1 files changed, 848 insertions, 0 deletions

diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
new file mode 100644
index 000000000..2cfed2e58
--- /dev/null
+++ b/drivers/block/rnbd/rnbd-srv.c
@@ -0,0 +1,848 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RDMA Network Block Driver
+ *
+ * Copyright (c) 2014 - 2018 ProfitBricks GmbH. All rights reserved.
+ * Copyright (c) 2018 - 2019 1&1 IONOS Cloud GmbH. All rights reserved.
+ * Copyright (c) 2019 - 2020 1&1 IONOS SE. All rights reserved.
+ */
+#undef pr_fmt
+#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt
+
+#include <linux/module.h>
+#include <linux/blkdev.h>
+
+#include "rnbd-srv.h"
+#include "rnbd-srv-trace.h"
+
+MODULE_DESCRIPTION("RDMA Network Block Device Server");
+MODULE_LICENSE("GPL");
+
+static u16 port_nr = RTRS_PORT;
+
+module_param_named(port_nr, port_nr, ushort, 0444);
+MODULE_PARM_DESC(port_nr,
+		 "The port number the server is listening on (default: "
+		 __stringify(RTRS_PORT)")");
+
+#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)
+{
+	const char *p = strrchr(val, '\n') ? : val + strlen(val);
+
+	if (strlen(val) >= sizeof(dev_search_path))
+		return -EINVAL;
+
+	snprintf(dev_search_path, sizeof(dev_search_path), "%.*s",
+		 (int)(p - val), val);
+
+	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 dev_search_path. When a device is mapped this path is prepended to the device path from the map device operation.  If %SESSNAME% is specified in a path, then device will be searched in a session namespace. (default: "
+		 DEFAULT_DEV_SEARCH_PATH ")");
+
+static DEFINE_MUTEX(sess_lock);
+static DEFINE_SPINLOCK(dev_lock);
+
+static LIST_HEAD(sess_list);
+static LIST_HEAD(dev_list);
+
+struct rnbd_io_private {
+	struct rtrs_srv_op		*id;
+	struct rnbd_srv_sess_dev	*sess_dev;
+};
+
+static void rnbd_sess_dev_release(struct kref *kref)
+{
+	struct rnbd_srv_sess_dev *sess_dev;
+
+	sess_dev = container_of(kref, struct rnbd_srv_sess_dev, kref);
+	complete(sess_dev->destroy_comp);
+}
+
+static inline void rnbd_put_sess_dev(struct rnbd_srv_sess_dev *sess_dev)
+{
+	kref_put(&sess_dev->kref, rnbd_sess_dev_release);
+}
+
+static struct rnbd_srv_sess_dev *
+rnbd_get_sess_dev(int dev_id, struct rnbd_srv_session *srv_sess)
+{
+	struct rnbd_srv_sess_dev *sess_dev;
+	int ret = 0;
+
+	rcu_read_lock();
+	sess_dev = xa_load(&srv_sess->index_idr, dev_id);
+	if (sess_dev)
+		ret = kref_get_unless_zero(&sess_dev->kref);
+	rcu_read_unlock();
+
+	if (!sess_dev || !ret)
+		return ERR_PTR(-ENXIO);
+
+	return sess_dev;
+}
+
+static void rnbd_dev_bi_end_io(struct bio *bio)
+{
+	struct rnbd_io_private *rnbd_priv = bio->bi_private;
+	struct rnbd_srv_sess_dev *sess_dev = rnbd_priv->sess_dev;
+
+	rnbd_put_sess_dev(sess_dev);
+	rtrs_srv_resp_rdma(rnbd_priv->id, blk_status_to_errno(bio->bi_status));
+
+	kfree(rnbd_priv);
+	bio_put(bio);
+}
+
+static int process_rdma(struct rnbd_srv_session *srv_sess,
+			struct rtrs_srv_op *id, void *data, u32 datalen,
+			const void *usr, size_t usrlen)
+{
+	const struct rnbd_msg_io *msg = usr;
+	struct rnbd_io_private *priv;
+	struct rnbd_srv_sess_dev *sess_dev;
+	u32 dev_id;
+	int err;
+	struct bio *bio;
+	short prio;
+
+	trace_process_rdma(srv_sess, msg, id, datalen, usrlen);
+
+	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_id = le32_to_cpu(msg->device_id);
