vfio/spapr: Postpone default window creation

Hello Alexey Kardashevskiy,

The patch d9c728949ddc: "vfio/spapr: Postpone default window creation" from Nov 30, 2016, leads to the following static checker warning:

	drivers/vfio/vfio_iommu_spapr_tce.c:1180 tce_iommu_ioctl()
	warn: inconsistent returns 'mutex:&container->lock'.

drivers/vfio/vfio_iommu_spapr_tce.c
1114 if (copy_from_user(&create, (void __user *)arg, minsz))
1115 return -EFAULT;
1116
1117 if (create.argsz < minsz)
1118 return -EINVAL;
1119
1120 if (create.flags)
1121 return -EINVAL;
1122

  1123                  mutex_lock(&container->lock);
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1124
1125 ret = tce_iommu_create_default_window(container);
1126 if (ret)
1127 return ret;

We can't return directly while holding the lock.

  1128  
  1129                  ret = tce_iommu_create_window(container, create.page_shift,
  1130                                  create.window_size, create.levels,
  1131                                  &create.start_addr);
  1132  
  1133                  mutex_unlock(&container->lock);
  1134  
  1135                  if (!ret && copy_to_user((void __user *)arg, &create, minsz))
  1136                          ret = -EFAULT;
  1137  
  1138                  return ret;
  1139          }

regards,
dan carpenter