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>

1 files changed, 30 insertions, 17 deletions

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index af68eca44abe..133b4132983e 100644
--- 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);