Moved, renamed, and deleted files

The original directory structure was scattered and unorganized.
Changes are basically to make it look like kernel structure.

1 files changed, 4203 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
new file mode 100644
index 00000000..211fc44f
--- /dev/null
+++ b/drivers/block/drbd/drbd_main.c
@@ -0,0 +1,4203 @@
+/*
+   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"
+
+struct after_state_chg_work {
+	struct drbd_work w;
+	union drbd_state os;
+	union drbd_state ns;
+	enum chg_state_flags flags;
+	struct completion *done;
+};
+
+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_after_state_ch(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
+			   union drbd_state ns, enum chg_state_flags flags);
+static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void md_sync_timer_fn(unsigned long data);
+static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static int w_go_diskless(struct drbd_conf *mdev, 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, "Maximum 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(cn_idx, uint, 0444);
+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;
+bool disable_sendpage;
+bool allow_oos;
+unsigned int cn_idx = CN_IDX_DRBD;
+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 drbd_conf **minor_table;
+
+struct kmem_cache *drbd_request_cache;
+struct kmem_cache *drbd_ee_cache;	/* epoch entries */
+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;
+
+/* 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,
+};
+
+#define ARRY_SIZE(A) (sizeof(A)/sizeof(A[0]))
+
+#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
+
+/**
+ * DOC: The transfer log
+ *
+ * The transfer log is a single linked list of &struct drbd_tl_epoch objects.
+ * mdev->newest_tle points to the head, mdev->oldest_tle points to the tail
+ * of the list. There is always at least one &struct drbd_tl_epoch object.
+ *
+ * Each &struct drbd_tl_epoch has a circular double linked list of requests
+ * attached.
+ */
+static int tl_init(struct drbd_conf *mdev)
+{
+	struct drbd_tl_epoch *b;
+
+	/* during device minor initialization, we may well use GFP_KERNEL */
+	b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_KERNEL);
+	if (!b)
+		return 0;
+	INIT_LIST_HEAD(&b->requests);
+	INIT_LIST_HEAD(&b->w.list);
+	b->next = NULL;
+	b->br_number = 4711;
+	b->n_writes = 0;
+	b->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
+
+	mdev->oldest_tle = b;
+	mdev->newest_tle = b;
+	INIT_LIST_HEAD(&mdev->out_of_sequence_requests);
+
+	mdev->tl_hash = NULL;
+	mdev->tl_hash_s = 0;
+
+	return 1;
+}
+
+static void tl_cleanup(struct drbd_conf *mdev)
+{
+	D_ASSERT(mdev->oldest_tle == mdev->newest_tle);
+	D_ASSERT(list_empty(&mdev->out_of_sequence_requests));
+	kfree(mdev->oldest_tle);
+	mdev->oldest_tle = NULL;
+	kfree(mdev->unused_spare_tle);
+	mdev->unused_spare_tle = NULL;
+	kfree(mdev->tl_hash);
+	mdev->tl_hash = NULL;
+	mdev->tl_hash_s = 0;
+}
+
+/**
+ * _tl_add_barrier() - Adds a barrier to the transfer log
+ * @mdev:	DRBD device.
+ * @new:	Barrier to be added before the current head of the TL.
+ *
+ * The caller must hold the req_lock.
+ */
+void _tl_add_barrier(struct drbd_conf *mdev, struct drbd_tl_epoch *new)
+{
+	struct drbd_tl_epoch *newest_before;
+
+	INIT_LIST_HEAD(&new->requests);
+	INIT_LIST_HEAD(&new->w.list);
+	new->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
+	new->next = NULL;
+	new->n_writes = 0;
+
+	newest_before = mdev->newest_tle;
+	/* never send a barrier number == 0, because that is special-cased
+	 * when using TCQ for our write ordering code */
+	new->br_number = (newest_before->br_number+1) ?: 1;
+	if (mdev->newest_tle != new) {
+		mdev->newest_tle->next = new;
+		mdev->newest_tle = new;
+	}
+}
+
+/**
+ * tl_release() - Free or recycle the oldest &struct drbd_tl_epoch object of the TL
+ * @mdev:	DRBD device.
+ * @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
+ * &struct drbd_tl_epoch objects this function will cause a termination
+ * of the connection.
+ */
+void tl_release(struct drbd_conf *mdev, unsigned int barrier_nr,
+		       unsigned int set_size)
+{
+	struct drbd_tl_epoch *b, *nob; /* next old barrier */
+	struct list_head *le, *tle;
+	struct drbd_request *r;
+
+	spin_lock_irq(&mdev->req_lock);
+
+	b = mdev->oldest_tle;
+
+	/* first some paranoia code */
+	if (b == NULL) {
+		dev_err(DEV, "BAD! BarrierAck #%u received, but no epoch in tl!?\n",
+			barrier_nr);
+		goto bail;
+	}
+	if (b->br_number != barrier_nr) {
+		dev_err(DEV, "BAD! BarrierAck #%u received, expected #%u!\n",
+			barrier_nr, b->br_number);
+		goto bail;
+	}
+	if (b->n_writes != set_size) {
+		dev_err(DEV, "BAD! BarrierAck #%u received with n_writes=%u, expected n_writes=%u!\n",
+			barrier_nr, set_size, b->n_writes);
+		goto bail;
+	}
+
+	/* Clean up list of requests processed during current epoch */
+	list_for_each_safe(le, tle, &b->requests) {
+		r = list_entry(le, struct drbd_request, tl_requests);
+		_req_mod(r, barrier_acked);
+	}
+	/* There could be requests on the list waiting for completion
+	   of the write to the local disk. To avoid corruptions of
+	   slab's data structures we have to remove the lists head.
+
+	   Also there could have been a barrier ack out of sequence, overtaking
+	   the write acks - which would be a bug and violating write ordering.
+	   To not deadlock in case we lose connection while such requests are
+	   still pending, we need some way to find them for the
+	   _req_mode(connection_lost_while_pending).
+
+	   These have been list_move'd to the out_of_sequence_requests list in
+	   _req_mod(, barrier_acked) above.
+	   */
+	list_del_init(&b->requests);
+
+	nob = b->next;
+	if (test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
+		_tl_add_barrier(mdev, b);
+		if (nob)
+			mdev->oldest_tle = nob;
+		/* if nob == NULL b was the only barrier, and becomes the new
+		   barrier. Therefore mdev->oldest_tle points already to b */
+	} else {
+		D_ASSERT(nob != NULL);
+		mdev->oldest_tle = nob;
+		kfree(b);
+	}
+
+	spin_unlock_irq(&mdev->req_lock);
+	dec_ap_pending(mdev);
+
+	return;
+
+bail:
+	spin_unlock_irq(&mdev->req_lock);
+	drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+}
+
+
+/**
+ * _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.
+ */
+static void _tl_restart(struct drbd_conf *mdev, enum drbd_req_event what)
+{
+	struct drbd_tl_epoch *b, *tmp, **pn;
+	struct list_head *le, *tle, carry_reads;
+	struct drbd_request *req;
+	int rv, n_writes, n_reads;
+
+	b = mdev->oldest_tle;
+	pn = &mdev->oldest_tle;
+	while (b) {
+		n_writes = 0;
+		n_reads = 0;
+		INIT_LIST_HEAD(&carry_reads);
+		list_for_each_safe(le, tle, &b->requests) {
+			req = list_entry(le, struct drbd_request, tl_requests);
+			rv = _req_mod(req, what);
+
+			n_writes += (rv & MR_WRITE) >> MR_WRITE_SHIFT;
+			n_reads  += (rv & MR_READ) >> MR_READ_SHIFT;
+		}
+		tmp = b->next;
+
+		if (n_writes) {
+			if (what == resend) {
+				b->n_writes = n_writes;
+				if (b->w.cb == NULL) {
+					b->w.cb = w_send_barrier;
+					inc_ap_pending(mdev);
+					set_bit(CREATE_BARRIER, &mdev->flags);
+				}
+
+				drbd_queue_work(&mdev->data.work, &b->w);
+			}
+			pn = &b->next;
+		} else {
+			if (n_reads)
+				list_add(&carry_reads, &b->requests);
+			/* there could still be requests on that ring list,
+			 * in case local io is still pending */
+			list_del(&b->requests);
+
+			/* dec_ap_pending corresponding to queue_barrier.
+			 * the newest barrier may not have been queued yet,
+			 * in which case w.cb is still NULL. */
+			if (b->w.cb != NULL)
+				dec_ap_pending(mdev);
+
+			if (b == mdev->newest_tle) {
+				/* recycle, but reinit! */
+				D_ASSERT(tmp == NULL);
+				INIT_LIST_HEAD(&b->requests);
+				list_splice(&carry_reads, &b->requests);
+				INIT_LIST_HEAD(&b->w.list);
+				b->w.cb = NULL;
+				b->br_number = net_random();
+				b->n_writes = 0;
+
+				*pn = b;
+				break;
+			}
+			*pn = tmp;
+			kfree(b);
+		}
+		b = tmp;
+		list_splice(&carry_reads, &b->requests);
+	}
+}
+
+
+/**
+ * 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_conf *mdev)
+{
+	struct list_head *le, *tle;
+	struct drbd_request *r;
+
+	spin_lock_irq(&mdev->req_lock);
+
+	_tl_restart(mdev, connection_lost_while_pending);
+
+	/* we expect this list to be empty. */
+	D_ASSERT(list_empty(&mdev->out_of_sequence_requests));
+
+	/* but just in case, clean it up anyways! */
+	list_for_each_safe(le, tle, &mdev->out_of_sequence_requests) {
+		r = list_entry(le, struct drbd_request, tl_requests);
+		/* It would be nice to complete outside of spinlock.
+		 * But this is easier for now. */
+		_req_mod(r, connection_lost_while_pending);
+	}
+
+	/* ensure bit indicating barrier is required is clear */
+	clear_bit(CREATE_BARRIER, &mdev->flags);
+
+	memset(mdev->app_reads_hash, 0, APP_R_HSIZE*sizeof(void *));
+
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+void tl_restart(struct drbd_conf *mdev, enum drbd_req_event what)
+{
+	spin_lock_irq(&mdev->req_lock);
+	_tl_restart(mdev, what);
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+/**
+ * cl_wide_st_chg() - true if the state change is a cluster wide one
+ * @mdev:	DRBD device.
+ * @os:		old (current) state.
+ * @ns:		new (wanted) state.
+ */
+static int cl_wide_st_chg(struct drbd_conf *mdev,
+			  union drbd_state os, union drbd_state ns)
+{
+	return (os.conn >= C_CONNECTED && ns.conn >= C_CONNECTED &&
+		 ((os.role != R_PRIMARY && ns.role == R_PRIMARY) ||
+		  (os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+		  (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S) ||
+		  (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))) ||
+		(os.conn >= C_CONNECTED && ns.conn == C_DISCONNECTING) ||
+		(os.conn == C_CONNECTED && ns.conn == C_VERIFY_S);
+}
+
+enum drbd_state_rv
+drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
+		  union drbd_state mask, union drbd_state val)
+{
+	unsigned long flags;
+	union drbd_state os, ns;
+	enum drbd_state_rv rv;
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	os = mdev->state;
+	ns.i = (os.i & ~mask.i) | val.i;
+	rv = _drbd_set_state(mdev, ns, f, NULL);
+	ns = mdev->state;
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	return rv;
+}
+
+/**
+ * drbd_force_state() - Impose a change which happens outside our control on our state
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ */
+void drbd_force_state(struct drbd_conf *mdev,
+	union drbd_state mask, union drbd_state val)
+{
+	drbd_change_state(mdev, CS_HARD, mask, val);
+}
+
+static enum drbd_state_rv is_valid_state(struct drbd_conf *, union drbd_state);
+static enum drbd_state_rv is_valid_state_transition(struct drbd_conf *,
+						    union drbd_state,
+						    union drbd_state);
+static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
+				       union drbd_state ns, const char **warn_sync_abort);
+int drbd_send_state_req(struct drbd_conf *,
+			union drbd_state, union drbd_state);
+
+static enum drbd_state_rv
+_req_st_cond(struct drbd_conf *mdev, union drbd_state mask,
+	     union drbd_state val)
+{
+	union drbd_state os, ns;
+	unsigned long flags;
+	enum drbd_state_rv rv;
+
+	if (test_and_clear_bit(CL_ST_CHG_SUCCESS, &mdev->flags))
+		return SS_CW_SUCCESS;
+
+	if (test_and_clear_bit(CL_ST_CHG_FAIL, &mdev->flags))
+		return SS_CW_FAILED_BY_PEER;
+
+	rv = 0;
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	os = mdev->state;
+	ns.i = (os.i & ~mask.i) | val.i;
+	ns = sanitize_state(mdev, os, ns, NULL);
+
+	if (!cl_wide_st_chg(mdev, os, ns))
+		rv = SS_CW_NO_NEED;
+	if (!rv) {
+		rv = is_valid_state(mdev, ns);
+		if (rv == SS_SUCCESS) {
+			rv = is_valid_state_transition(mdev, ns, os);
+			if (rv == SS_SUCCESS)
+				rv = SS_UNKNOWN_ERROR; /* cont waiting, otherwise fail. */
+		}
+	}
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	return rv;
+}
+
+/**
+ * drbd_req_state() - Perform an eventually cluster wide state change
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ * @f:		flags
+ *
+ * Should not be called directly, use drbd_request_state() or
+ * _drbd_request_state().
