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, 4678 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
new file mode 100644
index 00000000..43beaca5
--- /dev/null
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -0,0 +1,4678 @@
+/*
+   drbd_receiver.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/module.h>
+
+#include <asm/uaccess.h>
+#include <net/sock.h>
+
+#include <linux/drbd.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/in.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/pkt_sched.h>
+#define __KERNEL_SYSCALLS__
+#include <linux/unistd.h>
+#include <linux/vmalloc.h>
+#include <linux/random.h>
+#include <linux/string.h>
+#include <linux/scatterlist.h>
+#include "drbd_int.h"
+#include "drbd_req.h"
+
+#include "drbd_vli.h"
+
+enum finish_epoch {
+	FE_STILL_LIVE,
+	FE_DESTROYED,
+	FE_RECYCLED,
+};
+
+static int drbd_do_handshake(struct drbd_conf *mdev);
+static int drbd_do_auth(struct drbd_conf *mdev);
+
+static enum finish_epoch drbd_may_finish_epoch(struct drbd_conf *, struct drbd_epoch *, enum epoch_event);
+static int e_end_block(struct drbd_conf *, struct drbd_work *, int);
+
+
+#define GFP_TRY	(__GFP_HIGHMEM | __GFP_NOWARN)
+
+/*
+ * some helper functions to deal with single linked page lists,
+ * page->private being our "next" pointer.
+ */
+
+/* If at least n pages are linked at head, get n pages off.
+ * Otherwise, don't modify head, and return NULL.
+ * Locking is the responsibility of the caller.
+ */
+static struct page *page_chain_del(struct page **head, int n)
+{
+	struct page *page;
+	struct page *tmp;
+
+	BUG_ON(!n);
+	BUG_ON(!head);
+
+	page = *head;
+
+	if (!page)
+		return NULL;
+
+	while (page) {
+		tmp = page_chain_next(page);
+		if (--n == 0)
+			break; /* found sufficient pages */
+		if (tmp == NULL)
+			/* insufficient pages, don't use any of them. */
+			return NULL;
+		page = tmp;
+	}
+
+	/* add end of list marker for the returned list */
+	set_page_private(page, 0);
+	/* actual return value, and adjustment of head */
+	page = *head;
+	*head = tmp;
+	return page;
+}
+
+/* may be used outside of locks to find the tail of a (usually short)
+ * "private" page chain, before adding it back to a global chain head
+ * with page_chain_add() under a spinlock. */
+static struct page *page_chain_tail(struct page *page, int *len)
+{
+	struct page *tmp;
+	int i = 1;
+	while ((tmp = page_chain_next(page)))
+		++i, page = tmp;
+	if (len)
+		*len = i;
+	return page;
+}
+
+static int page_chain_free(struct page *page)
+{
+	struct page *tmp;
+	int i = 0;
+	page_chain_for_each_safe(page, tmp) {
+		put_page(page);
+		++i;
+	}
+	return i;
+}
+
+static void page_chain_add(struct page **head,
+		struct page *chain_first, struct page *chain_last)
+{
+#if 1
+	struct page *tmp;
+	tmp = page_chain_tail(chain_first, NULL);
+	BUG_ON(tmp != chain_last);
+#endif
+
+	/* add chain to head */
+	set_page_private(chain_last, (unsigned long)*head);
+	*head = chain_first;
+}
+
+static struct page *drbd_pp_first_pages_or_try_alloc(struct drbd_conf *mdev, int number)
+{
+	struct page *page = NULL;
+	struct page *tmp = NULL;
+	int i = 0;
+
+	/* Yes, testing drbd_pp_vacant outside the lock is racy.
+	 * So what. It saves a spin_lock. */
+	if (drbd_pp_vacant >= number) {
+		spin_lock(&drbd_pp_lock);
+		page = page_chain_del(&drbd_pp_pool, number);
+		if (page)
+			drbd_pp_vacant -= number;
+		spin_unlock(&drbd_pp_lock);
+		if (page)
+			return page;
+	}
+
+	/* GFP_TRY, because we must not cause arbitrary write-out: in a DRBD
+	 * "criss-cross" setup, that might cause write-out on some other DRBD,
+	 * which in turn might block on the other node at this very place.  */
+	for (i = 0; i < number; i++) {
+		tmp = alloc_page(GFP_TRY);
+		if (!tmp)
+			break;
+		set_page_private(tmp, (unsigned long)page);
+		page = tmp;
+	}
+
+	if (i == number)
+		return page;
+
+	/* Not enough pages immediately available this time.
+	 * No need to jump around here, drbd_pp_alloc will retry this
+	 * function "soon". */
+	if (page) {
+		tmp = page_chain_tail(page, NULL);
+		spin_lock(&drbd_pp_lock);
+		page_chain_add(&drbd_pp_pool, page, tmp);
+		drbd_pp_vacant += i;
+		spin_unlock(&drbd_pp_lock);
+	}
+	return NULL;
+}
+
+static void reclaim_net_ee(struct drbd_conf *mdev, struct list_head *to_be_freed)
+{
+	struct drbd_epoch_entry *e;
+	struct list_head *le, *tle;
+
+	/* The EEs are always appended to the end of the list. Since
+	   they are sent in order over the wire, they have to finish
+	   in order. As soon as we see the first not finished we can
+	   stop to examine the list... */
+
+	list_for_each_safe(le, tle, &mdev->net_ee) {
+		e = list_entry(le, struct drbd_epoch_entry, w.list);
+		if (drbd_ee_has_active_page(e))
+			break;
+		list_move(le, to_be_freed);
+	}
+}
+
+static void drbd_kick_lo_and_reclaim_net(struct drbd_conf *mdev)
+{
+	LIST_HEAD(reclaimed);
+	struct drbd_epoch_entry *e, *t;
+
+	spin_lock_irq(&mdev->req_lock);
+	reclaim_net_ee(mdev, &reclaimed);
+	spin_unlock_irq(&mdev->req_lock);
+
+	list_for_each_entry_safe(e, t, &reclaimed, w.list)
+		drbd_free_net_ee(mdev, e);
+}
+
+/**
+ * drbd_pp_alloc() - Returns @number pages, retries forever (or until signalled)
+ * @mdev:	DRBD device.
+ * @number:	number of pages requested
+ * @retry:	whether to retry, if not enough pages are available right now
+ *
+ * Tries to allocate number pages, first from our own page pool, then from
+ * the kernel, unless this allocation would exceed the max_buffers setting.
+ * Possibly retry until DRBD frees sufficient pages somewhere else.
+ *
+ * Returns a page chain linked via page->private.
+ */
+static struct page *drbd_pp_alloc(struct drbd_conf *mdev, unsigned number, bool retry)
+{
+	struct page *page = NULL;
+	DEFINE_WAIT(wait);
+
+	/* Yes, we may run up to @number over max_buffers. If we
+	 * follow it strictly, the admin will get it wrong anyways. */
+	if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers)
+		page = drbd_pp_first_pages_or_try_alloc(mdev, number);
+
+	while (page == NULL) {
+		prepare_to_wait(&drbd_pp_wait, &wait, TASK_INTERRUPTIBLE);
+
+		drbd_kick_lo_and_reclaim_net(mdev);
+
+		if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
+			page = drbd_pp_first_pages_or_try_alloc(mdev, number);
+			if (page)
+				break;
+		}
+
+		if (!retry)
+			break;
+
+		if (signal_pending(current)) {
+			dev_warn(DEV, "drbd_pp_alloc interrupted!\n");
+			break;
+		}
+
+		schedule();
+	}
+	finish_wait(&drbd_pp_wait, &wait);
+
+	if (page)
+		atomic_add(number, &mdev->pp_in_use);
+	return page;
+}
+
+/* Must not be used from irq, as that may deadlock: see drbd_pp_alloc.
+ * Is also used from inside an other spin_lock_irq(&mdev->req_lock);
+ * Either links the page chain back to the global pool,
+ * or returns all pages to the system. */
+static void drbd_pp_free(struct drbd_conf *mdev, struct page *page, int is_net)
+{
+	atomic_t *a = is_net ? &mdev->pp_in_use_by_net : &mdev->pp_in_use;
+	int i;
+
+	if (drbd_pp_vacant > (DRBD_MAX_BIO_SIZE/PAGE_SIZE)*minor_count)
+		i = page_chain_free(page);
+	else {
+		struct page *tmp;
+		tmp = page_chain_tail(page, &i);
+		spin_lock(&drbd_pp_lock);
+		page_chain_add(&drbd_pp_pool, page, tmp);
+		drbd_pp_vacant += i;
+		spin_unlock(&drbd_pp_lock);
+	}
+	i = atomic_sub_return(i, a);
+	if (i < 0)
+		dev_warn(DEV, "ASSERTION FAILED: %s: %d < 0\n",
+			is_net ? "pp_in_use_by_net" : "pp_in_use", i);
+	wake_up(&drbd_pp_wait);
+}
+
+/*
+You need to hold the req_lock:
+ _drbd_wait_ee_list_empty()
+
+You must not have the req_lock:
+ drbd_free_ee()
+ drbd_alloc_ee()
+ drbd_init_ee()
+ drbd_release_ee()
+ drbd_ee_fix_bhs()
+ drbd_process_done_ee()
+ drbd_clear_done_ee()
+ drbd_wait_ee_list_empty()
+*/
+
+struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
+				     u64 id,
+				     sector_t sector,
+				     unsigned int data_size,
+				     gfp_t gfp_mask) __must_hold(local)
+{
+	struct drbd_epoch_entry *e;
+	struct page *page;
+	unsigned nr_pages = (data_size + PAGE_SIZE -1) >> PAGE_SHIFT;
+
+	if (drbd_insert_fault(mdev, DRBD_FAULT_AL_EE))
+		return NULL;
+
+	e = mempool_alloc(drbd_ee_mempool, gfp_mask & ~__GFP_HIGHMEM);
+	if (!e) {
+		if (!(gfp_mask & __GFP_NOWARN))
+			dev_err(DEV, "alloc_ee: Allocation of an EE failed\n");
+		return NULL;
+	}
+
+	page = drbd_pp_alloc(mdev, nr_pages, (gfp_mask & __GFP_WAIT));
+	if (!page)
+		goto fail;
+
+	INIT_HLIST_NODE(&e->collision);
+	e->epoch = NULL;
+	e->mdev = mdev;
+	e->pages = page;
+	atomic_set(&e->pending_bios, 0);
+	e->size = data_size;
+	e->flags = 0;
+	e->sector = sector;
+	e->block_id = id;
+
+	return e;
+
+ fail:
+	mempool_free(e, drbd_ee_mempool);
+	return NULL;
+}
+
+void drbd_free_some_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e, int is_net)
+{
+	if (e->flags & EE_HAS_DIGEST)
+		kfree(e->digest);
+	drbd_pp_free(mdev, e->pages, is_net);
+	D_ASSERT(atomic_read(&e->pending_bios) == 0);
+	D_ASSERT(hlist_unhashed(&e->collision));
+	mempool_free(e, drbd_ee_mempool);
+}
+
+int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list)
+{
+	LIST_HEAD(work_list);
+	struct drbd_epoch_entry *e, *t;
+	int count = 0;
+	int is_net = list == &mdev->net_ee;
+
+	spin_lock_irq(&mdev->req_lock);
+	list_splice_init(list, &work_list);
+	spin_unlock_irq(&mdev->req_lock);
+
+	list_for_each_entry_safe(e, t, &work_list, w.list) {
+		drbd_free_some_ee(mdev, e, is_net);
+		count++;
+	}
+	return count;
+}
+
+
+/*
+ * This function is called from _asender only_
+ * but see also comments in _req_mod(,barrier_acked)
+ * and receive_Barrier.
+ *
+ * Move entries from net_ee to done_ee, if ready.
+ * Grab done_ee, call all callbacks, free the entries.
+ * The callbacks typically send out ACKs.
+ */
+static int drbd_process_done_ee(struct drbd_conf *mdev)
+{
+	LIST_HEAD(work_list);
+	LIST_HEAD(reclaimed);
+	struct drbd_epoch_entry *e, *t;
+	int ok = (mdev->state.conn >= C_WF_REPORT_PARAMS);
+
+	spin_lock_irq(&mdev->req_lock);
+	reclaim_net_ee(mdev, &reclaimed);
+	list_splice_init(&mdev->done_ee, &work_list);
+	spin_unlock_irq(&mdev->req_lock);
+
+	list_for_each_entry_safe(e, t, &reclaimed, w.list)
+		drbd_free_net_ee(mdev, e);
+
+	/* possible callbacks here:
+	 * e_end_block, and e_end_resync_block, e_send_discard_ack.
+	 * all ignore the last argument.
+	 */
+	list_for_each_entry_safe(e, t, &work_list, w.list) {
+		/* list_del not necessary, next/prev members not touched */
+		ok = e->w.cb(mdev, &e->w, !ok) && ok;
+		drbd_free_ee(mdev, e);
+	}
+	wake_up(&mdev->ee_wait);
+
+	return ok;
+}
+
+void _drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
+{
+	DEFINE_WAIT(wait);
+
+	/* avoids spin_lock/unlock
+	 * and calling prepare_to_wait in the fast path */
+	while (!list_empty(head)) {
+		prepare_to_wait(&mdev->ee_wait, &wait, TASK_UNINTERRUPTIBLE);
+		spin_unlock_irq(&mdev->req_lock);
+		io_schedule();
+		finish_wait(&mdev->ee_wait, &wait);
+		spin_lock_irq(&mdev->req_lock);
+	}
+}
+
+void drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
+{
+	spin_lock_irq(&mdev->req_lock);
+	_drbd_wait_ee_list_empty(mdev, head);
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+/* see also kernel_accept; which is only present since 2.6.18.
+ * also we want to log which part of it failed, exactly */
+static int drbd_accept(struct drbd_conf *mdev, const char **what,
+		struct socket *sock, struct socket **newsock)
+{
+	struct sock *sk = sock->sk;
+	int err = 0;
+
+	*what = "listen";
+	err = sock->ops->listen(sock, 5);
+	if (err < 0)
+		goto out;
+
+	*what = "sock_create_lite";
+	err = sock_create_lite(sk->sk_family, sk->sk_type, sk->sk_protocol,
+			       newsock);
+	if (err < 0)
+		goto out;
+
+	*what = "accept";
+	err = sock->ops->accept(sock, *newsock, 0);
+	if (err < 0) {
+		sock_release(*newsock);
+		*newsock = NULL;
+		goto out;
+	}
+	(*newsock)->ops  = sock->ops;
+
+out:
+	return err;
+}
+
+static int drbd_recv_short(struct drbd_conf *mdev, struct socket *sock,
+		    void *buf, size_t size, int flags)
+{
+	mm_segment_t oldfs;
+	struct kvec iov = {
+		.iov_base = buf,
+		.iov_len = size,
+	};
+	struct msghdr msg = {
+		.msg_iovlen = 1,
+		.msg_iov = (struct iovec *)&iov,
+		.msg_flags = (flags ? flags : MSG_WAITALL | MSG_NOSIGNAL)
+	};
+	int rv;
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	rv = sock_recvmsg(sock, &msg, size, msg.msg_flags);
+	set_fs(oldfs);
+
+	return rv;
+}
+
+static int drbd_recv(struct drbd_conf *mdev, void *buf, size_t size)
+{
+	mm_segment_t oldfs;
+	struct kvec iov = {
+		.iov_base = buf,
+		.iov_len = size,
+	};
+	struct msghdr msg = {
+		.msg_iovlen = 1,
+		.msg_iov = (struct iovec *)&iov,
+		.msg_flags = MSG_WAITALL | MSG_NOSIGNAL
+	};
+	int rv;
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+
+	for (;;) {
+		rv = sock_recvmsg(mdev->data.socket, &msg, size, msg.msg_flags);
+		if (rv == size)
+			break;
+
+		/* Note:
+		 * ECONNRESET	other side closed the connection
+		 * ERESTARTSYS	(on  sock) we got a signal
+		 */
+
+		if (rv < 0) {
+			if (rv == -ECONNRESET)
+				dev_info(DEV, "sock was reset by peer\n");
+			else if (rv != -ERESTARTSYS)
+				dev_err(DEV, "sock_recvmsg returned %d\n", rv);
+			break;
+		} else if (rv == 0) {
+			dev_info(DEV, "sock was shut down by peer\n");
+			break;
+		} else	{
+			/* signal came in, or peer/link went down,
+			 * after we read a partial message
+			 */
+			/* D_ASSERT(signal_pending(current)); */
+			break;
+		}
+	};
+
+	set_fs(oldfs);
+
+	if (rv != size)
+		drbd_force_state(mdev, NS(conn, C_BROKEN_PIPE));
+
+	return rv;
+}
+
+/* quoting tcp(7):
+ *   On individual connections, the socket buffer size must be set prior to the
+ *   listen(2) or connect(2) calls in order to have it take effect.
+ * This is our wrapper to do so.
+ */
+static void drbd_setbufsize(struct socket *sock, unsigned int snd,
+		unsigned int rcv)
+{
+	/* open coded SO_SNDBUF, SO_RCVBUF */
+	if (snd) {
+		sock->sk->sk_sndbuf = snd;
+		sock->sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
+	}
+	if (rcv) {
+		sock->sk->sk_rcvbuf = rcv;
+		sock->sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
+	}
+}
+
+static struct socket *drbd_try_connect(struct drbd_conf *mdev)
+{
+	const char *what;
+	struct socket *sock;
+	struct sockaddr_in6 src_in6;
+	int err;
+	int disconnect_on_error = 1;
+
+	if (!get_net_conf(mdev))
+		return NULL;
+
+	what = "sock_create_kern";
+	err = sock_create_kern(((struct sockaddr *)mdev->net_conf->my_addr)->sa_family,
+		SOCK_STREAM, IPPROTO_TCP, &sock);
+	if (err < 0) {
+		sock = NULL;
+		goto out;
+	}
+
+	sock->sk->sk_rcvtimeo =
+	sock->sk->sk_sndtimeo =  mdev->net_conf->try_connect_int*HZ;
+	drbd_setbufsize(sock, mdev->net_conf->sndbuf_size,
+			mdev->net_conf->rcvbuf_size);
+
+       /* explicitly bind to the configured IP as source IP
+	*  for the outgoing connections.
+	*  This is needed for multihomed hosts and to be
+	*  able to use lo: interfaces for drbd.
+	* Make sure to use 0 as port number, so linux selects
+	*  a free one dynamically.
+	*/
+	memcpy(&src_in6, mdev->net_conf->my_addr,
+	       min_t(int, mdev->net_conf->my_addr_len, sizeof(src_in6)));
+	if (((struct sockaddr *)mdev->net_conf->my_addr)->sa_family == AF_INET6)
+		src_in6.sin6_port = 0;
+	else
+		((struct sockaddr_in *)&src_in6)->sin_port = 0; /* AF_INET & AF_SCI */
+
+	what = "bind before connect";
+	err = sock->ops->bind(sock,
+			      (struct sockaddr *) &src_in6,
+			      mdev->net_conf->my_addr_len);
+	if (err < 0)
+		goto out;
+
+	/* connect may fail, peer not yet available.
