lightnvm: fix media mgr registration

This patch fixes two issues during media manager registration.

1. The ppa pool can be used at media manager registration. Allocate the
ppa pool before that.

2. If a media manager can't be found, this should not lead to the
device being unallocated. A media manager can be registered later, that
can manage the device. Only warn if a media manager fails
initialization.
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/core.c

@@ -97,15 +97,47 @@ static struct nvmm_type *nvm_find_mgr_type(const char *name)
 	return NULL;
 }
 
+struct nvmm_type *nvm_init_mgr(struct nvm_dev *dev)
+{
+	struct nvmm_type *mt;
+	int ret;
+
+	lockdep_assert_held(&nvm_lock);
+
+	list_for_each_entry(mt, &nvm_mgrs, list) {
+		ret = mt->register_mgr(dev);
+		if (ret < 0) {
+			pr_err("nvm: media mgr failed to init (%d) on dev %s\n",
+								ret, dev->name);
+			return NULL; /* initialization failed */
+		} else if (ret > 0)
+			return mt;
+	}
+
+	return NULL;
+}
+
 int nvm_register_mgr(struct nvmm_type *mt)
 {
+	struct nvm_dev *dev;
 	int ret = 0;
 
 	down_write(&nvm_lock);
-	if (nvm_find_mgr_type(mt->name))
+	if (nvm_find_mgr_type(mt->name)) {
 		ret = -EEXIST;
-	else
+		goto finish;
+	} else {
 		list_add(&mt->list, &nvm_mgrs);
+	}
+
+	/* try to register media mgr if any device have none configured */
+	list_for_each_entry(dev, &nvm_devices, devices) {
+		if (dev->mt)
+			continue;
+
+		dev->mt = nvm_init_mgr(dev);
+	}
+finish:
 	up_write(&nvm_lock);
 
 	return ret;
@@ -123,26 +155,6 @@ 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;
@@ -271,14 +283,6 @@ static int nvm_init(struct nvm_dev *dev)
 		goto err;
 	}
 
-	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,
 			dev->pgs_per_blk, dev->blks_per_lun, dev->nr_luns,
@@ -334,7 +338,9 @@ int nvm_register(struct request_queue *q, char *disk_name,
 		}
 	}
 
+	/* register device with a supported media manager */
 	down_write(&nvm_lock);
+	dev->mt = nvm_init_mgr(dev);
 	list_add(&dev->devices, &nvm_devices);
 	up_write(&nvm_lock);
 
@@ -379,19 +385,13 @@ static int nvm_create_target(struct nvm_dev *dev,
 	struct nvm_tgt_type *tt;
 	struct nvm_target *t;
 	void *targetdata;
-	int ret = 0;
 
-	down_write(&nvm_lock);
 	if (!dev->mt) {
-		ret = register_mgr(dev);
-		if (!ret)
-			ret = -ENODEV;
-		if (ret < 0) {
-			up_write(&nvm_lock);
-			return ret;
-		}
+		pr_info("nvm: device has no media manager registered.\n");
+		return -ENODEV;
 	}
 
+	down_write(&nvm_lock);
 	tt = nvm_find_target_type(create->tgttype);
 	if (!tt) {
 		pr_err("nvm: target type %s not found\n", create->tgttype);