[PATCH 19/24] ibnbd: server: main functionality

[Roman Pen <roman.penyaev@profitbricks.com>]

This is main functionality of ibnbd-server module, which handles IBTRS
events and IBNBD protocol requests, like map (open) or unmap (close)
device.  Also server side is responsible for processing incoming IBTRS
IO requests and forward them to local mapped devices.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Signed-off-by: Danil Kipnis <danil.kipnis@profitbricks.com>
Cc: Jack Wang <jinpu.wang@profitbricks.com>
---
 drivers/block/ibnbd/ibnbd-srv.c | 901 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 901 insertions(+)

diff --git a/drivers/block/ibnbd/ibnbd-srv.c b/drivers/block/ibnbd/ibnbd-srv.c
new file mode 100644
index 000000000000..a32d22ab67a3
--- /dev/null
+++ b/drivers/block/ibnbd/ibnbd-srv.c
@@ -0,0 +1,901 @@
+/*
+ * InfiniBand Network Block Driver
+ *
+ * Copyright (c) 2014 - 2017 ProfitBricks GmbH. All rights reserved.
+ * Authors: Fabian Holler <mail@fholler.de>
+ *          Jack Wang <jinpu.wang@profitbricks.com>
+ *          Kleber Souza <kleber.souza@profitbricks.com>
+ *          Danil Kipnis <danil.kipnis@profitbricks.com>
+ *          Roman Penyaev <roman.penyaev@profitbricks.com>
+ *          Milind Dumbare <Milind.dumbare@gmail.com>
+ *
+ * Copyright (c) 2017 - 2018 ProfitBricks GmbH. All rights reserved.
+ * Authors: Danil Kipnis <danil.kipnis@profitbricks.com>
+ *          Roman Penyaev <roman.penyaev@profitbricks.com>
+ *
+ * This program 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
+ * of the License, or (at your option) any later version.
+ *
+ * This program 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 this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#undef pr_fmt
+#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt
+
+#include <linux/module.h>
+#include <linux/blkdev.h>
+
+#include "ibnbd-srv.h"
+#include "ibnbd-srv-dev.h"
+
+MODULE_AUTHOR("ibnbd@profitbricks.com");
+MODULE_VERSION(IBNBD_VER_STRING);
+MODULE_DESCRIPTION("InfiniBand Network Block Device Server");
+MODULE_LICENSE("GPL");
+
+#define DEFAULT_DEV_SEARCH_PATH "/"
+
+static char dev_search_path[PATH_MAX] = DEFAULT_DEV_SEARCH_PATH;
+
+static int dev_search_path_set(const char *val, const struct kernel_param *kp)
+{
+	char *dup;
+
+	if (strlen(val) >= sizeof(dev_search_path))
+		return -EINVAL;
+
+	dup = kstrdup(val, GFP_KERNEL);
+
+	if (dup[strlen(dup) - 1] == '\n')
+		dup[strlen(dup) - 1] = '\0';
+
+	strlcpy(dev_search_path, dup, sizeof(dev_search_path));
+
+	kfree(dup);
+	pr_info("dev_search_path changed to '%s'\n", dev_search_path);
+
+	return 0;
+}
+
+static struct kparam_string dev_search_path_kparam_str = {
+	.maxlen	= sizeof(dev_search_path),
+	.string	= dev_search_path
+};
+
+static const struct kernel_param_ops dev_search_path_ops = {
+	.set	= dev_search_path_set,
+	.get	= param_get_string,
+};
+
+module_param_cb(dev_search_path, &dev_search_path_ops,
+		&dev_search_path_kparam_str, 0444);
+MODULE_PARM_DESC(dev_search_path, "Sets the device_search_path."
+		 " When a device is mapped this path is prepended to the"
+		 " device_path from the map_device operation."
+		 " (default: " DEFAULT_DEV_SEARCH_PATH ")");
+
+static int def_io_mode = IBNBD_BLOCKIO;
+module_param(def_io_mode, int, 0444);
+MODULE_PARM_DESC(def_io_mode, "By default, export devices in"
+		 " blockio(" __stringify(_IBNBD_BLOCKIO) ") or"
+		 " fileio(" __stringify(_IBNBD_FILEIO) ") mode."
