req", sizeof(struct drbd_request), 0, 0, NULL);
        if (drbd_request_cache == NULL)
                goto Enomem;

        drbd_ee_cache = kmem_cache_create(
                "drbd_ee", sizeof(struct drbd_peer_request), 0, 0, NULL);
        if (drbd_ee_cache == NULL)
                goto Enomem;

        drbd_bm_ext_cache = kmem_cache_create(
                "drbd_bm", sizeof(struct bm_extent), 0, 0, NULL);
        if (drbd_bm_ext_cache == NULL)
                goto Enomem;

        drbd_al_ext_cache = kmem_cache_create(
                "drbd_al", sizeof(struct lc_element), 0, 0, NULL);
        if (drbd_al_ext_cache == NULL)
                goto Enomem;

        /* mempools */
        drbd_md_io_bio_set = bioset_create(DRBD_MIN_POOL_PAGES, 0);
        if (drbd_md_io_bio_set == NULL)
                goto Enomem;

        drbd_md_io_page_pool = mempool_create_page_pool(DRBD_MIN_POOL_PAGES, 0);
        if (drbd_md_io_page_pool == NULL)
                goto Enomem;

        drbd_request_mempool = mempool_create(number,
                mempool_alloc_slab, mempool_free_slab, drbd_request_cache);
        if (drbd_request_mempool == NULL)
                goto Enomem;

        drbd_ee_mempool = mempool_create(number,
                mempool_alloc_slab, mempool_free_slab, drbd_ee_cache);
        if (drbd_ee_mempool == NULL)
                goto Enomem;

        /* drbd's page pool */
        spin_lock_init(&drbd_pp_lock);

        for (i = 0; i < number; i++) {
                page = alloc_page(GFP_HIGHUSER);
                if (!page)
                        goto Enomem;
                set_page_private(page, (unsigned long)drbd_pp_pool);
                drbd_pp_pool = page;
        }
        drbd_pp_vacant = number;

        return 0;

Enomem:
        drbd_destroy_mempools(); /* in case we allocated some */
        return -ENOMEM;
}

static int drbd_notify_sys(struct notifier_block *this, unsigned long code,
        void *unused)
{
        /* just so we have it.  you never know what interesting things we
         * might want to do here some day...
         */

        return NOTIFY_DONE;
}

static struct notifier_block drbd_notifier = {
        .notifier_call = drbd_notify_sys,
};

static void drbd_release_all_peer_reqs(struct drbd_conf *mdev)
{
        int rr;

        rr = drbd_free_peer_reqs(mdev, &mdev->active_ee);
        if (rr)
                dev_err(DEV, "%d EEs in active list found!\n", rr);

        rr = drbd_free_peer_reqs(mdev, &mdev->sync_ee);
        if (rr)
                dev_err(DEV, "%d EEs in sync list found!\n", rr);

        rr = drbd_free_peer_reqs(mdev, &mdev->read_ee);
        if (rr)
                dev_err(DEV, "%d EEs in read list found!\n", rr);

        rr = drbd_free_peer_reqs(mdev, &mdev->done_ee);
        if (rr)
                dev_err(DEV, "%d EEs in done list found!\n", rr);

        rr = drbd_free_peer_reqs(mdev, &mdev->net_ee);
        if (rr)
                dev_err(DEV, "%d EEs in net list found!\n", rr);
}

/* caution. no locking. */
void drbd_minor_destroy(struct kref *kref)
{
        struct drbd_conf *mdev = container_of(kref, struct drbd_conf, kref);
        struct drbd_tconn *tconn = mdev->tconn;

        del_timer_sync(&mdev->request_timer);

        /* paranoia asserts */
        D_ASSERT(mdev->open_cnt == 0);
        /* end paranoia asserts */

        /* cleanup stuff that may have been allocated during
         * device (re-)configuration or state changes */

        if (mdev->this_bdev)
                bdput(mdev->this_bdev);

        drbd_free_bc(mdev->ldev);
        mdev->ldev = NULL;

        drbd_release_all_peer_reqs(mdev);

        lc_destroy(mdev->act_log);
        lc_destroy(mdev->resync);

        kfree(mdev->p_uuid);
        /* mdev->p_uuid = NULL; */

        if (mdev->bitmap) /* should no longer be there. */
                drbd_bm_cleanup(mdev);
        __free_page(mdev->md_io_page);
        put_disk(mdev->vdisk);
        blk_cleanup_queue(mdev->rq_queue);
        kfree(mdev->rs_plan_s);
        kfree(mdev);

        kref_put(&tconn->kref, &conn_destroy);
}

/* One global retry thread, if we need to push back some bio and have it
 * reinserted through our make request function.
 */
static struct retry_worker {
        struct workqueue_struct *wq;
        struct work_struct worker;

        spinlock_t lock;
        struct list_head writes;
} retry;

static void do_retry(struct work_struct *ws)
{
        struct retry_worker *retry = container_of(ws, struct retry_worker, worker);
        LIST_HEAD(writes);
        struct drbd_request *req, *tmp;

        spin_lock_irq(&retry->lock);
        list_splice_init(&retry->writes, &writes);
        spin_unlock_irq(&retry->lock);

        list_for_each_entry_safe(req, tmp, &writes, tl_requests) {
                struct drbd_conf *mdev = req->w.mdev;
                struct bio *bio = req->master_bio;
                unsigned long start_time = req->start_time;

                /* We have exclusive access to this request object.
                 * If it had not been RQ_POSTPONED, the code path which queued
                 * it here would have completed and freed it already.
                 */
                mempool_free(req, drbd_request_mempool);

                /* A single suspended or otherwise blocking device may stall
                 * all others as well.  Fortunately, this code path is to
                 * recover from a situation that "should not happen":
                 * concurrent writes in multi-primary setup.
                 * In a "normal" lifecycle, this workqueue is supposed to be
                 * destroyed without ever doing anything.
                 * If it turns out to be an issue anyways, we can do per
                 * resource (replication group) or per device (minor) retry
                 * workqueues instead.
                 */

                /* We are not just doing generic_make_request(),
                 * as we want to keep the start_time information. */
                inc_ap_bio(mdev);
                __drbd_make_request(mdev, bio, start_time);
        }
}

void drbd_restart_request(struct drbd_request *req)
{
        unsigned long flags;
        spin_lock_irqsave(&retry.lock, flags);
        list_move_tail(&req->tl_requests, &retry.writes);
        spin_unlock_irqrestore(&retry.lock, flags);