+
+	sess_dev = rnbd_get_sess_dev(dev_id, srv_sess);
+	if (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;
+
+	bio = bio_alloc(sess_dev->bdev, 1,
+			rnbd_to_bio_flags(le32_to_cpu(msg->rw)), GFP_KERNEL);
+	if (bio_add_page(bio, virt_to_page(data), datalen,
+			offset_in_page(data)) != datalen) {
+		rnbd_srv_err(sess_dev, "Failed to map data to bio\n");
+		err = -EINVAL;
+		goto bio_put;
+	}
+
+	bio->bi_end_io = rnbd_dev_bi_end_io;
+	bio->bi_private = priv;
+	bio->bi_iter.bi_sector = le64_to_cpu(msg->sector);
+	bio->bi_iter.bi_size = le32_to_cpu(msg->bi_size);
+	prio = srv_sess->ver < RNBD_PROTO_VER_MAJOR ||
+	       usrlen < sizeof(*msg) ? 0 : le16_to_cpu(msg->prio);
+	bio_set_prio(bio, prio);
+
+	submit_bio(bio);
+
+	return 0;
+
+bio_put:
+	bio_put(bio);
+	rnbd_put_sess_dev(sess_dev);
+err:
+	kfree(priv);
+	return err;
+}
+
+static void destroy_device(struct kref *kref)
+{
+	struct rnbd_srv_dev *dev = container_of(kref, struct rnbd_srv_dev, kref);
+
+	WARN_ONCE(!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);
+
+	mutex_destroy(&dev->lock);
+	if (dev->dev_kobj.state_in_sysfs)
+		/*
+		 * Destroy kobj only if it was really created.
+		 */
+		rnbd_srv_destroy_dev_sysfs(dev);
+	else
+		kfree(dev);
+}
+
+static void rnbd_put_srv_dev(struct rnbd_srv_dev *dev)
+{
+	kref_put(&dev->kref, destroy_device);
+}
+
+void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev, bool keep_id)
+{
+	DECLARE_COMPLETION_ONSTACK(dc);
+
+	if (keep_id)
+		/* free the resources for the id but don't  */
+		/* allow to re-use the id itself because it */
+		/* is still used by the client              */
+		xa_cmpxchg(&sess_dev->sess->index_idr, sess_dev->device_id,
+			   sess_dev, NULL, 0);
+	else
+		xa_erase(&sess_dev->sess->index_idr, sess_dev->device_id);
+	synchronize_rcu();
+
+	sess_dev->destroy_comp = &dc;
+	rnbd_put_sess_dev(sess_dev);
+	wait_for_completion(&dc); /* wait for inflights to drop to zero */
+
+	blkdev_put(sess_dev->bdev, sess_dev->open_flags);
+	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);
+
+	rnbd_put_srv_dev(sess_dev->dev);
+
+	rnbd_srv_info(sess_dev, "Device closed\n");
+	kfree(sess_dev);
+}
+
+static void destroy_sess(struct rnbd_srv_session *srv_sess)
+{
+	struct rnbd_srv_sess_dev *sess_dev;
+	unsigned long index;
+
+	if (xa_empty(&srv_sess->index_idr))
+		goto out;
+
+	trace_destroy_sess(srv_sess);
+
+	mutex_lock(&srv_sess->lock);
+	xa_for_each(&srv_sess->index_idr, index, sess_dev)
+		rnbd_srv_destroy_dev_session_sysfs(sess_dev);
+	mutex_unlock(&srv_sess->lock);
+
+out:
+	xa_destroy(&srv_sess->index_idr);
+
+	pr_info("RTRS Session %s disconnected\n", srv_sess->sessname);
+
+	mutex_lock(&sess_lock);
+	list_del(&srv_sess->list);
+	mutex_unlock(&sess_lock);
+
+	mutex_destroy(&srv_sess->lock);
+	kfree(srv_sess);
+}
+
+static int create_sess(struct rtrs_srv_sess *rtrs)
+{
+	struct rnbd_srv_session *srv_sess;
+	char pathname[NAME_MAX];
+	int err;
+
+	err = rtrs_srv_get_path_name(rtrs, pathname, sizeof(pathname));
+	if (err) {
+		pr_err("rtrs_srv_get_path_name(%s): %d\n", pathname, err);
+
+		return err;
+	}
+	srv_sess = kzalloc(sizeof(*srv_sess), GFP_KERNEL);
+	if (!srv_sess)
+		return -ENOMEM;
+
+	srv_sess->queue_depth = rtrs_srv_get_queue_depth(rtrs);
