drm/i915: Remove insert-page shortcut from execbuf relocate_iomap()

We are not allowed to touch the GTT entries underneath an atomic section,
as they take a rpm wakelock (which is illegal from atomic context) and
in the near future acquiring the DMA address for a page within an object
may sleep for an allocation. This makes the current shortcircuit in
relocation_iomap() for performing a second relocation on an adjacent page
illegal, and we need to release the atomic iomapping, lookup the DMA,
insert it into the GTT before reentering the atomic iomap section.

As it happens, this is precisely what we do on if we are using an
iomapping over the full object and not just a single page and by
removing the shortcut, we do the right thing.

Fixes: 9c870d03 ("drm/i915: Use RPM as the barrier for controlling...")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028142756.3850-1-chris@chris-wilson.co.ukReviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -418,15 +418,6 @@ static void *reloc_iomap(struct drm_i915_gem_object *obj,
 	unsigned long offset;
 	void *vaddr;
 
-	if (cache->node.allocated) {
-		wmb();
-		ggtt->base.insert_page(&ggtt->base,
-				       i915_gem_object_get_dma_address(obj, page),
-				       cache->node.start, I915_CACHE_NONE, 0);
-		cache->page = page;
-		return unmask_page(cache->vaddr);
-	}
-
 	if (cache->vaddr) {
 		io_mapping_unmap_atomic((void __force __iomem *) unmask_page(cache->vaddr));
 	} else {
@@ -466,6 +457,7 @@ static void *reloc_iomap(struct drm_i915_gem_object *obj,
 
 	offset = cache->node.start;
 	if (cache->node.allocated) {
+		wmb();
 		ggtt->base.insert_page(&ggtt->base,
 				       i915_gem_object_get_dma_address(obj, page),
 				       offset, I915_CACHE_NONE, 0);