+		 " (default: " __stringify(_IBNBD_BLOCKIO) " (blockio))");
+
+static DEFINE_MUTEX(sess_lock);
+static DEFINE_SPINLOCK(dev_lock);
+
+static LIST_HEAD(sess_list);
+static LIST_HEAD(dev_list);
+
+struct ibnbd_io_private {
+	struct ibtrs_srv_op		*id;
+	struct ibnbd_srv_sess_dev	*sess_dev;
+};
+
+static void ibnbd_sess_dev_release(struct kref *kref)
+{
+	struct ibnbd_srv_sess_dev *sess_dev;
+
+	sess_dev = container_of(kref, struct ibnbd_srv_sess_dev, kref);
+	complete(sess_dev->destroy_comp);
+}
+
+static inline void ibnbd_put_sess_dev(struct ibnbd_srv_sess_dev *sess_dev)
+{
+	kref_put(&sess_dev->kref, ibnbd_sess_dev_release);
+}
+
+static void ibnbd_endio(void *priv, int error)
+{
+	struct ibnbd_io_private *ibnbd_priv = priv;
+	struct ibnbd_srv_sess_dev *sess_dev = ibnbd_priv->sess_dev;
+
+	ibnbd_put_sess_dev(sess_dev);
+
+	ibtrs_srv_resp_rdma(ibnbd_priv->id, error);
+
+	kfree(priv);
+}
+
+static struct ibnbd_srv_sess_dev *
+ibnbd_get_sess_dev(int dev_id, struct ibnbd_srv_session *srv_sess)
+{
+	struct ibnbd_srv_sess_dev *sess_dev;
+	int ret = 0;
+
+	read_lock(&srv_sess->index_lock);
+	sess_dev = idr_find(&srv_sess->index_idr, dev_id);
+	if (likely(sess_dev))
+		ret = kref_get_unless_zero(&sess_dev->kref);
+	read_unlock(&srv_sess->index_lock);
+
+	if (unlikely(!sess_dev || !ret))
+		return ERR_PTR(-ENXIO);
+
+	return sess_dev;
+}
+
+static int process_rdma(struct ibtrs_srv *sess,
+			struct ibnbd_srv_session *srv_sess,
+			struct ibtrs_srv_op *id, void *data, u32 datalen,
+			const void *usr, size_t usrlen)
+{
+	const struct ibnbd_msg_io *msg = usr;
+	struct ibnbd_io_private *priv;
+	struct ibnbd_srv_sess_dev *sess_dev;
+	u32 dev_id;
+	int err;
+
+	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
+	if (unlikely(!priv))
+		return -ENOMEM;
+
+	dev_id = le32_to_cpu(msg->device_id);
+
+	sess_dev = ibnbd_get_sess_dev(dev_id, srv_sess);
+	if (unlikely(IS_ERR(sess_dev))) {
+		pr_err_ratelimited("Got I/O request on session %s for "
+				   "unknown device id %d\n",
+				   srv_sess->sessname, dev_id);
+		err = -ENOTCONN;
+		goto err;
+	}
+
+	priv->sess_dev = sess_dev;
+	priv->id = id;
+
+	err = ibnbd_dev_submit_io(sess_dev->ibnbd_dev, le64_to_cpu(msg->sector),
+				  data, datalen, le32_to_cpu(msg->bi_size),
+				  le32_to_cpu(msg->rw), priv);
+	if (unlikely(err)) {
+		ibnbd_err(sess_dev,
+			  "Submitting I/O to device failed, err: %d\n", err);
+		goto sess_dev_put;
+	}
+
+	return 0;
+
+sess_dev_put:
+	ibnbd_put_sess_dev(sess_dev);
+err:
+	kfree(priv);
+	return err;
+}
+
+static void destroy_device(struct ibnbd_srv_dev *dev)
+{
+	WARN(!list_empty(&dev->sess_dev_list),
+	     "Device %s is being destroyed but still in use!\n",
+	     dev->id);
+
+	spin_lock(&dev_lock);
+	list_del(&dev->list);
+	spin_unlock(&dev_lock);
+
+	if (dev->dev_kobj.state_in_sysfs)
+		/*
+		 * Destroy kobj only if it was really created.
+		 * The following call should be sync, because
+		 *  we free the memory afterwards.