        /* Drop the extra reference that would otherwise
         * have been dropped by complete_master_bio.
         * do_retry() needs to grab a new one. */
        dec_ap_bio(req->w.mdev);

        queue_work(retry.wq, &retry.worker);
}


static void drbd_cleanup(void)
{
        unsigned int i;
        struct drbd_conf *mdev;
        struct drbd_tconn *tconn, *tmp;

        unregister_reboot_notifier(&drbd_notifier);

        /* first remove proc,
         * drbdsetup uses it's presence to detect
         * whether DRBD is loaded.
         * If we would get stuck in proc removal,
         * but have netlink already deregistered,
         * some drbdsetup commands may wait forever
         * for an answer.
         */
        if (drbd_proc)
                remove_proc_entry("drbd", NULL);

        if (retry.wq)
                destroy_workqueue(retry.wq);

        drbd_genl_unregister();

        idr_for_each_entry(&minors, mdev, i) {
                idr_remove(&minors, mdev_to_minor(mdev));
                idr_remove(&mdev->tconn->volumes, mdev->vnr);
                del_gendisk(mdev->vdisk);
                /* synchronize_rcu(); No other threads running at this point */
                kref_put(&mdev->kref, &drbd_minor_destroy);
        }

        /* not _rcu since, no other updater anymore. Genl already unregistered */
        list_for_each_entry_safe(tconn, tmp, &drbd_tconns, all_tconn) {
                list_del(&tconn->all_tconn); /* not _rcu no proc, not other threads */
                /* synchronize_rcu(); */
                kref_put(&tconn->kref, &conn_destroy);
        }

        drbd_destroy_mempools();
        unregister_blkdev(DRBD_MAJOR, "drbd");

        idr_destroy(&minors);

        printk(KERN_INFO "drbd: module cleanup done.\n");
}

/**
 * drbd_congested() - Callback for pdflush
 * @congested_data:     User data
 * @bdi_bits:           Bits pdflush is currently interested in
 *
 * Returns 1<<BDI_async_congested and/or 1<<BDI_sync_congested if we are congested.
 */
static int drbd_congested(void *congested_data, int bdi_bits)
{
        struct drbd_conf *mdev = congested_data;
        struct request_queue *q;
        char reason = '-';
        int r = 0;

        if (!may_inc_ap_bio(mdev)) {
                /* DRBD has frozen IO */
                r = bdi_bits;
                reason = 'd';
                goto out;
        }

        if (get_ldev(mdev)) {
                q = bdev_get_queue(mdev->ldev->backing_bdev);
                r = bdi_congested(&q->backing_dev_info, bdi_bits);
                put_ldev(mdev);
                if (r)
                        reason = 'b';
        }

        if (bdi_bits & (1 << BDI_async_congested) && test_bit(NET_CONGESTED, &mdev->tconn->flags)) {
                r |= (1 << BDI_async_congested);
                reason = reason == 'b' ? 'a' : 'n';
        }

out:
        mdev->congestion_reason = reason;
        return r;
}

static void drbd_init_workqueue(struct drbd_work_queue* wq)
{
        spin_lock_init(&wq->q_lock);
        INIT_LIST_HEAD(&wq->q);
        init_waitqueue_head(&wq->q_wait);
}

struct drbd_tconn *conn_get_by_name(const char *name)
{
        struct drbd_tconn *tconn;

        if (!name || !name[0])
                return NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(tconn, &drbd_tconns, all_tconn) {
                if (!strcmp(tconn->name, name)) {
                        kref_get(&tconn->kref);
                        goto found;
                }
        }
        tconn = NULL;
found:
        rcu_read_unlock();
        return tconn;
}

struct drbd_tconn *conn_get_by_addrs(void *my_addr, int my_addr_len,
                                     void *peer_addr, int peer_addr_len)
{
        struct drbd_tconn *tconn;

        rcu_read_lock();
        list_for_each_entry_rcu(tconn, &drbd_tconns, all_tconn) {
                if (tconn->my_addr_len == my_addr_len &&
                    tconn->peer_addr_len == peer_addr_len &&
                    !memcmp(&tconn->my_addr, my_addr, my_addr_len) &&
                    !memcmp(&tconn->peer_addr, peer_addr, peer_addr_len)) {
                        kref_get(&tconn->kref);
                        goto found;
                }
        }
        tconn = NULL;
found:
        rcu_read_unlock();
        return tconn;
}

static int drbd_alloc_socket(struct drbd_socket *socket)
{
        socket->rbuf = (void *) __get_free_page(GFP_KERNEL);
        if (!socket->rbuf)
                return -ENOMEM;
        socket->sbuf = (void *) __get_free_page(GFP_KERNEL);
        if (!socket->sbuf)
                return -ENOMEM;
        return 0;
}

static void drbd_free_socket(struct drbd_socket *socket)
{
        free_page((unsigned long) socket->sbuf);
        free_page((unsigned long) socket->rbuf);
}

void conn_free_crypto(struct drbd_tconn *tconn)
{
        drbd_free_sock(tconn);

        crypto_free_hash(tconn->csums_tfm);
        crypto_free_hash(tconn->verify_tfm);
        crypto_free_hash(tconn->cram_hmac_tfm);
        crypto_free_hash(tconn->integrity_tfm);
        crypto_free_hash(tconn->peer_integrity_tfm);
        kfree(tconn->int_dig_in);
        kfree(tconn->int_dig_vv);

        tconn->csums_tfm = NULL;
        tconn->verify_tfm = NULL;
        tconn->cram_hmac_tfm = NULL;
        tconn->integrity_tfm = NULL;
        tconn->peer_integrity_tfm = NULL;
        tconn->int_dig_in = NULL;
        tconn->int_dig_vv = NULL;
}

int set_resource_options(struct drbd_tconn *tconn, struct res_opts *res_opts)
{
        cpumask_var_t new_cpu_mask;
        int err;

        if (!zalloc_cpumask_var(&new_cpu_mask, GFP_KERNEL))
                return -ENOMEM;
                /*
                retcode = ERR_NOMEM;
                drbd_msg_put_info("unable to allocate cpumask");
                */

