drm: set dev_mapping before calling drm_open_helper

Some drivers (specifically vmwgfx) look at dev_mapping
in their open hook, so we have to set dev->dev_mapping
earlier in the process.

Reference:
http://lists.freedesktop.org/archives/dri-devel/2012-October/029420.html

Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reported-by: Thomas Hellstrom <thellstrom@vmware.com>
Cc: stable@vger.kernel.org
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index af68eca44abed7d46638a106d5f6b6cad79fe6e9..133b4132983e35e366884301a443ff26f45a2a05 100644 (file)
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -121,6 +121,8 @@ int drm_open(struct inode *inode, struct file *filp)
        int minor_id = iminor(inode);
        struct drm_minor *minor;
        int retcode = 0;
+       int need_setup = 0;
+       struct address_space *old_mapping;
 
        minor = idr_find(&drm_minors_idr, minor_id);
        if (!minor)
@@ -132,26 +134,37 @@ int drm_open(struct inode *inode, struct file *filp)
        if (drm_device_is_unplugged(dev))
                return -ENODEV;
 
+       if (!dev->open_count++)
+               need_setup = 1;
+       mutex_lock(&dev->struct_mutex);
+       old_mapping = dev->dev_mapping;
+       if (old_mapping == NULL)
+               dev->dev_mapping = &inode->i_data;
+       /* ihold ensures nobody can remove inode with our i_data */
+       ihold(container_of(dev->dev_mapping, struct inode, i_data));
+       inode->i_mapping = dev->dev_mapping;
+       filp->f_mapping = dev->dev_mapping;
+       mutex_unlock(&dev->struct_mutex);
+
        retcode = drm_open_helper(inode, filp, dev);
-       if (!retcode) {
-               atomic_inc(&dev->counts[_DRM_STAT_OPENS]);
-               if (!dev->open_count++) {
-                       retcode = drm_setup(dev);
-                       if (retcode)
-                               dev->open_count--;
-               }
-       }
-       if (!retcode) {
-               mutex_lock(&dev->struct_mutex);
-               if (dev->dev_mapping == NULL)
-                       dev->dev_mapping = &inode->i_data;
-               /* ihold ensures nobody can remove inode with our i_data */
-               ihold(container_of(dev->dev_mapping, struct inode, i_data));
-               inode->i_mapping = dev->dev_mapping;
-               filp->f_mapping = dev->dev_mapping;
-               mutex_unlock(&dev->struct_mutex);
+       if (retcode)
+               goto err_undo;
+       atomic_inc(&dev->counts[_DRM_STAT_OPENS]);
+       if (need_setup) {
+               retcode = drm_setup(dev);
+               if (retcode)
+                       goto err_undo;
        }
+       return 0;
 
+err_undo:
+       mutex_lock(&dev->struct_mutex);
+       filp->f_mapping = old_mapping;
+       inode->i_mapping = old_mapping;
+       iput(container_of(dev->dev_mapping, struct inode, i_data));
+       dev->dev_mapping = old_mapping;
+       mutex_unlock(&dev->struct_mutex);
+       dev->open_count--;
        return retcode;
 }
 EXPORT_SYMBOL(drm_open);