+	 * stay C_WF_CONNECTION, don't go Disconnecting! */
+	disconnect_on_error = 0;
+	what = "connect";
+	err = sock->ops->connect(sock,
+				 (struct sockaddr *)mdev->net_conf->peer_addr,
+				 mdev->net_conf->peer_addr_len, 0);
+
+out:
+	if (err < 0) {
+		if (sock) {
+			sock_release(sock);
+			sock = NULL;
+		}
+		switch (-err) {
+			/* timeout, busy, signal pending */
+		case ETIMEDOUT: case EAGAIN: case EINPROGRESS:
+		case EINTR: case ERESTARTSYS:
+			/* peer not (yet) available, network problem */
+		case ECONNREFUSED: case ENETUNREACH:
+		case EHOSTDOWN:    case EHOSTUNREACH:
+			disconnect_on_error = 0;
+			break;
+		default:
+			dev_err(DEV, "%s failed, err = %d\n", what, err);
+		}
+		if (disconnect_on_error)
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	}
+	put_net_conf(mdev);
+	return sock;
+}
+
+static struct socket *drbd_wait_for_connect(struct drbd_conf *mdev)
+{
+	int timeo, err;
+	struct socket *s_estab = NULL, *s_listen;
+	const char *what;
+
+	if (!get_net_conf(mdev))
+		return NULL;
+
+	what = "sock_create_kern";
+	err = sock_create_kern(((struct sockaddr *)mdev->net_conf->my_addr)->sa_family,
+		SOCK_STREAM, IPPROTO_TCP, &s_listen);
+	if (err) {
+		s_listen = NULL;
+		goto out;
+	}
+
+	timeo = mdev->net_conf->try_connect_int * HZ;
+	timeo += (random32() & 1) ? timeo / 7 : -timeo / 7; /* 28.5% random jitter */
+
+	s_listen->sk->sk_reuse    = 1; /* SO_REUSEADDR */
+	s_listen->sk->sk_rcvtimeo = timeo;
+	s_listen->sk->sk_sndtimeo = timeo;
+	drbd_setbufsize(s_listen, mdev->net_conf->sndbuf_size,
+			mdev->net_conf->rcvbuf_size);
+
+	what = "bind before listen";
+	err = s_listen->ops->bind(s_listen,
+			      (struct sockaddr *) mdev->net_conf->my_addr,
+			      mdev->net_conf->my_addr_len);
+	if (err < 0)
+		goto out;
+
+	err = drbd_accept(mdev, &what, s_listen, &s_estab);
+
+out:
+	if (s_listen)
+		sock_release(s_listen);
+	if (err < 0) {
+		if (err != -EAGAIN && err != -EINTR && err != -ERESTARTSYS) {
+			dev_err(DEV, "%s failed, err = %d\n", what, err);
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		}
+	}
+	put_net_conf(mdev);
+
+	return s_estab;
+}
+
+static int drbd_send_fp(struct drbd_conf *mdev,
+	struct socket *sock, enum drbd_packets cmd)
+{
+	struct p_header80 *h = &mdev->data.sbuf.header.h80;
+
+	return _drbd_send_cmd(mdev, sock, cmd, h, sizeof(*h), 0);
+}
+
+static enum drbd_packets drbd_recv_fp(struct drbd_conf *mdev, struct socket *sock)
+{
+	struct p_header80 *h = &mdev->data.rbuf.header.h80;
+	int rr;
+
+	rr = drbd_recv_short(mdev, sock, h, sizeof(*h), 0);
+
+	if (rr == sizeof(*h) && h->magic == BE_DRBD_MAGIC)
+		return be16_to_cpu(h->command);
+
+	return 0xffff;
+}
+
+/**
+ * drbd_socket_okay() - Free the socket if its connection is not okay
+ * @mdev:	DRBD device.
+ * @sock:	pointer to the pointer to the socket.
+ */
+static int drbd_socket_okay(struct drbd_conf *mdev, struct socket **sock)
+{
+	int rr;
+	char tb[4];
+
+	if (!*sock)
+		return false;
+
+	rr = drbd_recv_short(mdev, *sock, tb, 4, MSG_DONTWAIT | MSG_PEEK);
+
+	if (rr > 0 || rr == -EAGAIN) {
+		return true;
+	} else {
+		sock_release(*sock);
+		*sock = NULL;
+		return false;
+	}
+}
+
+/*
+ * return values:
+ *   1 yes, we have a valid connection
+ *   0 oops, did not work out, please try again
+ *  -1 peer talks different language,
+ *     no point in trying again, please go standalone.
+ *  -2 We do not have a network config...
+ */
+static int drbd_connect(struct drbd_conf *mdev)
+{
+	struct socket *s, *sock, *msock;
+	int try, h, ok;
+
+	D_ASSERT(!mdev->data.socket);
+
+	if (drbd_request_state(mdev, NS(conn, C_WF_CONNECTION)) < SS_SUCCESS)
+		return -2;
+
+	clear_bit(DISCARD_CONCURRENT, &mdev->flags);
+
+	sock  = NULL;
+	msock = NULL;
+
+	do {
+		for (try = 0;;) {
+			/* 3 tries, this should take less than a second! */
+			s = drbd_try_connect(mdev);
+			if (s || ++try >= 3)
+				break;
+			/* give the other side time to call bind() & listen() */
+			schedule_timeout_interruptible(HZ / 10);
+		}
+
+		if (s) {
+			if (!sock) {
+				drbd_send_fp(mdev, s, P_HAND_SHAKE_S);
+				sock = s;
+				s = NULL;
+			} else if (!msock) {
+				drbd_send_fp(mdev, s, P_HAND_SHAKE_M);
+				msock = s;
+				s = NULL;
+			} else {
+				dev_err(DEV, "Logic error in drbd_connect()\n");
+				goto out_release_sockets;
+			}
+		}
+
+		if (sock && msock) {
+			schedule_timeout_interruptible(mdev->net_conf->ping_timeo*HZ/10);
+			ok = drbd_socket_okay(mdev, &sock);
+			ok = drbd_socket_okay(mdev, &msock) && ok;
+			if (ok)
+				break;
+		}
+
+retry:
+		s = drbd_wait_for_connect(mdev);
+		if (s) {
+			try = drbd_recv_fp(mdev, s);
+			drbd_socket_okay(mdev, &sock);
+			drbd_socket_okay(mdev, &msock);
+			switch (try) {
+			case P_HAND_SHAKE_S:
+				if (sock) {
+					dev_warn(DEV, "initial packet S crossed\n");
+					sock_release(sock);
+				}
+				sock = s;
+				break;
+			case P_HAND_SHAKE_M:
+				if (msock) {
+					dev_warn(DEV, "initial packet M crossed\n");
+					sock_release(msock);
+				}
+				msock = s;
+				set_bit(DISCARD_CONCURRENT, &mdev->flags);
+				break;
+			default:
+				dev_warn(DEV, "Error receiving initial packet\n");
+				sock_release(s);
+				if (random32() & 1)
+					goto retry;
+			}
+		}
+
+		if (mdev->state.conn <= C_DISCONNECTING)
+			goto out_release_sockets;
+		if (signal_pending(current)) {
+			flush_signals(current);
+			smp_rmb();
+			if (get_t_state(&mdev->receiver) == Exiting)
+				goto out_release_sockets;
+		}
+
+		if (sock && msock) {
+			ok = drbd_socket_okay(mdev, &sock);
+			ok = drbd_socket_okay(mdev, &msock) && ok;
+			if (ok)
+				break;
+		}
+	} while (1);
+
+	msock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+	sock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+
+	sock->sk->sk_allocation = GFP_NOIO;
+	msock->sk->sk_allocation = GFP_NOIO;
+
+	sock->sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
+	msock->sk->sk_priority = TC_PRIO_INTERACTIVE;
+
+	/* NOT YET ...
+	 * sock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+	 * sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+	 * first set it to the P_HAND_SHAKE timeout,
+	 * which we set to 4x the configured ping_timeout. */
+	sock->sk->sk_sndtimeo =
+	sock->sk->sk_rcvtimeo = mdev->net_conf->ping_timeo*4*HZ/10;
+
+	msock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+	msock->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
+
+	/* we don't want delays.
+	 * we use TCP_CORK where appropriate, though */
+	drbd_tcp_nodelay(sock);
+	drbd_tcp_nodelay(msock);
+
+	mdev->data.socket = sock;
+	mdev->meta.socket = msock;
+	mdev->last_received = jiffies;
+
+	D_ASSERT(mdev->asender.task == NULL);
+
+	h = drbd_do_handshake(mdev);
+	if (h <= 0)
+		return h;
+
+	if (mdev->cram_hmac_tfm) {
+		/* drbd_request_state(mdev, NS(conn, WFAuth)); */
+		switch (drbd_do_auth(mdev)) {
+		case -1:
+			dev_err(DEV, "Authentication of peer failed\n");
+			return -1;
+		case 0:
+			dev_err(DEV, "Authentication of peer failed, trying again.\n");
+			return 0;
+		}
+	}
+
+	if (drbd_request_state(mdev, NS(conn, C_WF_REPORT_PARAMS)) < SS_SUCCESS)
+		return 0;
+
+	sock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+	sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+
+	atomic_set(&mdev->packet_seq, 0);
+	mdev->peer_seq = 0;
+
+	drbd_thread_start(&mdev->asender);
+
+	if (drbd_send_protocol(mdev) == -1)
+		return -1;
+	drbd_send_sync_param(mdev, &mdev->sync_conf);
+	drbd_send_sizes(mdev, 0, 0);
+	drbd_send_uuids(mdev);
+	drbd_send_state(mdev);
+	clear_bit(USE_DEGR_WFC_T, &mdev->flags);
+	clear_bit(RESIZE_PENDING, &mdev->flags);
+	mod_timer(&mdev->request_timer, jiffies + HZ); /* just start it here. */
+
+	return 1;
+
+out_release_sockets:
+	if (sock)
+		sock_release(sock);
+	if (msock)
+		sock_release(msock);
+	return -1;
+}
+
+static int drbd_recv_header(struct drbd_conf *mdev, enum drbd_packets *cmd, unsigned int *packet_size)
+{
+	union p_header *h = &mdev->data.rbuf.header;
+	int r;
+
+	r = drbd_recv(mdev, h, sizeof(*h));
+	if (unlikely(r != sizeof(*h))) {
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read expecting header on sock: r=%d\n", r);
+		return false;
+	}
+
+	if (likely(h->h80.magic == BE_DRBD_MAGIC)) {
+		*cmd = be16_to_cpu(h->h80.command);
+		*packet_size = be16_to_cpu(h->h80.length);
+	} else if (h->h95.magic == BE_DRBD_MAGIC_BIG) {
+		*cmd = be16_to_cpu(h->h95.command);
+		*packet_size = be32_to_cpu(h->h95.length);
+	} else {
+		dev_err(DEV, "magic?? on data m: 0x%08x c: %d l: %d\n",
+		    be32_to_cpu(h->h80.magic),
+		    be16_to_cpu(h->h80.command),
+		    be16_to_cpu(h->h80.length));
+		return false;
+	}
+	mdev->last_received = jiffies;
+
+	return true;
+}
+
+static void drbd_flush(struct drbd_conf *mdev)
+{
+	int rv;
+
+	if (mdev->write_ordering >= WO_bdev_flush && get_ldev(mdev)) {
+		rv = blkdev_issue_flush(mdev->ldev->backing_bdev, GFP_KERNEL,
+					NULL);
+		if (rv) {
+			dev_err(DEV, "local disk flush failed with status %d\n", rv);
+			/* would rather check on EOPNOTSUPP, but that is not reliable.
+			 * don't try again for ANY return value != 0
+			 * if (rv == -EOPNOTSUPP) */
+			drbd_bump_write_ordering(mdev, WO_drain_io);
+		}
+		put_ldev(mdev);
+	}
+}
+
+/**
+ * drbd_may_finish_epoch() - Applies an epoch_event to the epoch's state, eventually finishes it.
+ * @mdev:	DRBD device.
+ * @epoch:	Epoch object.
+ * @ev:		Epoch event.
+ */
+static enum finish_epoch drbd_may_finish_epoch(struct drbd_conf *mdev,
+					       struct drbd_epoch *epoch,
+					       enum epoch_event ev)
+{
+	int epoch_size;
+	struct drbd_epoch *next_epoch;
+	enum finish_epoch rv = FE_STILL_LIVE;
+
+	spin_lock(&mdev->epoch_lock);
+	do {
+		next_epoch = NULL;
+
+		epoch_size = atomic_read(&epoch->epoch_size);
+
+		switch (ev & ~EV_CLEANUP) {
+		case EV_PUT:
+			atomic_dec(&epoch->active);
+			break;
+		case EV_GOT_BARRIER_NR:
+			set_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags);
+			break;
+		case EV_BECAME_LAST:
+			/* nothing to do*/
+			break;
+		}
+
+		if (epoch_size != 0 &&
+		    atomic_read(&epoch->active) == 0 &&
+		    test_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags)) {
+			if (!(ev & EV_CLEANUP)) {
+				spin_unlock(&mdev->epoch_lock);
+				drbd_send_b_ack(mdev, epoch->barrier_nr, epoch_size);
+				spin_lock(&mdev->epoch_lock);
+			}
+			dec_unacked(mdev);
+
+			if (mdev->current_epoch != epoch) {
+				next_epoch = list_entry(epoch->list.next, struct drbd_epoch, list);
+				list_del(&epoch->list);
+				ev = EV_BECAME_LAST | (ev & EV_CLEANUP);
+				mdev->epochs--;
+				kfree(epoch);
+
+				if (rv == FE_STILL_LIVE)
+					rv = FE_DESTROYED;
+			} else {
+				epoch->flags = 0;
+				atomic_set(&epoch->epoch_size, 0);
+				/* atomic_set(&epoch->active, 0); is already zero */
+				if (rv == FE_STILL_LIVE)
+					rv = FE_RECYCLED;
+				wake_up(&mdev->ee_wait);
+			}
+		}
+
+		if (!next_epoch)
+			break;
+
+		epoch = next_epoch;
+	} while (1);
+
+	spin_unlock(&mdev->epoch_lock);
+
+	return rv;
+}
+
+/**
+ * drbd_bump_write_ordering() - Fall back to an other write ordering method
+ * @mdev:	DRBD device.
+ * @wo:		Write ordering method to try.
+ */
+void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo) __must_hold(local)
+{
+	enum write_ordering_e pwo;
+	static char *write_ordering_str[] = {
+		[WO_none] = "none",
+		[WO_drain_io] = "drain",
+		[WO_bdev_flush] = "flush",
+	};
+
+	pwo = mdev->write_ordering;
+	wo = min(pwo, wo);
+	if (wo == WO_bdev_flush && mdev->ldev->dc.no_disk_flush)
+		wo = WO_drain_io;
+	if (wo == WO_drain_io && mdev->ldev->dc.no_disk_drain)
+		wo = WO_none;
+	mdev->write_ordering = wo;
+	if (pwo != mdev->write_ordering || wo == WO_bdev_flush)
+		dev_info(DEV, "Method to ensure write ordering: %s\n", write_ordering_str[mdev->write_ordering]);
+}
+
+/**
+ * drbd_submit_ee()
+ * @mdev:	DRBD device.
+ * @e:		epoch entry
+ * @rw:		flag field, see bio->bi_rw
+ *
+ * May spread the pages to multiple bios,
+ * depending on bio_add_page restrictions.
+ *
+ * Returns 0 if all bios have been submitted,
+ * -ENOMEM if we could not allocate enough bios,
+ * -ENOSPC (any better suggestion?) if we have not been able to bio_add_page a
+ *  single page to an empty bio (which should never happen and likely indicates
+ *  that the lower level IO stack is in some way broken). This has been observed
+ *  on certain Xen deployments.
+ */
+/* TODO allocate from our own bio_set. */
+int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
+		const unsigned rw, const int fault_type)
+{
+	struct bio *bios = NULL;
+	struct bio *bio;
+	struct page *page = e->pages;
+	sector_t sector = e->sector;
+	unsigned ds = e->size;
+	unsigned n_bios = 0;
+	unsigned nr_pages = (ds + PAGE_SIZE -1) >> PAGE_SHIFT;
+	int err = -ENOMEM;
+
+	/* In most cases, we will only need one bio.  But in case the lower
+	 * level restrictions happen to be different at this offset on this
+	 * side than those of the sending peer, we may need to submit the
+	 * request in more than one bio. */
+next_bio:
+	bio = bio_alloc(GFP_NOIO, nr_pages);
+	if (!bio) {
+		dev_err(DEV, "submit_ee: Allocation of a bio failed\n");
+		goto fail;
+	}
+	/* > e->sector, unless this is the first bio */
+	bio->bi_sector = sector;
+	bio->bi_bdev = mdev->ldev->backing_bdev;
+	bio->bi_rw = rw;
+	bio->bi_private = e;
+	bio->bi_end_io = drbd_endio_sec;
+
+	bio->bi_next = bios;
+	bios = bio;
+	++n_bios;
+
+	page_chain_for_each(page) {
+		unsigned len = min_t(unsigned, ds, PAGE_SIZE);
+		if (!bio_add_page(bio, page, len, 0)) {
+			/* A single page must always be possible!
+			 * But in case it fails anyways,
+			 * we deal with it, and complain (below). */
+			if (bio->bi_vcnt == 0) {
+				dev_err(DEV,
+					"bio_add_page failed for len=%u, "
+					"bi_vcnt=0 (bi_sector=%llu)\n",
+					len, (unsigned long long)bio->bi_sector);
+				err = -ENOSPC;
+				goto fail;
+			}
+			goto next_bio;
+		}
+		ds -= len;
+		sector += len >> 9;
+		--nr_pages;
+	}
+	D_ASSERT(page == NULL);
+	D_ASSERT(ds == 0);
+
+	atomic_set(&e->pending_bios, n_bios);
+	do {
+		bio = bios;
+		bios = bios->bi_next;
+		bio->bi_next = NULL;
+
+		drbd_generic_make_request(mdev, fault_type, bio);
+	} while (bios);
+	return 0;
+
+fail:
+	while (bios) {
+		bio = bios;
+		bios = bios->bi_next;
+		bio_put(bio);
+	}
+	return err;
+}
+
+static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	int rv;
+	struct p_barrier *p = &mdev->data.rbuf.barrier;
+	struct drbd_epoch *epoch;
+
+	inc_unacked(mdev);
+
+	mdev->current_epoch->barrier_nr = p->barrier;
+	rv = drbd_may_finish_epoch(mdev, mdev->current_epoch, EV_GOT_BARRIER_NR);
+
+	/* P_BARRIER_ACK may imply that the corresponding extent is dropped from
+	 * the activity log, which means it would not be resynced in case the
+	 * R_PRIMARY crashes now.
+	 * Therefore we must send the barrier_ack after the barrier request was
+	 * completed. */
+	switch (mdev->write_ordering) {
+	case WO_none:
+		if (rv == FE_RECYCLED)
+			return true;
+
+		/* receiver context, in the writeout path of the other node.
+		 * avoid potential distributed deadlock */
+		epoch = kmalloc(sizeof(struct drbd_epoch), GFP_NOIO);
+		if (epoch)
+			break;
+		else
+			dev_warn(DEV, "Allocation of an epoch failed, slowing down\n");
+			/* Fall through */
+
+	case WO_bdev_flush:
+	case WO_drain_io:
+		drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+		drbd_flush(mdev);
+
+		if (atomic_read(&mdev->current_epoch->epoch_size)) {
+			epoch = kmalloc(sizeof(struct drbd_epoch), GFP_NOIO);
+			if (epoch)
+				break;
+		}
+
+		epoch = mdev->current_epoch;
+		wait_event(mdev->ee_wait, atomic_read(&epoch->epoch_size) == 0);
+
+		D_ASSERT(atomic_read(&epoch->active) == 0);
+		D_ASSERT(epoch->flags == 0);
+
+		return true;
+	default:
+		dev_err(DEV, "Strangeness in mdev->write_ordering %d\n", mdev->write_ordering);
+		return false;
+	}
+
+	epoch->flags = 0;
+	atomic_set(&epoch->epoch_size, 0);
+	atomic_set(&epoch->active, 0);
+
+	spin_lock(&mdev->epoch_lock);
+	if (atomic_read(&mdev->current_epoch->epoch_size)) {
+		list_add(&epoch->list, &mdev->current_epoch->list);
+		mdev->current_epoch = epoch;
+		mdev->epochs++;
+	} else {
+		/* The current_epoch got recycled while we allocated this one... */
+		kfree(epoch);
+	}
+	spin_unlock(&mdev->epoch_lock);
+
+	return true;
+}
+
+/* used from receive_RSDataReply (recv_resync_read)
+ * and from receive_Data */
+static struct drbd_epoch_entry *
+read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __must_hold(local)
+{
+	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+	struct drbd_epoch_entry *e;
+	struct page *page;
+	int dgs, ds, rr;
+	void *dig_in = mdev->int_dig_in;
+	void *dig_vv = mdev->int_dig_vv;
+	unsigned long *data;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+
+	if (dgs) {
+		rr = drbd_recv(mdev, dig_in, dgs);
+		if (rr != dgs) {
+			if (!signal_pending(current))
+				dev_warn(DEV,
+					"short read receiving data digest: read %d expected %d\n",
+					rr, dgs);
+			return NULL;
+		}
+	}
+
+	data_size -= dgs;
+
+	ERR_IF(data_size == 0) return NULL;
+	ERR_IF(data_size &  0x1ff) return NULL;
+	ERR_IF(data_size >  DRBD_MAX_BIO_SIZE) return NULL;
+
+	/* even though we trust out peer,
+	 * we sometimes have to double check. */
+	if (sector + (data_size>>9) > capacity) {
+		dev_err(DEV, "request from peer beyond end of local disk: "
+			"capacity: %llus < sector: %llus + size: %u\n",
+			(unsigned long long)capacity,
+			(unsigned long long)sector, data_size);
+		return NULL;
+	}
+
+	/* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
+	 * "criss-cross" setup, that might cause write-out on some other DRBD,
+	 * which in turn might block on the other node at this very place.  */
+	e = drbd_alloc_ee(mdev, id, sector, data_size, GFP_NOIO);
+	if (!e)
+		return NULL;
+
+	ds = data_size;
+	page = e->pages;
+	page_chain_for_each(page) {
+		unsigned len = min_t(int, ds, PAGE_SIZE);
+		data = kmap(page);
+		rr = drbd_recv(mdev, data, len);
+		if (drbd_insert_fault(mdev, DRBD_FAULT_RECEIVE)) {
+			dev_err(DEV, "Fault injection: Corrupting data on receive\n");
+			data[0] = data[0] ^ (unsigned long)-1;
+		}
+		kunmap(page);
+		if (rr != len) {
+			drbd_free_ee(mdev, e);
+			if (!signal_pending(current))
+				dev_warn(DEV, "short read receiving data: read %d expected %d\n",
+				rr, len);
+			return NULL;
+		}
+		ds -= rr;
+	}
+
+	if (dgs) {
+		drbd_csum_ee(mdev, mdev->integrity_r_tfm, e, dig_vv);
+		if (memcmp(dig_in, dig_vv, dgs)) {
+			dev_err(DEV, "Digest integrity check FAILED: %llus +%u\n",
+				(unsigned long long)sector, data_size);
+			drbd_bcast_ee(mdev, "digest failed",
+					dgs, dig_in, dig_vv, e);
+			drbd_free_ee(mdev, e);
+			return NULL;
+		}
+	}
+	mdev->recv_cnt += data_size>>9;
+	return e;
+}
+
+/* drbd_drain_block() just takes a data block
+ * out of the socket input buffer, and discards it.
