linux-kernel - [PATCH 7/8] vfio/mdev: Fix aborting mdev child device removal if one fails

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Date:   Fri, 22 Mar 2019 18:20:34 -0500
From:   Parav Pandit <parav@...lanox.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kwankhede@...dia.com, alex.williamson@...hat.com
Cc:     parav@...lanox.com
Subject: [PATCH 7/8] vfio/mdev: Fix aborting mdev child device removal if one fails

device_for_each_child() stops executing callback function for remaining
child devices, if callback hits an error.
Each child mdev device is independent of each other.
While unregistering parent device, mdev core must remove all child mdev
devices.
Therefore, mdev_device_remove_cb() always returns success so that
device_for_each_child doesn't abort if one child removal hits error.

While at it, improve remove and unregister functions for below simplicity.

There isn't need to pass forced flag pointer during mdev parent
removal which invokes mdev_device_remove(). So simplify the flow.

mdev_device_remove() is called from two paths.
1. mdev_unregister_driver()
     mdev_device_remove_cb()
       mdev_device_remove()
2. remove_store()
     mdev_device_remove()

When device is removed by user using remote_store(), device under
removal is mdev device.
When device is removed during parent device removal using generic child
iterator, mdev check is already done using dev_is_mdev().

Hence, remove the unnecessary loop in mdev_device_remove().

Fixes: 7b96953bc640 ("vfio: Mediated device Core driver")
Signed-off-by: Parav Pandit <parav@...lanox.com>
---
 drivers/vfio/mdev/mdev_core.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index ab05464..944a058 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -150,10 +150,10 @@ static int mdev_device_remove_ops(struct mdev_device *mdev, bool force_remove)
 
 static int mdev_device_remove_cb(struct device *dev, void *data)
 {
-	if (!dev_is_mdev(dev))
-		return 0;
+	if (dev_is_mdev(dev))
+		mdev_device_remove(dev, true);
 
-	return mdev_device_remove(dev, data ? *(bool *)data : true);
+	return 0;
 }
 
 /*
@@ -241,7 +241,6 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops)
 void mdev_unregister_device(struct device *dev)
 {
 	struct mdev_parent *parent;
-	bool force_remove = true;
 
 	mutex_lock(&parent_list_lock);
 	parent = __find_parent_device(dev);
@@ -255,8 +254,7 @@ void mdev_unregister_device(struct device *dev)
 	list_del(&parent->next);
 	class_compat_remove_link(mdev_bus_compat_class, dev, NULL);
 
-	device_for_each_child(dev, (void *)&force_remove,
-			      mdev_device_remove_cb);
+	device_for_each_child(dev, NULL, mdev_device_remove_cb);
 
 	parent_remove_sysfs_files(parent);
 
@@ -346,24 +344,12 @@ int mdev_device_create(struct kobject *kobj, struct device *dev, uuid_le uuid)
 
 int mdev_device_remove(struct device *dev, bool force_remove)
 {
-	struct mdev_device *mdev, *tmp;
+	struct mdev_device *mdev;
 	struct mdev_parent *parent;
 	struct mdev_type *type;
 	int ret;
 
 	mdev = to_mdev_device(dev);
-
-	mutex_lock(&mdev_list_lock);
-	list_for_each_entry(tmp, &mdev_list, next) {
-		if (tmp == mdev)
-			break;
-	}
-
-	if (tmp != mdev) {
-		mutex_unlock(&mdev_list_lock);
-		return -ENODEV;
-	}
-
 	if (!mdev->active) {
 		mutex_unlock(&mdev_list_lock);
 		return -EAGAIN;
-- 
1.8.3.1