        /* silently ignore cpu mask on UP kernel */
        if (nr_cpu_ids > 1 && res_opts->cpu_mask[0] != 0) {
                /* FIXME: Get rid of constant 32 here */
                err = bitmap_parse(res_opts->cpu_mask, 32,
                                   cpumask_bits(new_cpu_mask), nr_cpu_ids);
                if (err) {
                        conn_warn(tconn, "bitmap_parse() failed with %d\n", err);
                        /* retcode = ERR_CPU_MASK_PARSE; */
                        goto fail;
                }
        }
        tconn->res_opts = *res_opts;
        if (!cpumask_equal(tconn->cpu_mask, new_cpu_mask)) {
                cpumask_copy(tconn->cpu_mask, new_cpu_mask);
                drbd_calc_cpu_mask(tconn);
                tconn->receiver.reset_cpu_mask = 1;
                tconn->asender.reset_cpu_mask = 1;
                tconn->worker.reset_cpu_mask = 1;
        }
        err = 0;

fail:
        free_cpumask_var(new_cpu_mask);
        return err;

}

/* caller must be under genl_lock() */
struct drbd_tconn *conn_create(const char *name, struct res_opts *res_opts)
{
        struct drbd_tconn *tconn;

        tconn = kzalloc(sizeof(struct drbd_tconn), GFP_KERNEL);
        if (!tconn)
                return NULL;

        tconn->name = kstrdup(name, GFP_KERNEL);
        if (!tconn->name)
                goto fail;

        if (drbd_alloc_socket(&tconn->data))
                goto fail;
        if (drbd_alloc_socket(&tconn->meta))
                goto fail;

        if (!zalloc_cpumask_var(&tconn->cpu_mask, GFP_KERNEL))
                goto fail;

        if (set_resource_options(tconn, res_opts))
                goto fail;

        tconn->current_epoch = kzalloc(sizeof(struct drbd_epoch), GFP_KERNEL);
        if (!tconn->current_epoch)
                goto fail;

        INIT_LIST_HEAD(&tconn->transfer_log);

        INIT_LIST_HEAD(&tconn->current_epoch->list);
        tconn->epochs = 1;
        spin_lock_init(&tconn->epoch_lock);
        tconn->write_ordering = WO_bdev_flush;

        tconn->send.seen_any_write_yet = false;
        tconn->send.current_epoch_nr = 0;
        tconn->send.current_epoch_writes = 0;

        tconn->cstate = C_STANDALONE;
        mutex_init(&tconn->cstate_mutex);
        spin_lock_init(&tconn->req_lock);
        mutex_init(&tconn->conf_update);
        init_waitqueue_head(&tconn->ping_wait);
        idr_init(&tconn->volumes);

        drbd_init_workqueue(&tconn->sender_work);
        mutex_init(&tconn->data.mutex);
        mutex_init(&tconn->meta.mutex);

        drbd_thread_init(tconn, &tconn->receiver, drbdd_init, "receiver");
        drbd_thread_init(tconn, &tconn->worker, drbd_worker, "worker");
        drbd_thread_init(tconn, &tconn->asender, drbd_asender, "asender");

        kref_init(&tconn->kref);
        list_add_tail_rcu(&tconn->all_tconn, &drbd_tconns);

        return tconn;

fail:
        kfree(tconn->current_epoch);
        free_cpumask_var(tconn->cpu_mask);
        drbd_free_socket(&tconn->meta);
        drbd_free_socket(&tconn->data);
        kfree(tconn->name);
        kfree(tconn);

        return NULL;
}

void conn_destroy(struct kref *kref)
{
        struct drbd_tconn *tconn = container_of(kref, struct drbd_tconn, kref);

        if (atomic_read(&tconn->current_epoch->epoch_size) !=  0)
                conn_err(tconn, "epoch_size:%d\n", atomic_read(&tconn->current_epoch->epoch_size));
        kfree(tconn->current_epoch);

        idr_destroy(&tconn->volumes);

        free_cpumask_var(tconn->cpu_mask);
        drbd_free_socket(&tconn->meta);
        drbd_free_socket(&tconn->data);
        kfree(tconn->name);
        kfree(tconn->int_dig_in);
        kfree(tconn->int_dig_vv);
        kfree(tconn);
}

enum drbd_ret_code conn_new_minor(struct drbd_tconn *tconn, unsigned int minor, int vnr)
{
        struct drbd_conf *mdev;
        struct gendisk *disk;
        struct request_queue *q;
        int vnr_got = vnr;
        int minor_got = minor;
        enum drbd_ret_code err = ERR_NOMEM;

        mdev = minor_to_mdev(minor);
        if (mdev)
                return ERR_MINOR_EXISTS;

        /* GFP_KERNEL, we are outside of all write-out paths */
        mdev = kzalloc(sizeof(struct drbd_conf), GFP_KERNEL);
        if (!mdev)
                return ERR_NOMEM;

        kref_get(&tconn->kref);
        mdev->tconn = tconn;

        mdev->minor = minor;
        mdev->vnr = vnr;

        drbd_init_set_defaults(mdev);

        q = blk_alloc_queue(GFP_KERNEL);
        if (!q)
                goto out_no_q;
        mdev->rq_queue = q;
        q->queuedata   = mdev;

        disk = alloc_disk(1);
        if (!disk)
                goto out_no_disk;
        mdev->vdisk = disk;

        set_disk_ro(disk, true);

        disk->queue = q;
        disk->major = DRBD_MAJOR;
        disk->first_minor = minor;
        disk->fops = &drbd_ops;
        sprintf(disk->disk_name, "drbd%d", minor);
        disk->private_data = mdev;

        mdev->this_bdev = bdget(MKDEV(DRBD_MAJOR, minor));
        /* we have no partitions. we contain only ourselves. */
        mdev->this_bdev->bd_contains = mdev->this_bdev;

        q->backing_dev_info.congested_fn = drbd_congested;
        q->backing_dev_info.congested_data = mdev;

        blk_queue_make_request(q, drbd_make_request);
        /* Setting the max_hw_sectors to an odd value of 8kibyte here
           This triggers a max_bio_size message upon first attach or connect */
        blk_queue_max_hw_sectors(q, DRBD_MAX_BIO_SIZE_SAFE >> 8);
        blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
        blk_queue_merge_bvec(q, drbd_merge_bvec);
        q->queue_lock = &mdev->tconn->req_lock; /* needed since we use */

