iommu: Split iommu_group_add_device()

Move the list_add_tail() for the group_device into the critical region
that immediately follows in __iommu_probe_device(). This avoids one case
of unlocking and immediately re-locking the group->mutex.

Consistently make the caller responsible for setting dev->iommu_group,
prior patches moved this into iommu_init_device(), make the no-driver path
do this in iommu_group_add_device().

This completes making __iommu_group_free_device() and
iommu_group_alloc_device() into pair'd functions.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/9-v3-328044aa278c+45e49-iommu_probe_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 55b916e8da3bb7d87ae6cfcf9de5f202e9a88c9a..3129e5c50c87547a37e176dc8c1d3d4d03a9be6b 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -129,6 +129,8 @@ static int iommu_create_device_direct_mappings(struct iommu_domain *domain,
                                               struct device *dev);
 static ssize_t iommu_group_store_type(struct iommu_group *group,
                                      const char *buf, size_t count);
+static struct group_device *iommu_group_alloc_device(struct iommu_group *group,
+                                                    struct device *dev);
 
 #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store)          \
 struct iommu_group_attribute iommu_group_attr_##_name =                \
@@ -435,6 +437,7 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
        const struct iommu_ops *ops = dev->bus->iommu_ops;
        struct iommu_group *group;
        static DEFINE_MUTEX(iommu_probe_device_lock);
+       struct group_device *gdev;
        int ret;
 
        if (!ops)
@@ -459,16 +462,17 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
                goto out_unlock;
 
        group = dev->iommu_group;
-       ret = iommu_group_add_device(group, dev);
+       gdev = iommu_group_alloc_device(group, dev);
        mutex_lock(&group->mutex);
-       if (ret)
+       if (IS_ERR(gdev)) {
+               ret = PTR_ERR(gdev);
                goto err_put_group;
+       }
 
+       list_add_tail(&gdev->list, &group->devices);
        if (group_list && !group->default_domain && list_empty(&group->entry))
                list_add_tail(&group->entry, group_list);
        mutex_unlock(&group->mutex);
-       iommu_group_put(group);
-
        mutex_unlock(&iommu_probe_device_lock);
 
        return 0;
@@ -578,7 +582,10 @@ static void __iommu_group_remove_device(struct device *dev)
        }
        mutex_unlock(&group->mutex);
 
-       /* Pairs with the get in iommu_group_add_device() */
+       /*
+        * Pairs with the get in iommu_init_device() or
+        * iommu_group_add_device()
+        */
        iommu_group_put(group);
 }
 
@@ -1067,22 +1074,16 @@ out:
        return ret;
 }
 
-/**
- * iommu_group_add_device - add a device to an iommu group
- * @group: the group into which to add the device (reference should be held)
- * @dev: the device
- *
- * This function is called by an iommu driver to add a device into a
- * group.  Adding a device increments the group reference count.
- */
-int iommu_group_add_device(struct iommu_group *group, struct device *dev)
+/* This is undone by __iommu_group_free_device() */
+static struct group_device *iommu_group_alloc_device(struct iommu_group *group,
+                                                    struct device *dev)
 {
        int ret, i = 0;
        struct group_device *device;
 
        device = kzalloc(sizeof(*device), GFP_KERNEL);
        if (!device)
-               return -ENOMEM;
+               return ERR_PTR(-ENOMEM);
 
        device->dev = dev;
 
@@ -1113,17 +1114,11 @@ rename:
                goto err_free_name;
        }
 
-       iommu_group_ref_get(group);
-       dev->iommu_group = group;
-
-       mutex_lock(&group->mutex);
-       list_add_tail(&device->list, &group->devices);
-       mutex_unlock(&group->mutex);
        trace_add_device_to_group(group->id, dev);
 
        dev_info(dev, "Adding to iommu group %d\n", group->id);
 
-       return 0;
+       return device;
 
 err_free_name:
        kfree(device->name);
@@ -1132,7 +1127,32 @@ err_remove_link:
 err_free_device:
        kfree(device);
        dev_err(dev, "Failed to add to iommu group %d: %d\n", group->id, ret);
-       return ret;
+       return ERR_PTR(ret);
+}
+
+/**
+ * iommu_group_add_device - add a device to an iommu group
+ * @group: the group into which to add the device (reference should be held)
+ * @dev: the device
+ *
+ * This function is called by an iommu driver to add a device into a
+ * group.  Adding a device increments the group reference count.
+ */
+int iommu_group_add_device(struct iommu_group *group, struct device *dev)
+{
+       struct group_device *gdev;
+
+       gdev = iommu_group_alloc_device(group, dev);
+       if (IS_ERR(gdev))
+               return PTR_ERR(gdev);
+
+       iommu_group_ref_get(group);
+       dev->iommu_group = group;
+
+       mutex_lock(&group->mutex);
+       list_add_tail(&gdev->list, &group->devices);
+       mutex_unlock(&group->mutex);
+       return 0;
 }
 EXPORT_SYMBOL_GPL(iommu_group_add_device);