drm/i915/userptr: Make gup errors stickier

Keep any error reported by the gup_worker until we are notified that the
arena has changed (via the mmu-notifier). This has the importance of
making two consecutive calls to i915_gem_object_get_pages() reporting
the same error, and curtailing a loop of detecting a fault and requeueing
a gup_worker.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-19-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 57218cc..be54825 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -542,8 +542,6 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
                        }
                }
                obj->userptr.work = ERR_PTR(ret);
-               if (ret)
-                       __i915_gem_userptr_set_active(obj, false);
        }
 
        obj->userptr.workers--;
@@ -628,15 +626,14 @@ i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
         * to the vma (discard or cloning) which should prevent the more
         * egregious cases from causing harm.
         */
-       if (IS_ERR(obj->userptr.work)) {
-               /* active flag will have been dropped already by the worker */
-               ret = PTR_ERR(obj->userptr.work);
-               obj->userptr.work = NULL;
-               return ret;
-       }
-       if (obj->userptr.work)
+
+       if (obj->userptr.work) {
                /* active flag should still be held for the pending work */
-               return -EAGAIN;
+               if (IS_ERR(obj->userptr.work))
+                       return PTR_ERR(obj->userptr.work);
+               else
+                       return -EAGAIN;
+       }
 
        /* Let the mmu-notifier know that we have begun and need cancellation */
        ret = __i915_gem_userptr_set_active(obj, true);