        mdev->md_io_page = alloc_page(GFP_KERNEL);
        if (!mdev->md_io_page)
                goto out_no_io_page;

        if (drbd_bm_init(mdev))
                goto out_no_bitmap;
        mdev->read_requests = RB_ROOT;
        mdev->write_requests = RB_ROOT;

        if (!idr_pre_get(&minors, GFP_KERNEL))
                goto out_no_minor_idr;
        if (idr_get_new_above(&minors, mdev, minor, &minor_got))
                goto out_no_minor_idr;
        if (minor_got != minor) {
                err = ERR_MINOR_EXISTS;
                drbd_msg_put_info("requested minor exists already");
                goto out_idr_remove_minor;
        }

        if (!idr_pre_get(&tconn->volumes, GFP_KERNEL))
                goto out_idr_remove_minor;
        if (idr_get_new_above(&tconn->volumes, mdev, vnr, &vnr_got))
                goto out_idr_remove_minor;
        if (vnr_got != vnr) {
                err = ERR_INVALID_REQUEST;
                drbd_msg_put_info("requested volume exists already");
                goto out_idr_remove_vol;
        }
        add_disk(disk);
        kref_init(&mdev->kref); /* one ref for both idrs and the the add_disk */

        /* inherit the connection state */
        mdev->state.conn = tconn->cstate;
        if (mdev->state.conn == C_WF_REPORT_PARAMS)
                drbd_connected(mdev);

        return NO_ERROR;

out_idr_remove_vol:
        idr_remove(&tconn->volumes, vnr_got);
out_idr_remove_minor:
        idr_remove(&minors, minor_got);
        synchronize_rcu();
out_no_minor_idr:
        drbd_bm_cleanup(mdev);
out_no_bitmap:
        __free_page(mdev->md_io_page);
out_no_io_page:
        put_disk(disk);
out_no_disk:
        blk_cleanup_queue(q);
out_no_q:
        kfree(mdev);
        kref_put(&tconn->kref, &conn_destroy);
        return err;
}

int __init drbd_init(void)
{
        int err;

        if (minor_count < DRBD_MINOR_COUNT_MIN || minor_count > DRBD_MINOR_COUNT_MAX) {
                printk(KERN_ERR
                       "drbd: invalid minor_count (%d)\n", minor_count);
#ifdef MODULE
                return -EINVAL;
#else
                minor_count = DRBD_MINOR_COUNT_DEF;
#endif
        }

        err = register_blkdev(DRBD_MAJOR, "drbd");
        if (err) {
                printk(KERN_ERR
                       "drbd: unable to register block device major %d\n",
                       DRBD_MAJOR);
                return err;
        }

        err = drbd_genl_register();
        if (err) {
                printk(KERN_ERR "drbd: unable to register generic netlink family\n");
                goto fail;
        }


        register_reboot_notifier(&drbd_notifier);

        /*
         * allocate all necessary structs
         */
        err = -ENOMEM;

        init_waitqueue_head(&drbd_pp_wait);

        drbd_proc = NULL; /* play safe for drbd_cleanup */
        idr_init(&minors);

        err = drbd_create_mempools();
        if (err)
                goto fail;

        drbd_proc = proc_create_data("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops, NULL);
        if (!drbd_proc) {
                printk(KERN_ERR "drbd: unable to register proc file\n");
                goto fail;
        }

        rwlock_init(&global_state_lock);
        INIT_LIST_HEAD(&drbd_tconns);

        retry.wq = create_singlethread_workqueue("drbd-reissue");
        if (!retry.wq) {
                printk(KERN_ERR "drbd: unable to create retry workqueue\n");
                goto fail;
        }
        INIT_WORK(&retry.worker, do_retry);
        spin_lock_init(&retry.lock);
        INIT_LIST_HEAD(&retry.writes);

        printk(KERN_INFO "drbd: initialized. "
               "Version: " REL_VERSION " (api:%d/proto:%d-%d)\n",
               API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
        printk(KERN_INFO "drbd: %s\n", drbd_buildtag());
        printk(KERN_INFO "drbd: registered as block device major %d\n",
                DRBD_MAJOR);

        return 0; /* Success! */

fail:
        drbd_cleanup();
        if (err == -ENOMEM)
                /* currently always the case */
                printk(KERN_ERR "drbd: ran out of memory\n");
        else
                printk(KERN_ERR "drbd: initialization failure\n");
        return err;
}

void drbd_free_bc(struct drbd_backing_dev *ldev)
{
        if (ldev == NULL)
                return;

        blkdev_put(ldev->backing_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
        blkdev_put(ldev->md_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);

        kfree(ldev);
}

void drbd_free_sock(struct drbd_tconn *tconn)
{
        if (tconn->data.socket) {
                mutex_lock(&tconn->data.mutex);
                kernel_sock_shutdown(tconn->data.socket, SHUT_RDWR);
                sock_release(tconn->data.socket);
                tconn->data.socket = NULL;
                mutex_unlock(&tconn->data.mutex);
        }
        if (tconn->meta.socket) {
                mutex_lock(&tconn->meta.mutex);
                kernel_sock_shutdown(tconn->meta.socket, SHUT_RDWR);
                sock_release(tconn->meta.socket);
                tconn->meta.socket = NULL;
                mutex_unlock(&tconn->meta.mutex);
        }
}

/* meta data management */

struct meta_data_on_disk {
        u64 la_size;           /* last agreed size. */
        u64 uuid[UI_SIZE];   /* UUIDs. */
        u64 device_uuid;
        u64 reserved_u64_1;
        u32 flags;             /* MDF */
        u32 magic;
        u32 md_size_sect;
        u32 al_offset;         /* offset to this block */
        u32 al_nr_extents;     /* important for restoring the AL */
              /* `-- act_log->nr_elements <-- ldev->dc.al_extents */
        u32 bm_offset;         /* offset to the bitmap, from here */
        u32 bm_bytes_per_bit;  /* BM_BLOCK_SIZE */
        u32 la_peer_max_bio_size;   /* last peer max_bio_size */
        u32 reserved_u32[3];

} __packed;

/**
 * drbd_md_sync() - Writes the meta data super block if the MD_DIRTY flag bit is set
 * @mdev:       DRBD device.
 */
void drbd_md_sync(struct drbd_conf *mdev)
{
        struct meta_data_on_disk *buffer;
        sector_t sector;
        int i;

        del_timer(&mdev->md_sync_timer);
        /* timer may be rearmed by drbd_md_mark_dirty() now. */
        if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
                return;

