block/rnbd-srv: close a mapped device from server side.

The forceful close of an exported device is required
for the use case, when the client side hangs, is crashed,
or is not accessible.

There have been cases observed, where only some of
the devices are to be cleaned up, but the session shall
remain.

When the device is to be exported to a different
client host, server side cleanup is required.

Signed-off-by: Lutz Pogrell <lutz.pogrell@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rnbd/rnbd-srv-sysfs.c

@@ -120,10 +120,46 @@ static ssize_t mapping_path_show(struct kobject *kobj,
 static struct kobj_attribute rnbd_srv_dev_session_mapping_path_attr =
 	__ATTR_RO(mapping_path);
 
+static ssize_t rnbd_srv_dev_session_force_close_show(struct kobject *kobj,
+					struct kobj_attribute *attr, char *page)
+{
+	return scnprintf(page, PAGE_SIZE, "Usage: echo 1 > %s\n",
+			 attr->attr.name);
+}
+
+static ssize_t rnbd_srv_dev_session_force_close_store(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct rnbd_srv_sess_dev *sess_dev;
+
+	sess_dev = container_of(kobj, struct rnbd_srv_sess_dev, kobj);
+
+	if (!sysfs_streq(buf, "1")) {
+		rnbd_srv_err(sess_dev, "%s: invalid value: '%s'\n",
+			      attr->attr.name, buf);
+		return -EINVAL;
+	}
+
+	rnbd_srv_info(sess_dev, "force close requested\n");
+
+	/* first remove sysfs itself to avoid deadlock */
+	sysfs_remove_file_self(&sess_dev->kobj, &attr->attr);
+	rnbd_srv_sess_dev_force_close(sess_dev);
+
+	return count;
+}
+
+static struct kobj_attribute rnbd_srv_dev_session_force_close_attr =
+	__ATTR(force_close, 0644,
+	       rnbd_srv_dev_session_force_close_show,
+	       rnbd_srv_dev_session_force_close_store);
+
 static struct attribute *rnbd_srv_default_dev_sessions_attrs[] = {
 	&rnbd_srv_dev_session_access_mode_attr.attr,
 	&rnbd_srv_dev_session_ro_attr.attr,
 	&rnbd_srv_dev_session_mapping_path_attr.attr,
+	&rnbd_srv_dev_session_force_close_attr.attr,
 	NULL,
 };
 
@@ -145,7 +181,7 @@ static void rnbd_srv_sess_dev_release(struct kobject *kobj)
 	struct rnbd_srv_sess_dev *sess_dev;
 
 	sess_dev = container_of(kobj, struct rnbd_srv_sess_dev, kobj);
-	rnbd_destroy_sess_dev(sess_dev);
+	rnbd_destroy_sess_dev(sess_dev, sess_dev->keep_id);
 }
 
 static struct kobj_type rnbd_srv_sess_dev_ktype = {

drivers/block/rnbd/rnbd-srv.c

@@ -212,12 +212,20 @@ static void rnbd_put_srv_dev(struct rnbd_srv_dev *dev)
 	kref_put(&dev->kref, destroy_device_cb);
 }
 
-void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev)
+void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev, bool keep_id)
 {
 	DECLARE_COMPLETION_ONSTACK(dc);
 
-	xa_erase(&sess_dev->sess->index_idr, sess_dev->device_id);
+	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 */
@@ -328,6 +336,13 @@ static int rnbd_srv_link_ev(struct rtrs_srv *rtrs,
 	}
 }
 
+void rnbd_srv_sess_dev_force_close(struct rnbd_srv_sess_dev *sess_dev)
+{
+	rnbd_srv_destroy_dev_session_sysfs(sess_dev);
+	sess_dev->keep_id = true;
+
+}
+
 static int process_msg_close(struct rtrs_srv *rtrs,
 			     struct rnbd_srv_session *srv_sess,
 			     void *data, size_t datalen, const void *usr,

drivers/block/rnbd/rnbd-srv.h

@@ -56,13 +56,15 @@ struct rnbd_srv_sess_dev {
 	struct rnbd_srv_dev		*dev;
 	struct kobject                  kobj;
 	u32                             device_id;
+	bool				keep_id;
 	fmode_t                         open_flags;
 	struct kref			kref;
 	struct completion               *destroy_comp;
 	char				pathname[NAME_MAX];
 	enum rnbd_access_mode		access_mode;
 };
 
+void rnbd_srv_sess_dev_force_close(struct rnbd_srv_sess_dev *sess_dev);
 /* rnbd-srv-sysfs.c */
 
 int rnbd_srv_create_dev_sysfs(struct rnbd_srv_dev *dev,
@@ -73,6 +75,6 @@ int rnbd_srv_create_dev_session_sysfs(struct rnbd_srv_sess_dev *sess_dev);
 void rnbd_srv_destroy_dev_session_sysfs(struct rnbd_srv_sess_dev *sess_dev);
 int rnbd_srv_create_sysfs_files(void);
 void rnbd_srv_destroy_sysfs_files(void);
-void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev);
+void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev, bool keep_id);
 
 #endif /* RNBD_SRV_H */