lightnvm: missing nvm_lock acquire

To avoid race conditions, traverse dev, media manager,
and target lists and also register, unregister entries
to/from them, should be always under the nvm_lock control.
Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/core.c

@@ -123,6 +123,26 @@ void nvm_unregister_mgr(struct nvmm_type *mt)
 }
 EXPORT_SYMBOL(nvm_unregister_mgr);
 
+/* register with device with a supported manager */
+static int register_mgr(struct nvm_dev *dev)
+{
+	struct nvmm_type *mt;
+	int ret = 0;
+
+	list_for_each_entry(mt, &nvm_mgrs, list) {
+		ret = mt->register_mgr(dev);
+		if (ret > 0) {
+			dev->mt = mt;
+			break; /* successfully initialized */
+		}
+	}
+
+	if (!ret)
+		pr_info("nvm: no compatible nvm manager found.\n");
+
+	return ret;
+}
+
 static struct nvm_dev *nvm_find_nvm_dev(const char *name)
 {
 	struct nvm_dev *dev;
@@ -221,7 +241,6 @@ static void nvm_free(struct nvm_dev *dev)
 
 static int nvm_init(struct nvm_dev *dev)
 {
-	struct nvmm_type *mt;
 	int ret = -EINVAL;
 
 	if (!dev->q || !dev->ops)
@@ -252,21 +271,13 @@ static int nvm_init(struct nvm_dev *dev)
 		goto err;
 	}
 
-	/* register with device with a supported manager */
-	list_for_each_entry(mt, &nvm_mgrs, list) {
-		ret = mt->register_mgr(dev);
-		if (ret < 0)
-			goto err; /* initialization failed */
-		if (ret > 0) {
-			dev->mt = mt;
-			break; /* successfully initialized */
-		}
-	}
-
-	if (!ret) {
-		pr_info("nvm: no compatible manager found.\n");
+	down_write(&nvm_lock);
+	ret = register_mgr(dev);
+	up_write(&nvm_lock);
+	if (ret < 0)
+		goto err;
+	if (!ret)
 		return 0;
-	}
 
 	pr_info("nvm: registered %s [%u/%u/%u/%u/%u/%u]\n",
 			dev->name, dev->sec_per_pg, dev->nr_planes,
@@ -337,15 +348,17 @@ EXPORT_SYMBOL(nvm_register);
 
 void nvm_unregister(char *disk_name)
 {
-	struct nvm_dev *dev = nvm_find_nvm_dev(disk_name);
+	struct nvm_dev *dev;
 
+	down_write(&nvm_lock);
+	dev = nvm_find_nvm_dev(disk_name);
 	if (!dev) {
 		pr_err("nvm: could not find device %s to unregister\n",
 								disk_name);
+		up_write(&nvm_lock);
 		return;
 	}
 
-	down_write(&nvm_lock);
 	list_del(&dev->devices);
 	up_write(&nvm_lock);
 
@@ -363,38 +376,30 @@ static int nvm_create_target(struct nvm_dev *dev,
 {
 	struct nvm_ioctl_create_simple *s = &create->conf.s;
 	struct request_queue *tqueue;
-	struct nvmm_type *mt;
 	struct gendisk *tdisk;
 	struct nvm_tgt_type *tt;
 	struct nvm_target *t;
 	void *targetdata;
 	int ret = 0;
 
+	down_write(&nvm_lock);
 	if (!dev->mt) {
-		/* register with device with a supported NVM manager */
-		list_for_each_entry(mt, &nvm_mgrs, list) {
-			ret = mt->register_mgr(dev);
-			if (ret < 0)
-				return ret; /* initialization failed */
-			if (ret > 0) {
-				dev->mt = mt;
-				break; /* successfully initialized */
-			}
-		}
-
-		if (!ret) {
-			pr_info("nvm: no compatible nvm manager found.\n");
-			return -ENODEV;
+		ret = register_mgr(dev);
+		if (!ret)
+			ret = -ENODEV;
+		if (ret < 0) {
+			up_write(&nvm_lock);
+			return ret;
 		}
 	}
 
 	tt = nvm_find_target_type(create->tgttype);
 	if (!tt) {
 		pr_err("nvm: target type %s not found\n", create->tgttype);
+		up_write(&nvm_lock);
 		return -EINVAL;
 	}
 
-	down_write(&nvm_lock);
 	list_for_each_entry(t, &dev->online_targets, list) {
 		if (!strcmp(create->tgtname, t->disk->disk_name)) {
 			pr_err("nvm: target name already exists.\n");
@@ -478,7 +483,9 @@ static int __nvm_configure_create(struct nvm_ioctl_create *create)
 	struct nvm_dev *dev;
 	struct nvm_ioctl_create_simple *s;
 
+	down_write(&nvm_lock);
 	dev = nvm_find_nvm_dev(create->dev);
+	up_write(&nvm_lock);
 	if (!dev) {
 		pr_err("nvm: device not found\n");
 		return -EINVAL;
@@ -537,7 +544,9 @@ static int nvm_configure_show(const char *val)
 		return -EINVAL;
 	}
 
+	down_write(&nvm_lock);
 	dev = nvm_find_nvm_dev(devname);
+	up_write(&nvm_lock);
 	if (!dev) {
 		pr_err("nvm: device not found\n");
 		return -EINVAL;