+ */
+static enum drbd_state_rv
+drbd_req_state(struct drbd_conf *mdev, union drbd_state mask,
+	       union drbd_state val, enum chg_state_flags f)
+{
+	struct completion done;
+	unsigned long flags;
+	union drbd_state os, ns;
+	enum drbd_state_rv rv;
+
+	init_completion(&done);
+
+	if (f & CS_SERIALIZE)
+		mutex_lock(&mdev->state_mutex);
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	os = mdev->state;
+	ns.i = (os.i & ~mask.i) | val.i;
+	ns = sanitize_state(mdev, os, ns, NULL);
+
+	if (cl_wide_st_chg(mdev, os, ns)) {
+		rv = is_valid_state(mdev, ns);
+		if (rv == SS_SUCCESS)
+			rv = is_valid_state_transition(mdev, ns, os);
+		spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+		if (rv < SS_SUCCESS) {
+			if (f & CS_VERBOSE)
+				print_st_err(mdev, os, ns, rv);
+			goto abort;
+		}
+
+		drbd_state_lock(mdev);
+		if (!drbd_send_state_req(mdev, mask, val)) {
+			drbd_state_unlock(mdev);
+			rv = SS_CW_FAILED_BY_PEER;
+			if (f & CS_VERBOSE)
+				print_st_err(mdev, os, ns, rv);
+			goto abort;
+		}
+
+		wait_event(mdev->state_wait,
+			(rv = _req_st_cond(mdev, mask, val)));
+
+		if (rv < SS_SUCCESS) {
+			drbd_state_unlock(mdev);
+			if (f & CS_VERBOSE)
+				print_st_err(mdev, os, ns, rv);
+			goto abort;
+		}
+		spin_lock_irqsave(&mdev->req_lock, flags);
+		os = mdev->state;
+		ns.i = (os.i & ~mask.i) | val.i;
+		rv = _drbd_set_state(mdev, ns, f, &done);
+		drbd_state_unlock(mdev);
+	} else {
+		rv = _drbd_set_state(mdev, ns, f, &done);
+	}
+
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	if (f & CS_WAIT_COMPLETE && rv == SS_SUCCESS) {
+		D_ASSERT(current != mdev->worker.task);
+		wait_for_completion(&done);
+	}
+
+abort:
+	if (f & CS_SERIALIZE)
+		mutex_unlock(&mdev->state_mutex);
+
+	return rv;
+}
+
+/**
+ * _drbd_request_state() - Request a state change (with flags)
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ * @f:		flags
+ *
+ * Cousin of drbd_request_state(), useful with the CS_WAIT_COMPLETE
+ * flag, or when logging of failed state change requests is not desired.
+ */
+enum drbd_state_rv
+_drbd_request_state(struct drbd_conf *mdev, union drbd_state mask,
+		    union drbd_state val, enum chg_state_flags f)
+{
+	enum drbd_state_rv rv;
+
+	wait_event(mdev->state_wait,
+		   (rv = drbd_req_state(mdev, mask, val, f)) != SS_IN_TRANSIENT_STATE);
+
+	return rv;
+}
+
+static void print_st(struct drbd_conf *mdev, char *name, union drbd_state ns)
+{
+	dev_err(DEV, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c }\n",
+	    name,
+	    drbd_conn_str(ns.conn),
+	    drbd_role_str(ns.role),
+	    drbd_role_str(ns.peer),
+	    drbd_disk_str(ns.disk),
+	    drbd_disk_str(ns.pdsk),
+	    is_susp(ns) ? 's' : 'r',
+	    ns.aftr_isp ? 'a' : '-',
+	    ns.peer_isp ? 'p' : '-',
+	    ns.user_isp ? 'u' : '-'
+	    );
+}
+
+void print_st_err(struct drbd_conf *mdev, union drbd_state os,
+	          union drbd_state ns, enum drbd_state_rv err)
+{
+	if (err == SS_IN_TRANSIENT_STATE)
+		return;
+	dev_err(DEV, "State change failed: %s\n", drbd_set_st_err_str(err));
+	print_st(mdev, " state", os);
+	print_st(mdev, "wanted", ns);
+}
+
+
+/**
+ * is_valid_state() - Returns an SS_ error code if ns is not valid
+ * @mdev:	DRBD device.
+ * @ns:		State to consider.
+ */
+static enum drbd_state_rv
+is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
+{
+	/* See drbd_state_sw_errors in drbd_strings.c */
+
+	enum drbd_fencing_p fp;
+	enum drbd_state_rv rv = SS_SUCCESS;
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	if (get_net_conf(mdev)) {
+		if (!mdev->net_conf->two_primaries &&
+		    ns.role == R_PRIMARY && ns.peer == R_PRIMARY)
+			rv = SS_TWO_PRIMARIES;
+		put_net_conf(mdev);
+	}
+
+	if (rv <= 0)
+		/* already found a reason to abort */;
+	else if (ns.role == R_SECONDARY && mdev->open_cnt)
+		rv = SS_DEVICE_IN_USE;
+
+	else if (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.disk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if (fp >= FP_RESOURCE &&
+		 ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk >= D_UNKNOWN)
+		rv = SS_PRIMARY_NOP;
+
+	else if (ns.role == R_PRIMARY && ns.disk <= D_INCONSISTENT && ns.pdsk <= D_INCONSISTENT)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.disk < D_INCONSISTENT)
+		rv = SS_NO_LOCAL_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.pdsk < D_INCONSISTENT)
+		rv = SS_NO_REMOTE_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if ((ns.conn == C_CONNECTED ||
+		  ns.conn == C_WF_BITMAP_S ||
+		  ns.conn == C_SYNC_SOURCE ||
+		  ns.conn == C_PAUSED_SYNC_S) &&
+		  ns.disk == D_OUTDATED)
+		rv = SS_CONNECTED_OUTDATES;
+
+	else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+		 (mdev->sync_conf.verify_alg[0] == 0))
+		rv = SS_NO_VERIFY_ALG;
+
+	else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+		  mdev->agreed_pro_version < 88)
+		rv = SS_NOT_SUPPORTED;
+
+	else if (ns.conn >= C_CONNECTED && ns.pdsk == D_UNKNOWN)
+		rv = SS_CONNECTED_OUTDATES;
+
+	return rv;
+}
+
+/**
+ * is_valid_state_transition() - Returns an SS_ error code if the state transition is not possible
+ * @mdev:	DRBD device.
+ * @ns:		new state.
+ * @os:		old state.
+ */
+static enum drbd_state_rv
+is_valid_state_transition(struct drbd_conf *mdev, union drbd_state ns,
+			  union drbd_state os)
+{
+	enum drbd_state_rv rv = SS_SUCCESS;
+
+	if ((ns.conn == C_STARTING_SYNC_T || ns.conn == C_STARTING_SYNC_S) &&
+	    os.conn > C_CONNECTED)
+		rv = SS_RESYNC_RUNNING;
+
+	if (ns.conn == C_DISCONNECTING && os.conn == C_STANDALONE)
+		rv = SS_ALREADY_STANDALONE;
+
+	if (ns.disk > D_ATTACHING && os.disk == D_DISKLESS)
+		rv = SS_IS_DISKLESS;
+
+	if (ns.conn == C_WF_CONNECTION && os.conn < C_UNCONNECTED)
+		rv = SS_NO_NET_CONFIG;
+
+	if (ns.disk == D_OUTDATED && os.disk < D_OUTDATED && os.disk != D_ATTACHING)
+		rv = SS_LOWER_THAN_OUTDATED;
+
+	if (ns.conn == C_DISCONNECTING && os.conn == C_UNCONNECTED)
+		rv = SS_IN_TRANSIENT_STATE;
+
+	if (ns.conn == os.conn && ns.conn == C_WF_REPORT_PARAMS)
+		rv = SS_IN_TRANSIENT_STATE;
+
+	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) && os.conn < C_CONNECTED)
+		rv = SS_NEED_CONNECTION;
+
+	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+	    ns.conn != os.conn && os.conn > C_CONNECTED)
+		rv = SS_RESYNC_RUNNING;
+
+	if ((ns.conn == C_STARTING_SYNC_S || ns.conn == C_STARTING_SYNC_T) &&
+	    os.conn < C_CONNECTED)
+		rv = SS_NEED_CONNECTION;
+
+	if ((ns.conn == C_SYNC_TARGET || ns.conn == C_SYNC_SOURCE)
+	    && os.conn < C_WF_REPORT_PARAMS)
+		rv = SS_NEED_CONNECTION; /* No NetworkFailure -> SyncTarget etc... */
+
+	return rv;
+}
+
+/**
+ * sanitize_state() - Resolves implicitly necessary additional changes to a state transition
+ * @mdev:	DRBD device.
+ * @os:		old state.
+ * @ns:		new state.
+ * @warn_sync_abort:
+ *
+ * When we loose connection, we have to set the state of the peers disk (pdsk)
+ * to D_UNKNOWN. This rule and many more along those lines are in this function.
+ */
+static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
+				       union drbd_state ns, const char **warn_sync_abort)
+{
+	enum drbd_fencing_p fp;
+	enum drbd_disk_state disk_min, disk_max, pdsk_min, pdsk_max;
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	/* Disallow Network errors to configure a device's network part */
+	if ((ns.conn >= C_TIMEOUT && ns.conn <= C_TEAR_DOWN) &&
+	    os.conn <= C_DISCONNECTING)
+		ns.conn = os.conn;
+
+	/* After a network error (+C_TEAR_DOWN) only C_UNCONNECTED or C_DISCONNECTING can follow.
+	 * If you try to go into some Sync* state, that shall fail (elsewhere). */
+	if (os.conn >= C_TIMEOUT && os.conn <= C_TEAR_DOWN &&
+	    ns.conn != C_UNCONNECTED && ns.conn != C_DISCONNECTING && ns.conn <= C_TEAR_DOWN)
+		ns.conn = os.conn;
+
+	/* we cannot fail (again) if we already detached */
+	if (ns.disk == D_FAILED && os.disk == D_DISKLESS)
+		ns.disk = D_DISKLESS;
+
+	/* if we are only D_ATTACHING yet,
+	 * we can (and should) go directly to D_DISKLESS. */
+	if (ns.disk == D_FAILED && os.disk == D_ATTACHING)
+		ns.disk = D_DISKLESS;
+
+	/* After C_DISCONNECTING only C_STANDALONE may follow */
+	if (os.conn == C_DISCONNECTING && ns.conn != C_STANDALONE)
+		ns.conn = os.conn;
+
+	if (ns.conn < C_CONNECTED) {
+		ns.peer_isp = 0;
+		ns.peer = R_UNKNOWN;
+		if (ns.pdsk > D_UNKNOWN || ns.pdsk < D_INCONSISTENT)
+			ns.pdsk = D_UNKNOWN;
+	}
+
+	/* Clear the aftr_isp when becoming unconfigured */
+	if (ns.conn == C_STANDALONE && ns.disk == D_DISKLESS && ns.role == R_SECONDARY)
+		ns.aftr_isp = 0;
+
+	/* Abort resync if a disk fails/detaches */
+	if (os.conn > C_CONNECTED && ns.conn > C_CONNECTED &&
+	    (ns.disk <= D_FAILED || ns.pdsk <= D_FAILED)) {
+		if (warn_sync_abort)
+			*warn_sync_abort =
+				os.conn == C_VERIFY_S || os.conn == C_VERIFY_T ?
