drm/i915: Trylock the object when shrinking

We're working on requiring the obj->resv lock during unbind, fix
the shrinker to take the object lock.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211216142749.1966107-10-maarten.lankhorst@linux.intel.com

Author: mlankhorst

drivers/gpu/drm/i915/gem/i915_gem_shrinker.c

@@ -405,12 +405,18 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
 	list_for_each_entry_safe(vma, next,
 				 &i915->ggtt.vm.bound_list, vm_link) {
 		unsigned long count = vma->node.size >> PAGE_SHIFT;
+		struct drm_i915_gem_object *obj = vma->obj;
 
 		if (!vma->iomap || i915_vma_is_active(vma))
 			continue;
 
+		if (!i915_gem_object_trylock(obj))
+			continue;
+
 		if (__i915_vma_unbind(vma) == 0)
 			freed_pages += count;
+
+		i915_gem_object_unlock(obj);
 	}
 	mutex_unlock(&i915->ggtt.vm.mutex);