+		 */
+		ibnbd_srv_destroy_dev_sysfs(dev);
+
+	kfree(dev);
+}
+
+static void destroy_device_cb(struct kref *kref)
+{
+	struct ibnbd_srv_dev *dev;
+
+	dev = container_of(kref, struct ibnbd_srv_dev, kref);
+
+	destroy_device(dev);
+}
+
+static void ibnbd_put_srv_dev(struct ibnbd_srv_dev *dev)
+{
+	kref_put(&dev->kref, destroy_device_cb);
+}
+
+static void ibnbd_destroy_sess_dev(struct ibnbd_srv_sess_dev *sess_dev)
+{
+	DECLARE_COMPLETION_ONSTACK(dc);
+
+	write_lock(&sess_dev->sess->index_lock);
+	idr_remove(&sess_dev->sess->index_idr, sess_dev->device_id);
+	write_unlock(&sess_dev->sess->index_lock);
+
+	sess_dev->destroy_comp = &dc;
+	ibnbd_put_sess_dev(sess_dev);
+	wait_for_completion(&dc);
+
+	ibnbd_dev_close(sess_dev->ibnbd_dev);
+	list_del(&sess_dev->sess_list);
+	mutex_lock(&sess_dev->dev->lock);
+	list_del(&sess_dev->dev_list);
+	if (sess_dev->open_flags & FMODE_WRITE)
+		sess_dev->dev->open_write_cnt--;
+	mutex_unlock(&sess_dev->dev->lock);
+
+	ibnbd_put_srv_dev(sess_dev->dev);
+
+	ibnbd_info(sess_dev, "Device closed\n");
+	kfree(sess_dev);
+}
+
+static void destroy_sess(struct ibnbd_srv_session *srv_sess)
+{
+	struct ibnbd_srv_sess_dev *sess_dev, *tmp;
+
+	if (list_empty(&srv_sess->sess_dev_list))
+		goto out;
+
+	mutex_lock(&srv_sess->lock);
+	list_for_each_entry_safe(sess_dev, tmp, &srv_sess->sess_dev_list,
+				 sess_list) {
+		ibnbd_srv_destroy_dev_session_sysfs(sess_dev);
+		ibnbd_destroy_sess_dev(sess_dev);
+	}
+	mutex_unlock(&srv_sess->lock);
+
+out:
+	idr_destroy(&srv_sess->index_idr);
+	bioset_free(srv_sess->sess_bio_set);
+
+	pr_info("IBTRS Session %s disconnected\n", srv_sess->sessname);
+
+	mutex_lock(&sess_lock);
+	list_del(&srv_sess->list);
+	mutex_unlock(&sess_lock);
+
+	kfree(srv_sess);
+}
+
+static int create_sess(struct ibtrs_srv *ibtrs)
+{
+	struct ibnbd_srv_session *srv_sess;
+	char sessname[NAME_MAX];
+	int err;
+
+	err = ibtrs_srv_get_sess_name(ibtrs, sessname, sizeof(sessname));
+	if (unlikely(err)) {
+		pr_err("ibtrs_srv_get_sess_name(%s): %d\n", sessname, err);
+
+		return err;
+	}
+	srv_sess = kzalloc(sizeof(*srv_sess), GFP_KERNEL);
+	if (!srv_sess)
+		return -ENOMEM;
+	srv_sess->queue_depth = ibtrs_srv_get_queue_depth(ibtrs);
+	srv_sess->sess_bio_set = bioset_create(srv_sess->queue_depth, 0,
+					       BIOSET_NEED_BVECS);
+	if (!srv_sess->sess_bio_set) {
+		pr_err("Allocating srv_session for session %s failed\n",
+		       sessname);
+		kfree(srv_sess);
+		return -ENOMEM;
+	}
+
+	idr_init(&srv_sess->index_idr);
+	rwlock_init(&srv_sess->index_lock);
+	INIT_LIST_HEAD(&srv_sess->sess_dev_list);
+	mutex_init(&srv_sess->lock);
+	mutex_lock(&sess_lock);
+	list_add(&srv_sess->list, &sess_list);
+	mutex_unlock(&sess_lock);
+
+	srv_sess->ibtrs = ibtrs;
+	srv_sess->queue_depth = ibtrs_srv_get_queue_depth(ibtrs);
+	strlcpy(srv_sess->sessname, sessname, sizeof(srv_sess->sessname));
+
+	ibtrs_srv_set_sess_priv(ibtrs, srv_sess);
+
+	return 0;
+}
+
+static int ibnbd_srv_link_ev(struct ibtrs_srv *ibtrs,
+			     enum ibtrs_srv_link_ev ev, void *priv)
+{
+	struct ibnbd_srv_session *srv_sess = priv;
+
+	switch (ev) {
+	case IBTRS_SRV_LINK_EV_CONNECTED:
+		return create_sess(ibtrs);
+
+	case IBTRS_SRV_LINK_EV_DISCONNECTED:
+		if (WARN_ON(!srv_sess))
+			return -EINVAL;
+
+		destroy_sess(srv_sess);
+		return 0;
+
+	default:
+		pr_warn("Received unknown IBTRS session event %d from session"
+			" %s\n", ev, srv_sess->sessname);
+		return -EINVAL;