+ */
+static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
+{
+	struct page *page;
+	int rr, rv = 1;
+	void *data;
+
+	if (!data_size)
+		return true;
+
+	page = drbd_pp_alloc(mdev, 1, 1);
+
+	data = kmap(page);
+	while (data_size) {
+		rr = drbd_recv(mdev, data, min_t(int, data_size, PAGE_SIZE));
+		if (rr != min_t(int, data_size, PAGE_SIZE)) {
+			rv = 0;
+			if (!signal_pending(current))
+				dev_warn(DEV,
+					"short read receiving data: read %d expected %d\n",
+					rr, min_t(int, data_size, PAGE_SIZE));
+			break;
+		}
+		data_size -= rr;
+	}
+	kunmap(page);
+	drbd_pp_free(mdev, page, 0);
+	return rv;
+}
+
+static int recv_dless_read(struct drbd_conf *mdev, struct drbd_request *req,
+			   sector_t sector, int data_size)
+{
+	struct bio_vec *bvec;
+	struct bio *bio;
+	int dgs, rr, i, expect;
+	void *dig_in = mdev->int_dig_in;
+	void *dig_vv = mdev->int_dig_vv;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+
+	if (dgs) {
+		rr = drbd_recv(mdev, dig_in, dgs);
+		if (rr != dgs) {
+			if (!signal_pending(current))
+				dev_warn(DEV,
+					"short read receiving data reply digest: read %d expected %d\n",
+					rr, dgs);
+			return 0;
+		}
+	}
+
+	data_size -= dgs;
+
+	/* optimistically update recv_cnt.  if receiving fails below,
+	 * we disconnect anyways, and counters will be reset. */
+	mdev->recv_cnt += data_size>>9;
+
+	bio = req->master_bio;
+	D_ASSERT(sector == bio->bi_sector);
+
+	bio_for_each_segment(bvec, bio, i) {
+		expect = min_t(int, data_size, bvec->bv_len);
+		rr = drbd_recv(mdev,
+			     kmap(bvec->bv_page)+bvec->bv_offset,
+			     expect);
+		kunmap(bvec->bv_page);
+		if (rr != expect) {
+			if (!signal_pending(current))
+				dev_warn(DEV, "short read receiving data reply: "
+					"read %d expected %d\n",
+					rr, expect);
+			return 0;
+		}
+		data_size -= rr;
+	}
+
+	if (dgs) {
+		drbd_csum_bio(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+		if (memcmp(dig_in, dig_vv, dgs)) {
+			dev_err(DEV, "Digest integrity check FAILED. Broken NICs?\n");
+			return 0;
+		}
+	}
+
+	D_ASSERT(data_size == 0);
+	return 1;
+}
+
+/* e_end_resync_block() is called via
+ * drbd_process_done_ee() by asender only */
+static int e_end_resync_block(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	sector_t sector = e->sector;
+	int ok;
+
+	D_ASSERT(hlist_unhashed(&e->collision));
+
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
+		drbd_set_in_sync(mdev, sector, e->size);
+		ok = drbd_send_ack(mdev, P_RS_WRITE_ACK, e);
+	} else {
+		/* Record failure to sync */
+		drbd_rs_failed_io(mdev, sector, e->size);
+
+		ok  = drbd_send_ack(mdev, P_NEG_ACK, e);
+	}
+	dec_unacked(mdev);
+
+	return ok;
+}
+
+static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_size) __releases(local)
+{
+	struct drbd_epoch_entry *e;
+
+	e = read_in_block(mdev, ID_SYNCER, sector, data_size);
+	if (!e)
+		goto fail;
+
+	dec_rs_pending(mdev);
+
+	inc_unacked(mdev);
+	/* corresponding dec_unacked() in e_end_resync_block()
+	 * respective _drbd_clear_done_ee */
+
+	e->w.cb = e_end_resync_block;
+
+	spin_lock_irq(&mdev->req_lock);
+	list_add(&e->w.list, &mdev->sync_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	atomic_add(data_size >> 9, &mdev->rs_sect_ev);
+	if (drbd_submit_ee(mdev, e, WRITE, DRBD_FAULT_RS_WR) == 0)
+		return true;
+
+	/* don't care for the reason here */
+	dev_err(DEV, "submit failed, triggering re-connect\n");
+	spin_lock_irq(&mdev->req_lock);
+	list_del(&e->w.list);
+	spin_unlock_irq(&mdev->req_lock);
+
+	drbd_free_ee(mdev, e);
+fail:
+	put_ldev(mdev);
+	return false;
+}
+
+static int receive_DataReply(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct drbd_request *req;
+	sector_t sector;
+	int ok;
+	struct p_data *p = &mdev->data.rbuf.data;
+
+	sector = be64_to_cpu(p->sector);
+
+	spin_lock_irq(&mdev->req_lock);
+	req = _ar_id_to_req(mdev, p->block_id, sector);
+	spin_unlock_irq(&mdev->req_lock);
+	if (unlikely(!req)) {
+		dev_err(DEV, "Got a corrupt block_id/sector pair(1).\n");
+		return false;
+	}
+
+	/* hlist_del(&req->collision) is done in _req_may_be_done, to avoid
+	 * special casing it there for the various failure cases.
+	 * still no race with drbd_fail_pending_reads */
+	ok = recv_dless_read(mdev, req, sector, data_size);
+
+	if (ok)
+		req_mod(req, data_received);
+	/* else: nothing. handled from drbd_disconnect...
+	 * I don't think we may complete this just yet
+	 * in case we are "on-disconnect: freeze" */
+
+	return ok;
+}
+
+static int receive_RSDataReply(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	sector_t sector;
+	int ok;
+	struct p_data *p = &mdev->data.rbuf.data;
+
+	sector = be64_to_cpu(p->sector);
+	D_ASSERT(p->block_id == ID_SYNCER);
+
+	if (get_ldev(mdev)) {
+		/* data is submitted to disk within recv_resync_read.
+		 * corresponding put_ldev done below on error,
+		 * or in drbd_endio_write_sec. */
+		ok = recv_resync_read(mdev, sector, data_size);
+	} else {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Can not write resync data to local disk.\n");
+
+		ok = drbd_drain_block(mdev, data_size);
+
+		drbd_send_ack_dp(mdev, P_NEG_ACK, p, data_size);
+	}
+
+	atomic_add(data_size >> 9, &mdev->rs_sect_in);
+
+	return ok;
+}
+
+/* e_end_block() is called via drbd_process_done_ee().
+ * this means this function only runs in the asender thread
+ */
+static int e_end_block(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	sector_t sector = e->sector;
+	int ok = 1, pcmd;
+
+	if (mdev->net_conf->wire_protocol == DRBD_PROT_C) {
+		if (likely((e->flags & EE_WAS_ERROR) == 0)) {
+			pcmd = (mdev->state.conn >= C_SYNC_SOURCE &&
+				mdev->state.conn <= C_PAUSED_SYNC_T &&
+				e->flags & EE_MAY_SET_IN_SYNC) ?
+				P_RS_WRITE_ACK : P_WRITE_ACK;
+			ok &= drbd_send_ack(mdev, pcmd, e);
+			if (pcmd == P_RS_WRITE_ACK)
+				drbd_set_in_sync(mdev, sector, e->size);
+		} else {
+			ok  = drbd_send_ack(mdev, P_NEG_ACK, e);
+			/* we expect it to be marked out of sync anyways...
+			 * maybe assert this?  */
+		}
+		dec_unacked(mdev);
+	}
+	/* we delete from the conflict detection hash _after_ we sent out the
+	 * P_WRITE_ACK / P_NEG_ACK, to get the sequence number right.  */
+	if (mdev->net_conf->two_primaries) {
+		spin_lock_irq(&mdev->req_lock);
+		D_ASSERT(!hlist_unhashed(&e->collision));
+		hlist_del_init(&e->collision);
+		spin_unlock_irq(&mdev->req_lock);
+	} else {
+		D_ASSERT(hlist_unhashed(&e->collision));
+	}
+
+	drbd_may_finish_epoch(mdev, e->epoch, EV_PUT + (cancel ? EV_CLEANUP : 0));
+
+	return ok;
+}
+
+static int e_send_discard_ack(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	int ok = 1;
+
+	D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+	ok = drbd_send_ack(mdev, P_DISCARD_ACK, e);
+
+	spin_lock_irq(&mdev->req_lock);
+	D_ASSERT(!hlist_unhashed(&e->collision));
+	hlist_del_init(&e->collision);
+	spin_unlock_irq(&mdev->req_lock);
+
+	dec_unacked(mdev);
+
+	return ok;
+}
+
+/* Called from receive_Data.
+ * Synchronize packets on sock with packets on msock.
+ *
+ * This is here so even when a P_DATA packet traveling via sock overtook an Ack
+ * packet traveling on msock, they are still processed in the order they have
+ * been sent.
+ *
+ * Note: we don't care for Ack packets overtaking P_DATA packets.
+ *
+ * In case packet_seq is larger than mdev->peer_seq number, there are
+ * outstanding packets on the msock. We wait for them to arrive.
+ * In case we are the logically next packet, we update mdev->peer_seq
+ * ourselves. Correctly handles 32bit wrap around.
+ *
+ * Assume we have a 10 GBit connection, that is about 1<<30 byte per second,
+ * about 1<<21 sectors per second. So "worst" case, we have 1<<3 == 8 seconds
+ * for the 24bit wrap (historical atomic_t guarantee on some archs), and we have
+ * 1<<9 == 512 seconds aka ages for the 32bit wrap around...
+ *
+ * returns 0 if we may process the packet,
+ * -ERESTARTSYS if we were interrupted (by disconnect signal). */
+static int drbd_wait_peer_seq(struct drbd_conf *mdev, const u32 packet_seq)
+{
+	DEFINE_WAIT(wait);
+	unsigned int p_seq;
+	long timeout;
+	int ret = 0;
+	spin_lock(&mdev->peer_seq_lock);
+	for (;;) {
+		prepare_to_wait(&mdev->seq_wait, &wait, TASK_INTERRUPTIBLE);
+		if (seq_le(packet_seq, mdev->peer_seq+1))
+			break;
+		if (signal_pending(current)) {
+			ret = -ERESTARTSYS;
+			break;
+		}
+		p_seq = mdev->peer_seq;
+		spin_unlock(&mdev->peer_seq_lock);
+		timeout = schedule_timeout(30*HZ);
+		spin_lock(&mdev->peer_seq_lock);
+		if (timeout == 0 && p_seq == mdev->peer_seq) {
+			ret = -ETIMEDOUT;
+			dev_err(DEV, "ASSERT FAILED waited 30 seconds for sequence update, forcing reconnect\n");
+			break;
+		}
+	}
+	finish_wait(&mdev->seq_wait, &wait);
+	if (mdev->peer_seq+1 == packet_seq)
+		mdev->peer_seq++;
+	spin_unlock(&mdev->peer_seq_lock);
+	return ret;
+}
+
+/* see also bio_flags_to_wire()
+ * DRBD_REQ_*, because we need to semantically map the flags to data packet
+ * flags and back. We may replicate to other kernel versions. */
+static unsigned long wire_flags_to_bio(struct drbd_conf *mdev, u32 dpf)
+{
+	return  (dpf & DP_RW_SYNC ? REQ_SYNC : 0) |
+		(dpf & DP_FUA ? REQ_FUA : 0) |
+		(dpf & DP_FLUSH ? REQ_FLUSH : 0) |
+		(dpf & DP_DISCARD ? REQ_DISCARD : 0);
+}
+
+/* mirrored write */
+static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	sector_t sector;
+	struct drbd_epoch_entry *e;
+	struct p_data *p = &mdev->data.rbuf.data;
+	int rw = WRITE;
+	u32 dp_flags;
+
+	if (!get_ldev(mdev)) {
+		spin_lock(&mdev->peer_seq_lock);
+		if (mdev->peer_seq+1 == be32_to_cpu(p->seq_num))
+			mdev->peer_seq++;
+		spin_unlock(&mdev->peer_seq_lock);
+
+		drbd_send_ack_dp(mdev, P_NEG_ACK, p, data_size);
+		atomic_inc(&mdev->current_epoch->epoch_size);
+		return drbd_drain_block(mdev, data_size);
+	}
+
+	/* get_ldev(mdev) successful.
+	 * Corresponding put_ldev done either below (on various errors),
+	 * or in drbd_endio_write_sec, if we successfully submit the data at
+	 * the end of this function. */
+
+	sector = be64_to_cpu(p->sector);
+	e = read_in_block(mdev, p->block_id, sector, data_size);
+	if (!e) {
+		put_ldev(mdev);
+		return false;
+	}
+
+	e->w.cb = e_end_block;
+
+	dp_flags = be32_to_cpu(p->dp_flags);
+	rw |= wire_flags_to_bio(mdev, dp_flags);
+
+	if (dp_flags & DP_MAY_SET_IN_SYNC)
+		e->flags |= EE_MAY_SET_IN_SYNC;
+
+	spin_lock(&mdev->epoch_lock);
+	e->epoch = mdev->current_epoch;
+	atomic_inc(&e->epoch->epoch_size);
+	atomic_inc(&e->epoch->active);
+	spin_unlock(&mdev->epoch_lock);
+
+	/* I'm the receiver, I do hold a net_cnt reference. */
+	if (!mdev->net_conf->two_primaries) {
+		spin_lock_irq(&mdev->req_lock);
+	} else {
+		/* don't get the req_lock yet,
+		 * we may sleep in drbd_wait_peer_seq */
+		const int size = e->size;
+		const int discard = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+		DEFINE_WAIT(wait);
+		struct drbd_request *i;
+		struct hlist_node *n;
+		struct hlist_head *slot;
+		int first;
+
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		BUG_ON(mdev->ee_hash == NULL);
+		BUG_ON(mdev->tl_hash == NULL);
+
+		/* conflict detection and handling:
+		 * 1. wait on the sequence number,
+		 *    in case this data packet overtook ACK packets.
+		 * 2. check our hash tables for conflicting requests.
+		 *    we only need to walk the tl_hash, since an ee can not
+		 *    have a conflict with an other ee: on the submitting
+		 *    node, the corresponding req had already been conflicting,
+		 *    and a conflicting req is never sent.
+		 *
+		 * Note: for two_primaries, we are protocol C,
+		 * so there cannot be any request that is DONE
+		 * but still on the transfer log.
+		 *
+		 * unconditionally add to the ee_hash.
+		 *
+		 * if no conflicting request is found:
+		 *    submit.
+		 *
+		 * if any conflicting request is found
+		 * that has not yet been acked,
+		 * AND I have the "discard concurrent writes" flag:
+		 *	 queue (via done_ee) the P_DISCARD_ACK; OUT.
+		 *
+		 * if any conflicting request is found:
+		 *	 block the receiver, waiting on misc_wait
+		 *	 until no more conflicting requests are there,
+		 *	 or we get interrupted (disconnect).
+		 *
+		 *	 we do not just write after local io completion of those
+		 *	 requests, but only after req is done completely, i.e.
+		 *	 we wait for the P_DISCARD_ACK to arrive!
+		 *
+		 *	 then proceed normally, i.e. submit.
+		 */
+		if (drbd_wait_peer_seq(mdev, be32_to_cpu(p->seq_num)))
+			goto out_interrupted;
+
+		spin_lock_irq(&mdev->req_lock);
+
+		hlist_add_head(&e->collision, ee_hash_slot(mdev, sector));
+
+#define OVERLAPS overlaps(i->sector, i->size, sector, size)
+		slot = tl_hash_slot(mdev, sector);
+		first = 1;
+		for (;;) {
+			int have_unacked = 0;
+			int have_conflict = 0;
+			prepare_to_wait(&mdev->misc_wait, &wait,
+				TASK_INTERRUPTIBLE);
+			hlist_for_each_entry(i, n, slot, collision) {
+				if (OVERLAPS) {
+					/* only ALERT on first iteration,
+					 * we may be woken up early... */
+					if (first)
+						dev_alert(DEV, "%s[%u] Concurrent local write detected!"
+						      "	new: %llus +%u; pending: %llus +%u\n",
+						      current->comm, current->pid,
+						      (unsigned long long)sector, size,
+						      (unsigned long long)i->sector, i->size);
+					if (i->rq_state & RQ_NET_PENDING)
+						++have_unacked;
+					++have_conflict;
+				}
+			}
+#undef OVERLAPS
+			if (!have_conflict)
+				break;
+
+			/* Discard Ack only for the _first_ iteration */
+			if (first && discard && have_unacked) {
+				dev_alert(DEV, "Concurrent write! [DISCARD BY FLAG] sec=%llus\n",
+				     (unsigned long long)sector);
+				inc_unacked(mdev);
+				e->w.cb = e_send_discard_ack;
+				list_add_tail(&e->w.list, &mdev->done_ee);
+
+				spin_unlock_irq(&mdev->req_lock);
+
+				/* we could probably send that P_DISCARD_ACK ourselves,
+				 * but I don't like the receiver using the msock */
+
+				put_ldev(mdev);
+				wake_asender(mdev);
+				finish_wait(&mdev->misc_wait, &wait);
+				return true;
+			}
+
+			if (signal_pending(current)) {
+				hlist_del_init(&e->collision);
+
+				spin_unlock_irq(&mdev->req_lock);
+
+				finish_wait(&mdev->misc_wait, &wait);
+				goto out_interrupted;
+			}
+
+			spin_unlock_irq(&mdev->req_lock);
+			if (first) {
+				first = 0;
+				dev_alert(DEV, "Concurrent write! [W AFTERWARDS] "
+				     "sec=%llus\n", (unsigned long long)sector);
+			} else if (discard) {
+				/* we had none on the first iteration.
+				 * there must be none now. */
+				D_ASSERT(have_unacked == 0);
+			}
+			schedule();
+			spin_lock_irq(&mdev->req_lock);
+		}
+		finish_wait(&mdev->misc_wait, &wait);
+	}
+
+	list_add(&e->w.list, &mdev->active_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	switch (mdev->net_conf->wire_protocol) {
+	case DRBD_PROT_C:
+		inc_unacked(mdev);
+		/* corresponding dec_unacked() in e_end_block()
+		 * respective _drbd_clear_done_ee */
+		break;
+	case DRBD_PROT_B:
+		/* I really don't like it that the receiver thread
+		 * sends on the msock, but anyways */
+		drbd_send_ack(mdev, P_RECV_ACK, e);
+		break;
+	case DRBD_PROT_A:
+		/* nothing to do */
+		break;
+	}
+
+	if (mdev->state.pdsk < D_INCONSISTENT) {
+		/* In case we have the only disk of the cluster, */
+		drbd_set_out_of_sync(mdev, e->sector, e->size);
+		e->flags |= EE_CALL_AL_COMPLETE_IO;
+		e->flags &= ~EE_MAY_SET_IN_SYNC;
+		drbd_al_begin_io(mdev, e->sector);
+	}
+
+	if (drbd_submit_ee(mdev, e, rw, DRBD_FAULT_DT_WR) == 0)
+		return true;
+
+	/* don't care for the reason here */
+	dev_err(DEV, "submit failed, triggering re-connect\n");
+	spin_lock_irq(&mdev->req_lock);
+	list_del(&e->w.list);
+	hlist_del_init(&e->collision);
+	spin_unlock_irq(&mdev->req_lock);
+	if (e->flags & EE_CALL_AL_COMPLETE_IO)
+		drbd_al_complete_io(mdev, e->sector);
+
+out_interrupted:
+	drbd_may_finish_epoch(mdev, e->epoch, EV_PUT + EV_CLEANUP);
+	put_ldev(mdev);
+	drbd_free_ee(mdev, e);
+	return false;
+}
+
+/* We may throttle resync, if the lower device seems to be busy,
+ * and current sync rate is above c_min_rate.