+				"Online-verify" : "Resync";
+		ns.conn = C_CONNECTED;
+	}
+
+	/* Connection breaks down before we finished "Negotiating" */
+	if (ns.conn < C_CONNECTED && ns.disk == D_NEGOTIATING &&
+	    get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		if (mdev->ed_uuid == mdev->ldev->md.uuid[UI_CURRENT]) {
+			ns.disk = mdev->new_state_tmp.disk;
+			ns.pdsk = mdev->new_state_tmp.pdsk;
+		} else {
+			dev_alert(DEV, "Connection lost while negotiating, no data!\n");
+			ns.disk = D_DISKLESS;
+			ns.pdsk = D_UNKNOWN;
+		}
+		put_ldev(mdev);
+	}
+
+	/* D_CONSISTENT and D_OUTDATED vanish when we get connected */
+	if (ns.conn >= C_CONNECTED && ns.conn < C_AHEAD) {
+		if (ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED)
+			ns.disk = D_UP_TO_DATE;
+		if (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)
+			ns.pdsk = D_UP_TO_DATE;
+	}
+
+	/* Implications of the connection stat on the disk states */
+	disk_min = D_DISKLESS;
+	disk_max = D_UP_TO_DATE;
+	pdsk_min = D_INCONSISTENT;
+	pdsk_max = D_UNKNOWN;
+	switch ((enum drbd_conns)ns.conn) {
+	case C_WF_BITMAP_T:
+	case C_PAUSED_SYNC_T:
+	case C_STARTING_SYNC_T:
+	case C_WF_SYNC_UUID:
+	case C_BEHIND:
+		disk_min = D_INCONSISTENT;
+		disk_max = D_OUTDATED;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_VERIFY_S:
+	case C_VERIFY_T:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_CONNECTED:
+		disk_min = D_DISKLESS;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_DISKLESS;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_WF_BITMAP_S:
+	case C_PAUSED_SYNC_S:
+	case C_STARTING_SYNC_S:
+	case C_AHEAD:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_INCONSISTENT;
+		pdsk_max = D_CONSISTENT; /* D_OUTDATED would be nice. But explicit outdate necessary*/
+		break;
+	case C_SYNC_TARGET:
+		disk_min = D_INCONSISTENT;
+		disk_max = D_INCONSISTENT;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_SYNC_SOURCE:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_INCONSISTENT;
+		pdsk_max = D_INCONSISTENT;
+		break;
+	case C_STANDALONE:
+	case C_DISCONNECTING:
+	case C_UNCONNECTED:
+	case C_TIMEOUT:
+	case C_BROKEN_PIPE:
+	case C_NETWORK_FAILURE:
+	case C_PROTOCOL_ERROR:
+	case C_TEAR_DOWN:
+	case C_WF_CONNECTION:
+	case C_WF_REPORT_PARAMS:
+	case C_MASK:
+		break;
+	}
+	if (ns.disk > disk_max)
+		ns.disk = disk_max;
+
+	if (ns.disk < disk_min) {
+		dev_warn(DEV, "Implicitly set disk from %s to %s\n",
+			 drbd_disk_str(ns.disk), drbd_disk_str(disk_min));
+		ns.disk = disk_min;
+	}
+	if (ns.pdsk > pdsk_max)
+		ns.pdsk = pdsk_max;
+
+	if (ns.pdsk < pdsk_min) {
+		dev_warn(DEV, "Implicitly set pdsk from %s to %s\n",
+			 drbd_disk_str(ns.pdsk), drbd_disk_str(pdsk_min));
+		ns.pdsk = pdsk_min;
+	}
+
+	if (fp == FP_STONITH &&
+	    (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk > D_OUTDATED) &&
+	    !(os.role == R_PRIMARY && os.conn < C_CONNECTED && os.pdsk > D_OUTDATED))
+		ns.susp_fen = 1; /* Suspend IO while fence-peer handler runs (peer lost) */
+
+	if (mdev->sync_conf.on_no_data == OND_SUSPEND_IO &&
+	    (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE) &&
+	    !(os.role == R_PRIMARY && os.disk < D_UP_TO_DATE && os.pdsk < D_UP_TO_DATE))
+		ns.susp_nod = 1; /* Suspend IO while no data available (no accessible data available) */
+
+	if (ns.aftr_isp || ns.peer_isp || ns.user_isp) {
+		if (ns.conn == C_SYNC_SOURCE)
+			ns.conn = C_PAUSED_SYNC_S;
+		if (ns.conn == C_SYNC_TARGET)
+			ns.conn = C_PAUSED_SYNC_T;
+	} else {
+		if (ns.conn == C_PAUSED_SYNC_S)
+			ns.conn = C_SYNC_SOURCE;
+		if (ns.conn == C_PAUSED_SYNC_T)
+			ns.conn = C_SYNC_TARGET;
+	}
+
+	return ns;
+}
+
+/* helper for __drbd_set_state */
+static void set_ov_position(struct drbd_conf *mdev, enum drbd_conns cs)
+{
+	if (mdev->agreed_pro_version < 90)
+		mdev->ov_start_sector = 0;
+	mdev->rs_total = drbd_bm_bits(mdev);
+	mdev->ov_position = 0;
+	if (cs == C_VERIFY_T) {
+		/* starting online verify from an arbitrary position
+		 * does not fit well into the existing protocol.
+		 * on C_VERIFY_T, we initialize ov_left and friends
+		 * implicitly in receive_DataRequest once the
+		 * first P_OV_REQUEST is received */
+		mdev->ov_start_sector = ~(sector_t)0;
+	} else {
+		unsigned long bit = BM_SECT_TO_BIT(mdev->ov_start_sector);
+		if (bit >= mdev->rs_total) {
+			mdev->ov_start_sector =
+				BM_BIT_TO_SECT(mdev->rs_total - 1);
+			mdev->rs_total = 1;
+		} else
+			mdev->rs_total -= bit;
+		mdev->ov_position = mdev->ov_start_sector;
+	}
+	mdev->ov_left = mdev->rs_total;
+}
+
+static void drbd_resume_al(struct drbd_conf *mdev)
+{
+	if (test_and_clear_bit(AL_SUSPENDED, &mdev->flags))
+		dev_info(DEV, "Resumed AL updates\n");
+}
+
+/**
+ * __drbd_set_state() - Set a new DRBD state
+ * @mdev:	DRBD device.
+ * @ns:		new state.
+ * @flags:	Flags
+ * @done:	Optional completion, that will get completed after the after_state_ch() finished
+ *
+ * Caller needs to hold req_lock, and global_state_lock. Do not call directly.
+ */
+enum drbd_state_rv
+__drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
+	         enum chg_state_flags flags, struct completion *done)
+{
+	union drbd_state os;
+	enum drbd_state_rv rv = SS_SUCCESS;
+	const char *warn_sync_abort = NULL;
+	struct after_state_chg_work *ascw;
+
+	os = mdev->state;
+
+	ns = sanitize_state(mdev, os, ns, &warn_sync_abort);
+
+	if (ns.i == os.i)
+		return SS_NOTHING_TO_DO;
+
+	if (!(flags & CS_HARD)) {
+		/*  pre-state-change checks ; only look at ns  */
+		/* See drbd_state_sw_errors in drbd_strings.c */
+
+		rv = is_valid_state(mdev, ns);
+		if (rv < SS_SUCCESS) {
+			/* If the old state was illegal as well, then let
+			   this happen...*/
+
+			if (is_valid_state(mdev, os) == rv)
+				rv = is_valid_state_transition(mdev, ns, os);
+		} else
+			rv = is_valid_state_transition(mdev, ns, os);
+	}
+
+	if (rv < SS_SUCCESS) {
+		if (flags & CS_VERBOSE)
+			print_st_err(mdev, os, ns, rv);
+		return rv;
+	}
+
+	if (warn_sync_abort)
+		dev_warn(DEV, "%s aborted.\n", warn_sync_abort);
+
+	{
+	char *pbp, pb[300];
+	pbp = pb;
+	*pbp = 0;
+	if (ns.role != os.role)
+		pbp += sprintf(pbp, "role( %s -> %s ) ",
+			       drbd_role_str(os.role),
+			       drbd_role_str(ns.role));
+	if (ns.peer != os.peer)
+		pbp += sprintf(pbp, "peer( %s -> %s ) ",
+			       drbd_role_str(os.peer),
+			       drbd_role_str(ns.peer));
+	if (ns.conn != os.conn)
+		pbp += sprintf(pbp, "conn( %s -> %s ) ",
+			       drbd_conn_str(os.conn),
+			       drbd_conn_str(ns.conn));
+	if (ns.disk != os.disk)
+		pbp += sprintf(pbp, "disk( %s -> %s ) ",
+			       drbd_disk_str(os.disk),
+			       drbd_disk_str(ns.disk));
+	if (ns.pdsk != os.pdsk)
+		pbp += sprintf(pbp, "pdsk( %s -> %s ) ",
+			       drbd_disk_str(os.pdsk),
+			       drbd_disk_str(ns.pdsk));
+	if (is_susp(ns) != is_susp(os))
+		pbp += sprintf(pbp, "susp( %d -> %d ) ",
+			       is_susp(os),
+			       is_susp(ns));
+	if (ns.aftr_isp != os.aftr_isp)
+		pbp += sprintf(pbp, "aftr_isp( %d -> %d ) ",
+			       os.aftr_isp,
+			       ns.aftr_isp);
+	if (ns.peer_isp != os.peer_isp)
+		pbp += sprintf(pbp, "peer_isp( %d -> %d ) ",
+			       os.peer_isp,
+			       ns.peer_isp);
+	if (ns.user_isp != os.user_isp)
+		pbp += sprintf(pbp, "user_isp( %d -> %d ) ",
+			       os.user_isp,
+			       ns.user_isp);
+	dev_info(DEV, "%s\n", pb);
+	}
+
+	/* solve the race between becoming unconfigured,
+	 * worker doing the cleanup, and
+	 * admin reconfiguring us:
+	 * on (re)configure, first set CONFIG_PENDING,
+	 * then wait for a potentially exiting worker,
+	 * start the worker, and schedule one no_op.
+	 * then proceed with configuration.
+	 */
+	if (ns.disk == D_DISKLESS &&
+	    ns.conn == C_STANDALONE &&
+	    ns.role == R_SECONDARY &&
+	    !test_and_set_bit(CONFIG_PENDING, &mdev->flags))
+		set_bit(DEVICE_DYING, &mdev->flags);
+
+	/* if we are going -> D_FAILED or D_DISKLESS, grab one extra reference
+	 * on the ldev here, to be sure the transition -> D_DISKLESS resp.