+	}
+}
+
+static int process_msg_close(struct ibtrs_srv *ibtrs,
+			     struct ibnbd_srv_session *srv_sess,
+			     void *data, size_t datalen, const void *usr,
+			     size_t usrlen)
+{
+	const struct ibnbd_msg_close *close_msg = usr;
+	struct ibnbd_srv_sess_dev *sess_dev;
+
+	sess_dev = ibnbd_get_sess_dev(close_msg->device_id, srv_sess);
+	if (unlikely(IS_ERR(sess_dev)))
+		return 0;
+
+	ibnbd_srv_destroy_dev_session_sysfs(sess_dev);
+	ibnbd_put_sess_dev(sess_dev);
+	mutex_lock(&srv_sess->lock);
+	ibnbd_destroy_sess_dev(sess_dev);
+	mutex_unlock(&srv_sess->lock);
+	return 0;
+}
+
+static int process_msg_open(struct ibtrs_srv *ibtrs,
+			    struct ibnbd_srv_session *srv_sess,
+			    const void *msg, size_t len,
+			    void *data, size_t datalen);
+
+static int process_msg_sess_info(struct ibtrs_srv *ibtrs,
+				 struct ibnbd_srv_session *srv_sess,
+				 const void *msg, size_t len,
+				 void *data, size_t datalen);
+
+static int ibnbd_srv_rdma_ev(struct ibtrs_srv *ibtrs, void *priv,
+			     struct ibtrs_srv_op *id, int dir,
+			     void *data, size_t datalen, const void *usr,
+			     size_t usrlen)
+{
+	struct ibnbd_srv_session *srv_sess = priv;
+	const struct ibnbd_msg_hdr *hdr = usr;
+	int ret = 0;
+	u16 type;
+
+	if (unlikely(WARN_ON(!srv_sess)))
+		return -ENODEV;
+
+	type = le16_to_cpu(hdr->type);
+
+	switch (type) {
+	case IBNBD_MSG_IO:
+		return process_rdma(ibtrs, srv_sess, id, data, datalen, usr,
+				    usrlen);
+	case IBNBD_MSG_CLOSE:
+		ret = process_msg_close(ibtrs, srv_sess, data, datalen,
+					usr, usrlen);
+		break;
+	case IBNBD_MSG_OPEN:
+		ret = process_msg_open(ibtrs, srv_sess, usr, usrlen,
+				       data, datalen);
+		break;
+	case IBNBD_MSG_SESS_INFO:
+		ret = process_msg_sess_info(ibtrs, srv_sess, usr, usrlen,
+					    data, datalen);
+		break;
+	default:
+		pr_warn("Received unexpected message type %d with dir %d from"
+			" session %s\n", type, dir, srv_sess->sessname);
+		return -EINVAL;
+	}
+
+	ibtrs_srv_resp_rdma(id, ret);
+	return 0;
+}
+
+static struct ibnbd_srv_sess_dev
+*ibnbd_sess_dev_alloc(struct ibnbd_srv_session *srv_sess)
+{
+	struct ibnbd_srv_sess_dev *sess_dev;
+	int error;
+
+	sess_dev = kzalloc(sizeof(*sess_dev), GFP_KERNEL);
+	if (!sess_dev)
+		return ERR_PTR(-ENOMEM);
+
+	idr_preload(GFP_KERNEL);
+	write_lock(&srv_sess->index_lock);
+
+	error = idr_alloc(&srv_sess->index_idr, sess_dev, 0, -1, GFP_NOWAIT);
+	if (error < 0) {
+		pr_warn("Allocating idr failed, err: %d\n", error);
+		goto out_unlock;
+	}
+
+	sess_dev->device_id = error;
+	error = 0;
+
+out_unlock:
+	write_unlock(&srv_sess->index_lock);
+	idr_preload_end();
+	if (error) {
+		kfree(sess_dev);
+		return ERR_PTR(error);
+	}
+
+	return sess_dev;
+}
+
+static struct ibnbd_srv_dev *ibnbd_srv_init_srv_dev(const char *id,
+						    enum ibnbd_io_mode mode)
+{
+	struct ibnbd_srv_dev *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	strlcpy(dev->id, id, sizeof(dev->id));
+	dev->mode = mode;
+	kref_init(&dev->kref);
+	INIT_LIST_HEAD(&dev->sess_dev_list);
+	mutex_init(&dev->lock);
+
+	return dev;
+}
+
+static struct ibnbd_srv_dev *
+ibnbd_srv_find_or_add_srv_dev(struct ibnbd_srv_dev *new_dev)
+{
+	struct ibnbd_srv_dev *dev;
+
+	spin_lock(&dev_lock);
+	list_for_each_entry(dev, &dev_list, list) {
+		if (!strncmp(dev->id, new_dev->id, sizeof(dev->id))) {
+			if (!kref_get_unless_zero(&dev->kref))
+				/*
+				 * We lost the race, device is almost dead.