+ *
+ * To decide whether or not the lower device is busy, we use a scheme similar
+ * to MD RAID is_mddev_idle(): if the partition stats reveal "significant"
+ * (more than 64 sectors) of activity we cannot account for with our own resync
+ * activity, it obviously is "busy".
+ *
+ * The current sync rate used here uses only the most recent two step marks,
+ * to have a short time average so we can react faster.
+ */
+int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector)
+{
+	struct gendisk *disk = mdev->ldev->backing_bdev->bd_contains->bd_disk;
+	unsigned long db, dt, dbdt;
+	struct lc_element *tmp;
+	int curr_events;
+	int throttle = 0;
+
+	/* feature disabled? */
+	if (mdev->sync_conf.c_min_rate == 0)
+		return 0;
+
+	spin_lock_irq(&mdev->al_lock);
+	tmp = lc_find(mdev->resync, BM_SECT_TO_EXT(sector));
+	if (tmp) {
+		struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+		if (test_bit(BME_PRIORITY, &bm_ext->flags)) {
+			spin_unlock_irq(&mdev->al_lock);
+			return 0;
+		}
+		/* Do not slow down if app IO is already waiting for this extent */
+	}
+	spin_unlock_irq(&mdev->al_lock);
+
+	curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +
+		      (int)part_stat_read(&disk->part0, sectors[1]) -
+			atomic_read(&mdev->rs_sect_ev);
+
+	if (!mdev->rs_last_events || curr_events - mdev->rs_last_events > 64) {
+		unsigned long rs_left;
+		int i;
+
+		mdev->rs_last_events = curr_events;
+
+		/* sync speed average over the last 2*DRBD_SYNC_MARK_STEP,
+		 * approx. */
+		i = (mdev->rs_last_mark + DRBD_SYNC_MARKS-1) % DRBD_SYNC_MARKS;
+
+		if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
+			rs_left = mdev->ov_left;
+		else
+			rs_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
+
+		dt = ((long)jiffies - (long)mdev->rs_mark_time[i]) / HZ;
+		if (!dt)
+			dt++;
+		db = mdev->rs_mark_left[i] - rs_left;
+		dbdt = Bit2KB(db/dt);
+
+		if (dbdt > mdev->sync_conf.c_min_rate)
+			throttle = 1;
+	}
+	return throttle;
+}
+
+
+static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int digest_size)
+{
+	sector_t sector;
+	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+	struct drbd_epoch_entry *e;
+	struct digest_info *di = NULL;
+	int size, verb;
+	unsigned int fault_type;
+	struct p_block_req *p =	&mdev->data.rbuf.block_req;
+
+	sector = be64_to_cpu(p->sector);
+	size   = be32_to_cpu(p->blksize);
+
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_BIO_SIZE) {
+		dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
+				(unsigned long long)sector, size);
+		return false;
+	}
+	if (sector + (size>>9) > capacity) {
+		dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
+				(unsigned long long)sector, size);
+		return false;
+	}
+
+	if (!get_ldev_if_state(mdev, D_UP_TO_DATE)) {
+		verb = 1;
+		switch (cmd) {
+		case P_DATA_REQUEST:
+			drbd_send_ack_rp(mdev, P_NEG_DREPLY, p);
+			break;
+		case P_RS_DATA_REQUEST:
+		case P_CSUM_RS_REQUEST:
+		case P_OV_REQUEST:
+			drbd_send_ack_rp(mdev, P_NEG_RS_DREPLY , p);
+			break;
+		case P_OV_REPLY:
+			verb = 0;
+			dec_rs_pending(mdev);
+			drbd_send_ack_ex(mdev, P_OV_RESULT, sector, size, ID_IN_SYNC);
+			break;
+		default:
+			dev_err(DEV, "unexpected command (%s) in receive_DataRequest\n",
+				cmdname(cmd));
+		}
+		if (verb && __ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Can not satisfy peer's read request, "
+			    "no local data.\n");
+
+		/* drain possibly payload */
+		return drbd_drain_block(mdev, digest_size);
+	}
+
+	/* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
+	 * "criss-cross" setup, that might cause write-out on some other DRBD,
+	 * which in turn might block on the other node at this very place.  */
+	e = drbd_alloc_ee(mdev, p->block_id, sector, size, GFP_NOIO);
+	if (!e) {
+		put_ldev(mdev);
+		return false;
+	}
+
+	switch (cmd) {
+	case P_DATA_REQUEST:
+		e->w.cb = w_e_end_data_req;
+		fault_type = DRBD_FAULT_DT_RD;
+		/* application IO, don't drbd_rs_begin_io */
+		goto submit;
+
+	case P_RS_DATA_REQUEST:
+		e->w.cb = w_e_end_rsdata_req;
+		fault_type = DRBD_FAULT_RS_RD;
+		/* used in the sector offset progress display */
+		mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
+		break;
+
+	case P_OV_REPLY:
+	case P_CSUM_RS_REQUEST:
+		fault_type = DRBD_FAULT_RS_RD;
+		di = kmalloc(sizeof(*di) + digest_size, GFP_NOIO);
+		if (!di)
+			goto out_free_e;
+
+		di->digest_size = digest_size;
+		di->digest = (((char *)di)+sizeof(struct digest_info));
+
+		e->digest = di;
+		e->flags |= EE_HAS_DIGEST;
+
+		if (drbd_recv(mdev, di->digest, digest_size) != digest_size)
+			goto out_free_e;
+
+		if (cmd == P_CSUM_RS_REQUEST) {
+			D_ASSERT(mdev->agreed_pro_version >= 89);
+			e->w.cb = w_e_end_csum_rs_req;
+			/* used in the sector offset progress display */
+			mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
+		} else if (cmd == P_OV_REPLY) {
+			/* track progress, we may need to throttle */
+			atomic_add(size >> 9, &mdev->rs_sect_in);
+			e->w.cb = w_e_end_ov_reply;
+			dec_rs_pending(mdev);
+			/* drbd_rs_begin_io done when we sent this request,
+			 * but accounting still needs to be done. */
+			goto submit_for_resync;
+		}
+		break;
+
+	case P_OV_REQUEST:
+		if (mdev->ov_start_sector == ~(sector_t)0 &&
+		    mdev->agreed_pro_version >= 90) {
+			unsigned long now = jiffies;
+			int i;
+			mdev->ov_start_sector = sector;
+			mdev->ov_position = sector;
+			mdev->ov_left = drbd_bm_bits(mdev) - BM_SECT_TO_BIT(sector);
+			mdev->rs_total = mdev->ov_left;
+			for (i = 0; i < DRBD_SYNC_MARKS; i++) {
+				mdev->rs_mark_left[i] = mdev->ov_left;
+				mdev->rs_mark_time[i] = now;
+			}
+			dev_info(DEV, "Online Verify start sector: %llu\n",
+					(unsigned long long)sector);
+		}
+		e->w.cb = w_e_end_ov_req;
+		fault_type = DRBD_FAULT_RS_RD;
+		break;
+
+	default:
+		dev_err(DEV, "unexpected command (%s) in receive_DataRequest\n",
+		    cmdname(cmd));
+		fault_type = DRBD_FAULT_MAX;
+		goto out_free_e;
+	}
+
+	/* Throttle, drbd_rs_begin_io and submit should become asynchronous
+	 * wrt the receiver, but it is not as straightforward as it may seem.
+	 * Various places in the resync start and stop logic assume resync
+	 * requests are processed in order, requeuing this on the worker thread
+	 * introduces a bunch of new code for synchronization between threads.
+	 *
+	 * Unlimited throttling before drbd_rs_begin_io may stall the resync
+	 * "forever", throttling after drbd_rs_begin_io will lock that extent
+	 * for application writes for the same time.  For now, just throttle
+	 * here, where the rest of the code expects the receiver to sleep for
+	 * a while, anyways.
+	 */
+
+	/* Throttle before drbd_rs_begin_io, as that locks out application IO;
+	 * this defers syncer requests for some time, before letting at least
+	 * on request through.  The resync controller on the receiving side
+	 * will adapt to the incoming rate accordingly.
+	 *
+	 * We cannot throttle here if remote is Primary/SyncTarget:
+	 * we would also throttle its application reads.
+	 * In that case, throttling is done on the SyncTarget only.
+	 */
+	if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev, sector))
+		schedule_timeout_uninterruptible(HZ/10);
+	if (drbd_rs_begin_io(mdev, sector))
+		goto out_free_e;
+
+submit_for_resync:
+	atomic_add(size >> 9, &mdev->rs_sect_ev);
+
+submit:
+	inc_unacked(mdev);
+	spin_lock_irq(&mdev->req_lock);
+	list_add_tail(&e->w.list, &mdev->read_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (drbd_submit_ee(mdev, e, READ, fault_type) == 0)
+		return true;
+
+	/* don't care for the reason here */
+	dev_err(DEV, "submit failed, triggering re-connect\n");
+	spin_lock_irq(&mdev->req_lock);
+	list_del(&e->w.list);
+	spin_unlock_irq(&mdev->req_lock);
+	/* no drbd_rs_complete_io(), we are dropping the connection anyways */
+
+out_free_e:
+	put_ldev(mdev);
+	drbd_free_ee(mdev, e);
+	return false;
+}
+
+static int drbd_asb_recover_0p(struct drbd_conf *mdev) __must_hold(local)
+{
+	int self, peer, rv = -100;
+	unsigned long ch_self, ch_peer;
+
+	self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+	peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+	ch_peer = mdev->p_uuid[UI_SIZE];
+	ch_self = mdev->comm_bm_set;
+
+	switch (mdev->net_conf->after_sb_0p) {
+	case ASB_CONSENSUS:
+	case ASB_DISCARD_SECONDARY:
+	case ASB_CALL_HELPER:
+		dev_err(DEV, "Configuration error.\n");
+		break;
+	case ASB_DISCONNECT:
+		break;
+	case ASB_DISCARD_YOUNGER_PRI:
+		if (self == 0 && peer == 1) {
+			rv = -1;
+			break;
+		}
+		if (self == 1 && peer == 0) {
+			rv =  1;
+			break;
+		}
+		/* Else fall through to one of the other strategies... */
+	case ASB_DISCARD_OLDER_PRI:
+		if (self == 0 && peer == 1) {
+			rv = 1;
+			break;
+		}
+		if (self == 1 && peer == 0) {
+			rv = -1;
+			break;
+		}
+		/* Else fall through to one of the other strategies... */
+		dev_warn(DEV, "Discard younger/older primary did not find a decision\n"
+		     "Using discard-least-changes instead\n");
+	case ASB_DISCARD_ZERO_CHG:
+		if (ch_peer == 0 && ch_self == 0) {
+			rv = test_bit(DISCARD_CONCURRENT, &mdev->flags)
+				? -1 : 1;
+			break;
+		} else {
+			if (ch_peer == 0) { rv =  1; break; }
+			if (ch_self == 0) { rv = -1; break; }
+		}
+		if (mdev->net_conf->after_sb_0p == ASB_DISCARD_ZERO_CHG)
+			break;
+	case ASB_DISCARD_LEAST_CHG:
+		if	(ch_self < ch_peer)
+			rv = -1;
+		else if (ch_self > ch_peer)
+			rv =  1;
+		else /* ( ch_self == ch_peer ) */
+		     /* Well, then use something else. */
+			rv = test_bit(DISCARD_CONCURRENT, &mdev->flags)
+				? -1 : 1;
+		break;
+	case ASB_DISCARD_LOCAL:
+		rv = -1;
+		break;
+	case ASB_DISCARD_REMOTE:
+		rv =  1;
+	}
+
+	return rv;
+}
+
+static int drbd_asb_recover_1p(struct drbd_conf *mdev) __must_hold(local)
+{
+	int hg, rv = -100;
+
+	switch (mdev->net_conf->after_sb_1p) {
+	case ASB_DISCARD_YOUNGER_PRI:
+	case ASB_DISCARD_OLDER_PRI:
+	case ASB_DISCARD_LEAST_CHG:
+	case ASB_DISCARD_LOCAL:
+	case ASB_DISCARD_REMOTE:
+		dev_err(DEV, "Configuration error.\n");
+		break;
+	case ASB_DISCONNECT:
+		break;
+	case ASB_CONSENSUS:
+		hg = drbd_asb_recover_0p(mdev);
+		if (hg == -1 && mdev->state.role == R_SECONDARY)
+			rv = hg;
+		if (hg == 1  && mdev->state.role == R_PRIMARY)
+			rv = hg;
+		break;
+	case ASB_VIOLENTLY:
+		rv = drbd_asb_recover_0p(mdev);
+		break;
+	case ASB_DISCARD_SECONDARY:
+		return mdev->state.role == R_PRIMARY ? 1 : -1;
+	case ASB_CALL_HELPER:
+		hg = drbd_asb_recover_0p(mdev);
+		if (hg == -1 && mdev->state.role == R_PRIMARY) {
+			enum drbd_state_rv rv2;
+
+			drbd_set_role(mdev, R_SECONDARY, 0);
+			 /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
+			  * we might be here in C_WF_REPORT_PARAMS which is transient.
+			  * we do not need to wait for the after state change work either. */
+			rv2 = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+			if (rv2 != SS_SUCCESS) {
+				drbd_khelper(mdev, "pri-lost-after-sb");
+			} else {
+				dev_warn(DEV, "Successfully gave up primary role.\n");
+				rv = hg;
+			}
+		} else
+			rv = hg;
+	}
+
+	return rv;
+}
+
+static int drbd_asb_recover_2p(struct drbd_conf *mdev) __must_hold(local)
+{
+	int hg, rv = -100;
+
+	switch (mdev->net_conf->after_sb_2p) {
+	case ASB_DISCARD_YOUNGER_PRI:
+	case ASB_DISCARD_OLDER_PRI:
+	case ASB_DISCARD_LEAST_CHG:
+	case ASB_DISCARD_LOCAL:
+	case ASB_DISCARD_REMOTE:
+	case ASB_CONSENSUS:
+	case ASB_DISCARD_SECONDARY:
+		dev_err(DEV, "Configuration error.\n");
+		break;
+	case ASB_VIOLENTLY:
+		rv = drbd_asb_recover_0p(mdev);
+		break;
+	case ASB_DISCONNECT:
+		break;
+	case ASB_CALL_HELPER:
+		hg = drbd_asb_recover_0p(mdev);
+		if (hg == -1) {
+			enum drbd_state_rv rv2;
+
+			 /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
+			  * we might be here in C_WF_REPORT_PARAMS which is transient.
+			  * we do not need to wait for the after state change work either. */
+			rv2 = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+			if (rv2 != SS_SUCCESS) {
+				drbd_khelper(mdev, "pri-lost-after-sb");
+			} else {
+				dev_warn(DEV, "Successfully gave up primary role.\n");
+				rv = hg;
+			}
+		} else
+			rv = hg;
+	}
+
+	return rv;
+}
+
+static void drbd_uuid_dump(struct drbd_conf *mdev, char *text, u64 *uuid,
+			   u64 bits, u64 flags)
+{
+	if (!uuid) {
+		dev_info(DEV, "%s uuid info vanished while I was looking!\n", text);
+		return;
+	}
+	dev_info(DEV, "%s %016llX:%016llX:%016llX:%016llX bits:%llu flags:%llX\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],
+	     (unsigned long long)bits,
+	     (unsigned long long)flags);
+}
+
+/*
+  100	after split brain try auto recover
+    2	C_SYNC_SOURCE set BitMap
+    1	C_SYNC_SOURCE use BitMap
+    0	no Sync
+   -1	C_SYNC_TARGET use BitMap
+   -2	C_SYNC_TARGET set BitMap
+ -100	after split brain, disconnect
+-1000	unrelated data
+-1091   requires proto 91
+-1096   requires proto 96
+ */
+static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(local)
+{
+	u64 self, peer;
+	int i, j;
+
+	self = mdev->ldev->md.uuid[UI_CURRENT] & ~((u64)1);
+	peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+
+	*rule_nr = 10;
+	if (self == UUID_JUST_CREATED && peer == UUID_JUST_CREATED)
+		return 0;
+
+	*rule_nr = 20;
+	if ((self == UUID_JUST_CREATED || self == (u64)0) &&
+	     peer != UUID_JUST_CREATED)
+		return -2;
+
+	*rule_nr = 30;
+	if (self != UUID_JUST_CREATED &&
+	    (peer == UUID_JUST_CREATED || peer == (u64)0))
+		return 2;
+
+	if (self == peer) {
+		int rct, dc; /* roles at crash time */
+
+		if (mdev->p_uuid[UI_BITMAP] == (u64)0 && mdev->ldev->md.uuid[UI_BITMAP] != (u64)0) {
+
+			if (mdev->agreed_pro_version < 91)
+				return -1091;
+
+			if ((mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
+			    (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1))) {
+				dev_info(DEV, "was SyncSource, missed the resync finished event, corrected myself:\n");
+				drbd_uuid_set_bm(mdev, 0UL);
+
+				drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
+					       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
+				*rule_nr = 34;
+			} else {
+				dev_info(DEV, "was SyncSource (peer failed to write sync_uuid)\n");
+				*rule_nr = 36;
+			}
+
+			return 1;
+		}
+
+		if (mdev->ldev->md.uuid[UI_BITMAP] == (u64)0 && mdev->p_uuid[UI_BITMAP] != (u64)0) {
+
+			if (mdev->agreed_pro_version < 91)
+				return -1091;
+
+			if ((mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_BITMAP] & ~((u64)1)) &&
+			    (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1))) {
+				dev_info(DEV, "was SyncTarget, peer missed the resync finished event, corrected peer:\n");
+
+				mdev->p_uuid[UI_HISTORY_START + 1] = mdev->p_uuid[UI_HISTORY_START];
+				mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_BITMAP];
+				mdev->p_uuid[UI_BITMAP] = 0UL;
+
+				drbd_uuid_dump(mdev, "peer", mdev->p_uuid, mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+				*rule_nr = 35;
+			} else {
+				dev_info(DEV, "was SyncTarget (failed to write sync_uuid)\n");
+				*rule_nr = 37;
+			}
+
+			return -1;
+		}
+
+		/* Common power [off|failure] */
+		rct = (test_bit(CRASHED_PRIMARY, &mdev->flags) ? 1 : 0) +
+			(mdev->p_uuid[UI_FLAGS] & 2);
+		/* lowest bit is set when we were primary,
+		 * next bit (weight 2) is set when peer was primary */
+		*rule_nr = 40;
+
+		switch (rct) {
+		case 0: /* !self_pri && !peer_pri */ return 0;
+		case 1: /*  self_pri && !peer_pri */ return 1;
+		case 2: /* !self_pri &&  peer_pri */ return -1;
+		case 3: /*  self_pri &&  peer_pri */
+			dc = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+			return dc ? -1 : 1;
+		}
+	}
+
+	*rule_nr = 50;
+	peer = mdev->p_uuid[UI_BITMAP] & ~((u64)1);
+	if (self == peer)
+		return -1;
+
+	*rule_nr = 51;
+	peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
+	if (self == peer) {
+		if (mdev->agreed_pro_version < 96 ?
+		    (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) ==
+		    (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1)) :
+		    peer + UUID_NEW_BM_OFFSET == (mdev->p_uuid[UI_BITMAP] & ~((u64)1))) {
+			/* The last P_SYNC_UUID did not get though. Undo the last start of
+			   resync as sync source modifications of the peer's UUIDs. */
+
+			if (mdev->agreed_pro_version < 91)
+				return -1091;
+
+			mdev->p_uuid[UI_BITMAP] = mdev->p_uuid[UI_HISTORY_START];
+			mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_HISTORY_START + 1];
+
+			dev_info(DEV, "Did not got last syncUUID packet, corrected:\n");
+			drbd_uuid_dump(mdev, "peer", mdev->p_uuid, mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+
+			return -1;
+		}
+	}
+
+	*rule_nr = 60;
+	self = mdev->ldev->md.uuid[UI_CURRENT] & ~((u64)1);
+	for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+		peer = mdev->p_uuid[i] & ~((u64)1);
+		if (self == peer)
+			return -2;
+	}
+
+	*rule_nr = 70;
+	self = mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1);
+	peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+	if (self == peer)
+		return 1;
+
+	*rule_nr = 71;
+	self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
+	if (self == peer) {
+		if (mdev->agreed_pro_version < 96 ?