+	xa_init_flags(&srv_sess->index_idr, XA_FLAGS_ALLOC);
+	mutex_init(&srv_sess->lock);
+	mutex_lock(&sess_lock);
+	list_add(&srv_sess->list, &sess_list);
+	mutex_unlock(&sess_lock);
+
+	srv_sess->rtrs = rtrs;
+	strscpy(srv_sess->sessname, pathname, sizeof(srv_sess->sessname));
+
+	rtrs_srv_set_sess_priv(rtrs, srv_sess);
+
+	trace_create_sess(srv_sess);
+
+	return 0;
+}
+
+static int rnbd_srv_link_ev(struct rtrs_srv_sess *rtrs,
+			     enum rtrs_srv_link_ev ev, void *priv)
+{
+	struct rnbd_srv_session *srv_sess = priv;
+
+	switch (ev) {
+	case RTRS_SRV_LINK_EV_CONNECTED:
+		return create_sess(rtrs);
+
+	case RTRS_SRV_LINK_EV_DISCONNECTED:
+		if (WARN_ON_ONCE(!srv_sess))
+			return -EINVAL;
+
+		destroy_sess(srv_sess);
+		return 0;
+
+	default:
+		pr_warn("Received unknown RTRS session event %d from session %s\n",
+			ev, srv_sess->sessname);
+		return -EINVAL;
+	}
+}
+
+void rnbd_srv_sess_dev_force_close(struct rnbd_srv_sess_dev *sess_dev,
+				   struct kobj_attribute *attr)
+{
+	struct rnbd_srv_session	*sess = sess_dev->sess;
+
+	/* It is already started to close by client's close message. */
+	if (!mutex_trylock(&sess->lock))
+		return;
+
+	sess_dev->keep_id = true;
+	/* first remove sysfs itself to avoid deadlock */
+	sysfs_remove_file_self(&sess_dev->kobj, &attr->attr);
+	rnbd_srv_destroy_dev_session_sysfs(sess_dev);
+	mutex_unlock(&sess->lock);
+}
+
+static void process_msg_close(struct rnbd_srv_session *srv_sess,
+			     void *data, size_t datalen, const void *usr,
+			     size_t usrlen)
+{
+	const struct rnbd_msg_close *close_msg = usr;
+	struct rnbd_srv_sess_dev *sess_dev;
+
+	trace_process_msg_close(srv_sess, close_msg);
+
+	sess_dev = rnbd_get_sess_dev(le32_to_cpu(close_msg->device_id),
+				      srv_sess);
+	if (IS_ERR(sess_dev))
+		return;
+
+	rnbd_put_sess_dev(sess_dev);
+	mutex_lock(&srv_sess->lock);
+	rnbd_srv_destroy_dev_session_sysfs(sess_dev);
+	mutex_unlock(&srv_sess->lock);
+}
+
+static int process_msg_open(struct rnbd_srv_session *srv_sess,
+			    const void *msg, size_t len,
+			    void *data, size_t datalen);
+
+static int process_msg_sess_info(struct rnbd_srv_session *srv_sess,
+				 const void *msg, size_t len,
+				 void *data, size_t datalen);
+
+static int rnbd_srv_rdma_ev(void *priv, struct rtrs_srv_op *id,
+			    void *data, size_t datalen,
+			    const void *usr, size_t usrlen)
+{
+	struct rnbd_srv_session *srv_sess = priv;
+	const struct rnbd_msg_hdr *hdr = usr;
+	int ret = 0;
+	u16 type;
+
+	if (WARN_ON_ONCE(!srv_sess))
+		return -ENODEV;
+
+	type = le16_to_cpu(hdr->type);
+
+	switch (type) {
+	case RNBD_MSG_IO:
+		return process_rdma(srv_sess, id, data, datalen, usr, usrlen);
+	case RNBD_MSG_CLOSE:
+		process_msg_close(srv_sess, data, datalen, usr, usrlen);
+		break;
+	case RNBD_MSG_OPEN:
+		ret = process_msg_open(srv_sess, usr, usrlen, data, datalen);
+		break;
+	case RNBD_MSG_SESS_INFO:
+		ret = process_msg_sess_info(srv_sess, usr, usrlen, data,
+					    datalen);
+		break;
+	default:
+		pr_warn("Received unexpected message type %d from session %s\n",
+			type, srv_sess->sessname);
+		return -EINVAL;
+	}
+
+	/*
+	 * Since ret is passed to rtrs to handle the failure case, we
+	 * just return 0 at the end otherwise callers in rtrs would call
+	 * send_io_resp_imm again to print redundant err message.