+	 * drbd_ldev_destroy() won't happen before our corresponding
+	 * after_state_ch works run, where we put_ldev again. */
+	if ((os.disk != D_FAILED && ns.disk == D_FAILED) ||
+	    (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))
+		atomic_inc(&mdev->local_cnt);
+
+	mdev->state = ns;
+
+	if (os.disk == D_ATTACHING && ns.disk >= D_NEGOTIATING)
+		drbd_print_uuids(mdev, "attached to UUIDs");
+
+	wake_up(&mdev->misc_wait);
+	wake_up(&mdev->state_wait);
+
+	/* aborted verify run. log the last position */
+	if ((os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) &&
+	    ns.conn < C_CONNECTED) {
+		mdev->ov_start_sector =
+			BM_BIT_TO_SECT(drbd_bm_bits(mdev) - mdev->ov_left);
+		dev_info(DEV, "Online Verify reached sector %llu\n",
+			(unsigned long long)mdev->ov_start_sector);
+	}
+
+	if ((os.conn == C_PAUSED_SYNC_T || os.conn == C_PAUSED_SYNC_S) &&
+	    (ns.conn == C_SYNC_TARGET  || ns.conn == C_SYNC_SOURCE)) {
+		dev_info(DEV, "Syncer continues.\n");
+		mdev->rs_paused += (long)jiffies
+				  -(long)mdev->rs_mark_time[mdev->rs_last_mark];
+		if (ns.conn == C_SYNC_TARGET)
+			mod_timer(&mdev->resync_timer, jiffies);
+	}
+
+	if ((os.conn == C_SYNC_TARGET  || os.conn == C_SYNC_SOURCE) &&
+	    (ns.conn == C_PAUSED_SYNC_T || ns.conn == C_PAUSED_SYNC_S)) {
+		dev_info(DEV, "Resync suspended\n");
+		mdev->rs_mark_time[mdev->rs_last_mark] = jiffies;
+	}
+
+	if (os.conn == C_CONNECTED &&
+	    (ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T)) {
+		unsigned long now = jiffies;
+		int i;
+
+		set_ov_position(mdev, ns.conn);
+		mdev->rs_start = now;
+		mdev->rs_last_events = 0;
+		mdev->rs_last_sect_ev = 0;
+		mdev->ov_last_oos_size = 0;
+		mdev->ov_last_oos_start = 0;
+
+		for (i = 0; i < DRBD_SYNC_MARKS; i++) {
+			mdev->rs_mark_left[i] = mdev->ov_left;
+			mdev->rs_mark_time[i] = now;
+		}
+
+		drbd_rs_controller_reset(mdev);
+
+		if (ns.conn == C_VERIFY_S) {
+			dev_info(DEV, "Starting Online Verify from sector %llu\n",
+					(unsigned long long)mdev->ov_position);
+			mod_timer(&mdev->resync_timer, jiffies);
+		}
+	}
+
+	if (get_ldev(mdev)) {
+		u32 mdf = mdev->ldev->md.flags & ~(MDF_CONSISTENT|MDF_PRIMARY_IND|
+						 MDF_CONNECTED_IND|MDF_WAS_UP_TO_DATE|
+						 MDF_PEER_OUT_DATED|MDF_CRASHED_PRIMARY);
+
+		if (test_bit(CRASHED_PRIMARY, &mdev->flags))
+			mdf |= MDF_CRASHED_PRIMARY;
+		if (mdev->state.role == R_PRIMARY ||
+		    (mdev->state.pdsk < D_INCONSISTENT && mdev->state.peer == R_PRIMARY))
+			mdf |= MDF_PRIMARY_IND;
+		if (mdev->state.conn > C_WF_REPORT_PARAMS)
+			mdf |= MDF_CONNECTED_IND;
+		if (mdev->state.disk > D_INCONSISTENT)
+			mdf |= MDF_CONSISTENT;
+		if (mdev->state.disk > D_OUTDATED)
+			mdf |= MDF_WAS_UP_TO_DATE;
+		if (mdev->state.pdsk <= D_OUTDATED && mdev->state.pdsk >= D_INCONSISTENT)
+			mdf |= MDF_PEER_OUT_DATED;
+		if (mdf != mdev->ldev->md.flags) {
+			mdev->ldev->md.flags = mdf;
+			drbd_md_mark_dirty(mdev);
+		}
+		if (os.disk < D_CONSISTENT && ns.disk >= D_CONSISTENT)
+			drbd_set_ed_uuid(mdev, mdev->ldev->md.uuid[UI_CURRENT]);
+		put_ldev(mdev);
+	}
+
+	/* Peer was forced D_UP_TO_DATE & R_PRIMARY, consider to resync */
+	if (os.disk == D_INCONSISTENT && os.pdsk == D_INCONSISTENT &&
+	    os.peer == R_SECONDARY && ns.peer == R_PRIMARY)
+		set_bit(CONSIDER_RESYNC, &mdev->flags);
+
+	/* Receiver should clean up itself */
+	if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
+		drbd_thread_stop_nowait(&mdev->receiver);
+
+	/* Now the receiver finished cleaning up itself, it should die */
+	if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
+		drbd_thread_stop_nowait(&mdev->receiver);
+
+	/* Upon network failure, we need to restart the receiver. */
+	if (os.conn > C_TEAR_DOWN &&
+	    ns.conn <= C_TEAR_DOWN && ns.conn >= C_TIMEOUT)
+		drbd_thread_restart_nowait(&mdev->receiver);
+
+	/* Resume AL writing if we get a connection */
+	if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)
+		drbd_resume_al(mdev);
+
+	ascw = kmalloc(sizeof(*ascw), GFP_ATOMIC);
+	if (ascw) {
+		ascw->os = os;
+		ascw->ns = ns;
+		ascw->flags = flags;
+		ascw->w.cb = w_after_state_ch;
+		ascw->done = done;
+		drbd_queue_work(&mdev->data.work, &ascw->w);
+	} else {
+		dev_warn(DEV, "Could not kmalloc an ascw\n");
+	}
+
+	return rv;
+}
+
+static int w_after_state_ch(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct after_state_chg_work *ascw =
+		container_of(w, struct after_state_chg_work, w);
+	after_state_ch(mdev, ascw->os, ascw->ns, ascw->flags);
+	if (ascw->flags & CS_WAIT_COMPLETE) {
+		D_ASSERT(ascw->done != NULL);
+		complete(ascw->done);
+	}
+	kfree(ascw);
+
+	return 1;
+}
+
+static void abw_start_sync(struct drbd_conf *mdev, int rv)
+{
+	if (rv) {
+		dev_err(DEV, "Writing the bitmap failed not starting resync.\n");
+		_drbd_request_state(mdev, NS(conn, C_CONNECTED), CS_VERBOSE);
+		return;
+	}
+
+	switch (mdev->state.conn) {
+	case C_STARTING_SYNC_T:
+		_drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+		break;
+	case C_STARTING_SYNC_S:
+		drbd_start_resync(mdev, C_SYNC_SOURCE);
+		break;
+	}
+}
+
+int drbd_bitmap_io_from_worker(struct drbd_conf *mdev,
+		int (*io_fn)(struct drbd_conf *),
+		char *why, enum bm_flag flags)
+{
+	int rv;
+
+	D_ASSERT(current == mdev->worker.task);
+
+	/* open coded non-blocking drbd_suspend_io(mdev); */
+	set_bit(SUSPEND_IO, &mdev->flags);
+
+	drbd_bm_lock(mdev, why, flags);
+	rv = io_fn(mdev);
+	drbd_bm_unlock(mdev);
+
+	drbd_resume_io(mdev);
+
+	return rv;
+}
+
+/**
+ * after_state_ch() - Perform after state change actions that may sleep
+ * @mdev:	DRBD device.
+ * @os:		old state.
+ * @ns:		new state.
+ * @flags:	Flags
+ */
+static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
+			   union drbd_state ns, enum chg_state_flags flags)
+{
+	enum drbd_fencing_p fp;
+	enum drbd_req_event what = nothing;
+	union drbd_state nsm = (union drbd_state){ .i = -1 };
+
+	if (os.conn != C_CONNECTED && ns.conn == C_CONNECTED) {
+		clear_bit(CRASHED_PRIMARY, &mdev->flags);
+		if (mdev->p_uuid)
+			mdev->p_uuid[UI_FLAGS] &= ~((u64)2);
+	}
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	/* Inform userspace about the change... */
+	drbd_bcast_state(mdev, ns);
+
+	if (!(os.role == R_PRIMARY && os.disk < D_UP_TO_DATE && os.pdsk < D_UP_TO_DATE) &&
+	    (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE))
+		drbd_khelper(mdev, "pri-on-incon-degr");
+
+	/* Here we have the actions that are performed after a
+	   state change. This function might sleep */
+
+	nsm.i = -1;
+	if (ns.susp_nod) {
+		if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)
+			what = resend;
+
+		if (os.disk == D_ATTACHING && ns.disk > D_ATTACHING)
+			what = restart_frozen_disk_io;
+
+		if (what != nothing)
+			nsm.susp_nod = 0;
+	}
+
+	if (ns.susp_fen) {
+		/* case1: The outdate peer handler is successful: */
+		if (os.pdsk > D_OUTDATED  && ns.pdsk <= D_OUTDATED) {
+			tl_clear(mdev);
+			if (test_bit(NEW_CUR_UUID, &mdev->flags)) {
+				drbd_uuid_new_current(mdev);
+				clear_bit(NEW_CUR_UUID, &mdev->flags);
+			}
+			spin_lock_irq(&mdev->req_lock);
+			_drbd_set_state(_NS(mdev, susp_fen, 0), CS_VERBOSE, NULL);
+			spin_unlock_irq(&mdev->req_lock);
+		}
+		/* case2: The connection was established again: */
+		if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED) {
+			clear_bit(NEW_CUR_UUID, &mdev->flags);
+			what = resend;
+			nsm.susp_fen = 0;
+		}
+	}
+
+	if (what != nothing) {
+		spin_lock_irq(&mdev->req_lock);
+		_tl_restart(mdev, what);
+		nsm.i &= mdev->state.i;
+		_drbd_set_state(mdev, nsm, CS_VERBOSE, NULL);
+		spin_unlock_irq(&mdev->req_lock);
+	}
+
+	/* Became sync source.  With protocol >= 96, we still need to send out
+	 * the sync uuid now. Need to do that before any drbd_send_state, or
+	 * the other side may go "paused sync" before receiving the sync uuids,
+	 * which is unexpected. */
+	if ((os.conn != C_SYNC_SOURCE && os.conn != C_PAUSED_SYNC_S) &&
+	    (ns.conn == C_SYNC_SOURCE || ns.conn == C_PAUSED_SYNC_S) &&
+	    mdev->agreed_pro_version >= 96 && get_ldev(mdev)) {
+		drbd_gen_and_send_sync_uuid(mdev);
+		put_ldev(mdev);
+	}
+
+	/* Do not change the order of the if above and the two below... */
+	if (os.pdsk == D_DISKLESS && ns.pdsk > D_DISKLESS) {      /* attach on the peer */
+		drbd_send_uuids(mdev);
+		drbd_send_state(mdev);
+	}
+	/* No point in queuing send_bitmap if we don't have a connection
+	 * anymore, so check also the _current_ state, not only the new state
+	 * at the time this work was queued. */
+	if (os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S &&
+	    mdev->state.conn == C_WF_BITMAP_S)
+		drbd_queue_bitmap_io(mdev, &drbd_send_bitmap, NULL,
+				"send_bitmap (WFBitMapS)",
+				BM_LOCKED_TEST_ALLOWED);
+
+	/* Lost contact to peer's copy of the data */
+	if ((os.pdsk >= D_INCONSISTENT &&
+	     os.pdsk != D_UNKNOWN &&
+	     os.pdsk != D_OUTDATED)
+	&&  (ns.pdsk < D_INCONSISTENT ||
+	     ns.pdsk == D_UNKNOWN ||
+	     ns.pdsk == D_OUTDATED)) {
+		if (get_ldev(mdev)) {
+			if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
+			    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
+				if (is_susp(mdev->state)) {
+					set_bit(NEW_CUR_UUID, &mdev->flags);
+				} else {
+					drbd_uuid_new_current(mdev);
+					drbd_send_uuids(mdev);
+				}
+			}
+			put_ldev(mdev);
+		}
+	}
+
+	if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
+		if (ns.peer == R_PRIMARY && mdev->ldev->md.uuid[UI_BITMAP] == 0) {
+			drbd_uuid_new_current(mdev);
+			drbd_send_uuids(mdev);
+		}
+
+		/* D_DISKLESS Peer becomes secondary */
+		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
+			/* We may still be Primary ourselves.
+			 * No harm done if the bitmap still changes,
+			 * redirtied pages will follow later. */
+			drbd_bitmap_io_from_worker(mdev, &drbd_bm_write,
+				"demote diskless peer", BM_LOCKED_SET_ALLOWED);
+		put_ldev(mdev);
+	}
+
+	/* Write out all changed bits on demote.
