scsi: iscsi: Release endpoint ID when its freed

We can't release the endpoint ID until all references to the endpoint have
been dropped or it could be allocated while in use. This has us use an idr
instead of looping over all conns to find a free ID and then free the ID
when all references have been dropped instead of when the device is only
deleted.

Link: https://lore.kernel.org/r/20220408001314.5014-4-michael.christie@oracle.com
Tested-by: Manish Rangankar <mrangankar@marvell.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Chris Leech <cleech@redhat.com>
Reviewed-by: Wu Bo <wubo40@huawei.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: mikechristie

drivers/scsi/scsi_transport_iscsi.c

@@ -86,6 +86,9 @@ struct iscsi_internal {
 	struct transport_container session_cont;
 };
 
+static DEFINE_IDR(iscsi_ep_idr);
+static DEFINE_MUTEX(iscsi_ep_idr_mutex);
+
 static atomic_t iscsi_session_nr; /* sysfs session id for next new session */
 
 static struct workqueue_struct *iscsi_conn_cleanup_workq;
@@ -168,6 +171,11 @@ struct device_attribute dev_attr_##_prefix##_##_name =	\
 static void iscsi_endpoint_release(struct device *dev)
 {
 	struct iscsi_endpoint *ep = iscsi_dev_to_endpoint(dev);
+
+	mutex_lock(&iscsi_ep_idr_mutex);
+	idr_remove(&iscsi_ep_idr, ep->id);
+	mutex_unlock(&iscsi_ep_idr_mutex);
+
 	kfree(ep);
 }
 
@@ -180,7 +188,7 @@ static ssize_t
 show_ep_handle(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct iscsi_endpoint *ep = iscsi_dev_to_endpoint(dev);
-	return sysfs_emit(buf, "%llu\n", (unsigned long long) ep->id);
+	return sysfs_emit(buf, "%d\n", ep->id);
 }
 static ISCSI_ATTR(ep, handle, S_IRUGO, show_ep_handle, NULL);
 
@@ -193,48 +201,32 @@ static struct attribute_group iscsi_endpoint_group = {
 	.attrs = iscsi_endpoint_attrs,
 };
 
-#define ISCSI_MAX_EPID -1
-
-static int iscsi_match_epid(struct device *dev, const void *data)
-{
-	struct iscsi_endpoint *ep = iscsi_dev_to_endpoint(dev);
-	const uint64_t *epid = data;
-
-	return *epid == ep->id;
-}
-
 struct iscsi_endpoint *
 iscsi_create_endpoint(int dd_size)
 {
-	struct device *dev;
 	struct iscsi_endpoint *ep;
-	uint64_t id;
-	int err;
-
-	for (id = 1; id < ISCSI_MAX_EPID; id++) {
-		dev = class_find_device(&iscsi_endpoint_class, NULL, &id,
-					iscsi_match_epid);
-		if (!dev)
-			break;
-		else
-			put_device(dev);
-	}
-	if (id == ISCSI_MAX_EPID) {
-		printk(KERN_ERR "Too many connections. Max supported %u\n",
-		       ISCSI_MAX_EPID - 1);
-		return NULL;
-	}
+	int err, id;
 
 	ep = kzalloc(sizeof(*ep) + dd_size, GFP_KERNEL);
 	if (!ep)
 		return NULL;
 
+	mutex_lock(&iscsi_ep_idr_mutex);
+	id = idr_alloc(&iscsi_ep_idr, ep, 0, -1, GFP_NOIO);
+	if (id < 0) {
+		mutex_unlock(&iscsi_ep_idr_mutex);
+		printk(KERN_ERR "Could not allocate endpoint ID. Error %d.\n",
+		       id);
+		goto free_ep;
+	}
+	mutex_unlock(&iscsi_ep_idr_mutex);
+
 	ep->id = id;
 	ep->dev.class = &iscsi_endpoint_class;
-	dev_set_name(&ep->dev, "ep-%llu", (unsigned long long) id);
+	dev_set_name(&ep->dev, "ep-%d", id);
 	err = device_register(&ep->dev);
         if (err)
-                goto free_ep;
+		goto free_id;
 
 	err = sysfs_create_group(&ep->dev.kobj, &iscsi_endpoint_group);
 	if (err)
@@ -248,6 +240,10 @@ iscsi_create_endpoint(int dd_size)
 	device_unregister(&ep->dev);
 	return NULL;
 
+free_id:
+	mutex_lock(&iscsi_ep_idr_mutex);
+	idr_remove(&iscsi_ep_idr, id);
+	mutex_unlock(&iscsi_ep_idr_mutex);
 free_ep:
 	kfree(ep);
 	return NULL;
@@ -275,14 +271,17 @@ EXPORT_SYMBOL_GPL(iscsi_put_endpoint);
  */
 struct iscsi_endpoint *iscsi_lookup_endpoint(u64 handle)
 {
-	struct device *dev;
+	struct iscsi_endpoint *ep;
 
-	dev = class_find_device(&iscsi_endpoint_class, NULL, &handle,
-				iscsi_match_epid);
-	if (!dev)
-		return NULL;
+	mutex_lock(&iscsi_ep_idr_mutex);
+	ep = idr_find(&iscsi_ep_idr, handle);
+	if (!ep)
+		goto unlock;
 
-	return iscsi_dev_to_endpoint(dev);
+	get_device(&ep->dev);
+unlock:
+	mutex_unlock(&iscsi_ep_idr_mutex);
+	return ep;
 }
 EXPORT_SYMBOL_GPL(iscsi_lookup_endpoint);
 

include/scsi/scsi_transport_iscsi.h

@@ -295,7 +295,7 @@ extern void iscsi_host_for_each_session(struct Scsi_Host *shost,
 struct iscsi_endpoint {
 	void *dd_data;			/* LLD private data */
 	struct device dev;
-	uint64_t id;
+	int id;
 	struct iscsi_cls_conn *conn;
 };