+	 */
+	rtrs_srv_resp_rdma(id, ret);
+	return 0;
+}
+
+static struct rnbd_srv_sess_dev
+*rnbd_sess_dev_alloc(struct rnbd_srv_session *srv_sess)
+{
+	struct rnbd_srv_sess_dev *sess_dev;
+	int error;
+
+	sess_dev = kzalloc(sizeof(*sess_dev), GFP_KERNEL);
+	if (!sess_dev)
+		return ERR_PTR(-ENOMEM);
+
+	error = xa_alloc(&srv_sess->index_idr, &sess_dev->device_id, sess_dev,
+			 xa_limit_32b, GFP_NOWAIT);
+	if (error < 0) {
+		pr_warn("Allocating idr failed, err: %d\n", error);
+		kfree(sess_dev);
+		return ERR_PTR(error);
+	}
+
+	return sess_dev;
+}
+
+static struct rnbd_srv_dev *rnbd_srv_init_srv_dev(struct block_device *bdev)
+{
+	struct rnbd_srv_dev *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	snprintf(dev->id, sizeof(dev->id), "%pg", bdev);
+	kref_init(&dev->kref);
+	INIT_LIST_HEAD(&dev->sess_dev_list);
+	mutex_init(&dev->lock);
+
+	return dev;
+}
+
+static struct rnbd_srv_dev *
+rnbd_srv_find_or_add_srv_dev(struct rnbd_srv_dev *new_dev)
+{
+	struct rnbd_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 rnbd_srv_check_update_open_perm(struct rnbd_srv_dev *srv_dev,
+					    struct rnbd_srv_session *srv_sess,
+					    enum rnbd_access_mode access_mode)
+{
+	int ret = -EPERM;
+
+	mutex_lock(&srv_dev->lock);
+
+	switch (access_mode) {
+	case RNBD_ACCESS_RO:
+		ret = 0;
+		break;
+	case RNBD_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), access mode %s.\n",
+			       srv_dev->id, srv_sess->sessname,
+			       srv_dev->open_write_cnt,
+			       rnbd_access_mode_str(access_mode));
+		}
+		break;
+	case RNBD_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), access mode %s.\n",
+			       srv_dev->id, srv_sess->sessname,
+			       srv_dev->open_write_cnt,
+			       rnbd_access_mode_str(access_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;
+	}
+
+	mutex_unlock(&srv_dev->lock);
+
+	return ret;
+}
+
+static struct rnbd_srv_dev *
+rnbd_srv_get_or_create_srv_dev(struct block_device *bdev,
+				struct rnbd_srv_session *srv_sess,
+				enum rnbd_access_mode access_mode)
+{
+	int ret;
+	struct rnbd_srv_dev *new_dev, *dev;
+
+	new_dev = rnbd_srv_init_srv_dev(bdev);
+	if (IS_ERR(new_dev))
+		return new_dev;
+
+	dev = rnbd_srv_find_or_add_srv_dev(new_dev);
+	if (dev != new_dev)
+		kfree(new_dev);
+
+	ret = rnbd_srv_check_update_open_perm(dev, srv_sess, access_mode);
+	if (ret) {
+		rnbd_put_srv_dev(dev);
+		return ERR_PTR(ret);
+	}
+
+	return dev;
+}
+
+static void rnbd_srv_fill_msg_open_rsp(struct rnbd_msg_open_rsp *rsp,
+					struct rnbd_srv_sess_dev *sess_dev)
+{
+	struct block_device *bdev = sess_dev->bdev;
+
+	rsp->hdr.type = cpu_to_le16(RNBD_MSG_OPEN_RSP);
+	rsp->device_id = cpu_to_le32(sess_dev->device_id);
+	rsp->nsectors = cpu_to_le64(bdev_nr_sectors(bdev));
+	rsp->logical_block_size	= cpu_to_le16(bdev_logical_block_size(bdev));
+	rsp->physical_block_size = cpu_to_le16(bdev_physical_block_size(bdev));