+	 * Though, no need to da that just yet
+	 * if there is a resync going on still */
+	if (os.role == R_PRIMARY && ns.role == R_SECONDARY &&
+		mdev->state.conn <= C_CONNECTED && get_ldev(mdev)) {
+		/* No changes to the bitmap expected this time, so assert that,
+		 * even though no harm was done if it did change. */
+		drbd_bitmap_io_from_worker(mdev, &drbd_bm_write,
+				"demote", BM_LOCKED_TEST_ALLOWED);
+		put_ldev(mdev);
+	}
+
+	/* Last part of the attaching process ... */
+	if (ns.conn >= C_CONNECTED &&
+	    os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
+		drbd_send_sizes(mdev, 0, 0);  /* to start sync... */
+		drbd_send_uuids(mdev);
+		drbd_send_state(mdev);
+	}
+
+	/* We want to pause/continue resync, tell peer. */
+	if (ns.conn >= C_CONNECTED &&
+	     ((os.aftr_isp != ns.aftr_isp) ||
+	      (os.user_isp != ns.user_isp)))
+		drbd_send_state(mdev);
+
+	/* In case one of the isp bits got set, suspend other devices. */
+	if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
+	    (ns.aftr_isp || ns.peer_isp || ns.user_isp))
+		suspend_other_sg(mdev);
+
+	/* Make sure the peer gets informed about eventual state
+	   changes (ISP bits) while we were in WFReportParams. */
+	if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
+		drbd_send_state(mdev);
+
+	if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
+		drbd_send_state(mdev);
+
+	/* We are in the progress to start a full sync... */
+	if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+	    (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S))
+		/* no other bitmap changes expected during this phase */
+		drbd_queue_bitmap_io(mdev,
+			&drbd_bmio_set_n_write, &abw_start_sync,
+			"set_n_write from StartingSync", BM_LOCKED_TEST_ALLOWED);
+
+	/* We are invalidating our self... */
+	if (os.conn < C_CONNECTED && ns.conn < C_CONNECTED &&
+	    os.disk > D_INCONSISTENT && ns.disk == D_INCONSISTENT)
+		/* other bitmap operation expected during this phase */
+		drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, NULL,
+			"set_n_write from invalidate", BM_LOCKED_MASK);
+
+	/* first half of local IO error, failure to attach,
+	 * or administrative detach */
+	if (os.disk != D_FAILED && ns.disk == D_FAILED) {
+		enum drbd_io_error_p eh;
+		int was_io_error;
+		/* corresponding get_ldev was in __drbd_set_state, to serialize
+		 * our cleanup here with the transition to D_DISKLESS,
+		 * so it is safe to dreference ldev here. */
+		eh = mdev->ldev->dc.on_io_error;
+		was_io_error = test_and_clear_bit(WAS_IO_ERROR, &mdev->flags);
+
+		/* current state still has to be D_FAILED,
+		 * there is only one way out: to D_DISKLESS,
+		 * and that may only happen after our put_ldev below. */
+		if (mdev->state.disk != D_FAILED)
+			dev_err(DEV,
+				"ASSERT FAILED: disk is %s during detach\n",
+				drbd_disk_str(mdev->state.disk));
+
+		if (drbd_send_state(mdev))
+			dev_warn(DEV, "Notified peer that I am detaching my disk\n");
+		else
+			dev_err(DEV, "Sending state for detaching disk failed\n");
+
+		drbd_rs_cancel_all(mdev);
+
+		/* In case we want to get something to stable storage still,
+		 * this may be the last chance.
+		 * Following put_ldev may transition to D_DISKLESS. */
+		drbd_md_sync(mdev);
+		put_ldev(mdev);
+
+		if (was_io_error && eh == EP_CALL_HELPER)
+			drbd_khelper(mdev, "local-io-error");
+	}
+
+        /* second half of local IO error, failure to attach,
+         * or administrative detach,
+         * after local_cnt references have reached zero again */
+        if (os.disk != D_DISKLESS && ns.disk == D_DISKLESS) {
+                /* We must still be diskless,
+                 * re-attach has to be serialized with this! */
+                if (mdev->state.disk != D_DISKLESS)
+                        dev_err(DEV,
+                                "ASSERT FAILED: disk is %s while going diskless\n",
+                                drbd_disk_str(mdev->state.disk));
+
+                mdev->rs_total = 0;
+                mdev->rs_failed = 0;
+                atomic_set(&mdev->rs_pending_cnt, 0);
+
+		if (drbd_send_state(mdev))
+			dev_warn(DEV, "Notified peer that I'm now diskless.\n");
+		/* corresponding get_ldev in __drbd_set_state
+		 * this may finally trigger drbd_ldev_destroy. */
+		put_ldev(mdev);
+	}
+
+	/* Notify peer that I had a local IO error, and did not detached.. */
+	if (os.disk == D_UP_TO_DATE && ns.disk == D_INCONSISTENT)
+		drbd_send_state(mdev);
+
+	/* Disks got bigger while they were detached */
+	if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
+	    test_and_clear_bit(RESYNC_AFTER_NEG, &mdev->flags)) {
+		if (ns.conn == C_CONNECTED)
+			resync_after_online_grow(mdev);
+	}
+
+	/* A resync finished or aborted, wake paused devices... */
+	if ((os.conn > C_CONNECTED && ns.conn <= C_CONNECTED) ||
+	    (os.peer_isp && !ns.peer_isp) ||
+	    (os.user_isp && !ns.user_isp))
+		resume_next_sg(mdev);
+
+	/* sync target done with resync.  Explicitly notify peer, even though
+	 * it should (at least for non-empty resyncs) already know itself. */
+	if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
+		drbd_send_state(mdev);
+
+	/* This triggers bitmap writeout of potentially still unwritten pages
+	 * if the resync finished cleanly, or aborted because of peer disk
+	 * failure, or because of connection loss.
+	 * For resync aborted because of local disk failure, we cannot do
+	 * any bitmap writeout anymore.
+	 * No harm done if some bits change during this phase.
+	 */
+	if (os.conn > C_CONNECTED && ns.conn <= C_CONNECTED && get_ldev(mdev)) {
+		drbd_queue_bitmap_io(mdev, &drbd_bm_write, NULL,
+			"write from resync_finished", BM_LOCKED_SET_ALLOWED);
+		put_ldev(mdev);
+	}
+
+	/* free tl_hash if we Got thawed and are C_STANDALONE */
+	if (ns.conn == C_STANDALONE && !is_susp(ns) && mdev->tl_hash)
+		drbd_free_tl_hash(mdev);
+
+	/* Upon network connection, we need to start the receiver */
+	if (os.conn == C_STANDALONE && ns.conn == C_UNCONNECTED)
+		drbd_thread_start(&mdev->receiver);
+
+	/* Terminate worker thread if we are unconfigured - it will be
+	   restarted as needed... */
+	if (ns.disk == D_DISKLESS &&
+	    ns.conn == C_STANDALONE &&
+	    ns.role == R_SECONDARY) {
+		if (os.aftr_isp != ns.aftr_isp)
+			resume_next_sg(mdev);
+		/* set in __drbd_set_state, unless CONFIG_PENDING was set */
+		if (test_bit(DEVICE_DYING, &mdev->flags))
+			drbd_thread_stop_nowait(&mdev->worker);
+	}
+
+	drbd_md_sync(mdev);
+}
+
+
+static int drbd_thread_setup(void *arg)
+{
+	struct drbd_thread *thi = (struct drbd_thread *) arg;
+	struct drbd_conf *mdev = thi->mdev;
+	unsigned long flags;
+	int retval;
+
+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) {
+		dev_info(DEV, "Restarting %s\n", current->comm);
+		thi->t_state = Running;
+		spin_unlock_irqrestore(&thi->t_lock, flags);
+		goto restart;
+	}
+
+	thi->task = NULL;
+	thi->t_state = None;
+	smp_mb();
+	complete(&thi->stop);
+	spin_unlock_irqrestore(&thi->t_lock, flags);
+
+	dev_info(DEV, "Terminating %s\n", current->comm);
+
+	/* Release mod reference taken when thread was started */
+	module_put(THIS_MODULE);
+	return retval;
+}
+
+static void drbd_thread_init(struct drbd_conf *mdev, struct drbd_thread *thi,
+		      int (*func) (struct drbd_thread *))
+{
+	spin_lock_init(&thi->t_lock);
+	thi->task    = NULL;
+	thi->t_state = None;
+	thi->function = func;
+	thi->mdev = mdev;
+}
+
+int drbd_thread_start(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	struct task_struct *nt;
+	unsigned long flags;
+
+	const char *me =
+		thi == &mdev->receiver ? "receiver" :
+		thi == &mdev->asender  ? "asender"  :
+		thi == &mdev->worker   ? "worker"   : "NONSENSE";
+
+	/* 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:
+		dev_info(DEV, "Starting %s thread (from %s [%d])\n",
+				me, current->comm, current->pid);
+
+		/* Get ref on module for thread - this is released when thread exits */
+		if (!try_module_get(THIS_MODULE)) {
+			dev_err(DEV, "Failed to get module reference in drbd_thread_start\n");
+			spin_unlock_irqrestore(&thi->t_lock, flags);
+			return false;
+		}
+
+		init_completion(&thi->stop);
+		D_ASSERT(thi->task == NULL);
+		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%d_%s", mdev_to_minor(mdev), me);
+
+		if (IS_ERR(nt)) {
+			dev_err(DEV, "Couldn't start thread\n");
+
+			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;
+		dev_info(DEV, "Restarting %s thread (from %s [%d])\n",
+				me, 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);
+}
+
+#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_conf *mdev)
+{
+	int ord, cpu;
+
+	/* user override. */
+	if (cpumask_weight(mdev->cpu_mask))
+		return;
+
+	ord = mdev_to_minor(mdev) % cpumask_weight(cpu_online_mask);
+	for_each_online_cpu(cpu) {
+		if (ord-- == 0) {
+			cpumask_set_cpu(cpu, mdev->cpu_mask);
+			return;
+		}
+	}
+	/* should not be reached */
+	cpumask_setall(mdev->cpu_mask);
+}
+
+/**
+ * drbd_thread_current_set_cpu() - modifies the cpu mask of the _current_ thread
+ * @mdev:	DRBD device.
+ *
+ * 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_conf *mdev)
+{
+	struct task_struct *p = current;
+	struct drbd_thread *thi =
+		p == mdev->asender.task  ? &mdev->asender  :
+		p == mdev->receiver.task ? &mdev->receiver :
+		p == mdev->worker.task   ? &mdev->worker   :
+		NULL;
+	ERR_IF(thi == NULL)
+		return;
+	if (!thi->reset_cpu_mask)
+		return;
+	thi->reset_cpu_mask = 0;
+	set_cpus_allowed_ptr(p, mdev->cpu_mask);
+}
+#endif
+
+/* the appropriate socket mutex must be held already */
+int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
+			  enum drbd_packets cmd, struct p_header80 *h,
+			  size_t size, unsigned msg_flags)
+{
+	int sent, ok;
+
+	ERR_IF(!h) return false;
+	ERR_IF(!size) return false;
+
+	h->magic   = BE_DRBD_MAGIC;
+	h->command = cpu_to_be16(cmd);
+	h->length  = cpu_to_be16(size-sizeof(struct p_header80));
+
+	sent = drbd_send(mdev, sock, h, size, msg_flags);
+
+	ok = (sent == size);
+	if (!ok && !signal_pending(current))
+		dev_warn(DEV, "short sent %s size=%d sent=%d\n",
+		    cmdname(cmd), (int)size, sent);
+	return ok;
+}
+
+/* don't pass the socket. we may only look at it
+ * when we hold the appropriate socket mutex.
