[PATCH v2 16/16] lightnvm: track inflight target creations

[Igor Konopko <igor.j.konopko@intel.com>]

This patch adds a counter, which is responsible for tracking inflight
target creations.

When creation process is still in progress, target is not yet on
targets list. This causes a chance for removing whole lightnvm
subsystem by calling nvm_unregister() in the meantime and finally by
causing kernel panic inside target init function.

With this patch we are able to track such a scenarios and wait with
completing nvm_unregister() and freeing memory until target creation
will be completed.

Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
---
 drivers/lightnvm/core.c  | 19 ++++++++++++++++++-
 include/linux/lightnvm.h |  2 ++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index c01f83b..1edb9d8 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -1083,6 +1083,7 @@ static int nvm_core_init(struct nvm_dev *dev)
 	INIT_LIST_HEAD(&dev->targets);
 	mutex_init(&dev->mlock);
 	spin_lock_init(&dev->lock);
+	dev->create_inflight = 0;
 
 	ret = nvm_register_map(dev);
 	if (ret)
@@ -1180,6 +1181,11 @@ void nvm_unregister(struct nvm_dev *dev)
 	struct nvm_target *t, *tmp;
 
 	mutex_lock(&dev->mlock);
+	while (dev->create_inflight > 0) {
+		mutex_unlock(&dev->mlock);
+		io_schedule();
+		mutex_lock(&dev->mlock);
+	}
 	list_for_each_entry_safe(t, tmp, &dev->targets, list) {
 		if (t->dev->parent != dev)
 			continue;
@@ -1198,6 +1204,7 @@ EXPORT_SYMBOL(nvm_unregister);
 static int __nvm_configure_create(struct nvm_ioctl_create *create)
 {
 	struct nvm_dev *dev;
+	int ret;
 
 	down_write(&nvm_lock);
 	dev = nvm_find_nvm_dev(create->dev);
@@ -1208,7 +1215,17 @@ static int __nvm_configure_create(struct nvm_ioctl_create *create)
 		return -EINVAL;
 	}
 
-	return nvm_create_tgt(dev, create);
+	mutex_lock(&dev->mlock);
+	dev->create_inflight++;
+	mutex_unlock(&dev->mlock);
+
+	ret = nvm_create_tgt(dev, create);
+
+	mutex_lock(&dev->mlock);
+	dev->create_inflight--;
+	mutex_unlock(&dev->mlock);
+
+	return ret;
 }
 
 static long nvm_ioctl_info(struct file *file, void __user *arg)
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index d3b0270..e462d1d 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -428,6 +428,8 @@ struct nvm_dev {
 	char name[DISK_NAME_LEN];
 	void *private_data;
 
+	int create_inflight;
+
 	void *rmap;
 
 	struct mutex mlock;
-- 
2.9.5