+				 *  Continue traversing to find a valid one.
+				 */
+				continue;
+			spin_unlock(&dev_lock);
+			return dev;
+		}
+	}
+	list_add(&new_dev->list, &dev_list);
+	spin_unlock(&dev_lock);
+
+	return new_dev;
+}
+
+static int ibnbd_srv_check_update_open_perm(struct ibnbd_srv_dev *srv_dev,
+					    struct ibnbd_srv_session *srv_sess,
+					    enum ibnbd_io_mode io_mode,
+					    enum ibnbd_access_mode access_mode)
+{
+	int ret = -EPERM;
+
+	mutex_lock(&srv_dev->lock);
+
+	if (srv_dev->mode != io_mode) {
+		pr_err("Mapping device '%s' for session %s in %s mode forbidden,"
+		       " device is already mapped from other client(s) in"
+		       " %s mode\n", srv_dev->id, srv_sess->sessname,
+		       ibnbd_io_mode_str(io_mode),
+		       ibnbd_io_mode_str(srv_dev->mode));
+		goto out;
+	}
+
+	switch (access_mode) {
+	case IBNBD_ACCESS_RO:
+		ret = 0;
+		break;
+	case IBNBD_ACCESS_RW:
+		if (srv_dev->open_write_cnt == 0)  {
+			srv_dev->open_write_cnt++;
+			ret = 0;
+		} else {
+			pr_err("Mapping device '%s' for session %s with"
+			       " RW permissions failed. Device already opened"
+			       " as 'RW' by %d client(s) in %s mode.\n",
+			       srv_dev->id, srv_sess->sessname,
+			       srv_dev->open_write_cnt,
+			       ibnbd_io_mode_str(srv_dev->mode));
+		}
+		break;
+	case IBNBD_ACCESS_MIGRATION:
+		if (srv_dev->open_write_cnt < 2) {
+			srv_dev->open_write_cnt++;
+			ret = 0;
+		} else {
+			pr_err("Mapping device '%s' for session %s with"
+			       " migration permissions failed. Device already"
+			       " opened as 'RW' by %d client(s) in %s mode.\n",
+			       srv_dev->id, srv_sess->sessname,
+			       srv_dev->open_write_cnt,
+			       ibnbd_io_mode_str(srv_dev->mode));
+		}
+		break;
+	default:
+		pr_err("Received mapping request for device '%s' on session %s"
+		       " with invalid access mode: %d\n", srv_dev->id,
+		       srv_sess->sessname, access_mode);
+		ret = -EINVAL;
+	}
+
+out:
+	mutex_unlock(&srv_dev->lock);
+
+	return ret;
+}
+
+static struct ibnbd_srv_dev *
+ibnbd_srv_get_or_create_srv_dev(struct ibnbd_dev *ibnbd_dev,
+				struct ibnbd_srv_session *srv_sess,
+				enum ibnbd_io_mode io_mode,
+				enum ibnbd_access_mode access_mode)
+{
+	int ret;
+	struct ibnbd_srv_dev *new_dev, *dev;
+
+	new_dev = ibnbd_srv_init_srv_dev(ibnbd_dev->name, io_mode);
+	if (IS_ERR(new_dev))
+		return new_dev;
+
+	dev = ibnbd_srv_find_or_add_srv_dev(new_dev);
+	if (dev != new_dev)
+		kfree(new_dev);
+
+	ret = ibnbd_srv_check_update_open_perm(dev, srv_sess, io_mode,
+					       access_mode);
+	if (ret) {
+		ibnbd_put_srv_dev(dev);
+		return ERR_PTR(ret);
+	}
+
+	return dev;
+}
+
+static void ibnbd_srv_fill_msg_open_rsp(struct ibnbd_msg_open_rsp *rsp,
+					struct ibnbd_srv_sess_dev *sess_dev)
+{
+	struct ibnbd_dev *ibnbd_dev = sess_dev->ibnbd_dev;
+
+	rsp->hdr.type = cpu_to_le16(IBNBD_MSG_OPEN_RSP);
+	rsp->device_id =
+		cpu_to_le32(sess_dev->device_id);