+ */
+int drbd_send_cmd(struct drbd_conf *mdev, int use_data_socket,
+		  enum drbd_packets cmd, struct p_header80 *h, size_t size)
+{
+	int ok = 0;
+	struct socket *sock;
+
+	if (use_data_socket) {
+		mutex_lock(&mdev->data.mutex);
+		sock = mdev->data.socket;
+	} else {
+		mutex_lock(&mdev->meta.mutex);
+		sock = mdev->meta.socket;
+	}
+
+	/* drbd_disconnect() could have called drbd_free_sock()
+	 * while we were waiting in down()... */
+	if (likely(sock != NULL))
+		ok = _drbd_send_cmd(mdev, sock, cmd, h, size, 0);
+
+	if (use_data_socket)
+		mutex_unlock(&mdev->data.mutex);
+	else
+		mutex_unlock(&mdev->meta.mutex);
+	return ok;
+}
+
+int drbd_send_cmd2(struct drbd_conf *mdev, enum drbd_packets cmd, char *data,
+		   size_t size)
+{
+	struct p_header80 h;
+	int ok;
+
+	h.magic   = BE_DRBD_MAGIC;
+	h.command = cpu_to_be16(cmd);
+	h.length  = cpu_to_be16(size);
+
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+
+	ok = (sizeof(h) ==
+		drbd_send(mdev, mdev->data.socket, &h, sizeof(h), 0));
+	ok = ok && (size ==
+		drbd_send(mdev, mdev->data.socket, data, size, 0));
+
+	drbd_put_data_sock(mdev);
+
+	return ok;
+}
+
+int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc)
+{
+	struct p_rs_param_95 *p;
+	struct socket *sock;
+	int size, rv;
+	const int apv = mdev->agreed_pro_version;
+
+	size = apv <= 87 ? sizeof(struct p_rs_param)
+		: apv == 88 ? sizeof(struct p_rs_param)
+			+ strlen(mdev->sync_conf.verify_alg) + 1
+		: apv <= 94 ? sizeof(struct p_rs_param_89)
+		: /* apv >= 95 */ sizeof(struct p_rs_param_95);
+
+	/* used from admin command context and receiver/worker context.
+	 * to avoid kmalloc, grab the socket right here,
+	 * then use the pre-allocated sbuf there */
+	mutex_lock(&mdev->data.mutex);
+	sock = mdev->data.socket;
+
+	if (likely(sock != NULL)) {
+		enum drbd_packets cmd = apv >= 89 ? P_SYNC_PARAM89 : P_SYNC_PARAM;
+
+		p = &mdev->data.sbuf.rs_param_95;
+
+		/* initialize verify_alg and csums_alg */
+		memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+
+		p->rate = cpu_to_be32(sc->rate);
+		p->c_plan_ahead = cpu_to_be32(sc->c_plan_ahead);
+		p->c_delay_target = cpu_to_be32(sc->c_delay_target);
+		p->c_fill_target = cpu_to_be32(sc->c_fill_target);
+		p->c_max_rate = cpu_to_be32(sc->c_max_rate);
+
+		if (apv >= 88)
+			strcpy(p->verify_alg, mdev->sync_conf.verify_alg);
+		if (apv >= 89)
+			strcpy(p->csums_alg, mdev->sync_conf.csums_alg);
+
+		rv = _drbd_send_cmd(mdev, sock, cmd, &p->head, size, 0);
+	} else
+		rv = 0; /* not ok */
+
+	mutex_unlock(&mdev->data.mutex);
+
+	return rv;
+}
+
+int drbd_send_protocol(struct drbd_conf *mdev)
+{
+	struct p_protocol *p;
+	int size, cf, rv;
+
+	size = sizeof(struct p_protocol);
+
+	if (mdev->agreed_pro_version >= 87)
+		size += strlen(mdev->net_conf->integrity_alg) + 1;
+
+	/* we must not recurse into our own queue,
+	 * as that is blocked during handshake */
+	p = kmalloc(size, GFP_NOIO);
+	if (p == NULL)
+		return 0;
+
+	p->protocol      = cpu_to_be32(mdev->net_conf->wire_protocol);
+	p->after_sb_0p   = cpu_to_be32(mdev->net_conf->after_sb_0p);
+	p->after_sb_1p   = cpu_to_be32(mdev->net_conf->after_sb_1p);
+	p->after_sb_2p   = cpu_to_be32(mdev->net_conf->after_sb_2p);
+	p->two_primaries = cpu_to_be32(mdev->net_conf->two_primaries);
+
+	cf = 0;
+	if (mdev->net_conf->want_lose)
+		cf |= CF_WANT_LOSE;
+	if (mdev->net_conf->dry_run) {
+		if (mdev->agreed_pro_version >= 92)
+			cf |= CF_DRY_RUN;
+		else {
+			dev_err(DEV, "--dry-run is not supported by peer");
+			kfree(p);
+			return -1;
+		}
+	}
+	p->conn_flags    = cpu_to_be32(cf);
+
+	if (mdev->agreed_pro_version >= 87)
+		strcpy(p->integrity_alg, mdev->net_conf->integrity_alg);
+
+	rv = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_PROTOCOL,
+			   (struct p_header80 *)p, size);
+	kfree(p);
+	return rv;
+}
+
+int _drbd_send_uuids(struct drbd_conf *mdev, u64 uuid_flags)
+{
+	struct p_uuids p;
+	int i;
+
+	if (!get_ldev_if_state(mdev, D_NEGOTIATING))
+		return 1;
+
+	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);
+	uuid_flags |= mdev->net_conf->want_lose ? 1 : 0;
+	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_cmd(mdev, USE_DATA_SOCKET, P_UUIDS,
+			     (struct p_header80 *)&p, sizeof(p));
+}
+
+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);
+	}
+}
+
+int drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev)
+{
+	struct p_rs_uuid p;
+	u64 uuid;
+
+	D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
+
+	uuid = mdev->ldev->md.uuid[UI_BITMAP] + UUID_NEW_BM_OFFSET;
+	drbd_uuid_set(mdev, UI_BITMAP, uuid);
+	drbd_print_uuids(mdev, "updated sync UUID");
+	drbd_md_sync(mdev);
+	p.uuid = cpu_to_be64(uuid);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SYNC_UUID,
+			     (struct p_header80 *)&p, sizeof(p));
+}
+
+int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags)
+{
+	struct p_sizes p;
+	sector_t d_size, u_size;
+	int q_order_type, max_bio_size;
+	int ok;
+
+	if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		D_ASSERT(mdev->ldev->backing_bdev);
+		d_size = drbd_get_max_capacity(mdev->ldev);
+		u_size = mdev->ldev->dc.disk_size;
+		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 */
+	}
+
+	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);
+
+	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SIZES,
+			   (struct p_header80 *)&p, sizeof(p));
+	return ok;
+}
+
+/**
+ * drbd_send_state() - Sends the drbd state to the peer
+ * @mdev:	DRBD device.
+ */
+int drbd_send_state(struct drbd_conf *mdev)
+{
+	struct socket *sock;
+	struct p_state p;
+	int ok = 0;
+
+	/* Grab state lock so we wont send state if we're in the middle
+	 * of a cluster wide state change on another thread */
+	drbd_state_lock(mdev);
+
+	mutex_lock(&mdev->data.mutex);
+
+	p.state = cpu_to_be32(mdev->state.i); /* Within the send mutex */
+	sock = mdev->data.socket;
+
+	if (likely(sock != NULL)) {
+		ok = _drbd_send_cmd(mdev, sock, P_STATE,
+				    (struct p_header80 *)&p, sizeof(p), 0);
+	}
+
+	mutex_unlock(&mdev->data.mutex);
+
+	drbd_state_unlock(mdev);
+	return ok;
+}
+
+int drbd_send_state_req(struct drbd_conf *mdev,
+	union drbd_state mask, union drbd_state val)
+{
+	struct p_req_state p;
+
+	p.mask    = cpu_to_be32(mask.i);
+	p.val     = cpu_to_be32(val.i);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_STATE_CHG_REQ,
+			     (struct p_header80 *)&p, sizeof(p));
+}
+
+int drbd_send_sr_reply(struct drbd_conf *mdev, enum drbd_state_rv retcode)
+{
+	struct p_req_state_reply p;
+
+	p.retcode    = cpu_to_be32(retcode);
+
+	return drbd_send_cmd(mdev, USE_META_SOCKET, P_STATE_CHG_REPLY,
+			     (struct p_header80 *)&p, sizeof(p));
+}
+
+int fill_bitmap_rle_bits(struct drbd_conf *mdev,
+	struct p_compressed_bm *p,
+	struct bm_xfer_ctx *c)
+{
+	struct bitstream bs;
+	unsigned long plain_bits;
+	unsigned long tmp;
+	unsigned long rl;
+	unsigned len;
+	unsigned toggle;
+	int bits;
+
+	/* may we use this feature? */
+	if ((mdev->sync_conf.use_rle == 0) ||
+		(mdev->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, BM_PACKET_VLI_BYTES_MAX, 0);
+	memset(p->code, 0, BM_PACKET_VLI_BYTES_MAX);
+	/* 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 p_header80 *h, struct bm_xfer_ctx *c)
+{
+	struct p_compressed_bm *p = (void*)h;
+	unsigned long num_words;
+	int len;
+	int ok;
+
+	len = fill_bitmap_rle_bits(mdev, p, c);
+
+	if (len < 0)
+		return -EIO;
+
+	if (len) {
+		DCBP_set_code(p, RLE_VLI_Bits);
+		ok = _drbd_send_cmd(mdev, mdev->data.socket, P_COMPRESSED_BITMAP, h,
+			sizeof(*p) + len, 0);
+
+		c->packets[0]++;
+		c->bytes[0] += 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. */
+		num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
+		len = num_words * sizeof(long);
+		if (len)
+			drbd_bm_get_lel(mdev, c->word_offset, num_words, (unsigned long*)h->payload);
+		ok = _drbd_send_cmd(mdev, mdev->data.socket, P_BITMAP,
+				   h, sizeof(struct p_header80) + len, 0);
+		c->word_offset += num_words;
+		c->bit_offset = c->word_offset * BITS_PER_LONG;
+
+		c->packets[1]++;
+		c->bytes[1] += sizeof(struct p_header80) + len;
+
+		if (c->bit_offset > c->bm_bits)
+			c->bit_offset = c->bm_bits;
+	}
+	if (ok) {
+		if (len == 0) {
+			INFO_bm_xfer_stats(mdev, "send", c);
+			return 0;
+		} else
+			return 1;
+	}
+	return -EIO;
+}
+
+/* See the comment at receive_bitmap() */
+int _drbd_send_bitmap(struct drbd_conf *mdev)
+{
+	struct bm_xfer_ctx c;
+	struct p_header80 *p;
+	int err;
+
+	ERR_IF(!mdev->bitmap) return false;
+
+	/* maybe we should use some per thread scratch page,
+	 * and allocate that during initial device creation? */
+	p = (struct p_header80 *) __get_free_page(GFP_NOIO);
+	if (!p) {
+		dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
+		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, p, &c);
+	} while (err > 0);
+
+	free_page((unsigned long) p);
+	return err == 0;
+}
+
+int drbd_send_bitmap(struct drbd_conf *mdev)
+{
+	int err;
+
+	if (!drbd_get_data_sock(mdev))
+		return -1;
+	err = !_drbd_send_bitmap(mdev);
+	drbd_put_data_sock(mdev);
+	return err;
+}
+
+int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr, u32 set_size)
+{
+	int ok;
+	struct p_barrier_ack p;
+
+	p.barrier  = barrier_nr;
+	p.set_size = cpu_to_be32(set_size);
+
+	if (mdev->state.conn < C_CONNECTED)
+		return false;
+	ok = drbd_send_cmd(mdev, USE_META_SOCKET, P_BARRIER_ACK,
+			(struct p_header80 *)&p, sizeof(p));
+	return ok;
+}
+
+/**
+ * _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_packets cmd,
+			  u64 sector,
+			  u32 blksize,
+			  u64 block_id)
+{
+	int ok;
+	struct p_block_ack p;
+
+	p.sector   = sector;
+	p.block_id = block_id;
+	p.blksize  = blksize;
+	p.seq_num  = cpu_to_be32(atomic_add_return(1, &mdev->packet_seq));
+
+	if (!mdev->meta.socket || mdev->state.conn < C_CONNECTED)
+		return false;
+	ok = drbd_send_cmd(mdev, USE_META_SOCKET, cmd,
+				(struct p_header80 *)&p, sizeof(p));
+	return ok;
+}
+
+/* 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. */
+int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
+		     struct p_data *dp, int data_size)
+{
+	data_size -= (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+	return _drbd_send_ack(mdev, cmd, dp->sector, cpu_to_be32(data_size),
+			      dp->block_id);
+}
+
+int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
+		     struct p_block_req *rp)
+{
+	return _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.