+		    (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) ==
+		    (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) :
+		    self + UUID_NEW_BM_OFFSET == (mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1))) {
+			/* The last P_SYNC_UUID did not get though. Undo the last start of
+			   resync as sync source modifications of our UUIDs. */
+
+			if (mdev->agreed_pro_version < 91)
+				return -1091;
+
+			_drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_HISTORY_START]);
+			_drbd_uuid_set(mdev, UI_HISTORY_START, mdev->ldev->md.uuid[UI_HISTORY_START + 1]);
+
+			dev_info(DEV, "Last syncUUID did not get through, corrected:\n");
+			drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
+				       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
+
+			return 1;
+		}
+	}
+
+
+	*rule_nr = 80;
+	peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+	for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+		self = mdev->ldev->md.uuid[i] & ~((u64)1);
+		if (self == peer)
+			return 2;
+	}
+
+	*rule_nr = 90;
+	self = mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1);
+	peer = mdev->p_uuid[UI_BITMAP] & ~((u64)1);
+	if (self == peer && self != ((u64)0))
+		return 100;
+
+	*rule_nr = 100;
+	for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+		self = mdev->ldev->md.uuid[i] & ~((u64)1);
+		for (j = UI_HISTORY_START; j <= UI_HISTORY_END; j++) {
+			peer = mdev->p_uuid[j] & ~((u64)1);
+			if (self == peer)
+				return -100;
+		}
+	}
+
+	return -1000;
+}
+
+/* drbd_sync_handshake() returns the new conn state on success, or
+   CONN_MASK (-1) on failure.
+ */
+static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_role peer_role,
+					   enum drbd_disk_state peer_disk) __must_hold(local)
+{
+	int hg, rule_nr;
+	enum drbd_conns rv = C_MASK;
+	enum drbd_disk_state mydisk;
+
+	mydisk = mdev->state.disk;
+	if (mydisk == D_NEGOTIATING)
+		mydisk = mdev->new_state_tmp.disk;
+
+	dev_info(DEV, "drbd_sync_handshake:\n");
+	drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid, mdev->comm_bm_set, 0);
+	drbd_uuid_dump(mdev, "peer", mdev->p_uuid,
+		       mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+
+	hg = drbd_uuid_compare(mdev, &rule_nr);
+
+	dev_info(DEV, "uuid_compare()=%d by rule %d\n", hg, rule_nr);
+
+	if (hg == -1000) {
+		dev_alert(DEV, "Unrelated data, aborting!\n");
+		return C_MASK;
+	}
+	if (hg < -1000) {
+		dev_alert(DEV, "To resolve this both sides have to support at least protocol %d\n", -hg - 1000);
+		return C_MASK;
+	}
+
+	if    ((mydisk == D_INCONSISTENT && peer_disk > D_INCONSISTENT) ||
+	    (peer_disk == D_INCONSISTENT && mydisk    > D_INCONSISTENT)) {
+		int f = (hg == -100) || abs(hg) == 2;
+		hg = mydisk > D_INCONSISTENT ? 1 : -1;
+		if (f)
+			hg = hg*2;
+		dev_info(DEV, "Becoming sync %s due to disk states.\n",
+		     hg > 0 ? "source" : "target");
+	}
+
+	if (abs(hg) == 100)
+		drbd_khelper(mdev, "initial-split-brain");
+
+	if (hg == 100 || (hg == -100 && mdev->net_conf->always_asbp)) {
+		int pcount = (mdev->state.role == R_PRIMARY)
+			   + (peer_role == R_PRIMARY);
+		int forced = (hg == -100);
+
+		switch (pcount) {
+		case 0:
+			hg = drbd_asb_recover_0p(mdev);
+			break;
+		case 1:
+			hg = drbd_asb_recover_1p(mdev);
+			break;
+		case 2:
+			hg = drbd_asb_recover_2p(mdev);
+			break;
+		}
+		if (abs(hg) < 100) {
+			dev_warn(DEV, "Split-Brain detected, %d primaries, "
+			     "automatically solved. Sync from %s node\n",
+			     pcount, (hg < 0) ? "peer" : "this");
+			if (forced) {
+				dev_warn(DEV, "Doing a full sync, since"
+				     " UUIDs where ambiguous.\n");
+				hg = hg*2;
+			}
+		}
+	}
+
+	if (hg == -100) {
+		if (mdev->net_conf->want_lose && !(mdev->p_uuid[UI_FLAGS]&1))
+			hg = -1;
+		if (!mdev->net_conf->want_lose && (mdev->p_uuid[UI_FLAGS]&1))
+			hg = 1;
+
+		if (abs(hg) < 100)
+			dev_warn(DEV, "Split-Brain detected, manually solved. "
+			     "Sync from %s node\n",
+			     (hg < 0) ? "peer" : "this");
+	}
+
+	if (hg == -100) {
+		/* FIXME this log message is not correct if we end up here
+		 * after an attempted attach on a diskless node.
+		 * We just refuse to attach -- well, we drop the "connection"
+		 * to that disk, in a way... */
+		dev_alert(DEV, "Split-Brain detected but unresolved, dropping connection!\n");
+		drbd_khelper(mdev, "split-brain");
+		return C_MASK;
+	}
+
+	if (hg > 0 && mydisk <= D_INCONSISTENT) {
+		dev_err(DEV, "I shall become SyncSource, but I am inconsistent!\n");
+		return C_MASK;
+	}
+
+	if (hg < 0 && /* by intention we do not use mydisk here. */
+	    mdev->state.role == R_PRIMARY && mdev->state.disk >= D_CONSISTENT) {
+		switch (mdev->net_conf->rr_conflict) {
+		case ASB_CALL_HELPER:
+			drbd_khelper(mdev, "pri-lost");
+			/* fall through */
+		case ASB_DISCONNECT:
+			dev_err(DEV, "I shall become SyncTarget, but I am primary!\n");
+			return C_MASK;
+		case ASB_VIOLENTLY:
+			dev_warn(DEV, "Becoming SyncTarget, violating the stable-data"
+			     "assumption\n");
+		}
+	}
+
+	if (mdev->net_conf->dry_run || test_bit(CONN_DRY_RUN, &mdev->flags)) {
+		if (hg == 0)
+			dev_info(DEV, "dry-run connect: No resync, would become Connected immediately.\n");
+		else
+			dev_info(DEV, "dry-run connect: Would become %s, doing a %s resync.",
+				 drbd_conn_str(hg > 0 ? C_SYNC_SOURCE : C_SYNC_TARGET),
+				 abs(hg) >= 2 ? "full" : "bit-map based");
+		return C_MASK;
+	}
+
+	if (abs(hg) >= 2) {
+		dev_info(DEV, "Writing the whole bitmap, full sync required after drbd_sync_handshake.\n");
+		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from sync_handshake",
+					BM_LOCKED_SET_ALLOWED))
+			return C_MASK;
+	}
+
+	if (hg > 0) { /* become sync source. */
+		rv = C_WF_BITMAP_S;
+	} else if (hg < 0) { /* become sync target */
+		rv = C_WF_BITMAP_T;
+	} else {
+		rv = C_CONNECTED;
+		if (drbd_bm_total_weight(mdev)) {
+			dev_info(DEV, "No resync, but %lu bits in bitmap!\n",
+			     drbd_bm_total_weight(mdev));
+		}
+	}
+
+	return rv;
+}
+
+/* returns 1 if invalid */
+static int cmp_after_sb(enum drbd_after_sb_p peer, enum drbd_after_sb_p self)
+{
+	/* ASB_DISCARD_REMOTE - ASB_DISCARD_LOCAL is valid */
+	if ((peer == ASB_DISCARD_REMOTE && self == ASB_DISCARD_LOCAL) ||
+	    (self == ASB_DISCARD_REMOTE && peer == ASB_DISCARD_LOCAL))
+		return 0;
+
+	/* any other things with ASB_DISCARD_REMOTE or ASB_DISCARD_LOCAL are invalid */
+	if (peer == ASB_DISCARD_REMOTE || peer == ASB_DISCARD_LOCAL ||
+	    self == ASB_DISCARD_REMOTE || self == ASB_DISCARD_LOCAL)
+		return 1;
+
+	/* everything else is valid if they are equal on both sides. */
+	if (peer == self)
+		return 0;
+
+	/* everything es is invalid. */
+	return 1;
+}
+
+static int receive_protocol(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_protocol *p = &mdev->data.rbuf.protocol;
+	int p_proto, p_after_sb_0p, p_after_sb_1p, p_after_sb_2p;
+	int p_want_lose, p_two_primaries, cf;
+	char p_integrity_alg[SHARED_SECRET_MAX] = "";
+
+	p_proto		= be32_to_cpu(p->protocol);
+	p_after_sb_0p	= be32_to_cpu(p->after_sb_0p);
+	p_after_sb_1p	= be32_to_cpu(p->after_sb_1p);
+	p_after_sb_2p	= be32_to_cpu(p->after_sb_2p);
+	p_two_primaries = be32_to_cpu(p->two_primaries);
+	cf		= be32_to_cpu(p->conn_flags);
+	p_want_lose = cf & CF_WANT_LOSE;
+
+	clear_bit(CONN_DRY_RUN, &mdev->flags);
+
+	if (cf & CF_DRY_RUN)
+		set_bit(CONN_DRY_RUN, &mdev->flags);
+
+	if (p_proto != mdev->net_conf->wire_protocol) {
+		dev_err(DEV, "incompatible communication protocols\n");
+		goto disconnect;
+	}
+
+	if (cmp_after_sb(p_after_sb_0p, mdev->net_conf->after_sb_0p)) {
+		dev_err(DEV, "incompatible after-sb-0pri settings\n");
+		goto disconnect;
+	}
+
+	if (cmp_after_sb(p_after_sb_1p, mdev->net_conf->after_sb_1p)) {
+		dev_err(DEV, "incompatible after-sb-1pri settings\n");
+		goto disconnect;
+	}
+
+	if (cmp_after_sb(p_after_sb_2p, mdev->net_conf->after_sb_2p)) {
+		dev_err(DEV, "incompatible after-sb-2pri settings\n");
+		goto disconnect;
+	}
+
+	if (p_want_lose && mdev->net_conf->want_lose) {
+		dev_err(DEV, "both sides have the 'want_lose' flag set\n");
+		goto disconnect;
+	}
+
+	if (p_two_primaries != mdev->net_conf->two_primaries) {
+		dev_err(DEV, "incompatible setting of the two-primaries options\n");
+		goto disconnect;
+	}
+
+	if (mdev->agreed_pro_version >= 87) {
+		unsigned char *my_alg = mdev->net_conf->integrity_alg;
+
+		if (drbd_recv(mdev, p_integrity_alg, data_size) != data_size)
+			return false;
+
+		p_integrity_alg[SHARED_SECRET_MAX-1] = 0;
+		if (strcmp(p_integrity_alg, my_alg)) {
+			dev_err(DEV, "incompatible setting of the data-integrity-alg\n");
+			goto disconnect;
+		}
+		dev_info(DEV, "data-integrity-alg: %s\n",
+		     my_alg[0] ? my_alg : (unsigned char *)"<not-used>");
+	}
+
+	return true;
+
+disconnect:
+	drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	return false;
+}
+
+/* helper function
+ * input: alg name, feature name
+ * return: NULL (alg name was "")
+ *         ERR_PTR(error) if something goes wrong
+ *         or the crypto hash ptr, if it worked out ok. */
+struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_conf *mdev,
+		const char *alg, const char *name)
+{
+	struct crypto_hash *tfm;
+
+	if (!alg[0])
+		return NULL;
+
+	tfm = crypto_alloc_hash(alg, 0, CRYPTO_ALG_ASYNC);
+	if (IS_ERR(tfm)) {
+		dev_err(DEV, "Can not allocate \"%s\" as %s (reason: %ld)\n",
+			alg, name, PTR_ERR(tfm));
+		return tfm;
+	}
+	if (!drbd_crypto_is_hash(crypto_hash_tfm(tfm))) {
+		crypto_free_hash(tfm);
+		dev_err(DEV, "\"%s\" is not a digest (%s)\n", alg, name);
+		return ERR_PTR(-EINVAL);
+	}
+	return tfm;
+}
+
+static int receive_SyncParam(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int packet_size)
+{
+	int ok = true;
+	struct p_rs_param_95 *p = &mdev->data.rbuf.rs_param_95;
+	unsigned int header_size, data_size, exp_max_sz;
+	struct crypto_hash *verify_tfm = NULL;
+	struct crypto_hash *csums_tfm = NULL;
+	const int apv = mdev->agreed_pro_version;
+	int *rs_plan_s = NULL;
+	int fifo_size = 0;
+
+	exp_max_sz  = apv <= 87 ? sizeof(struct p_rs_param)
+		    : apv == 88 ? sizeof(struct p_rs_param)
+					+ SHARED_SECRET_MAX
+		    : apv <= 94 ? sizeof(struct p_rs_param_89)
+		    : /* apv >= 95 */ sizeof(struct p_rs_param_95);
+
+	if (packet_size > exp_max_sz) {
+		dev_err(DEV, "SyncParam packet too long: received %u, expected <= %u bytes\n",
+		    packet_size, exp_max_sz);
+		return false;
+	}
+
+	if (apv <= 88) {
+		header_size = sizeof(struct p_rs_param) - sizeof(struct p_header80);
+		data_size   = packet_size  - header_size;
+	} else if (apv <= 94) {
+		header_size = sizeof(struct p_rs_param_89) - sizeof(struct p_header80);
+		data_size   = packet_size  - header_size;
+		D_ASSERT(data_size == 0);
+	} else {
+		header_size = sizeof(struct p_rs_param_95) - sizeof(struct p_header80);
+		data_size   = packet_size  - header_size;
+		D_ASSERT(data_size == 0);
+	}
+
+	/* initialize verify_alg and csums_alg */
+	memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+
+	if (drbd_recv(mdev, &p->head.payload, header_size) != header_size)
+		return false;
+
+	mdev->sync_conf.rate	  = be32_to_cpu(p->rate);
+
+	if (apv >= 88) {
+		if (apv == 88) {
+			if (data_size > SHARED_SECRET_MAX) {
+				dev_err(DEV, "verify-alg too long, "
+				    "peer wants %u, accepting only %u byte\n",
+						data_size, SHARED_SECRET_MAX);
+				return false;
+			}
+
+			if (drbd_recv(mdev, p->verify_alg, data_size) != data_size)
+				return false;
+
+			/* we expect NUL terminated string */
+			/* but just in case someone tries to be evil */
+			D_ASSERT(p->verify_alg[data_size-1] == 0);
+			p->verify_alg[data_size-1] = 0;
+
+		} else /* apv >= 89 */ {
+			/* we still expect NUL terminated strings */
+			/* but just in case someone tries to be evil */
+			D_ASSERT(p->verify_alg[SHARED_SECRET_MAX-1] == 0);
+			D_ASSERT(p->csums_alg[SHARED_SECRET_MAX-1] == 0);
+			p->verify_alg[SHARED_SECRET_MAX-1] = 0;
+			p->csums_alg[SHARED_SECRET_MAX-1] = 0;
+		}
+
+		if (strcmp(mdev->sync_conf.verify_alg, p->verify_alg)) {
+			if (mdev->state.conn == C_WF_REPORT_PARAMS) {
+				dev_err(DEV, "Different verify-alg settings. me=\"%s\" peer=\"%s\"\n",
+				    mdev->sync_conf.verify_alg, p->verify_alg);
+				goto disconnect;
+			}
+			verify_tfm = drbd_crypto_alloc_digest_safe(mdev,
+					p->verify_alg, "verify-alg");
+			if (IS_ERR(verify_tfm)) {
+				verify_tfm = NULL;
+				goto disconnect;
+			}
+		}
+
+		if (apv >= 89 && strcmp(mdev->sync_conf.csums_alg, p->csums_alg)) {
+			if (mdev->state.conn == C_WF_REPORT_PARAMS) {
+				dev_err(DEV, "Different csums-alg settings. me=\"%s\" peer=\"%s\"\n",
+				    mdev->sync_conf.csums_alg, p->csums_alg);
+				goto disconnect;
+			}
+			csums_tfm = drbd_crypto_alloc_digest_safe(mdev,
+					p->csums_alg, "csums-alg");
+			if (IS_ERR(csums_tfm)) {
+				csums_tfm = NULL;
+				goto disconnect;
+			}
+		}
+
+		if (apv > 94) {
+			mdev->sync_conf.rate	  = be32_to_cpu(p->rate);
+			mdev->sync_conf.c_plan_ahead = be32_to_cpu(p->c_plan_ahead);
+			mdev->sync_conf.c_delay_target = be32_to_cpu(p->c_delay_target);
+			mdev->sync_conf.c_fill_target = be32_to_cpu(p->c_fill_target);
+			mdev->sync_conf.c_max_rate = be32_to_cpu(p->c_max_rate);
+
+			fifo_size = (mdev->sync_conf.c_plan_ahead * 10 * SLEEP_TIME) / HZ;
+			if (fifo_size != mdev->rs_plan_s.size && fifo_size > 0) {
+				rs_plan_s   = kzalloc(sizeof(int) * fifo_size, GFP_KERNEL);
+				if (!rs_plan_s) {
+					dev_err(DEV, "kmalloc of fifo_buffer failed");
+					goto disconnect;
+				}
+			}
+		}
+
+		spin_lock(&mdev->peer_seq_lock);
+		/* lock against drbd_nl_syncer_conf() */
+		if (verify_tfm) {
+			strcpy(mdev->sync_conf.verify_alg, p->verify_alg);
+			mdev->sync_conf.verify_alg_len = strlen(p->verify_alg) + 1;
+			crypto_free_hash(mdev->verify_tfm);
+			mdev->verify_tfm = verify_tfm;
+			dev_info(DEV, "using verify-alg: \"%s\"\n", p->verify_alg);
+		}
+		if (csums_tfm) {
+			strcpy(mdev->sync_conf.csums_alg, p->csums_alg);
+			mdev->sync_conf.csums_alg_len = strlen(p->csums_alg) + 1;
+			crypto_free_hash(mdev->csums_tfm);
+			mdev->csums_tfm = csums_tfm;
+			dev_info(DEV, "using csums-alg: \"%s\"\n", p->csums_alg);
+		}
+		if (fifo_size != mdev->rs_plan_s.size) {
+			kfree(mdev->rs_plan_s.values);
+			mdev->rs_plan_s.values = rs_plan_s;
+			mdev->rs_plan_s.size   = fifo_size;
+			mdev->rs_planed = 0;
+		}
+		spin_unlock(&mdev->peer_seq_lock);
+	}
+
+	return ok;
+disconnect:
+	/* just for completeness: actually not needed,
+	 * as this is not reached if csums_tfm was ok. */
+	crypto_free_hash(csums_tfm);
+	/* but free the verify_tfm again, if csums_tfm did not work out */
+	crypto_free_hash(verify_tfm);
+	drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	return false;
+}
+
+/* warn if the arguments differ by more than 12.5% */
+static void warn_if_differ_considerably(struct drbd_conf *mdev,
+	const char *s, sector_t a, sector_t b)
+{
+	sector_t d;
+	if (a == 0 || b == 0)
+		return;
+	d = (a > b) ? (a - b) : (b - a);
+	if (d > (a>>3) || d > (b>>3))
+		dev_warn(DEV, "Considerable difference in %s: %llus vs. %llus\n", s,
+		     (unsigned long long)a, (unsigned long long)b);
+}
+
+static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_sizes *p = &mdev->data.rbuf.sizes;
+	enum determine_dev_size dd = unchanged;
+	sector_t p_size, p_usize, my_usize;
+	int ldsc = 0; /* local disk size changed */
+	enum dds_flags ddsf;
+
+	p_size = be64_to_cpu(p->d_size);
+	p_usize = be64_to_cpu(p->u_size);
+
+	if (p_size == 0 && mdev->state.disk == D_DISKLESS) {
+		dev_err(DEV, "some backing storage is needed\n");
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		return false;
+	}
+
+	/* just store the peer's disk size for now.
+	 * we still need to figure out whether we accept that. */
+	mdev->p_size = p_size;
+
+	if (get_ldev(mdev)) {
+		warn_if_differ_considerably(mdev, "lower level device sizes",
+			   p_size, drbd_get_max_capacity(mdev->ldev));
+		warn_if_differ_considerably(mdev, "user requested size",
+					    p_usize, mdev->ldev->dc.disk_size);
+
+		/* if this is the first connect, or an otherwise expected
+		 * param exchange, choose the minimum */
+		if (mdev->state.conn == C_WF_REPORT_PARAMS)
+			p_usize = min_not_zero((sector_t)mdev->ldev->dc.disk_size,
+					     p_usize);
+
+		my_usize = mdev->ldev->dc.disk_size;
+
+		if (mdev->ldev->dc.disk_size != p_usize) {
+			mdev->ldev->dc.disk_size = p_usize;
+			dev_info(DEV, "Peer sets u_size to %lu sectors\n",
+			     (unsigned long)mdev->ldev->dc.disk_size);
+		}
+
+		/* Never shrink a device with usable data during connect.