        /* We use here D_FAILED and not D_ATTACHING because we try to write
         * metadata even if we detach due to a disk failure! */
        if (!get_ldev_if_state(mdev, D_FAILED))
                return;

        buffer = drbd_md_get_buffer(mdev);
        if (!buffer)
                goto out;

        memset(buffer, 0, 512);

        buffer->la_size = cpu_to_be64(drbd_get_capacity(mdev->this_bdev));
        for (i = UI_CURRENT; i < UI_SIZE; i++)
                buffer->uuid[i] = cpu_to_be64(mdev->ldev->md.uuid[i]);
        buffer->flags = cpu_to_be32(mdev->ldev->md.flags);
        buffer->magic = cpu_to_be32(DRBD_MD_MAGIC_84_UNCLEAN);

        buffer->md_size_sect  = cpu_to_be32(mdev->ldev->md.md_size_sect);
        buffer->al_offset     = cpu_to_be32(mdev->ldev->md.al_offset);
        buffer->al_nr_extents = cpu_to_be32(mdev->act_log->nr_elements);
        buffer->bm_bytes_per_bit = cpu_to_be32(BM_BLOCK_SIZE);
        buffer->device_uuid = cpu_to_be64(mdev->ldev->md.device_uuid);

        buffer->bm_offset = cpu_to_be32(mdev->ldev->md.bm_offset);
        buffer->la_peer_max_bio_size = cpu_to_be32(mdev->peer_max_bio_size);

        D_ASSERT(drbd_md_ss__(mdev, mdev->ldev) == mdev->ldev->md.md_offset);
        sector = mdev->ldev->md.md_offset;

        if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
                /* this was a try anyways ... */
                dev_err(DEV, "meta data update failed!\n");
                drbd_chk_io_error(mdev, 1, true);
        }

        /* Update mdev->ldev->md.la_size_sect,
         * since we updated it on metadata. */
        mdev->ldev->md.la_size_sect = drbd_get_capacity(mdev->this_bdev);

        drbd_md_put_buffer(mdev);
out:
        put_ldev(mdev);
}

/**
 * drbd_md_read() - Reads in the meta data super block
 * @mdev:       DRBD device.
 * @bdev:       Device from which the meta data should be read in.
 *
 * Return 0 (NO_ERROR) on success, and an enum drbd_ret_code in case
 * something goes wrong.
 */
int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
{
        struct meta_data_on_disk *buffer;
        u32 magic, flags;
        int i, rv = NO_ERROR;

        if (!get_ldev_if_state(mdev, D_ATTACHING))
                return ERR_IO_MD_DISK;

        buffer = drbd_md_get_buffer(mdev);
        if (!buffer)
                goto out;

        if (drbd_md_sync_page_io(mdev, bdev, bdev->md.md_offset, READ)) {
                /* NOTE: can't do normal error processing here as this is
                   called BEFORE disk is attached */
                dev_err(DEV, "Error while reading metadata.\n");
                rv = ERR_IO_MD_DISK;
                goto err;
        }

        magic = be32_to_cpu(buffer->magic);
        flags = be32_to_cpu(buffer->flags);
        if (magic == DRBD_MD_MAGIC_84_UNCLEAN ||
            (magic == DRBD_MD_MAGIC_08 && !(flags & MDF_AL_CLEAN))) {
                        /* btw: that's Activity Log clean, not "all" clean. */
                dev_err(DEV, "Found unclean meta data. Did you \"drbdadm apply-al\"?\n");
                rv = ERR_MD_UNCLEAN;
                goto err;
        }
        if (magic != DRBD_MD_MAGIC_08) {
                if (magic == DRBD_MD_MAGIC_07)
                        dev_err(DEV, "Found old (0.7) meta data magic. Did you \"drbdadm create-md\"?\n");
                else
                        dev_err(DEV, "Meta data magic not found. Did you \"drbdadm create-md\"?\n");
                rv = ERR_MD_INVALID;
                goto err;
        }
        if (be32_to_cpu(buffer->al_offset) != bdev->md.al_offset) {
                dev_err(DEV, "unexpected al_offset: %d (expected %d)\n",
                    be32_to_cpu(buffer->al_offset), bdev->md.al_offset);
                rv = ERR_MD_INVALID;
                goto err;
        }
        if (be32_to_cpu(buffer->bm_offset) != bdev->md.bm_offset) {
                dev_err(DEV, "unexpected bm_offset: %d (expected %d)\n",
                    be32_to_cpu(buffer->bm_offset), bdev->md.bm_offset);
                rv = ERR_MD_INVALID;
                goto err;
        }
        if (be32_to_cpu(buffer->md_size_sect) != bdev->md.md_size_sect) {
                dev_err(DEV, "unexpected md_size: %u (expected %u)\n",
                    be32_to_cpu(buffer->md_size_sect), bdev->md.md_size_sect);
                rv = ERR_MD_INVALID;
                goto err;
        }

        if (be32_to_cpu(buffer->bm_bytes_per_bit) != BM_BLOCK_SIZE) {
                dev_err(DEV, "unexpected bm_bytes_per_bit: %u (expected %u)\n",
                    be32_to_cpu(buffer->bm_bytes_per_bit), BM_BLOCK_SIZE);
                rv = ERR_MD_INVALID;
                goto err;
        }

        bdev->md.la_size_sect = be64_to_cpu(buffer->la_size);
        for (i = UI_CURRENT; i < UI_SIZE; i++)
                bdev->md.uuid[i] = be64_to_cpu(buffer->uuid[i]);
        bdev->md.flags = be32_to_cpu(buffer->flags);
        bdev->md.device_uuid = be64_to_cpu(buffer->device_uuid);

        spin_lock_irq(&mdev->tconn->req_lock);
        if (mdev->state.conn < C_CONNECTED) {
                int peer;
                peer = be32_to_cpu(buffer->la_peer_max_bio_size);
                peer = max_t(int, peer, DRBD_MAX_BIO_SIZE_SAFE);
                mdev->peer_max_bio_size = peer;
        }
        spin_unlock_irq(&mdev->tconn->req_lock);

 err:
        drbd_md_put_buffer(mdev);
 out:
        put_ldev(mdev);