+	rsp->max_segments = cpu_to_le16(bdev_max_segments(bdev));
+	rsp->max_hw_sectors =
+		cpu_to_le32(queue_max_hw_sectors(bdev_get_queue(bdev)));
+	rsp->max_write_same_sectors = 0;
+	rsp->max_discard_sectors = cpu_to_le32(bdev_max_discard_sectors(bdev));
+	rsp->discard_granularity = cpu_to_le32(bdev_discard_granularity(bdev));
+	rsp->discard_alignment = cpu_to_le32(bdev_discard_alignment(bdev));
+	rsp->secure_discard = cpu_to_le16(bdev_max_secure_erase_sectors(bdev));
+	rsp->cache_policy = 0;
+	if (bdev_write_cache(bdev))
+		rsp->cache_policy |= RNBD_WRITEBACK;
+	if (bdev_fua(bdev))
+		rsp->cache_policy |= RNBD_FUA;
+}
+
+static struct rnbd_srv_sess_dev *
+rnbd_srv_create_set_sess_dev(struct rnbd_srv_session *srv_sess,
+			      const struct rnbd_msg_open *open_msg,
+			      struct block_device *bdev, fmode_t open_flags,
+			      struct rnbd_srv_dev *srv_dev)
+{
+	struct rnbd_srv_sess_dev *sdev = rnbd_sess_dev_alloc(srv_sess);
+
+	if (IS_ERR(sdev))
+		return sdev;
+
+	kref_init(&sdev->kref);
+
+	strscpy(sdev->pathname, open_msg->dev_name, sizeof(sdev->pathname));
+
+	sdev->bdev		= bdev;
+	sdev->sess		= srv_sess;
+	sdev->dev		= srv_dev;
+	sdev->open_flags	= open_flags;
+	sdev->access_mode	= open_msg->access_mode;
+
+	return sdev;
+}
+
+static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess,
+				     const char *dev_name)
+{
+	char *full_path;
+	char *a, *b;
+
+	full_path = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!full_path)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * Replace %SESSNAME% with a real session name in order to
+	 * create device namespace.
+	 */
+	a = strnstr(dev_search_path, "%SESSNAME%", sizeof(dev_search_path));
+	if (a) {
+		int len = a - dev_search_path;
+
+		len = snprintf(full_path, PATH_MAX, "%.*s/%s/%s", len,
+			       dev_search_path, srv_sess->sessname, dev_name);
+		if (len >= PATH_MAX) {
+			pr_err("Too long path: %s, %s, %s\n",
+			       dev_search_path, srv_sess->sessname, dev_name);
+			kfree(full_path);
+			return ERR_PTR(-EINVAL);
+		}
+	} else {
+		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 rnbd_srv_session *srv_sess,
+				 const void *msg, size_t len,
+				 void *data, size_t datalen)
+{
+	const struct rnbd_msg_sess_info *sess_info_msg = msg;
+	struct rnbd_msg_sess_info_rsp *rsp = data;
+
+	srv_sess->ver = min_t(u8, sess_info_msg->ver, RNBD_PROTO_VER_MAJOR);
+
+	trace_process_msg_sess_info(srv_sess, sess_info_msg);
+
+	rsp->hdr.type = cpu_to_le16(RNBD_MSG_SESS_INFO_RSP);
+	rsp->ver = srv_sess->ver;
+
+	return 0;
+}
+
+/**
+ * find_srv_sess_dev() - a dev is already opened by this name
+ * @srv_sess:	the session to search.
+ * @dev_name:	string containing the name of the device.
+ *
+ * Return struct rnbd_srv_sess_dev if srv_sess already opened the dev_name
+ * NULL if the session didn't open the device yet.