+		   But allow online shrinking if we are connected. */
+		if (drbd_new_dev_size(mdev, mdev->ldev, 0) <
+		   drbd_get_capacity(mdev->this_bdev) &&
+		   mdev->state.disk >= D_OUTDATED &&
+		   mdev->state.conn < C_CONNECTED) {
+			dev_err(DEV, "The peer's disk size is too small!\n");
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+			mdev->ldev->dc.disk_size = my_usize;
+			put_ldev(mdev);
+			return false;
+		}
+		put_ldev(mdev);
+	}
+
+	ddsf = be16_to_cpu(p->dds_flags);
+	if (get_ldev(mdev)) {
+		dd = drbd_determine_dev_size(mdev, ddsf);
+		put_ldev(mdev);
+		if (dd == dev_size_error)
+			return false;
+		drbd_md_sync(mdev);
+	} else {
+		/* I am diskless, need to accept the peer's size. */
+		drbd_set_my_capacity(mdev, p_size);
+	}
+
+	mdev->peer_max_bio_size = be32_to_cpu(p->max_bio_size);
+	drbd_reconsider_max_bio_size(mdev);
+
+	if (get_ldev(mdev)) {
+		if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
+			mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
+			ldsc = 1;
+		}
+
+		put_ldev(mdev);
+	}
+
+	if (mdev->state.conn > C_WF_REPORT_PARAMS) {
+		if (be64_to_cpu(p->c_size) !=
+		    drbd_get_capacity(mdev->this_bdev) || ldsc) {
+			/* we have different sizes, probably peer
+			 * needs to know my new size... */
+			drbd_send_sizes(mdev, 0, ddsf);
+		}
+		if (test_and_clear_bit(RESIZE_PENDING, &mdev->flags) ||
+		    (dd == grew && mdev->state.conn == C_CONNECTED)) {
+			if (mdev->state.pdsk >= D_INCONSISTENT &&
+			    mdev->state.disk >= D_INCONSISTENT) {
+				if (ddsf & DDSF_NO_RESYNC)
+					dev_info(DEV, "Resync of new storage suppressed with --assume-clean\n");
+				else
+					resync_after_online_grow(mdev);
+			} else
+				set_bit(RESYNC_AFTER_NEG, &mdev->flags);
+		}
+	}
+
+	return true;
+}
+
+static int receive_uuids(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_uuids *p = &mdev->data.rbuf.uuids;
+	u64 *p_uuid;
+	int i, updated_uuids = 0;
+
+	p_uuid = kmalloc(sizeof(u64)*UI_EXTENDED_SIZE, GFP_NOIO);
+
+	for (i = UI_CURRENT; i < UI_EXTENDED_SIZE; i++)
+		p_uuid[i] = be64_to_cpu(p->uuid[i]);
+
+	kfree(mdev->p_uuid);
+	mdev->p_uuid = p_uuid;
+
+	if (mdev->state.conn < C_CONNECTED &&
+	    mdev->state.disk < D_INCONSISTENT &&
+	    mdev->state.role == R_PRIMARY &&
+	    (mdev->ed_uuid & ~((u64)1)) != (p_uuid[UI_CURRENT] & ~((u64)1))) {
+		dev_err(DEV, "Can only connect to data with current UUID=%016llX\n",
+		    (unsigned long long)mdev->ed_uuid);
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		return false;
+	}
+
+	if (get_ldev(mdev)) {
+		int skip_initial_sync =
+			mdev->state.conn == C_CONNECTED &&
+			mdev->agreed_pro_version >= 90 &&
+			mdev->ldev->md.uuid[UI_CURRENT] == UUID_JUST_CREATED &&
+			(p_uuid[UI_FLAGS] & 8);
+		if (skip_initial_sync) {
+			dev_info(DEV, "Accepted new current UUID, preparing to skip initial sync\n");
+			drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write,
+					"clear_n_write from receive_uuids",
+					BM_LOCKED_TEST_ALLOWED);
+			_drbd_uuid_set(mdev, UI_CURRENT, p_uuid[UI_CURRENT]);
+			_drbd_uuid_set(mdev, UI_BITMAP, 0);
+			_drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
+					CS_VERBOSE, NULL);
+			drbd_md_sync(mdev);
+			updated_uuids = 1;
+		}
+		put_ldev(mdev);
+	} else if (mdev->state.disk < D_INCONSISTENT &&
+		   mdev->state.role == R_PRIMARY) {
+		/* I am a diskless primary, the peer just created a new current UUID
+		   for me. */
+		updated_uuids = drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
+	}
+
+	/* Before we test for the disk state, we should wait until an eventually
+	   ongoing cluster wide state change is finished. That is important if
+	   we are primary and are detaching from our disk. We need to see the
+	   new disk state... */
+	wait_event(mdev->misc_wait, !test_bit(CLUSTER_ST_CHANGE, &mdev->flags));
+	if (mdev->state.conn >= C_CONNECTED && mdev->state.disk < D_INCONSISTENT)
+		updated_uuids |= drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
+
+	if (updated_uuids)
+		drbd_print_uuids(mdev, "receiver updated UUIDs to");
+
+	return true;
+}
+
+/**
+ * convert_state() - Converts the peer's view of the cluster state to our point of view
+ * @ps:		The state as seen by the peer.
+ */
+static union drbd_state convert_state(union drbd_state ps)
+{
+	union drbd_state ms;
+
+	static enum drbd_conns c_tab[] = {
+		[C_CONNECTED] = C_CONNECTED,
+
+		[C_STARTING_SYNC_S] = C_STARTING_SYNC_T,
+		[C_STARTING_SYNC_T] = C_STARTING_SYNC_S,
+		[C_DISCONNECTING] = C_TEAR_DOWN, /* C_NETWORK_FAILURE, */
+		[C_VERIFY_S]       = C_VERIFY_T,
+		[C_MASK]   = C_MASK,
+	};
+
+	ms.i = ps.i;
+
+	ms.conn = c_tab[ps.conn];
+	ms.peer = ps.role;
+	ms.role = ps.peer;
+	ms.pdsk = ps.disk;
+	ms.disk = ps.pdsk;
+	ms.peer_isp = (ps.aftr_isp | ps.user_isp);
+
+	return ms;
+}
+
+static int receive_req_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_req_state *p = &mdev->data.rbuf.req_state;
+	union drbd_state mask, val;
+	enum drbd_state_rv rv;
+
+	mask.i = be32_to_cpu(p->mask);
+	val.i = be32_to_cpu(p->val);
+
+	if (test_bit(DISCARD_CONCURRENT, &mdev->flags) &&
+	    test_bit(CLUSTER_ST_CHANGE, &mdev->flags)) {
+		drbd_send_sr_reply(mdev, SS_CONCURRENT_ST_CHG);
+		return true;
+	}
+
+	mask = convert_state(mask);
+	val = convert_state(val);
+
+	rv = drbd_change_state(mdev, CS_VERBOSE, mask, val);
+
+	drbd_send_sr_reply(mdev, rv);
+	drbd_md_sync(mdev);
+
+	return true;
+}
+
+static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_state *p = &mdev->data.rbuf.state;
+	union drbd_state os, ns, peer_state;
+	enum drbd_disk_state real_peer_disk;
+	enum chg_state_flags cs_flags;
+	int rv;
+
+	peer_state.i = be32_to_cpu(p->state);
+
+	real_peer_disk = peer_state.disk;
+	if (peer_state.disk == D_NEGOTIATING) {
+		real_peer_disk = mdev->p_uuid[UI_FLAGS] & 4 ? D_INCONSISTENT : D_CONSISTENT;
+		dev_info(DEV, "real peer disk state = %s\n", drbd_disk_str(real_peer_disk));
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+ retry:
+	os = ns = mdev->state;
+	spin_unlock_irq(&mdev->req_lock);
+
+	/* peer says his disk is uptodate, while we think it is inconsistent,
+	 * and this happens while we think we have a sync going on. */
+	if (os.pdsk == D_INCONSISTENT && real_peer_disk == D_UP_TO_DATE &&
+	    os.conn > C_CONNECTED && os.disk == D_UP_TO_DATE) {
+		/* If we are (becoming) SyncSource, but peer is still in sync
+		 * preparation, ignore its uptodate-ness to avoid flapping, it
+		 * will change to inconsistent once the peer reaches active
+		 * syncing states.
+		 * It may have changed syncer-paused flags, however, so we
+		 * cannot ignore this completely. */
+		if (peer_state.conn > C_CONNECTED &&
+		    peer_state.conn < C_SYNC_SOURCE)
+			real_peer_disk = D_INCONSISTENT;
+
+		/* if peer_state changes to connected at the same time,
+		 * it explicitly notifies us that it finished resync.
+		 * Maybe we should finish it up, too? */
+		else if (os.conn >= C_SYNC_SOURCE &&
+			 peer_state.conn == C_CONNECTED) {
+			if (drbd_bm_total_weight(mdev) <= mdev->rs_failed)
+				drbd_resync_finished(mdev);
+			return true;
+		}
+	}
+
+	/* peer says his disk is inconsistent, while we think it is uptodate,
+	 * and this happens while the peer still thinks we have a sync going on,
+	 * but we think we are already done with the sync.
+	 * We ignore this to avoid flapping pdsk.
+	 * This should not happen, if the peer is a recent version of drbd. */
+	if (os.pdsk == D_UP_TO_DATE && real_peer_disk == D_INCONSISTENT &&
+	    os.conn == C_CONNECTED && peer_state.conn > C_SYNC_SOURCE)
+		real_peer_disk = D_UP_TO_DATE;
+
+	if (ns.conn == C_WF_REPORT_PARAMS)
+		ns.conn = C_CONNECTED;
+
+	if (peer_state.conn == C_AHEAD)
+		ns.conn = C_BEHIND;
+
+	if (mdev->p_uuid && peer_state.disk >= D_NEGOTIATING &&
+	    get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		int cr; /* consider resync */
+
+		/* if we established a new connection */
+		cr  = (os.conn < C_CONNECTED);
+		/* if we had an established connection
+		 * and one of the nodes newly attaches a disk */
+		cr |= (os.conn == C_CONNECTED &&
+		       (peer_state.disk == D_NEGOTIATING ||
+			os.disk == D_NEGOTIATING));
+		/* if we have both been inconsistent, and the peer has been
+		 * forced to be UpToDate with --overwrite-data */
+		cr |= test_bit(CONSIDER_RESYNC, &mdev->flags);
+		/* if we had been plain connected, and the admin requested to
+		 * start a sync by "invalidate" or "invalidate-remote" */
+		cr |= (os.conn == C_CONNECTED &&
+				(peer_state.conn >= C_STARTING_SYNC_S &&
+				 peer_state.conn <= C_WF_BITMAP_T));
+
+		if (cr)
+			ns.conn = drbd_sync_handshake(mdev, peer_state.role, real_peer_disk);
+
+		put_ldev(mdev);
+		if (ns.conn == C_MASK) {
+			ns.conn = C_CONNECTED;
+			if (mdev->state.disk == D_NEGOTIATING) {
+				drbd_force_state(mdev, NS(disk, D_FAILED));
+			} else if (peer_state.disk == D_NEGOTIATING) {
+				dev_err(DEV, "Disk attach process on the peer node was aborted.\n");
+				peer_state.disk = D_DISKLESS;
+				real_peer_disk = D_DISKLESS;
+			} else {
+				if (test_and_clear_bit(CONN_DRY_RUN, &mdev->flags))
+					return false;
+				D_ASSERT(os.conn == C_WF_REPORT_PARAMS);
+				drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+				return false;
+			}
+		}
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	if (mdev->state.i != os.i)
+		goto retry;
+	clear_bit(CONSIDER_RESYNC, &mdev->flags);
+	ns.peer = peer_state.role;
+	ns.pdsk = real_peer_disk;
+	ns.peer_isp = (peer_state.aftr_isp | peer_state.user_isp);
+	if ((ns.conn == C_CONNECTED || ns.conn == C_WF_BITMAP_S) && ns.disk == D_NEGOTIATING)
+		ns.disk = mdev->new_state_tmp.disk;
+	cs_flags = CS_VERBOSE + (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED ? 0 : CS_HARD);
+	if (ns.pdsk == D_CONSISTENT && is_susp(ns) && ns.conn == C_CONNECTED && os.conn < C_CONNECTED &&
+	    test_bit(NEW_CUR_UUID, &mdev->flags)) {
+		/* Do not allow tl_restart(resend) for a rebooted peer. We can only allow this
+		   for temporal network outages! */
+		spin_unlock_irq(&mdev->req_lock);
+		dev_err(DEV, "Aborting Connect, can not thaw IO with an only Consistent peer\n");
+		tl_clear(mdev);
+		drbd_uuid_new_current(mdev);
+		clear_bit(NEW_CUR_UUID, &mdev->flags);
+		drbd_force_state(mdev, NS2(conn, C_PROTOCOL_ERROR, susp, 0));
+		return false;
+	}
+	rv = _drbd_set_state(mdev, ns, cs_flags, NULL);
+	ns = mdev->state;
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (rv < SS_SUCCESS) {
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		return false;
+	}
+
+	if (os.conn > C_WF_REPORT_PARAMS) {
+		if (ns.conn > C_CONNECTED && peer_state.conn <= C_CONNECTED &&
+		    peer_state.disk != D_NEGOTIATING ) {
+			/* we want resync, peer has not yet decided to sync... */
+			/* Nowadays only used when forcing a node into primary role and
+			   setting its disk to UpToDate with that */
+			drbd_send_uuids(mdev);
+			drbd_send_state(mdev);
+		}
+	}
+
+	mdev->net_conf->want_lose = 0;
+
+	drbd_md_sync(mdev); /* update connected indicator, la_size, ... */
+
+	return true;
+}
+
+static int receive_sync_uuid(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_rs_uuid *p = &mdev->data.rbuf.rs_uuid;
+
+	wait_event(mdev->misc_wait,
+		   mdev->state.conn == C_WF_SYNC_UUID ||
+		   mdev->state.conn == C_BEHIND ||
+		   mdev->state.conn < C_CONNECTED ||
+		   mdev->state.disk < D_NEGOTIATING);
+
+	/* D_ASSERT( mdev->state.conn == C_WF_SYNC_UUID ); */
+
+	/* Here the _drbd_uuid_ functions are right, current should
+	   _not_ be rotated into the history */
+	if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		_drbd_uuid_set(mdev, UI_CURRENT, be64_to_cpu(p->uuid));
+		_drbd_uuid_set(mdev, UI_BITMAP, 0UL);
+
+		drbd_print_uuids(mdev, "updated sync uuid");
+		drbd_start_resync(mdev, C_SYNC_TARGET);
+
+		put_ldev(mdev);
+	} else
+		dev_err(DEV, "Ignoring SyncUUID packet!\n");
+
+	return true;
+}
+
+/**
+ * receive_bitmap_plain
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
+receive_bitmap_plain(struct drbd_conf *mdev, unsigned int data_size,
+		     unsigned long *buffer, struct bm_xfer_ctx *c)
+{
+	unsigned num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
+	unsigned want = num_words * sizeof(long);
+	int err;
+
+	if (want != data_size) {
+		dev_err(DEV, "%s:want (%u) != data_size (%u)\n", __func__, want, data_size);
+		return -EIO;
+	}
+	if (want == 0)
+		return 0;
+	err = drbd_recv(mdev, buffer, want);
+	if (err != want) {
+		if (err >= 0)
+			err = -EIO;
+		return err;
+	}
+
+	drbd_bm_merge_lel(mdev, c->word_offset, num_words, buffer);
+
+	c->word_offset += num_words;
+	c->bit_offset = c->word_offset * BITS_PER_LONG;
+	if (c->bit_offset > c->bm_bits)
+		c->bit_offset = c->bm_bits;
+
+	return 1;
+}
+
+/**
+ * recv_bm_rle_bits
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
+recv_bm_rle_bits(struct drbd_conf *mdev,
+		struct p_compressed_bm *p,
+		struct bm_xfer_ctx *c)
+{
+	struct bitstream bs;
+	u64 look_ahead;
+	u64 rl;
+	u64 tmp;
+	unsigned long s = c->bit_offset;
+	unsigned long e;
+	int len = be16_to_cpu(p->head.length) - (sizeof(*p) - sizeof(p->head));
+	int toggle = DCBP_get_start(p);
+	int have;
+	int bits;
+
+	bitstream_init(&bs, p->code, len, DCBP_get_pad_bits(p));
+
+	bits = bitstream_get_bits(&bs, &look_ahead, 64);
+	if (bits < 0)
+		return -EIO;
+
+	for (have = bits; have > 0; s += rl, toggle = !toggle) {
+		bits = vli_decode_bits(&rl, look_ahead);
+		if (bits <= 0)
+			return -EIO;
+
+		if (toggle) {
+			e = s + rl -1;
+			if (e >= c->bm_bits) {
+				dev_err(DEV, "bitmap overflow (e:%lu) while decoding bm RLE packet\n", e);
+				return -EIO;
+			}
+			_drbd_bm_set_bits(mdev, s, e);
+		}
+
+		if (have < bits) {
+			dev_err(DEV, "bitmap decoding error: h:%d b:%d la:0x%08llx l:%u/%u\n",
+				have, bits, look_ahead,
+				(unsigned int)(bs.cur.b - p->code),
+				(unsigned int)bs.buf_len);
+			return -EIO;
+		}
+		look_ahead >>= bits;
+		have -= bits;
+
+		bits = bitstream_get_bits(&bs, &tmp, 64 - have);
+		if (bits < 0)
+			return -EIO;
+		look_ahead |= tmp << have;
+		have += bits;
+	}
+
+	c->bit_offset = s;
+	bm_xfer_ctx_bit_to_word_offset(c);
+
+	return (s != c->bm_bits);
+}
+
+/**
+ * decode_bitmap_c
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
+decode_bitmap_c(struct drbd_conf *mdev,
+		struct p_compressed_bm *p,
+		struct bm_xfer_ctx *c)
+{
+	if (DCBP_get_code(p) == RLE_VLI_Bits)
+		return recv_bm_rle_bits(mdev, p, c);
+
+	/* other variants had been implemented for evaluation,
+	 * but have been dropped as this one turned out to be "best"
+	 * during all our tests. */
+
+	dev_err(DEV, "receive_bitmap_c: unknown encoding %u\n", p->encoding);
+	drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+	return -EIO;
+}
+
+void INFO_bm_xfer_stats(struct drbd_conf *mdev,
+		const char *direction, struct bm_xfer_ctx *c)
+{
+	/* what would it take to transfer it "plaintext" */
+	unsigned plain = sizeof(struct p_header80) *
+		((c->bm_words+BM_PACKET_WORDS-1)/BM_PACKET_WORDS+1)
+		+ c->bm_words * sizeof(long);
+	unsigned total = c->bytes[0] + c->bytes[1];
+	unsigned r;
+
+	/* total can not be zero. but just in case: */
+	if (total == 0)
+		return;
+
+	/* don't report if not compressed */
+	if (total >= plain)
+		return;
+
+	/* total < plain. check for overflow, still */
+	r = (total > UINT_MAX/1000) ? (total / (plain/1000))
+		                    : (1000 * total / plain);
+
+	if (r > 1000)
+		r = 1000;
+
+	r = 1000 - r;
+	dev_info(DEV, "%s bitmap stats [Bytes(packets)]: plain %u(%u), RLE %u(%u), "
+	     "total %u; compression: %u.%u%%\n",
+			direction,
+			c->bytes[1], c->packets[1],
+			c->bytes[0], c->packets[0],
+			total, r/10, r % 10);
+}
+
+/* Since we are processing the bitfield from lower addresses to higher,
+   it does not matter if the process it in 32 bit chunks or 64 bit
+   chunks as long as it is little endian. (Understand it as byte stream,
+   beginning with the lowest byte...) If we would use big endian
+   we would need to process it from the highest address to the lowest,
+   in order to be agnostic to the 32 vs 64 bits issue.