+ * @e:		Epoch entry.
+ */
+int drbd_send_ack(struct drbd_conf *mdev,
+	enum drbd_packets cmd, struct drbd_epoch_entry *e)
+{
+	return _drbd_send_ack(mdev, cmd,
+			      cpu_to_be64(e->sector),
+			      cpu_to_be32(e->size),
+			      e->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_packets 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)
+{
+	int ok;
+	struct p_block_req p;
+
+	p.sector   = cpu_to_be64(sector);
+	p.block_id = block_id;
+	p.blksize  = cpu_to_be32(size);
+
+	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, cmd,
+				(struct p_header80 *)&p, sizeof(p));
+	return ok;
+}
+
+int drbd_send_drequest_csum(struct drbd_conf *mdev,
+			    sector_t sector, int size,
+			    void *digest, int digest_size,
+			    enum drbd_packets cmd)
+{
+	int ok;
+	struct p_block_req p;
+
+	p.sector   = cpu_to_be64(sector);
+	p.block_id = BE_DRBD_MAGIC + 0xbeef;
+	p.blksize  = cpu_to_be32(size);
+
+	p.head.magic   = BE_DRBD_MAGIC;
+	p.head.command = cpu_to_be16(cmd);
+	p.head.length  = cpu_to_be16(sizeof(p) - sizeof(struct p_header80) + digest_size);
+
+	mutex_lock(&mdev->data.mutex);
+
+	ok = (sizeof(p) == drbd_send(mdev, mdev->data.socket, &p, sizeof(p), 0));
+	ok = ok && (digest_size == drbd_send(mdev, mdev->data.socket, digest, digest_size, 0));
+
+	mutex_unlock(&mdev->data.mutex);
+
+	return ok;
+}
+
+int drbd_send_ov_request(struct drbd_conf *mdev, sector_t sector, int size)
+{
+	int ok;
+	struct p_block_req p;
+
+	p.sector   = cpu_to_be64(sector);
+	p.block_id = BE_DRBD_MAGIC + 0xbabe;
+	p.blksize  = cpu_to_be32(size);
+
+	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_OV_REQUEST,
+			   (struct p_header80 *)&p, sizeof(p));
+	return ok;
+}
+
+/* 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_conf *mdev, struct socket *sock)
+{
+	int drop_it;
+	/* long elapsed = (long)(jiffies - mdev->last_received); */
+
+	drop_it =   mdev->meta.socket == sock
+		|| !mdev->asender.task
+		|| get_t_state(&mdev->asender) != Running
+		|| mdev->state.conn < C_CONNECTED;
+
+	if (drop_it)
+		return true;
+
+	drop_it = !--mdev->ko_count;
+	if (!drop_it) {
+		dev_err(DEV, "[%s/%d] sock_sendmsg time expired, ko = %u\n",
+		       current->comm, current->pid, mdev->ko_count);
+		request_ping(mdev);
+	}
+
+	return drop_it; /* && (mdev->state == R_PRIMARY) */;
+}
+
+/* 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)
+{
+	int sent = drbd_send(mdev, mdev->data.socket, kmap(page) + offset, size, msg_flags);
+	kunmap(page);
+	if (sent == size)
+		mdev->send_cnt += size>>9;
+	return sent == size;
+}
+
+static int _drbd_send_page(struct drbd_conf *mdev, struct page *page,
+		    int offset, size_t size, unsigned msg_flags)
+{
+	mm_segment_t oldfs = get_fs();
+	int sent, ok;
+	int len = size;
+
+	/* 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);
+	set_fs(KERNEL_DS);
+	do {
+		sent = mdev->data.socket->ops->sendpage(mdev->data.socket, page,
+							offset, len,
+							msg_flags);
+		if (sent == -EAGAIN) {
+			if (we_should_drop_the_connection(mdev,
+							  mdev->data.socket))
+				break;
+			else
+				continue;
+		}
+		if (sent <= 0) {
+			dev_warn(DEV, "%s: size=%d len=%d sent=%d\n",
+			     __func__, (int)size, len, sent);
+			break;
+		}
+		len    -= sent;
+		offset += sent;
+	} while (len > 0 /* THINK && mdev->cstate >= C_CONNECTED*/);
+	set_fs(oldfs);
+	clear_bit(NET_CONGESTED, &mdev->flags);
+
+	ok = (len == 0);
+	if (likely(ok))
+		mdev->send_cnt += size>>9;
+	return ok;
+}
+
+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, 0) {
+		if (!_drbd_no_send_page(mdev, bvec->bv_page,
+				     bvec->bv_offset, bvec->bv_len,
+				     i == bio->bi_vcnt -1 ? 0 : MSG_MORE))
+			return 0;
+	}
+	return 1;
+}
+
+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, 0) {
+		if (!_drbd_send_page(mdev, bvec->bv_page,
+				     bvec->bv_offset, bvec->bv_len,
+				     i == bio->bi_vcnt -1 ? 0 : MSG_MORE))
+			return 0;
+	}
+	return 1;
+}
+
+static int _drbd_send_zc_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
+{
+	struct page *page = e->pages;
+	unsigned len = e->size;
+	/* hint all but last page with MSG_MORE */
+	page_chain_for_each(page) {
+		unsigned l = min_t(unsigned, len, PAGE_SIZE);
+		if (!_drbd_send_page(mdev, page, 0, l,
+				page_chain_next(page) ? MSG_MORE : 0))
+			return 0;
+		len -= l;
+	}
+	return 1;
+}
+
+static u32 bio_flags_to_wire(struct drbd_conf *mdev, unsigned long bi_rw)
+{
+	if (mdev->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)
+{
+	int ok = 1;
+	struct p_data p;
+	unsigned int dp_flags = 0;
+	void *dgb;
+	int dgs;
+
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_w_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_w_tfm) : 0;
+
+	if (req->size <= DRBD_MAX_SIZE_H80_PACKET) {
+		p.head.h80.magic   = BE_DRBD_MAGIC;
+		p.head.h80.command = cpu_to_be16(P_DATA);
+		p.head.h80.length  =
+			cpu_to_be16(sizeof(p) - sizeof(union p_header) + dgs + req->size);
+	} else {
+		p.head.h95.magic   = BE_DRBD_MAGIC_BIG;
+		p.head.h95.command = cpu_to_be16(P_DATA);
+		p.head.h95.length  =
+			cpu_to_be32(sizeof(p) - sizeof(union p_header) + dgs + req->size);
+	}
+
+	p.sector   = cpu_to_be64(req->sector);
+	p.block_id = (unsigned long)req;
+	p.seq_num  = cpu_to_be32(req->seq_num =
+				 atomic_add_return(1, &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;
+
+	p.dp_flags = cpu_to_be32(dp_flags);
+	set_bit(UNPLUG_REMOTE, &mdev->flags);
+	ok = (sizeof(p) ==
+		drbd_send(mdev, mdev->data.socket, &p, sizeof(p), dgs ? MSG_MORE : 0));
+	if (ok && dgs) {
+		dgb = mdev->int_dig_out;
+		drbd_csum_bio(mdev, mdev->integrity_w_tfm, req->master_bio, dgb);
+		ok = dgs == drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
+	}
+	if (ok) {
+		/* 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 (mdev->net_conf->wire_protocol == DRBD_PROT_A || dgs)
+			ok = _drbd_send_bio(mdev, req->master_bio);
+		else
+			ok = _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->integrity_w_tfm, req->master_bio, digest);
+			if (memcmp(mdev->int_dig_out, digest, dgs)) {
+				dev_warn(DEV,
+					"Digest mismatch, buffer modified by upper layers during write: %llus +%u\n",
+					(unsigned long long)req->sector, req->size);
+			}
+		} /* else if (dgs > 64) {
+		     ... Be noisy about digest too large ...
+		} */
+	}
+
+	drbd_put_data_sock(mdev);
+
+	return ok;
+}
+
+/* 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_packets cmd,
+		    struct drbd_epoch_entry *e)
+{
+	int ok;
+	struct p_data p;
+	void *dgb;
+	int dgs;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_w_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_w_tfm) : 0;
+
+	if (e->size <= DRBD_MAX_SIZE_H80_PACKET) {
+		p.head.h80.magic   = BE_DRBD_MAGIC;
+		p.head.h80.command = cpu_to_be16(cmd);
+		p.head.h80.length  =
+			cpu_to_be16(sizeof(p) - sizeof(struct p_header80) + dgs + e->size);
+	} else {
+		p.head.h95.magic   = BE_DRBD_MAGIC_BIG;
+		p.head.h95.command = cpu_to_be16(cmd);
+		p.head.h95.length  =
+			cpu_to_be32(sizeof(p) - sizeof(struct p_header80) + dgs + e->size);
+	}
+
+	p.sector   = cpu_to_be64(e->sector);
+	p.block_id = e->block_id;
+	/* p.seq_num  = 0;    No sequence numbers here.. */
+
+	/* Only called by our kernel thread.
+	 * This one may be interrupted by DRBD_SIG and/or DRBD_SIGKILL
+	 * in response to admin command or module unload.
+	 */
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+
+	ok = sizeof(p) == drbd_send(mdev, mdev->data.socket, &p, sizeof(p), dgs ? MSG_MORE : 0);
+	if (ok && dgs) {
+		dgb = mdev->int_dig_out;
+		drbd_csum_ee(mdev, mdev->integrity_w_tfm, e, dgb);
+		ok = dgs == drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
+	}
+	if (ok)
+		ok = _drbd_send_zc_ee(mdev, e);
+
+	drbd_put_data_sock(mdev);
+
+	return ok;
+}
+
+int drbd_send_oos(struct drbd_conf *mdev, struct drbd_request *req)
+{
+	struct p_block_desc p;
+
+	p.sector  = cpu_to_be64(req->sector);
+	p.blksize = cpu_to_be32(req->size);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_OUT_OF_SYNC, &p.head, sizeof(p));
+}
+
+/*
+  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_conf *mdev, struct socket *sock,
+	      void *buf, size_t size, unsigned msg_flags)
+{
+	struct kvec iov;
+	struct msghdr msg;
+	int rv, sent = 0;
+
+	if (!sock)
+		return -1000;
+
+	/* 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 == mdev->data.socket) {
+		mdev->ko_count = mdev->net_conf->ko_count;
+		drbd_update_congested(mdev);
+	}
+	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(mdev, sock))
+				break;
+			else
+				continue;
+		}
+		D_ASSERT(rv != 0);
+		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 == mdev->data.socket)
+		clear_bit(NET_CONGESTED, &mdev->flags);
+
+	if (rv <= 0) {
+		if (rv != -EAGAIN) {
+			dev_err(DEV, "%s_sendmsg returned %d\n",
+			    sock == mdev->meta.socket ? "msock" : "sock",
+			    rv);
+			drbd_force_state(mdev, NS(conn, C_BROKEN_PIPE));
+		} else
+			drbd_force_state(mdev, NS(conn, C_TIMEOUT));
+	}
+
+	return sent;
+}
+
+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->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->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)
+{
+	/* This way we get a compile error when sync_conf grows,
+	   and we forgot to initialize it here */
+	mdev->sync_conf = (struct syncer_conf) {
+		/* .rate = */		DRBD_RATE_DEF,
+		/* .after = */		DRBD_AFTER_DEF,
+		/* .al_extents = */	DRBD_AL_EXTENTS_DEF,
+		/* .verify_alg = */	{}, 0,
+		/* .cpu_mask = */	{}, 0,
+		/* .csums_alg = */	{}, 0,
+		/* .use_rle = */	0,
+		/* .on_no_data = */	DRBD_ON_NO_DATA_DEF,
+		/* .c_plan_ahead = */	DRBD_C_PLAN_AHEAD_DEF,
+		/* .c_delay_target = */	DRBD_C_DELAY_TARGET_DEF,
+		/* .c_fill_target = */	DRBD_C_FILL_TARGET_DEF,
+		/* .c_max_rate = */	DRBD_C_MAX_RATE_DEF,
+		/* .c_min_rate = */	DRBD_C_MIN_RATE_DEF
+	};
+
+	/* Have to use that way, because the layout differs between
+	   big endian and little endian */
+	mdev->state = (union drbd_state) {
+		{ .role = R_SECONDARY,
+		  .peer = R_UNKNOWN,
+		  .conn = C_STANDALONE,
+		  .disk = D_DISKLESS,
+		  .pdsk = D_UNKNOWN,
+		  .susp = 0,
+		  .susp_nod = 0,
+		  .susp_fen = 0
+		} };
+}
+
+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->net_cnt, 0);
+	atomic_set(&mdev->packet_seq, 0);
+	atomic_set(&mdev->pp_in_use, 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);
+
+	mutex_init(&mdev->md_io_mutex);
+	mutex_init(&mdev->data.mutex);
+	mutex_init(&mdev->meta.mutex);
+	sema_init(&mdev->data.work.s, 0);
+	sema_init(&mdev->meta.work.s, 0);
+	mutex_init(&mdev->state_mutex);
+
+	spin_lock_init(&mdev->data.work.q_lock);
+	spin_lock_init(&mdev->meta.work.q_lock);
+
+	spin_lock_init(&mdev->al_lock);
+	spin_lock_init(&mdev->req_lock);
+	spin_lock_init(&mdev->peer_seq_lock);
+	spin_lock_init(&mdev->epoch_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->data.work.q);
+	INIT_LIST_HEAD(&mdev->meta.work.q);
+	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;
+	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->net_cnt_wait);
+	init_waitqueue_head(&mdev->ee_wait);
+	init_waitqueue_head(&mdev->al_wait);
+	init_waitqueue_head(&mdev->seq_wait);
+
+	drbd_thread_init(mdev, &mdev->receiver, drbdd_init);
+	drbd_thread_init(mdev, &mdev->worker, drbd_worker);
+	drbd_thread_init(mdev, &mdev->asender, drbd_asender);
+
+	mdev->agreed_pro_version = PRO_VERSION_MAX;
+	mdev->write_ordering = WO_bdev_flush;
+	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->receiver.t_state != None)
+		dev_err(DEV, "ASSERT FAILED: receiver t_state == %d expected 0.\n",
+				mdev->receiver.t_state);
+
+	/* no need to lock it, I'm the only thread alive */
+	if (atomic_read(&mdev->current_epoch->epoch_size) !=  0)
+		dev_err(DEV, "epoch_size:%d\n", atomic_read(&mdev->current_epoch->epoch_size));
+	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->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_resources(mdev);
+	clear_bit(AL_SUSPENDED, &mdev->flags);
+
+	/*
+	 * currently we drbd_init_ee only on module load, so
+	 * we may do drbd_release_ee only on module unload!