+	rsp->nsectors =
+		cpu_to_le64(get_capacity(ibnbd_dev->bdev->bd_disk));
+	rsp->logical_block_size	=
+		cpu_to_le16(ibnbd_dev_get_logical_bsize(ibnbd_dev));
+	rsp->physical_block_size =
+		cpu_to_le16(ibnbd_dev_get_phys_bsize(ibnbd_dev));
+	rsp->max_segments =
+		cpu_to_le16(ibnbd_dev_get_max_segs(ibnbd_dev));
+	rsp->max_hw_sectors =
+		cpu_to_le32(ibnbd_dev_get_max_hw_sects(ibnbd_dev));
+	rsp->max_write_same_sectors =
+		cpu_to_le32(ibnbd_dev_get_max_write_same_sects(ibnbd_dev));
+	rsp->max_discard_sectors =
+		cpu_to_le32(ibnbd_dev_get_max_discard_sects(ibnbd_dev));
+	rsp->discard_granularity =
+		cpu_to_le32(ibnbd_dev_get_discard_granularity(ibnbd_dev));
+	rsp->discard_alignment =
+		cpu_to_le32(ibnbd_dev_get_discard_alignment(ibnbd_dev));
+	rsp->secure_discard =
+		cpu_to_le16(ibnbd_dev_get_secure_discard(ibnbd_dev));
+	rsp->rotational =
+		!blk_queue_nonrot(bdev_get_queue(ibnbd_dev->bdev));
+	rsp->io_mode =
+		ibnbd_dev->mode;
+}
+
+static struct ibnbd_srv_sess_dev *
+ibnbd_srv_create_set_sess_dev(struct ibnbd_srv_session *srv_sess,
+			      const struct ibnbd_msg_open *open_msg,
+			      struct ibnbd_dev *ibnbd_dev, fmode_t open_flags,
+			      struct ibnbd_srv_dev *srv_dev)
+{
+	struct ibnbd_srv_sess_dev *sdev = ibnbd_sess_dev_alloc(srv_sess);
+
+	if (IS_ERR(sdev))
+		return sdev;
+
+	kref_init(&sdev->kref);
+
+	strlcpy(sdev->pathname, open_msg->dev_name, sizeof(sdev->pathname));
+
+	sdev->ibnbd_dev		= ibnbd_dev;
+	sdev->sess		= srv_sess;
+	sdev->dev		= srv_dev;
+	sdev->open_flags	= open_flags;
+
+	return sdev;
+}
+
+static char *ibnbd_srv_get_full_path(const char *dev_name)
+{
+	char *full_path;
+	char *a, *b;
+
+	full_path = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!full_path)
+		return ERR_PTR(-ENOMEM);
+
+	snprintf(full_path, PATH_MAX, "%s/%s", dev_search_path, dev_name);
+
+	/* eliminitate duplicated slashes */
+	a = strchr(full_path, '/');
+	b = a;
+	while (*b != '\0') {
+		if (*b == '/' && *a == '/') {
+			b++;
+		} else {
+			a++;
+			*a = *b;
+			b++;
+		}
+	}
+	a++;
+	*a = '\0';
+
+	return full_path;
+}
+
+static int process_msg_sess_info(struct ibtrs_srv *ibtrs,
+				 struct ibnbd_srv_session *srv_sess,
+				 const void *msg, size_t len,
+				 void *data, size_t datalen)
+{
+	const struct ibnbd_msg_sess_info *sess_info_msg = msg;
+	struct ibnbd_msg_sess_info_rsp *rsp = data;
+
+	srv_sess->ver = min_t(u8, sess_info_msg->ver, IBNBD_VER_MAJOR);
+	pr_debug("Session %s using protocol version %d (client version: %d,"
+		 " server version: %d)\n", srv_sess->sessname,
+		 srv_sess->ver, sess_info_msg->ver, IBNBD_VER_MAJOR);
+
+	rsp->hdr.type = cpu_to_le16(IBNBD_MSG_SESS_INFO_RSP);
+	rsp->ver = srv_sess->ver;
+
+	return 0;
+}
+
+/**
+ * find_srv_sess_dev() - a dev is already opened by this name
+ *
+ * Return struct ibnbd_srv_sess_dev if srv_sess already opened the dev_name
+ * NULL if the session didn't open the device yet.