+
+   returns 0 on failure, 1 if we successfully received it. */
+static int receive_bitmap(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct bm_xfer_ctx c;
+	void *buffer;
+	int err;
+	int ok = false;
+	struct p_header80 *h = &mdev->data.rbuf.header.h80;
+
+	drbd_bm_lock(mdev, "receive bitmap", BM_LOCKED_SET_ALLOWED);
+	/* you are supposed to send additional out-of-sync information
+	 * if you actually set bits during this phase */
+
+	/* maybe we should use some per thread scratch page,
+	 * and allocate that during initial device creation? */
+	buffer	 = (unsigned long *) __get_free_page(GFP_NOIO);
+	if (!buffer) {
+		dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
+		goto out;
+	}
+
+	c = (struct bm_xfer_ctx) {
+		.bm_bits = drbd_bm_bits(mdev),
+		.bm_words = drbd_bm_words(mdev),
+	};
+
+	for(;;) {
+		if (cmd == P_BITMAP) {
+			err = receive_bitmap_plain(mdev, data_size, buffer, &c);
+		} else if (cmd == P_COMPRESSED_BITMAP) {
+			/* MAYBE: sanity check that we speak proto >= 90,
+			 * and the feature is enabled! */
+			struct p_compressed_bm *p;
+
+			if (data_size > BM_PACKET_PAYLOAD_BYTES) {
+				dev_err(DEV, "ReportCBitmap packet too large\n");
+				goto out;
+			}
+			/* use the page buff */
+			p = buffer;
+			memcpy(p, h, sizeof(*h));
+			if (drbd_recv(mdev, p->head.payload, data_size) != data_size)
+				goto out;
+			if (data_size <= (sizeof(*p) - sizeof(p->head))) {
+				dev_err(DEV, "ReportCBitmap packet too small (l:%u)\n", data_size);
+				goto out;
+			}
+			err = decode_bitmap_c(mdev, p, &c);
+		} else {
+			dev_warn(DEV, "receive_bitmap: cmd neither ReportBitMap nor ReportCBitMap (is 0x%x)", cmd);
+			goto out;
+		}
+
+		c.packets[cmd == P_BITMAP]++;
+		c.bytes[cmd == P_BITMAP] += sizeof(struct p_header80) + data_size;
+
+		if (err <= 0) {
+			if (err < 0)
+				goto out;
+			break;
+		}
+		if (!drbd_recv_header(mdev, &cmd, &data_size))
+			goto out;
+	}
+
+	INFO_bm_xfer_stats(mdev, "receive", &c);
+
+	if (mdev->state.conn == C_WF_BITMAP_T) {
+		enum drbd_state_rv rv;
+
+		ok = !drbd_send_bitmap(mdev);
+		if (!ok)
+			goto out;
+		/* Omit CS_ORDERED with this state transition to avoid deadlocks. */
+		rv = _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+		D_ASSERT(rv == SS_SUCCESS);
+	} else if (mdev->state.conn != C_WF_BITMAP_S) {
+		/* admin may have requested C_DISCONNECTING,
+		 * other threads may have noticed network errors */
+		dev_info(DEV, "unexpected cstate (%s) in receive_bitmap\n",
+		    drbd_conn_str(mdev->state.conn));
+	}
+
+	ok = true;
+ out:
+	drbd_bm_unlock(mdev);
+	if (ok && mdev->state.conn == C_WF_BITMAP_S)
+		drbd_start_resync(mdev, C_SYNC_SOURCE);
+	free_page((unsigned long) buffer);
+	return ok;
+}
+
+static int receive_skip(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	/* TODO zero copy sink :) */
+	static char sink[128];
+	int size, want, r;
+
+	dev_warn(DEV, "skipping unknown optional packet type %d, l: %d!\n",
+		 cmd, data_size);
+
+	size = data_size;
+	while (size > 0) {
+		want = min_t(int, size, sizeof(sink));
+		r = drbd_recv(mdev, sink, want);
+		ERR_IF(r <= 0) break;
+		size -= r;
+	}
+	return size == 0;
+}
+
+static int receive_UnplugRemote(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	/* Make sure we've acked all the TCP data associated
+	 * with the data requests being unplugged */
+	drbd_tcp_quickack(mdev->data.socket);
+
+	return true;
+}
+
+static int receive_out_of_sync(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_block_desc *p = &mdev->data.rbuf.block_desc;
+
+	switch (mdev->state.conn) {
+	case C_WF_SYNC_UUID:
+	case C_WF_BITMAP_T:
+	case C_BEHIND:
+			break;
+	default:
+		dev_err(DEV, "ASSERT FAILED cstate = %s, expected: WFSyncUUID|WFBitMapT|Behind\n",
+				drbd_conn_str(mdev->state.conn));
+	}
+
+	drbd_set_out_of_sync(mdev, be64_to_cpu(p->sector), be32_to_cpu(p->blksize));
+
+	return true;
+}
+
+typedef int (*drbd_cmd_handler_f)(struct drbd_conf *, enum drbd_packets cmd, unsigned int to_receive);
+
+struct data_cmd {
+	int expect_payload;
+	size_t pkt_size;
+	drbd_cmd_handler_f function;
+};
+
+static struct data_cmd drbd_cmd_handler[] = {
+	[P_DATA]	    = { 1, sizeof(struct p_data), receive_Data },
+	[P_DATA_REPLY]	    = { 1, sizeof(struct p_data), receive_DataReply },
+	[P_RS_DATA_REPLY]   = { 1, sizeof(struct p_data), receive_RSDataReply } ,
+	[P_BARRIER]	    = { 0, sizeof(struct p_barrier), receive_Barrier } ,
+	[P_BITMAP]	    = { 1, sizeof(struct p_header80), receive_bitmap } ,
+	[P_COMPRESSED_BITMAP] = { 1, sizeof(struct p_header80), receive_bitmap } ,
+	[P_UNPLUG_REMOTE]   = { 0, sizeof(struct p_header80), receive_UnplugRemote },
+	[P_DATA_REQUEST]    = { 0, sizeof(struct p_block_req), receive_DataRequest },
+	[P_RS_DATA_REQUEST] = { 0, sizeof(struct p_block_req), receive_DataRequest },
+	[P_SYNC_PARAM]	    = { 1, sizeof(struct p_header80), receive_SyncParam },
+	[P_SYNC_PARAM89]    = { 1, sizeof(struct p_header80), receive_SyncParam },
+	[P_PROTOCOL]        = { 1, sizeof(struct p_protocol), receive_protocol },
+	[P_UUIDS]	    = { 0, sizeof(struct p_uuids), receive_uuids },
+	[P_SIZES]	    = { 0, sizeof(struct p_sizes), receive_sizes },
+	[P_STATE]	    = { 0, sizeof(struct p_state), receive_state },
+	[P_STATE_CHG_REQ]   = { 0, sizeof(struct p_req_state), receive_req_state },
+	[P_SYNC_UUID]       = { 0, sizeof(struct p_rs_uuid), receive_sync_uuid },
+	[P_OV_REQUEST]      = { 0, sizeof(struct p_block_req), receive_DataRequest },
+	[P_OV_REPLY]        = { 1, sizeof(struct p_block_req), receive_DataRequest },
+	[P_CSUM_RS_REQUEST] = { 1, sizeof(struct p_block_req), receive_DataRequest },
+	[P_DELAY_PROBE]     = { 0, sizeof(struct p_delay_probe93), receive_skip },
+	[P_OUT_OF_SYNC]     = { 0, sizeof(struct p_block_desc), receive_out_of_sync },
+	/* anything missing from this table is in
+	 * the asender_tbl, see get_asender_cmd */
+	[P_MAX_CMD]	    = { 0, 0, NULL },
+};
+
+/* All handler functions that expect a sub-header get that sub-heder in
+   mdev->data.rbuf.header.head.payload.
+
+   Usually in mdev->data.rbuf.header.head the callback can find the usual
+   p_header, but they may not rely on that. Since there is also p_header95 !
+ */
+
+static void drbdd(struct drbd_conf *mdev)
+{
+	union p_header *header = &mdev->data.rbuf.header;
+	unsigned int packet_size;
+	enum drbd_packets cmd;
+	size_t shs; /* sub header size */
+	int rv;
+
+	while (get_t_state(&mdev->receiver) == Running) {
+		drbd_thread_current_set_cpu(mdev);
+		if (!drbd_recv_header(mdev, &cmd, &packet_size))
+			goto err_out;
+
+		if (unlikely(cmd >= P_MAX_CMD || !drbd_cmd_handler[cmd].function)) {
+			dev_err(DEV, "unknown packet type %d, l: %d!\n", cmd, packet_size);
+			goto err_out;
+		}
+
+		shs = drbd_cmd_handler[cmd].pkt_size - sizeof(union p_header);
+		if (packet_size - shs > 0 && !drbd_cmd_handler[cmd].expect_payload) {
+			dev_err(DEV, "No payload expected %s l:%d\n", cmdname(cmd), packet_size);
+			goto err_out;
+		}
+
+		if (shs) {
+			rv = drbd_recv(mdev, &header->h80.payload, shs);
+			if (unlikely(rv != shs)) {
+				if (!signal_pending(current))
+					dev_warn(DEV, "short read while reading sub header: rv=%d\n", rv);
+				goto err_out;
+			}
+		}
+
+		rv = drbd_cmd_handler[cmd].function(mdev, cmd, packet_size - shs);
+
+		if (unlikely(!rv)) {
+			dev_err(DEV, "error receiving %s, l: %d!\n",
+			    cmdname(cmd), packet_size);
+			goto err_out;
+		}
+	}
+
+	if (0) {
+	err_out:
+		drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+	}
+	/* If we leave here, we probably want to update at least the
+	 * "Connected" indicator on stable storage. Do so explicitly here. */
+	drbd_md_sync(mdev);
+}
+
+void drbd_flush_workqueue(struct drbd_conf *mdev)
+{
+	struct drbd_wq_barrier barr;
+
+	barr.w.cb = w_prev_work_done;
+	init_completion(&barr.done);
+	drbd_queue_work(&mdev->data.work, &barr.w);
+	wait_for_completion(&barr.done);
+}
+
+void drbd_free_tl_hash(struct drbd_conf *mdev)
+{
+	struct hlist_head *h;
+
+	spin_lock_irq(&mdev->req_lock);
+
+	if (!mdev->tl_hash || mdev->state.conn != C_STANDALONE) {
+		spin_unlock_irq(&mdev->req_lock);
+		return;
+	}
+	/* paranoia code */
+	for (h = mdev->ee_hash; h < mdev->ee_hash + mdev->ee_hash_s; h++)
+		if (h->first)
+			dev_err(DEV, "ASSERT FAILED ee_hash[%u].first == %p, expected NULL\n",
+				(int)(h - mdev->ee_hash), h->first);
+	kfree(mdev->ee_hash);
+	mdev->ee_hash = NULL;
+	mdev->ee_hash_s = 0;
+
+	/* paranoia code */
+	for (h = mdev->tl_hash; h < mdev->tl_hash + mdev->tl_hash_s; h++)
+		if (h->first)
+			dev_err(DEV, "ASSERT FAILED tl_hash[%u] == %p, expected NULL\n",
+				(int)(h - mdev->tl_hash), h->first);
+	kfree(mdev->tl_hash);
+	mdev->tl_hash = NULL;
+	mdev->tl_hash_s = 0;
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+static void drbd_disconnect(struct drbd_conf *mdev)
+{
+	enum drbd_fencing_p fp;
+	union drbd_state os, ns;
+	int rv = SS_UNKNOWN_ERROR;
+	unsigned int i;
+
+	if (mdev->state.conn == C_STANDALONE)
+		return;
+
+	/* asender does not clean up anything. it must not interfere, either */
+	drbd_thread_stop(&mdev->asender);
+	drbd_free_sock(mdev);
+
+	/* wait for current activity to cease. */
+	spin_lock_irq(&mdev->req_lock);
+	_drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+	_drbd_wait_ee_list_empty(mdev, &mdev->sync_ee);
+	_drbd_wait_ee_list_empty(mdev, &mdev->read_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	/* We do not have data structures that would allow us to
+	 * get the rs_pending_cnt down to 0 again.
+	 *  * On C_SYNC_TARGET we do not have any data structures describing
+	 *    the pending RSDataRequest's we have sent.
+	 *  * On C_SYNC_SOURCE there is no data structure that tracks
+	 *    the P_RS_DATA_REPLY blocks that we sent to the SyncTarget.
+	 *  And no, it is not the sum of the reference counts in the
+	 *  resync_LRU. The resync_LRU tracks the whole operation including
+	 *  the disk-IO, while the rs_pending_cnt only tracks the blocks
+	 *  on the fly. */
+	drbd_rs_cancel_all(mdev);
+	mdev->rs_total = 0;
+	mdev->rs_failed = 0;
+	atomic_set(&mdev->rs_pending_cnt, 0);
+	wake_up(&mdev->misc_wait);
+
+	del_timer(&mdev->request_timer);
+
+	/* make sure syncer is stopped and w_resume_next_sg queued */
+	del_timer_sync(&mdev->resync_timer);
+	resync_timer_fn((unsigned long)mdev);
+
+	/* wait for all w_e_end_data_req, w_e_end_rsdata_req, w_send_barrier,
+	 * w_make_resync_request etc. which may still be on the worker queue
+	 * to be "canceled" */
+	drbd_flush_workqueue(mdev);
+
+	/* This also does reclaim_net_ee().  If we do this too early, we might
+	 * miss some resync ee and pages.*/
+	drbd_process_done_ee(mdev);
+
+	kfree(mdev->p_uuid);
+	mdev->p_uuid = NULL;
+
+	if (!is_susp(mdev->state))
+		tl_clear(mdev);
+
+	dev_info(DEV, "Connection closed\n");
+
+	drbd_md_sync(mdev);
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	if (mdev->state.role == R_PRIMARY && fp >= FP_RESOURCE && mdev->state.pdsk >= D_UNKNOWN)
+		drbd_try_outdate_peer_async(mdev);
+
+	spin_lock_irq(&mdev->req_lock);
+	os = mdev->state;
+	if (os.conn >= C_UNCONNECTED) {
+		/* Do not restart in case we are C_DISCONNECTING */
+		ns = os;
+		ns.conn = C_UNCONNECTED;
+		rv = _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+	}
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (os.conn == C_DISCONNECTING) {
+		wait_event(mdev->net_cnt_wait, atomic_read(&mdev->net_cnt) == 0);
+
+		crypto_free_hash(mdev->cram_hmac_tfm);
+		mdev->cram_hmac_tfm = NULL;
+
+		kfree(mdev->net_conf);
+		mdev->net_conf = NULL;
+		drbd_request_state(mdev, NS(conn, C_STANDALONE));
+	}
+
+	/* serialize with bitmap writeout triggered by the state change,
+	 * if any. */
+	wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
+
+	/* tcp_close and release of sendpage pages can be deferred.  I don't
+	 * want to use SO_LINGER, because apparently it can be deferred for
+	 * more than 20 seconds (longest time I checked).
+	 *
+	 * Actually we don't care for exactly when the network stack does its
+	 * put_page(), but release our reference on these pages right here.
+	 */
+	i = drbd_release_ee(mdev, &mdev->net_ee);
+	if (i)
+		dev_info(DEV, "net_ee not empty, killed %u entries\n", i);
+	i = atomic_read(&mdev->pp_in_use_by_net);
+	if (i)
+		dev_info(DEV, "pp_in_use_by_net = %d, expected 0\n", i);
+	i = atomic_read(&mdev->pp_in_use);
+	if (i)
+		dev_info(DEV, "pp_in_use = %d, expected 0\n", i);
+
+	D_ASSERT(list_empty(&mdev->read_ee));
+	D_ASSERT(list_empty(&mdev->active_ee));
+	D_ASSERT(list_empty(&mdev->sync_ee));
+	D_ASSERT(list_empty(&mdev->done_ee));
+
+	/* ok, no more ee's on the fly, it is safe to reset the epoch_size */
+	atomic_set(&mdev->current_epoch->epoch_size, 0);
+	D_ASSERT(list_empty(&mdev->current_epoch->list));
+}
+
+/*
+ * We support PRO_VERSION_MIN to PRO_VERSION_MAX. The protocol version
+ * we can agree on is stored in agreed_pro_version.
+ *
+ * feature flags and the reserved array should be enough room for future
+ * enhancements of the handshake protocol, and possible plugins...
+ *
+ * for now, they are expected to be zero, but ignored.
+ */
+static int drbd_send_handshake(struct drbd_conf *mdev)
+{
+	/* ASSERT current == mdev->receiver ... */
+	struct p_handshake *p = &mdev->data.sbuf.handshake;
+	int ok;
+
+	if (mutex_lock_interruptible(&mdev->data.mutex)) {
+		dev_err(DEV, "interrupted during initial handshake\n");
+		return 0; /* interrupted. not ok. */
+	}
+
+	if (mdev->data.socket == NULL) {
+		mutex_unlock(&mdev->data.mutex);
+		return 0;
+	}
+
+	memset(p, 0, sizeof(*p));
+	p->protocol_min = cpu_to_be32(PRO_VERSION_MIN);
+	p->protocol_max = cpu_to_be32(PRO_VERSION_MAX);
+	ok = _drbd_send_cmd( mdev, mdev->data.socket, P_HAND_SHAKE,
+			     (struct p_header80 *)p, sizeof(*p), 0 );
+	mutex_unlock(&mdev->data.mutex);
+	return ok;
+}
+
+/*
+ * return values:
+ *   1 yes, we have a valid connection
+ *   0 oops, did not work out, please try again
+ *  -1 peer talks different language,
+ *     no point in trying again, please go standalone.
+ */
+static int drbd_do_handshake(struct drbd_conf *mdev)
+{
+	/* ASSERT current == mdev->receiver ... */
+	struct p_handshake *p = &mdev->data.rbuf.handshake;
+	const int expect = sizeof(struct p_handshake) - sizeof(struct p_header80);
+	unsigned int length;
+	enum drbd_packets cmd;
+	int rv;
+
+	rv = drbd_send_handshake(mdev);
+	if (!rv)
+		return 0;
+
+	rv = drbd_recv_header(mdev, &cmd, &length);
+	if (!rv)
+		return 0;
+
+	if (cmd != P_HAND_SHAKE) {
+		dev_err(DEV, "expected HandShake packet, received: %s (0x%04x)\n",
+		     cmdname(cmd), cmd);
+		return -1;
+	}
+
+	if (length != expect) {
+		dev_err(DEV, "expected HandShake length: %u, received: %u\n",
+		     expect, length);
+		return -1;
+	}
+
+	rv = drbd_recv(mdev, &p->head.payload, expect);
+
+	if (rv != expect) {
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read receiving handshake packet: l=%u\n", rv);
+		return 0;
+	}
+
+	p->protocol_min = be32_to_cpu(p->protocol_min);
+	p->protocol_max = be32_to_cpu(p->protocol_max);
+	if (p->protocol_max == 0)
+		p->protocol_max = p->protocol_min;
+
+	if (PRO_VERSION_MAX < p->protocol_min ||
+	    PRO_VERSION_MIN > p->protocol_max)
+		goto incompat;
+
+	mdev->agreed_pro_version = min_t(int, PRO_VERSION_MAX, p->protocol_max);
+
+	dev_info(DEV, "Handshake successful: "
+	     "Agreed network protocol version %d\n", mdev->agreed_pro_version);
+
+	return 1;
+
+ incompat:
+	dev_err(DEV, "incompatible DRBD dialects: "
+	    "I support %d-%d, peer supports %d-%d\n",
+	    PRO_VERSION_MIN, PRO_VERSION_MAX,
+	    p->protocol_min, p->protocol_max);
+	return -1;
+}
+
+#if !defined(CONFIG_CRYPTO_HMAC) && !defined(CONFIG_CRYPTO_HMAC_MODULE)
+static int drbd_do_auth(struct drbd_conf *mdev)
+{
+	dev_err(DEV, "This kernel was build without CONFIG_CRYPTO_HMAC.\n");
+	dev_err(DEV, "You need to disable 'cram-hmac-alg' in drbd.conf.\n");
+	return -1;
+}
+#else
+#define CHALLENGE_LEN 64
+
+/* Return value:
+	1 - auth succeeded,
+	0 - failed, try again (network error),
+	-1 - auth failed, don't try again.