        return rv;
}

/**
 * drbd_md_mark_dirty() - Mark meta data super block as dirty
 * @mdev:       DRBD device.
 *
 * Call this function if you change anything that should be written to
 * the meta-data super block. This function sets MD_DIRTY, and starts a
 * timer that ensures that within five seconds you have to call drbd_md_sync().
 */
#ifdef DEBUG
void drbd_md_mark_dirty_(struct drbd_conf *mdev, unsigned int line, const char *func)
{
        if (!test_and_set_bit(MD_DIRTY, &mdev->flags)) {
                mod_timer(&mdev->md_sync_timer, jiffies + HZ);
                mdev->last_md_mark_dirty.line = line;
                mdev->last_md_mark_dirty.func = func;
        }
}
#else
void drbd_md_mark_dirty(struct drbd_conf *mdev)
{
        if (!test_and_set_bit(MD_DIRTY, &mdev->flags))
                mod_timer(&mdev->md_sync_timer, jiffies + 5*HZ);
}
#endif

static void drbd_uuid_move_history(struct drbd_conf *mdev) __must_hold(local)
{
        int i;

        for (i = UI_HISTORY_START; i < UI_HISTORY_END; i++)
                mdev->ldev->md.uuid[i+1] = mdev->ldev->md.uuid[i];
}

void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
{
        if (idx == UI_CURRENT) {
                if (mdev->state.role == R_PRIMARY)
                        val |= 1;
                else
                        val &= ~((u64)1);

                drbd_set_ed_uuid(mdev, val);
        }

        mdev->ldev->md.uuid[idx] = val;
        drbd_md_mark_dirty(mdev);
}


void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
{
        if (mdev->ldev->md.uuid[idx]) {
                drbd_uuid_move_history(mdev);
                mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[idx];
        }
        _drbd_uuid_set(mdev, idx, val);
}

/**
 * drbd_uuid_new_current() - Creates a new current UUID
 * @mdev:       DRBD device.
 *
 * Creates a new current UUID, and rotates the old current UUID into
 * the bitmap slot. Causes an incremental resync upon next connect.
 */
void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local)
{
        u64 val;
        unsigned long long bm_uuid = mdev->ldev->md.uuid[UI_BITMAP];

        if (bm_uuid)
                dev_warn(DEV, "bm UUID was already set: %llX\n", bm_uuid);

        mdev->ldev->md.uuid[UI_BITMAP] = mdev->ldev->md.uuid[UI_CURRENT];

        get_random_bytes(&val, sizeof(u64));
        _drbd_uuid_set(mdev, UI_CURRENT, val);
        drbd_print_uuids(mdev, "new current UUID");
        /* get it to stable storage _now_ */
        drbd_md_sync(mdev);
}

void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local)
{
        if (mdev->ldev->md.uuid[UI_BITMAP] == 0 && val == 0)
                return;

        if (val == 0) {
                drbd_uuid_move_history(mdev);
                mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[UI_BITMAP];
                mdev->ldev->md.uuid[UI_BITMAP] = 0;
        } else {
                unsigned long long bm_uuid = mdev->ldev->md.uuid[UI_BITMAP];
                if (bm_uuid)
                        dev_warn(DEV, "bm UUID was already set: %llX\n", bm_uuid);

                mdev->ldev->md.uuid[UI_BITMAP] = val & ~((u64)1);
        }
        drbd_md_mark_dirty(mdev);
}

/**
 * drbd_bmio_set_n_write() - io_fn for drbd_queue_bitmap_io() or drbd_bitmap_io()
 * @mdev:       DRBD device.
 *
 * Sets all bits in the bitmap and writes the whole bitmap to stable storage.
 */
int drbd_bmio_set_n_write(struct drbd_conf *mdev)
{
        int rv = -EIO;

        if (get_ldev_if_state(mdev, D_ATTACHING)) {
                drbd_md_set_flag(mdev, MDF_FULL_SYNC);
                drbd_md_sync(mdev);
                drbd_bm_set_all(mdev);

                rv = drbd_bm_write(mdev);

                if (!rv) {
                        drbd_md_clear_flag(mdev, MDF_FULL_SYNC);
                        drbd_md_sync(mdev);
                }

                put_ldev(mdev);
        }

        return rv;
}

/**
 * drbd_bmio_clear_n_write() - io_fn for drbd_queue_bitmap_io() or drbd_bitmap_io()
 * @mdev:       DRBD device.
 *
 * Clears all bits in the bitmap and writes the whole bitmap to stable storage.
 */
int drbd_bmio_clear_n_write(struct drbd_conf *mdev)
{
        int rv = -EIO;

        drbd_resume_al(mdev);
        if (get_ldev_if_state(mdev, D_ATTACHING)) {
                drbd_bm_clear_all(mdev);
                rv = drbd_bm_write(mdev);
                put_ldev(mdev);
        }

        return rv;
}

static int w_bitmap_io(struct drbd_work *w, int unused)
{
        struct bm_io_work *work = container_of(w, struct bm_io_work, w);
        struct drbd_conf *mdev = w->mdev;
        int rv = -EIO;

        D_ASSERT(atomic_read(&mdev->ap_bio_cnt) == 0);

        if (get_ldev(mdev)) {
                drbd_bm_lock(mdev, work->why, work->flags);
                rv = work->io_fn(mdev);
                drbd_bm_unlock(mdev);
                put_ldev(mdev);
        }

        clear_bit_unlock(BITMAP_IO, &mdev->flags);
        wake_up(&mdev->misc_wait);

        if (work->done)
                work->done(mdev, rv);

        clear_bit(BITMAP_IO_QUEUED, &mdev->flags);
        work->why = NULL;
        work->flags = 0;

        return 0;
}

void drbd_ldev_destroy(struct drbd_conf *mdev)
{
        lc_destroy(mdev->resync);
        mdev->resync = NULL;
        lc_destroy(mdev->act_log);
        mdev->act_log = NULL;
        __no_warn(local,
                drbd_free_bc(mdev->ldev);
                mdev->ldev = NULL;);

        clear_bit(GO_DISKLESS, &mdev->flags);
}

static int w_go_diskless(struct drbd_work *w, int unused)
{
        struct drbd_conf *mdev = w->mdev;