+ */
+static struct ibnbd_srv_sess_dev *
+find_srv_sess_dev(struct ibnbd_srv_session *srv_sess, const char *dev_name)
+{
+	struct ibnbd_srv_sess_dev *sess_dev;
+
+	if (list_empty(&srv_sess->sess_dev_list))
+		return NULL;
+
+	list_for_each_entry(sess_dev, &srv_sess->sess_dev_list, sess_list)
+		if (!strcmp(sess_dev->pathname, dev_name))
+			return sess_dev;
+
+	return NULL;
+}
+
+static int process_msg_open(struct ibtrs_srv *ibtrs,
+			    struct ibnbd_srv_session *srv_sess,
+			    const void *msg, size_t len,
+			    void *data, size_t datalen)
+{
+	int ret;
+	struct ibnbd_srv_dev *srv_dev;
+	struct ibnbd_srv_sess_dev *srv_sess_dev;
+	const struct ibnbd_msg_open *open_msg = msg;
+	fmode_t open_flags;
+	char *full_path;
+	struct ibnbd_dev *ibnbd_dev;
+	enum ibnbd_io_mode io_mode;
+	struct ibnbd_msg_open_rsp *rsp = data;
+
+	pr_debug("Open message received: session='%s' path='%s' access_mode=%d"
+		 " io_mode=%d\n", srv_sess->sessname, open_msg->dev_name,
+		 open_msg->access_mode, open_msg->io_mode);
+	open_flags = FMODE_READ;
+	if (open_msg->access_mode != IBNBD_ACCESS_RO)
+		open_flags |= FMODE_WRITE;
+
+	mutex_lock(&srv_sess->lock);
+
+	srv_sess_dev = find_srv_sess_dev(srv_sess, open_msg->dev_name);
+	if (srv_sess_dev)
+		goto fill_response;
+
+	if ((strlen(dev_search_path) + strlen(open_msg->dev_name))
+	    >= PATH_MAX) {
+		pr_err("Opening device for session %s failed, device path too"
+		       " long. '%s/%s' is longer than PATH_MAX (%d)\n",
+		       srv_sess->sessname, dev_search_path, open_msg->dev_name,
+		       PATH_MAX);
+		ret = -EINVAL;
+		goto reject;
+	}
+	full_path = ibnbd_srv_get_full_path(open_msg->dev_name);
+	if (IS_ERR(full_path)) {
+		ret = PTR_ERR(full_path);
+		pr_err("Opening device '%s' for client %s failed,"
+		       " failed to get device full path, err: %d\n",
+		       open_msg->dev_name, srv_sess->sessname, ret);
+		goto reject;
+	}
+
+	if (open_msg->io_mode == IBNBD_BLOCKIO)
+		io_mode = IBNBD_BLOCKIO;
+	else if (open_msg->io_mode == IBNBD_FILEIO)
+		io_mode = IBNBD_FILEIO;
+	else
+		io_mode = def_io_mode;
+
+	ibnbd_dev = ibnbd_dev_open(full_path, open_flags, io_mode,
+				   srv_sess->sess_bio_set, ibnbd_endio);
+	if (IS_ERR(ibnbd_dev)) {
+		pr_err("Opening device '%s' on session %s failed,"
+		       " failed to open the block device, err: %ld\n",
+		       full_path, srv_sess->sessname, PTR_ERR(ibnbd_dev));
+		ret = PTR_ERR(ibnbd_dev);
+		goto free_path;
+	}
+
+	srv_dev = ibnbd_srv_get_or_create_srv_dev(ibnbd_dev, srv_sess, io_mode,
+						  open_msg->access_mode);
+	if (IS_ERR(srv_dev)) {
+		pr_err("Opening device '%s' on session %s failed,"
+		       " creating srv_dev failed, err: %ld\n",
+		       full_path, srv_sess->sessname, PTR_ERR(srv_dev));
+		ret = PTR_ERR(srv_dev);
+		goto ibnbd_dev_close;
+	}
+
+	srv_sess_dev = ibnbd_srv_create_set_sess_dev(srv_sess, open_msg,
+						     ibnbd_dev, open_flags,
+						     srv_dev);
+	if (IS_ERR(srv_sess_dev)) {
+		pr_err("Opening device '%s' on session %s failed,"
+		       " creating sess_dev failed, err: %ld\n",
+		       full_path, srv_sess->sessname, PTR_ERR(srv_sess_dev));
+		ret = PTR_ERR(srv_sess_dev);
+		goto srv_dev_put;
+	}
+
+	/* Create the srv_dev sysfs files if they haven't been created yet. The
+	 * reason to delay the creation is not to create the sysfs files before
+	 * we are sure the device can be opened.