+ */
+static struct rnbd_srv_sess_dev *
+find_srv_sess_dev(struct rnbd_srv_session *srv_sess, const char *dev_name)
+{
+	struct rnbd_srv_sess_dev *sess_dev;
+	unsigned long index;
+
+	if (xa_empty(&srv_sess->index_idr))
+		return NULL;
+
+	xa_for_each(&srv_sess->index_idr, index, sess_dev)
+		if (!strcmp(sess_dev->pathname, dev_name))
+			return sess_dev;
+
+	return NULL;
+}
+
+static int process_msg_open(struct rnbd_srv_session *srv_sess,
+			    const void *msg, size_t len,
+			    void *data, size_t datalen)
+{
+	int ret;
+	struct rnbd_srv_dev *srv_dev;
+	struct rnbd_srv_sess_dev *srv_sess_dev;
+	const struct rnbd_msg_open *open_msg = msg;
+	struct block_device *bdev;
+	fmode_t open_flags;
+	char *full_path;
+	struct rnbd_msg_open_rsp *rsp = data;
+
+	trace_process_msg_open(srv_sess, open_msg);
+
+	open_flags = FMODE_READ;
+	if (open_msg->access_mode != RNBD_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;
+	}
+	if (strstr(open_msg->dev_name, "..")) {
+		pr_err("Opening device for session %s failed, device path %s contains relative path ..\n",
+		       srv_sess->sessname, open_msg->dev_name);
+		ret = -EINVAL;
+		goto reject;
+	}
+	full_path = rnbd_srv_get_full_path(srv_sess, 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;
+	}
+
+	bdev = blkdev_get_by_path(full_path, open_flags, THIS_MODULE);
+	if (IS_ERR(bdev)) {
+		ret = PTR_ERR(bdev);
+		pr_err("Opening device '%s' on session %s failed, failed to open the block device, err: %d\n",
+		       full_path, srv_sess->sessname, ret);
+		goto free_path;
+	}
+
+	srv_dev = rnbd_srv_get_or_create_srv_dev(bdev, srv_sess,
+						  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 blkdev_put;
+	}
+
+	srv_sess_dev = rnbd_srv_create_set_sess_dev(srv_sess, open_msg,
+						     bdev, 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 = rnbd_srv_create_dev_sysfs(srv_dev, bdev);
+		if (ret) {
+			mutex_unlock(&srv_dev->lock);
+			rnbd_srv_err(srv_sess_dev,
+				      "Opening device failed, failed to create device sysfs files, err: %d\n",
+				      ret);
+			goto free_srv_sess_dev;
+		}
+	}
+
+	ret = rnbd_srv_create_dev_session_sysfs(srv_sess_dev);
+	if (ret) {
+		mutex_unlock(&srv_dev->lock);
+		rnbd_srv_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);
+
+	rnbd_srv_info(srv_sess_dev, "Opened device '%s'\n", srv_dev->id);
+
+	kfree(full_path);
+
+fill_response:
+	rnbd_srv_fill_msg_open_rsp(rsp, srv_sess_dev);
+	mutex_unlock(&srv_sess->lock);
+	return 0;
+
+free_srv_sess_dev:
+	xa_erase(&srv_sess->index_idr, srv_sess_dev->device_id);
+	synchronize_rcu();
+	kfree(srv_sess_dev);
+srv_dev_put:
+	if (open_msg->access_mode != RNBD_ACCESS_RO) {
+		mutex_lock(&srv_dev->lock);
+		srv_dev->open_write_cnt--;
+		mutex_unlock(&srv_dev->lock);
+	}
+	rnbd_put_srv_dev(srv_dev);
+blkdev_put:
+	blkdev_put(bdev, open_flags);
+free_path:
+	kfree(full_path);
+reject:
+	mutex_unlock(&srv_sess->lock);
+	return ret;
+}
+
+static struct rtrs_srv_ctx *rtrs_ctx;
+
+static struct rtrs_srv_ops rtrs_ops;
+static int __init rnbd_srv_init_module(void)
+{
+	int err;
+
+	BUILD_BUG_ON(sizeof(struct rnbd_msg_hdr) != 4);
+	BUILD_BUG_ON(sizeof(struct rnbd_msg_sess_info) != 36);
+	BUILD_BUG_ON(sizeof(struct rnbd_msg_sess_info_rsp) != 36);
+	BUILD_BUG_ON(sizeof(struct rnbd_msg_open) != 264);
+	BUILD_BUG_ON(sizeof(struct rnbd_msg_close) != 8);
+	BUILD_BUG_ON(sizeof(struct rnbd_msg_open_rsp) != 56);
+	rtrs_ops = (struct rtrs_srv_ops) {
+		.rdma_ev = rnbd_srv_rdma_ev,
+		.link_ev = rnbd_srv_link_ev,
+	};
+	rtrs_ctx = rtrs_srv_open(&rtrs_ops, port_nr);
+	if (IS_ERR(rtrs_ctx)) {
+		err = PTR_ERR(rtrs_ctx);
+		pr_err("rtrs_srv_open(), err: %d\n", err);
+		return err;
+	}
+
+	err = rnbd_srv_create_sysfs_files();
+	if (err) {
+		pr_err("rnbd_srv_create_sysfs_files(), err: %d\n", err);
+		rtrs_srv_close(rtrs_ctx);
+		return err;
+	}
+
+	return 0;
+}
+
+static void __exit rnbd_srv_cleanup_module(void)
+{
+	rtrs_srv_close(rtrs_ctx);
+	WARN_ON(!list_empty(&sess_list));
+	rnbd_srv_destroy_sysfs_files();
+}
+
+module_init(rnbd_srv_init_module);
+module_exit(rnbd_srv_cleanup_module);