        D_ASSERT(mdev->state.disk == D_FAILED);
        /* we cannot assert local_cnt == 0 here, as get_ldev_if_state will
         * inc/dec it frequently. Once we are D_DISKLESS, no one will touch
         * the protected members anymore, though, so once put_ldev reaches zero
         * again, it will be safe to free them. */
        drbd_force_state(mdev, NS(disk, D_DISKLESS));
        return 0;
}

void drbd_go_diskless(struct drbd_conf *mdev)
{
        D_ASSERT(mdev->state.disk == D_FAILED);
        if (!test_and_set_bit(GO_DISKLESS, &mdev->flags))
                drbd_queue_work(&mdev->tconn->sender_work, &mdev->go_diskless);
}

/**
 * drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
 * @mdev:       DRBD device.
 * @io_fn:      IO callback to be called when bitmap IO is possible
 * @done:       callback to be called after the bitmap IO was performed
 * @why:        Descriptive text of the reason for doing the IO
 *
 * While IO on the bitmap happens we freeze application IO thus we ensure
 * that drbd_set_out_of_sync() can not be called. This function MAY ONLY be
 * called from worker context. It MUST NOT be used while a previous such
 * work is still pending!
 */
void drbd_queue_bitmap_io(struct drbd_conf *mdev,
                          int (*io_fn)(struct drbd_conf *),
                          void (*done)(struct drbd_conf *, int),
                          char *why, enum bm_flag flags)
{
        D_ASSERT(current == mdev->tconn->worker.task);

        D_ASSERT(!test_bit(BITMAP_IO_QUEUED, &mdev->flags));
        D_ASSERT(!test_bit(BITMAP_IO, &mdev->flags));
        D_ASSERT(list_empty(&mdev->bm_io_work.w.list));
        if (mdev->bm_io_work.why)
                dev_err(DEV, "FIXME going to queue '%s' but '%s' still pending?\n",
                        why, mdev->bm_io_work.why);

        mdev->bm_io_work.io_fn = io_fn;
        mdev->bm_io_work.done = done;
        mdev->bm_io_work.why = why;
        mdev->bm_io_work.flags = flags;

        spin_lock_irq(&mdev->tconn->req_lock);
        set_bit(BITMAP_IO, &mdev->flags);
        if (atomic_read(&mdev->ap_bio_cnt) == 0) {
                if (!test_and_set_bit(BITMAP_IO_QUEUED, &mdev->flags))
                        drbd_queue_work(&mdev->tconn->sender_work, &mdev->bm_io_work.w);
        }
        spin_unlock_irq(&mdev->tconn->req_lock);
}

/**
 * drbd_bitmap_io() -  Does an IO operation on the whole bitmap
 * @mdev:       DRBD device.
 * @io_fn:      IO callback to be called when bitmap IO is possible
 * @why:        Descriptive text of the reason for doing the IO
 *
 * freezes application IO while that the actual IO operations runs. This
 * functions MAY NOT be called from worker context.
 */
int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *),
                char *why, enum bm_flag flags)
{
        int rv;

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

        if ((flags & BM_LOCKED_SET_ALLOWED) == 0)
                drbd_suspend_io(mdev);

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

        if ((flags & BM_LOCKED_SET_ALLOWED) == 0)
                drbd_resume_io(mdev);

        return rv;
}

void drbd_md_set_flag(struct drbd_conf *mdev, int flag) __must_hold(local)
{
        if ((mdev->ldev->md.flags & flag) != flag) {
                drbd_md_mark_dirty(mdev);
                mdev->ldev->md.flags |= flag;
        }
}

void drbd_md_clear_flag(struct drbd_conf *mdev, int flag) __must_hold(local)
{
        if ((mdev->ldev->md.flags & flag) != 0) {
                drbd_md_mark_dirty(mdev);
                mdev->ldev->md.flags &= ~flag;
        }
}
int drbd_md_test_flag(struct drbd_backing_dev *bdev, int flag)
{
        return (bdev->md.flags & flag) != 0;
}

static void md_sync_timer_fn(unsigned long data)
{
        struct drbd_conf *mdev = (struct drbd_conf *) data;

        drbd_queue_work_front(&mdev->tconn->sender_work, &mdev->md_sync_work);
}

static int w_md_sync(struct drbd_work *w, int unused)
{
        struct drbd_conf *mdev = w->mdev;

        dev_warn(DEV, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
#ifdef DEBUG
        dev_warn(DEV, "last md_mark_dirty: %s:%u\n",
                mdev->last_md_mark_dirty.func, mdev->last_md_mark_dirty.line);
#endif
        drbd_md_sync(mdev);
        return 0;
}

const char *cmdname(enum drbd_packet cmd)
{
        /* THINK may need to become several global tables
         * when we want to support more than
         * one PRO_VERSION */
        static const char *cmdnames[] = {
                [P_DATA]                = "Data",
                [P_DATA_REPLY]          = "DataReply",
                [P_RS_DATA_REPLY]       = "RSDataReply",
                [P_BARRIER]             = "Barrier",
                [P_BITMAP]              = "ReportBitMap",
                [P_BECOME_SYNC_TARGET]  = "BecomeSyncTarget",
                [P_BECOME_SYNC_SOURCE]  = "BecomeSyncSource",
                [P_UNPLUG_REMOTE]       = "UnplugRemote",
                [P_DATA_REQUEST]        = "DataRequest",
                [P_RS_DATA_REQUEST]     = "RSDataRequest",
                [P_SYNC_PARAM]          = "SyncParam",
                [P_SYNC_PARAM89]        = "SyncParam89",
                [P_PROTOCOL]            = "ReportProtocol",
                [P_UUIDS]               = "ReportUUIDs",
                [P_SIZES]               = "ReportSizes",
                [P_STATE]               = "ReportState",
                [P_SYNC_UUID]           = "ReportSyncUUID",
                [P_AUTH_CHALLENGE]      = "AuthChallenge",
                [P_AUTH_RESPONSE]       = "AuthResponse",
                [P_PING]                = "Ping",
                [P_PING_ACK]            = "PingAck",
                [P_RECV_ACK]            = "RecvAck",
                [P_WRITE_ACK]           = "WriteAck",
                [P_RS_WRITE_ACK]        = "RSWriteAck",
                [P_DISCARD_WRITE]        = "DiscardWrite",
                [P_NEG_ACK]             = "NegAck",
                [P_NEG_DREPLY]          = "NegDReply",
                [P_NEG_RS_DREPLY]       = "NegRSDReply",
                [P_BARRIER_ACK]         = "BarrierAck",
                [P_STATE_CHG_REQ]       = "StateChgRequest",
                [P_STATE_CHG_REPLY]     = "StateChgReply",
                [P_OV_REQUEST]          = "OVRequest",
                [P_OV_REPLY]            = "OVReply",
                [P_OV_RESULT]           = "OVResult",
                [P_CSUM_RS_REQUEST]     = "CsumRSRequest",
                [P_RS_IS_IN_SYNC]       = "CsumRSIsInSync",
                [P_COMPRESSED_BITMAP]   = "CBitmap",
                [P_DELAY_PROBE]         = "DelayProbe",
                [P_OUT_OF_SYNC]         = "OutOfSync",
                [P_RETRY_WRITE]         = "RetryWrite",
                [P_RS_CANCEL]           = "RSCancel",
                [P_CONN_ST_CHG_REQ]     = "conn_st_chg_req",
                [P_CONN_ST_CHG_REPLY]   = "conn_st_chg_reply",
                [P_RETRY_WRITE]         = "retry_write",
                [P_PROTOCOL_UPDATE]     = "protocol_update",