+*/
+
+static int drbd_do_auth(struct drbd_conf *mdev)
+{
+	char my_challenge[CHALLENGE_LEN];  /* 64 Bytes... */
+	struct scatterlist sg;
+	char *response = NULL;
+	char *right_response = NULL;
+	char *peers_ch = NULL;
+	unsigned int key_len = strlen(mdev->net_conf->shared_secret);
+	unsigned int resp_size;
+	struct hash_desc desc;
+	enum drbd_packets cmd;
+	unsigned int length;
+	int rv;
+
+	desc.tfm = mdev->cram_hmac_tfm;
+	desc.flags = 0;
+
+	rv = crypto_hash_setkey(mdev->cram_hmac_tfm,
+				(u8 *)mdev->net_conf->shared_secret, key_len);
+	if (rv) {
+		dev_err(DEV, "crypto_hash_setkey() failed with %d\n", rv);
+		rv = -1;
+		goto fail;
+	}
+
+	get_random_bytes(my_challenge, CHALLENGE_LEN);
+
+	rv = drbd_send_cmd2(mdev, P_AUTH_CHALLENGE, my_challenge, CHALLENGE_LEN);
+	if (!rv)
+		goto fail;
+
+	rv = drbd_recv_header(mdev, &cmd, &length);
+	if (!rv)
+		goto fail;
+
+	if (cmd != P_AUTH_CHALLENGE) {
+		dev_err(DEV, "expected AuthChallenge packet, received: %s (0x%04x)\n",
+		    cmdname(cmd), cmd);
+		rv = 0;
+		goto fail;
+	}
+
+	if (length > CHALLENGE_LEN * 2) {
+		dev_err(DEV, "expected AuthChallenge payload too big.\n");
+		rv = -1;
+		goto fail;
+	}
+
+	peers_ch = kmalloc(length, GFP_NOIO);
+	if (peers_ch == NULL) {
+		dev_err(DEV, "kmalloc of peers_ch failed\n");
+		rv = -1;
+		goto fail;
+	}
+
+	rv = drbd_recv(mdev, peers_ch, length);
+
+	if (rv != length) {
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read AuthChallenge: l=%u\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	resp_size = crypto_hash_digestsize(mdev->cram_hmac_tfm);
+	response = kmalloc(resp_size, GFP_NOIO);
+	if (response == NULL) {
+		dev_err(DEV, "kmalloc of response failed\n");
+		rv = -1;
+		goto fail;
+	}
+
+	sg_init_table(&sg, 1);
+	sg_set_buf(&sg, peers_ch, length);
+
+	rv = crypto_hash_digest(&desc, &sg, sg.length, response);
+	if (rv) {
+		dev_err(DEV, "crypto_hash_digest() failed with %d\n", rv);
+		rv = -1;
+		goto fail;
+	}
+
+	rv = drbd_send_cmd2(mdev, P_AUTH_RESPONSE, response, resp_size);
+	if (!rv)
+		goto fail;
+
+	rv = drbd_recv_header(mdev, &cmd, &length);
+	if (!rv)
+		goto fail;
+
+	if (cmd != P_AUTH_RESPONSE) {
+		dev_err(DEV, "expected AuthResponse packet, received: %s (0x%04x)\n",
+			cmdname(cmd), cmd);
+		rv = 0;
+		goto fail;
+	}
+
+	if (length != resp_size) {
+		dev_err(DEV, "expected AuthResponse payload of wrong size\n");
+		rv = 0;
+		goto fail;
+	}
+
+	rv = drbd_recv(mdev, response , resp_size);
+
+	if (rv != resp_size) {
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read receiving AuthResponse: l=%u\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	right_response = kmalloc(resp_size, GFP_NOIO);
+	if (right_response == NULL) {
+		dev_err(DEV, "kmalloc of right_response failed\n");
+		rv = -1;
+		goto fail;
+	}
+
+	sg_set_buf(&sg, my_challenge, CHALLENGE_LEN);
+
+	rv = crypto_hash_digest(&desc, &sg, sg.length, right_response);
+	if (rv) {
+		dev_err(DEV, "crypto_hash_digest() failed with %d\n", rv);
+		rv = -1;
+		goto fail;
+	}
+
+	rv = !memcmp(response, right_response, resp_size);
+
+	if (rv)
+		dev_info(DEV, "Peer authenticated using %d bytes of '%s' HMAC\n",
+		     resp_size, mdev->net_conf->cram_hmac_alg);
+	else
+		rv = -1;
+
+ fail:
+	kfree(peers_ch);
+	kfree(response);
+	kfree(right_response);
+
+	return rv;
+}
+#endif
+
+int drbdd_init(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	unsigned int minor = mdev_to_minor(mdev);
+	int h;
+
+	sprintf(current->comm, "drbd%d_receiver", minor);
+
+	dev_info(DEV, "receiver (re)started\n");
+
+	do {
+		h = drbd_connect(mdev);
+		if (h == 0) {
+			drbd_disconnect(mdev);
+			schedule_timeout_interruptible(HZ);
+		}
+		if (h == -1) {
+			dev_warn(DEV, "Discarding network configuration.\n");
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		}
+	} while (h == 0);
+
+	if (h > 0) {
+		if (get_net_conf(mdev)) {
+			drbdd(mdev);
+			put_net_conf(mdev);
+		}
+	}
+
+	drbd_disconnect(mdev);
+
+	dev_info(DEV, "receiver terminated\n");
+	return 0;
+}
+
+/* ********* acknowledge sender ******** */
+
+static int got_RqSReply(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_req_state_reply *p = (struct p_req_state_reply *)h;
+
+	int retcode = be32_to_cpu(p->retcode);
+
+	if (retcode >= SS_SUCCESS) {
+		set_bit(CL_ST_CHG_SUCCESS, &mdev->flags);
+	} else {
+		set_bit(CL_ST_CHG_FAIL, &mdev->flags);
+		dev_err(DEV, "Requested state change failed by peer: %s (%d)\n",
+		    drbd_set_st_err_str(retcode), retcode);
+	}
+	wake_up(&mdev->state_wait);
+
+	return true;
+}
+
+static int got_Ping(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	return drbd_send_ping_ack(mdev);
+
+}
+
+static int got_PingAck(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	/* restore idle timeout */
+	mdev->meta.socket->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
+	if (!test_and_set_bit(GOT_PING_ACK, &mdev->flags))
+		wake_up(&mdev->misc_wait);
+
+	return true;
+}
+
+static int got_IsInSync(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+	int blksize = be32_to_cpu(p->blksize);
+
+	D_ASSERT(mdev->agreed_pro_version >= 89);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (get_ldev(mdev)) {
+		drbd_rs_complete_io(mdev, sector);
+		drbd_set_in_sync(mdev, sector, blksize);
+		/* rs_same_csums is supposed to count in units of BM_BLOCK_SIZE */
+		mdev->rs_same_csum += (blksize >> BM_BLOCK_SHIFT);
+		put_ldev(mdev);
+	}
+	dec_rs_pending(mdev);
+	atomic_add(blksize >> 9, &mdev->rs_sect_in);
+
+	return true;
+}
+
+/* when we receive the ACK for a write request,
+ * verify that we actually know about it */
+static struct drbd_request *_ack_id_to_req(struct drbd_conf *mdev,
+	u64 id, sector_t sector)
+{
+	struct hlist_head *slot = tl_hash_slot(mdev, sector);
+	struct hlist_node *n;
+	struct drbd_request *req;
+
+	hlist_for_each_entry(req, n, slot, collision) {
+		if ((unsigned long)req == (unsigned long)id) {
+			if (req->sector != sector) {
+				dev_err(DEV, "_ack_id_to_req: found req %p but it has "
+				    "wrong sector (%llus versus %llus)\n", req,
+				    (unsigned long long)req->sector,
+				    (unsigned long long)sector);
+				break;
+			}
+			return req;
+		}
+	}
+	return NULL;
+}
+
+typedef struct drbd_request *(req_validator_fn)
+	(struct drbd_conf *mdev, u64 id, sector_t sector);
+
+static int validate_req_change_req_state(struct drbd_conf *mdev,
+	u64 id, sector_t sector, req_validator_fn validator,
+	const char *func, enum drbd_req_event what)
+{
+	struct drbd_request *req;
+	struct bio_and_error m;
+
+	spin_lock_irq(&mdev->req_lock);
+	req = validator(mdev, id, sector);
+	if (unlikely(!req)) {
+		spin_unlock_irq(&mdev->req_lock);
+
+		dev_err(DEV, "%s: failed to find req %p, sector %llus\n", func,
+			(void *)(unsigned long)id, (unsigned long long)sector);
+		return false;
+	}
+	__req_mod(req, what, &m);
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+	return true;
+}
+
+static int got_BlockAck(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+	int blksize = be32_to_cpu(p->blksize);
+	enum drbd_req_event what;
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (is_syncer_block_id(p->block_id)) {
+		drbd_set_in_sync(mdev, sector, blksize);
+		dec_rs_pending(mdev);
+		return true;
+	}
+	switch (be16_to_cpu(h->command)) {
+	case P_RS_WRITE_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		what = write_acked_by_peer_and_sis;
+		break;
+	case P_WRITE_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		what = write_acked_by_peer;
+		break;
+	case P_RECV_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_B);
+		what = recv_acked_by_peer;
+		break;
+	case P_DISCARD_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		what = conflict_discarded_by_peer;
+		break;
+	default:
+		D_ASSERT(0);
+		return false;
+	}
+
+	return validate_req_change_req_state(mdev, p->block_id, sector,
+		_ack_id_to_req, __func__ , what);
+}
+
+static int got_NegAck(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+	int size = be32_to_cpu(p->blksize);
+	struct drbd_request *req;
+	struct bio_and_error m;
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (is_syncer_block_id(p->block_id)) {
+		dec_rs_pending(mdev);
+		drbd_rs_failed_io(mdev, sector, size);
+		return true;
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	req = _ack_id_to_req(mdev, p->block_id, sector);
+	if (!req) {
+		spin_unlock_irq(&mdev->req_lock);
+		if (mdev->net_conf->wire_protocol == DRBD_PROT_A ||
+		    mdev->net_conf->wire_protocol == DRBD_PROT_B) {
+			/* Protocol A has no P_WRITE_ACKs, but has P_NEG_ACKs.
+			   The master bio might already be completed, therefore the
+			   request is no longer in the collision hash.
+			   => Do not try to validate block_id as request. */
+			/* In Protocol B we might already have got a P_RECV_ACK
+			   but then get a P_NEG_ACK after wards. */
+			drbd_set_out_of_sync(mdev, sector, size);
+			return true;
+		} else {
+			dev_err(DEV, "%s: failed to find req %p, sector %llus\n", __func__,
+				(void *)(unsigned long)p->block_id, (unsigned long long)sector);
+			return false;
+		}
+	}
+	__req_mod(req, neg_acked, &m);
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+	return true;
+}
+
+static int got_NegDReply(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+	dev_err(DEV, "Got NegDReply; Sector %llus, len %u; Fail original request.\n",
+	    (unsigned long long)sector, be32_to_cpu(p->blksize));
+
+	return validate_req_change_req_state(mdev, p->block_id, sector,
+		_ar_id_to_req, __func__ , neg_acked);
+}
+
+static int got_NegRSDReply(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	sector_t sector;
+	int size;
+	struct p_block_ack *p = (struct p_block_ack *)h;
+
+	sector = be64_to_cpu(p->sector);
+	size = be32_to_cpu(p->blksize);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	dec_rs_pending(mdev);
+
+	if (get_ldev_if_state(mdev, D_FAILED)) {
+		drbd_rs_complete_io(mdev, sector);
+		switch (be16_to_cpu(h->command)) {
+		case P_NEG_RS_DREPLY:
+			drbd_rs_failed_io(mdev, sector, size);
+		case P_RS_CANCEL:
+			break;
+		default:
+			D_ASSERT(0);
+			put_ldev(mdev);
+			return false;
+		}
+		put_ldev(mdev);
+	}
+
+	return true;
+}
+
+static int got_BarrierAck(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_barrier_ack *p = (struct p_barrier_ack *)h;
+
+	tl_release(mdev, p->barrier, be32_to_cpu(p->set_size));
+
+	if (mdev->state.conn == C_AHEAD &&
+	    atomic_read(&mdev->ap_in_flight) == 0 &&
+	    !test_and_set_bit(AHEAD_TO_SYNC_SOURCE, &mdev->current_epoch->flags)) {
+		mdev->start_resync_timer.expires = jiffies + HZ;
+		add_timer(&mdev->start_resync_timer);
+	}
+
+	return true;
+}
+
+static int got_OVResult(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	struct drbd_work *w;
+	sector_t sector;
+	int size;
+
+	sector = be64_to_cpu(p->sector);
+	size = be32_to_cpu(p->blksize);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (be64_to_cpu(p->block_id) == ID_OUT_OF_SYNC)
+		drbd_ov_oos_found(mdev, sector, size);
+	else
+		ov_oos_print(mdev);
+
+	if (!get_ldev(mdev))
+		return true;
+
+	drbd_rs_complete_io(mdev, sector);
+	dec_rs_pending(mdev);
+
+	--mdev->ov_left;
+
+	/* let's advance progress step marks only for every other megabyte */
+	if ((mdev->ov_left & 0x200) == 0x200)
+		drbd_advance_rs_marks(mdev, mdev->ov_left);
+
+	if (mdev->ov_left == 0) {
+		w = kmalloc(sizeof(*w), GFP_NOIO);
+		if (w) {
+			w->cb = w_ov_finished;
+			drbd_queue_work_front(&mdev->data.work, w);
+		} else {
+			dev_err(DEV, "kmalloc(w) failed.");
+			ov_oos_print(mdev);
+			drbd_resync_finished(mdev);
+		}
+	}
+	put_ldev(mdev);
+	return true;
+}
+
+static int got_skip(struct drbd_conf *mdev, struct p_header80 *h)
+{
+	return true;
+}
+
+struct asender_cmd {
+	size_t pkt_size;
+	int (*process)(struct drbd_conf *mdev, struct p_header80 *h);
+};
+
+static struct asender_cmd *get_asender_cmd(int cmd)
+{
+	static struct asender_cmd asender_tbl[] = {
+		/* anything missing from this table is in
+		 * the drbd_cmd_handler (drbd_default_handler) table,
+		 * see the beginning of drbdd() */
+	[P_PING]	    = { sizeof(struct p_header80), got_Ping },
+	[P_PING_ACK]	    = { sizeof(struct p_header80), got_PingAck },
+	[P_RECV_ACK]	    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_WRITE_ACK]	    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_RS_WRITE_ACK]    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_DISCARD_ACK]	    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_NEG_ACK]	    = { sizeof(struct p_block_ack), got_NegAck },
+	[P_NEG_DREPLY]	    = { sizeof(struct p_block_ack), got_NegDReply },
+	[P_NEG_RS_DREPLY]   = { sizeof(struct p_block_ack), got_NegRSDReply},
+	[P_OV_RESULT]	    = { sizeof(struct p_block_ack), got_OVResult },
+	[P_BARRIER_ACK]	    = { sizeof(struct p_barrier_ack), got_BarrierAck },
+	[P_STATE_CHG_REPLY] = { sizeof(struct p_req_state_reply), got_RqSReply },
+	[P_RS_IS_IN_SYNC]   = { sizeof(struct p_block_ack), got_IsInSync },
+	[P_DELAY_PROBE]     = { sizeof(struct p_delay_probe93), got_skip },
+	[P_RS_CANCEL]       = { sizeof(struct p_block_ack), got_NegRSDReply},
+	[P_MAX_CMD]	    = { 0, NULL },
+	};
+	if (cmd > P_MAX_CMD || asender_tbl[cmd].process == NULL)
+		return NULL;
+	return &asender_tbl[cmd];
+}
+
+int drbd_asender(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	struct p_header80 *h = &mdev->meta.rbuf.header.h80;
+	struct asender_cmd *cmd = NULL;
+
+	int rv, len;
+	void *buf    = h;
+	int received = 0;
+	int expect   = sizeof(struct p_header80);
+	int empty;
+	int ping_timeout_active = 0;
+
+	sprintf(current->comm, "drbd%d_asender", mdev_to_minor(mdev));
+
+	current->policy = SCHED_RR;  /* Make this a realtime task! */
+	current->rt_priority = 2;    /* more important than all other tasks */
+
+	while (get_t_state(thi) == Running) {
+		drbd_thread_current_set_cpu(mdev);
+		if (test_and_clear_bit(SEND_PING, &mdev->flags)) {
+			ERR_IF(!drbd_send_ping(mdev)) goto reconnect;
+			mdev->meta.socket->sk->sk_rcvtimeo =
+				mdev->net_conf->ping_timeo*HZ/10;
+			ping_timeout_active = 1;
+		}
+
+		/* conditionally cork;
+		 * it may hurt latency if we cork without much to send */
+		if (!mdev->net_conf->no_cork &&
+			3 < atomic_read(&mdev->unacked_cnt))
+			drbd_tcp_cork(mdev->meta.socket);
+		while (1) {
+			clear_bit(SIGNAL_ASENDER, &mdev->flags);
+			flush_signals(current);
+			if (!drbd_process_done_ee(mdev))
+				goto reconnect;
+			/* to avoid race with newly queued ACKs */
+			set_bit(SIGNAL_ASENDER, &mdev->flags);
+			spin_lock_irq(&mdev->req_lock);
+			empty = list_empty(&mdev->done_ee);
+			spin_unlock_irq(&mdev->req_lock);
+			/* new ack may have been queued right here,
+			 * but then there is also a signal pending,
+			 * and we start over... */
+			if (empty)
+				break;
+		}
+		/* but unconditionally uncork unless disabled */
+		if (!mdev->net_conf->no_cork)
+			drbd_tcp_uncork(mdev->meta.socket);
+
+		/* short circuit, recv_msg would return EINTR anyways. */
+		if (signal_pending(current))
+			continue;
+
+		rv = drbd_recv_short(mdev, mdev->meta.socket,
+				     buf, expect-received, 0);
+		clear_bit(SIGNAL_ASENDER, &mdev->flags);
+
+		flush_signals(current);
+
+		/* Note:
+		 * -EINTR	 (on meta) we got a signal
+		 * -EAGAIN	 (on meta) rcvtimeo expired
+		 * -ECONNRESET	 other side closed the connection
+		 * -ERESTARTSYS  (on data) we got a signal
+		 * rv <  0	 other than above: unexpected error!
+		 * rv == expected: full header or command
+		 * rv <  expected: "woken" by signal during receive
+		 * rv == 0	 : "connection shut down by peer"
+		 */
+		if (likely(rv > 0)) {
+			received += rv;
+			buf	 += rv;
+		} else if (rv == 0) {
+			dev_err(DEV, "meta connection shut down by peer.\n");
+			goto reconnect;
+		} else if (rv == -EAGAIN) {
+			/* If the data socket received something meanwhile,
+			 * that is good enough: peer is still alive. */
+			if (time_after(mdev->last_received,
+				jiffies - mdev->meta.socket->sk->sk_rcvtimeo))
+				continue;
+			if (ping_timeout_active) {
+				dev_err(DEV, "PingAck did not arrive in time.\n");
+				goto reconnect;
+			}
+			set_bit(SEND_PING, &mdev->flags);
+			continue;
+		} else if (rv == -EINTR) {
+			continue;
+		} else {
+			dev_err(DEV, "sock_recvmsg returned %d\n", rv);
+			goto reconnect;
+		}
+
+		if (received == expect && cmd == NULL) {
+			if (unlikely(h->magic != BE_DRBD_MAGIC)) {
+				dev_err(DEV, "magic?? on meta m: 0x%08x c: %d l: %d\n",
+				    be32_to_cpu(h->magic),
+				    be16_to_cpu(h->command),
+				    be16_to_cpu(h->length));
+				goto reconnect;
+			}
+			cmd = get_asender_cmd(be16_to_cpu(h->command));
+			len = be16_to_cpu(h->length);
+			if (unlikely(cmd == NULL)) {
+				dev_err(DEV, "unknown command?? on meta m: 0x%08x c: %d l: %d\n",
+				    be32_to_cpu(h->magic),
+				    be16_to_cpu(h->command),
+				    be16_to_cpu(h->length));
+				goto disconnect;
+			}
+			expect = cmd->pkt_size;
+			ERR_IF(len != expect-sizeof(struct p_header80))
+				goto reconnect;
+		}
+		if (received == expect) {
+			mdev->last_received = jiffies;
+			D_ASSERT(cmd != NULL);
+			if (!cmd->process(mdev, h))
+				goto reconnect;
+
+			/* the idle_timeout (ping-int)
+			 * has been restored in got_PingAck() */
+			if (cmd == get_asender_cmd(P_PING_ACK))
+				ping_timeout_active = 0;
+
+			buf	 = h;
+			received = 0;
+			expect	 = sizeof(struct p_header80);
+			cmd	 = NULL;
+		}
+	}
+
+	if (0) {
+reconnect:
+		drbd_force_state(mdev, NS(conn, C_NETWORK_FAILURE));
+		drbd_md_sync(mdev);
+	}
+	if (0) {
+disconnect:
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		drbd_md_sync(mdev);
+	}
+	clear_bit(SIGNAL_ASENDER, &mdev->flags);
+
+	D_ASSERT(mdev->state.conn < C_CONNECTED);
+	dev_info(DEV, "asender terminated\n");
+
+	return 0;
+}