+	 */
+	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->data.work.q));
+	D_ASSERT(list_empty(&mdev->meta.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_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_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;
+
+	/* 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_epoch_entry), 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_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_ee_lists(struct drbd_conf *mdev)
+{
+	int rr;
+
+	rr = drbd_release_ee(mdev, &mdev->active_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in active list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->sync_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in sync list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->read_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in read list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->done_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in done list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->net_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in net list found!\n", rr);
+}
+
+/* caution. no locking.
+ * currently only used from module cleanup code. */
+static void drbd_delete_device(unsigned int minor)
+{
+	struct drbd_conf *mdev = minor_to_mdev(minor);
+
+	if (!mdev)
+		return;
+
+	/* paranoia asserts */
+	if (mdev->open_cnt != 0)
+		dev_err(DEV, "open_cnt = %d in %s:%u", mdev->open_cnt,
+				__FILE__ , __LINE__);
+
+	ERR_IF (!list_empty(&mdev->data.work.q)) {
+		struct list_head *lp;
+		list_for_each(lp, &mdev->data.work.q) {
+			dev_err(DEV, "lp = %p\n", lp);
+		}
+	};
+	/* end paranoia asserts */
+
+	del_gendisk(mdev->vdisk);
+
+	/* cleanup stuff that may have been allocated during
+	 * device (re-)configuration or state changes */
+
+	if (mdev->this_bdev)
+		bdput(mdev->this_bdev);
+
+	drbd_free_resources(mdev);
+
+	drbd_release_ee_lists(mdev);
+
+	/* should be freed on disconnect? */
+	kfree(mdev->ee_hash);
+	/*
+	mdev->ee_hash_s = 0;
+	mdev->ee_hash = NULL;
+	*/
+
+	lc_destroy(mdev->act_log);
+	lc_destroy(mdev->resync);
+
+	kfree(mdev->p_uuid);
+	/* mdev->p_uuid = NULL; */
+
+	kfree(mdev->int_dig_out);
+	kfree(mdev->int_dig_in);
+	kfree(mdev->int_dig_vv);
+
+	/* cleanup the rest that has been
+	 * allocated from drbd_new_device
+	 * and actually free the mdev itself */
+	drbd_free_mdev(mdev);
+}
+
+static void drbd_cleanup(void)
+{
+	unsigned int i;
+
+	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);
+
+	drbd_nl_cleanup();
+
+	if (minor_table) {
+		i = minor_count;
+		while (i--)
+			drbd_delete_device(i);
+		drbd_destroy_mempools();
+	}
+
+	kfree(minor_table);
+
+	unregister_blkdev(DRBD_MAJOR, "drbd");
+
+	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->flags)) {
+		r |= (1 << BDI_async_congested);
+		reason = reason == 'b' ? 'a' : 'n';
+	}
+
+out:
+	mdev->congestion_reason = reason;
+	return r;
+}
+
+struct drbd_conf *drbd_new_device(unsigned int minor)
+{
+	struct drbd_conf *mdev;
+	struct gendisk *disk;
+	struct request_queue *q;
+
+	/* GFP_KERNEL, we are outside of all write-out paths */
+	mdev = kzalloc(sizeof(struct drbd_conf), GFP_KERNEL);
+	if (!mdev)
+		return NULL;
+	if (!zalloc_cpumask_var(&mdev->cpu_mask, GFP_KERNEL))
+		goto out_no_cpumask;
+
+	mdev->minor = minor;
+
+	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->req_lock;
+
+	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;
+	/* no need to lock access, we are still initializing this minor device. */
+	if (!tl_init(mdev))
+		goto out_no_tl;
+
+	mdev->app_reads_hash = kzalloc(APP_R_HSIZE*sizeof(void *), GFP_KERNEL);
+	if (!mdev->app_reads_hash)
+		goto out_no_app_reads;
+
+	mdev->current_epoch = kzalloc(sizeof(struct drbd_epoch), GFP_KERNEL);
+	if (!mdev->current_epoch)
+		goto out_no_epoch;
+
+	INIT_LIST_HEAD(&mdev->current_epoch->list);
+	mdev->epochs = 1;
+
+	return mdev;
+
+/* out_whatever_else:
+	kfree(mdev->current_epoch); */
+out_no_epoch:
+	kfree(mdev->app_reads_hash);
+out_no_app_reads:
+	tl_cleanup(mdev);
+out_no_tl:
+	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:
+	free_cpumask_var(mdev->cpu_mask);
+out_no_cpumask:
+	kfree(mdev);
+	return NULL;
+}
+
+/* counterpart of drbd_new_device.
+ * last part of drbd_delete_device. */
+void drbd_free_mdev(struct drbd_conf *mdev)
+{
+	kfree(mdev->current_epoch);
+	kfree(mdev->app_reads_hash);
+	tl_cleanup(mdev);
+	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);
+	free_cpumask_var(mdev->cpu_mask);
+	drbd_free_tl_hash(mdev);
+	kfree(mdev);
+}
+
+
+int __init drbd_init(void)
+{
+	int err;
+
+	if (sizeof(struct p_handshake) != 80) {
+		printk(KERN_ERR
+		       "drbd: never change the size or layout "
+		       "of the HandShake packet.\n");
+		return -EINVAL;
+	}
+
+	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 = 8;
+#endif
+	}
+
+	err = drbd_nl_init();
+	if (err)
+		return err;
+
+	err = register_blkdev(DRBD_MAJOR, "drbd");
+	if (err) {
+		printk(KERN_ERR
+		       "drbd: unable to register block device major %d\n",
+		       DRBD_MAJOR);
+		return err;
+	}
+
+	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 */
+	minor_table = kzalloc(sizeof(struct drbd_conf *)*minor_count,
+				GFP_KERNEL);
+	if (!minor_table)
+		goto Enomem;
+
+	err = drbd_create_mempools();
+	if (err)
+		goto Enomem;
+
+	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 Enomem;
+	}
+
+	rwlock_init(&global_state_lock);
+
+	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);
+	printk(KERN_INFO "drbd: minor_table @ 0x%p\n", minor_table);
+
+	return 0; /* Success! */
+
+Enomem:
+	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_conf *mdev)
+{
+	if (mdev->data.socket) {
+		mutex_lock(&mdev->data.mutex);
+		kernel_sock_shutdown(mdev->data.socket, SHUT_RDWR);
+		sock_release(mdev->data.socket);
+		mdev->data.socket = NULL;
+		mutex_unlock(&mdev->data.mutex);
+	}
+	if (mdev->meta.socket) {
+		mutex_lock(&mdev->meta.mutex);
+		kernel_sock_shutdown(mdev->meta.socket, SHUT_RDWR);
+		sock_release(mdev->meta.socket);
+		mdev->meta.socket = NULL;
+		mutex_unlock(&mdev->meta.mutex);
+	}
+}
+
+
+void drbd_free_resources(struct drbd_conf *mdev)
+{
+	crypto_free_hash(mdev->csums_tfm);
+	mdev->csums_tfm = NULL;
+	crypto_free_hash(mdev->verify_tfm);
+	mdev->verify_tfm = NULL;
+	crypto_free_hash(mdev->cram_hmac_tfm);
+	mdev->cram_hmac_tfm = NULL;
+	crypto_free_hash(mdev->integrity_w_tfm);
+	mdev->integrity_w_tfm = NULL;
+	crypto_free_hash(mdev->integrity_r_tfm);
+	mdev->integrity_r_tfm = NULL;
+
+	drbd_free_sock(mdev);
+
+	__no_warn(local,
+		  drbd_free_bc(mdev->ldev);
+		  mdev->ldev = NULL;);
+}
+
+/* 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 <-- sync_conf.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;
+
+	mutex_lock(&mdev->md_io_mutex);
+	buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+	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);
+
+	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);
+
+	mutex_unlock(&mdev->md_io_mutex);
+	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.  Currently only: ERR_IO_MD_DISK, ERR_MD_INVALID.
+ */
+int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+	struct meta_data_on_disk *buffer;
+	int i, rv = NO_ERROR;
+
+	if (!get_ldev_if_state(mdev, D_ATTACHING))
+		return ERR_IO_MD_DISK;
+
+	mutex_lock(&mdev->md_io_mutex);
+	buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+
+	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;
+	}
+
+	if (be32_to_cpu(buffer->magic) != DRBD_MD_MAGIC) {
+		dev_err(DEV, "Error while reading metadata, magic not found.\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);
+	mdev->sync_conf.al_extents = be32_to_cpu(buffer->al_nr_extents);
+	bdev->md.device_uuid = be64_to_cpu(buffer->device_uuid);
+
+	spin_lock_irq(&mdev->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->req_lock);
+
+	if (mdev->sync_conf.al_extents < 7)
+		mdev->sync_conf.al_extents = 127;
+
+ err:
+	mutex_unlock(&mdev->md_io_mutex);
+	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_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct bm_io_work *work = container_of(w, struct bm_io_work, w);
+	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(BITMAP_IO, &mdev->flags);
+	smp_mb__after_clear_bit();
+	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 1;
+}
+
+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;);
+
+	if (mdev->md_io_tmpp) {
+		__free_page(mdev->md_io_tmpp);
+		mdev->md_io_tmpp = NULL;
+	}
+	clear_bit(GO_DISKLESS, &mdev->flags);
+}
+
+static int w_go_diskless(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	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 1;
+}
+
+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->data.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->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->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->data.work, &mdev->bm_io_work.w);
+	}
+	spin_unlock_irq(&mdev->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->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->data.work, &mdev->md_sync_work);
+}
+
+static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	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 1;
+}
+
+#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);