+	 */
+	mutex_lock(&srv_dev->lock);
+	if (!srv_dev->dev_kobj.state_in_sysfs) {
+		ret = ibnbd_srv_create_dev_sysfs(srv_dev, ibnbd_dev->bdev,
+						 ibnbd_dev->name);
+		if (ret) {
+			mutex_unlock(&srv_dev->lock);
+			ibnbd_err(srv_sess_dev, "Opening device failed, failed to"
+				  " create device sysfs files, err: %d\n",
+				  ret);
+			goto free_srv_sess_dev;
+		}
+	}
+
+	ret = ibnbd_srv_create_dev_session_sysfs(srv_sess_dev);
+	if (ret) {
+		mutex_unlock(&srv_dev->lock);
+		ibnbd_err(srv_sess_dev, "Opening device failed, failed to create"
+			  " dev client sysfs files, err: %d\n", ret);
+		goto free_srv_sess_dev;
+	}
+
+	list_add(&srv_sess_dev->dev_list, &srv_dev->sess_dev_list);
+	mutex_unlock(&srv_dev->lock);
+
+	list_add(&srv_sess_dev->sess_list, &srv_sess->sess_dev_list);
+
+	ibnbd_info(srv_sess_dev, "Opened device '%s' in %s mode\n",
+		   srv_dev->id, ibnbd_io_mode_str(io_mode));
+
+	kfree(full_path);
+
+fill_response:
+	ibnbd_srv_fill_msg_open_rsp(rsp, srv_sess_dev);
+	mutex_unlock(&srv_sess->lock);
+	return 0;
+
+free_srv_sess_dev:
+	write_lock(&srv_sess->index_lock);
+	idr_remove(&srv_sess->index_idr, srv_sess_dev->device_id);
+	write_unlock(&srv_sess->index_lock);
+	kfree(srv_sess_dev);
+srv_dev_put:
+	if (open_msg->access_mode != IBNBD_ACCESS_RO) {
+		mutex_lock(&srv_dev->lock);
+		srv_dev->open_write_cnt--;
+		mutex_unlock(&srv_dev->lock);
+	}
+	ibnbd_put_srv_dev(srv_dev);
+ibnbd_dev_close:
+	ibnbd_dev_close(ibnbd_dev);
+free_path:
+	kfree(full_path);
+reject:
+	mutex_unlock(&srv_sess->lock);
+	return ret;
+}
+
+static struct ibtrs_srv_ctx *ibtrs_ctx;
+
+static int __init ibnbd_srv_init_module(void)
+{
+	int err;
+
+	pr_info("Loading module %s, version %s\n",
+		KBUILD_MODNAME, IBNBD_VER_STRING);
+
+	ibtrs_ctx = ibtrs_srv_open(ibnbd_srv_rdma_ev, ibnbd_srv_link_ev,
+				   IBTRS_PORT);
+	if (unlikely(IS_ERR(ibtrs_ctx))) {
+		err = PTR_ERR(ibtrs_ctx);
+		pr_err("ibtrs_srv_open(), err: %d\n", err);
+		goto out;
+	}
+	err = ibnbd_dev_init();
+	if (err) {
+		pr_err("ibnbd_dev_init(), err: %d\n", err);
+		goto srv_close;
+	}
+
+	err = ibnbd_srv_create_sysfs_files();
+	if (err) {
+		pr_err("ibnbd_srv_create_sysfs_files(), err: %d\n", err);
+		goto dev_destroy;
+	}
+
+	return 0;
+
+dev_destroy:
+	ibnbd_dev_destroy();
+srv_close:
+	ibtrs_srv_close(ibtrs_ctx);
+out:
+
+	return err;
+}
+
+static void __exit ibnbd_srv_cleanup_module(void)
+{
+	ibtrs_srv_close(ibtrs_ctx);
+	WARN_ON(!list_empty(&sess_list));
+	ibnbd_srv_destroy_sysfs_files();
+	ibnbd_dev_destroy();
+	pr_info("Module unloaded\n");
+}
+
+module_init(ibnbd_srv_init_module);
+module_exit(ibnbd_srv_cleanup_module);
-- 
2.13.1