                /* enum drbd_packet, but not commands - obsoleted flags:
                 *      P_MAY_IGNORE
                 *      P_MAX_OPT_CMD
                 */
        };

        /* too big for the array: 0xfffX */
        if (cmd == P_INITIAL_META)
                return "InitialMeta";
        if (cmd == P_INITIAL_DATA)
                return "InitialData";
        if (cmd == P_CONNECTION_FEATURES)
                return "ConnectionFeatures";
        if (cmd >= ARRAY_SIZE(cmdnames))
                return "Unknown";
        return cmdnames[cmd];
}

/**
 * drbd_wait_misc  -  wait for a request to make progress
 * @mdev:       device associated with the request
 * @i:          the struct drbd_interval embedded in struct drbd_request or
 *              struct drbd_peer_request
 */
int drbd_wait_misc(struct drbd_conf *mdev, struct drbd_interval *i)
{
        struct net_conf *nc;
        DEFINE_WAIT(wait);
        long timeout;

        rcu_read_lock();
        nc = rcu_dereference(mdev->tconn->net_conf);
        if (!nc) {
                rcu_read_unlock();
                return -ETIMEDOUT;
        }
        timeout = nc->ko_count ? nc->timeout * HZ / 10 * nc->ko_count : MAX_SCHEDULE_TIMEOUT;
        rcu_read_unlock();

        /* Indicate to wake up mdev->misc_wait on progress.  */
        i->waiting = true;
        prepare_to_wait(&mdev->misc_wait, &wait, TASK_INTERRUPTIBLE);
        spin_unlock_irq(&mdev->tconn->req_lock);
        timeout = schedule_timeout(timeout);
        finish_wait(&mdev->misc_wait, &wait);
        spin_lock_irq(&mdev->tconn->req_lock);
        if (!timeout || mdev->state.conn < C_CONNECTED)
                return -ETIMEDOUT;
        if (signal_pending(current))
                return -ERESTARTSYS;
        return 0;
}

#ifdef CONFIG_DRBD_FAULT_INJECTION
/* Fault insertion support including random number generator shamelessly
 * stolen from kernel/rcutorture.c */
struct fault_random_state {
        unsigned long state;
        unsigned long count;
};

#define FAULT_RANDOM_MULT 39916801  /* prime */
#define FAULT_RANDOM_ADD        479001701 /* prime */
#define FAULT_RANDOM_REFRESH 10000

/*
 * Crude but fast random-number generator.  Uses a linear congruential
 * generator, with occasional help from get_random_bytes().
 */
static unsigned long
_drbd_fault_random(struct fault_random_state *rsp)
{
        long refresh;

        if (!rsp->count--) {
                get_random_bytes(&refresh, sizeof(refresh));
                rsp->state += refresh;
                rsp->count = FAULT_RANDOM_REFRESH;
        }
        rsp->state = rsp->state * FAULT_RANDOM_MULT + FAULT_RANDOM_ADD;
        return swahw32(rsp->state);
}

static char *
_drbd_fault_str(unsigned int type) {
        static char *_faults[] = {
                [DRBD_FAULT_MD_WR] = "Meta-data write",
                [DRBD_FAULT_MD_RD] = "Meta-data read",
                [DRBD_FAULT_RS_WR] = "Resync write",
                [DRBD_FAULT_RS_RD] = "Resync read",
                [DRBD_FAULT_DT_WR] = "Data write",
                [DRBD_FAULT_DT_RD] = "Data read",
                [DRBD_FAULT_DT_RA] = "Data read ahead",
                [DRBD_FAULT_BM_ALLOC] = "BM allocation",
                [DRBD_FAULT_AL_EE] = "EE allocation",
                [DRBD_FAULT_RECEIVE] = "receive data corruption",
        };

        return (type < DRBD_FAULT_MAX) ? _faults[type] : "**Unknown**";
}

unsigned int
_drbd_insert_fault(struct drbd_conf *mdev, unsigned int type)
{
        static struct fault_random_state rrs = {0, 0};

        unsigned int ret = (
                (fault_devs == 0 ||
                        ((1 << mdev_to_minor(mdev)) & fault_devs) != 0) &&
                (((_drbd_fault_random(&rrs) % 100) + 1) <= fault_rate));

        if (ret) {
                fault_count++;

                if (__ratelimit(&drbd_ratelimit_state))
                        dev_warn(DEV, "***Simulating %s failure\n",
                                _drbd_fault_str(type));
        }

        return ret;
}
#endif

const char *drbd_buildtag(void)
{
        /* DRBD built from external sources has here a reference to the
           git hash of the source code. */

        static char buildtag[38] = "\0uilt-in";

        if (buildtag[0] == 0) {
#ifdef CONFIG_MODULES
                if (THIS_MODULE != NULL)
                        sprintf(buildtag, "srcversion: %-24s", THIS_MODULE->srcversion);
                else
#endif
                        buildtag[0] = 'b';
        }

        return buildtag;
}

module_init(drbd_init)
module_exit(drbd_cleanup)

EXPORT_SYMBOL(drbd_conn_str);
EXPORT_SYMBOL(drbd_role_str);
EXPORT_SYMBOL(drbd_disk_str);
EXPORT_SYMBOL(drbd_set_st_err_str);