drm: make minor->index available early

Instead of allocating the minor-index during registration, we now do this
during allocation. This way, debug-messages between minor-allocation and
minor-registration will now use the correct minor instead of 0. Same is
done for unregistration vs. free, so debug-messages between
device-shutdown and device-destruction show proper indices.

Even though minor-indices are allocated early, we don't enable minor
lookup early. Instead, we keep the entry set to NULL and replace it during
registration / unregistration. This way, the index is allocated but lookup
only works if registered.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>

1 files changed, 46 insertions, 38 deletions

diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index b249f14f66a9..8b24db51116e 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -256,6 +256,8 @@ static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
 static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 {
         struct drm_minor *minor;
+        unsigned long flags;
+        int r;
 
         minor = kzalloc(sizeof(*minor), GFP_KERNEL);
         if (!minor)
@@ -264,57 +266,68 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
         minor->type = type;
         minor->dev = dev;
 
+        idr_preload(GFP_KERNEL);
+        spin_lock_irqsave(&drm_minor_lock, flags);
+        r = idr_alloc(&drm_minors_idr,
+                      NULL,
+                      64 * type,
+                      64 * (type + 1),
+                      GFP_NOWAIT);
+        spin_unlock_irqrestore(&drm_minor_lock, flags);
+        idr_preload_end();
+
+        if (r < 0)
+                goto err_free;
+
+        minor->index = r;
+
         *drm_minor_get_slot(dev, type) = minor;
         return 0;
+
+err_free:
+        kfree(minor);
+        return r;
 }
 
 static void drm_minor_free(struct drm_device *dev, unsigned int type)
 {
-        struct drm_minor **slot;
+        struct drm_minor **slot, *minor;
+        unsigned long flags;
 
         slot = drm_minor_get_slot(dev, type);
-        if (*slot) {
-                drm_mode_group_destroy(&(*slot)->mode_group);
-                kfree(*slot);
-                *slot = NULL;
-        }
+        minor = *slot;
+        if (!minor)
+                return;
+
+        drm_mode_group_destroy(&minor->mode_group);
+
+        spin_lock_irqsave(&drm_minor_lock, flags);
+        idr_remove(&drm_minors_idr, minor->index);
+        spin_unlock_irqrestore(&drm_minor_lock, flags);
+
+        kfree(minor);
+        *slot = NULL;
 }
 
 static int drm_minor_register(struct drm_device *dev, unsigned int type)
 {
-        struct drm_minor *new_minor;
+        struct drm_minor *minor;
         unsigned long flags;
         int ret;
-        int minor_id;
 
         DRM_DEBUG("\n");
 
-        new_minor = *drm_minor_get_slot(dev, type);
-        if (!new_minor)
+        minor = *drm_minor_get_slot(dev, type);
+        if (!minor)
                 return 0;
 
-        idr_preload(GFP_KERNEL);
-        spin_lock_irqsave(&drm_minor_lock, flags);
-        minor_id = idr_alloc(&drm_minors_idr,
-                             NULL,
-                             64 * type,
-                             64 * (type + 1),
-                             GFP_NOWAIT);
-        spin_unlock_irqrestore(&drm_minor_lock, flags);
-        idr_preload_end();
-
-        if (minor_id < 0)
-                return minor_id;
-
-        new_minor->index = minor_id;
-
-        ret = drm_debugfs_init(new_minor, minor_id, drm_debugfs_root);
+        ret = drm_debugfs_init(minor, minor->index, drm_debugfs_root);
         if (ret) {
                 DRM_ERROR("DRM: Failed to initialize /sys/kernel/debug/dri.\n");
-                goto err_id;
+                return ret;
         }
 
-        ret = drm_sysfs_device_add(new_minor);
+        ret = drm_sysfs_device_add(minor);
         if (ret) {
                 DRM_ERROR("DRM: Error sysfs_device_add.\n");
                 goto err_debugfs;
@@ -322,19 +335,14 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type)
 
         /* replace NULL with @minor so lookups will succeed from now on */
         spin_lock_irqsave(&drm_minor_lock, flags);
-        idr_replace(&drm_minors_idr, new_minor, new_minor->index);
+        idr_replace(&drm_minors_idr, minor, minor->index);
         spin_unlock_irqrestore(&drm_minor_lock, flags);
 
-        DRM_DEBUG("new minor assigned %d\n", minor_id);
+        DRM_DEBUG("new minor registered %d\n", minor->index);
         return 0;
 
 err_debugfs:
-        drm_debugfs_cleanup(new_minor);
-err_id:
-        spin_lock_irqsave(&drm_minor_lock, flags);
-        idr_remove(&drm_minors_idr, minor_id);
-        spin_unlock_irqrestore(&drm_minor_lock, flags);
-        new_minor->index = 0;
+        drm_debugfs_cleanup(minor);
         return ret;
 }
 
@@ -347,10 +355,10 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
         if (!minor || !minor->kdev)
                 return;
 
+        /* replace @minor with NULL so lookups will fail from now on */
         spin_lock_irqsave(&drm_minor_lock, flags);
-        idr_remove(&drm_minors_idr, minor->index);
+        idr_replace(&drm_minors_idr, NULL, minor->index);
         spin_unlock_irqrestore(&drm_minor_lock, flags);
-        minor->index = 0;
 
         drm_debugfs_cleanup(minor);
         drm_sysfs_device_remove(minor);