drm/i915/ttm: Drop region reference counting

There is an interesting refcounting loop:
struct intel_memory_region has a struct ttm_resource_manager,
ttm_resource_manager->move may hold a reference to i915_request,
i915_request may hold a reference to intel_context,
intel_context may hold a reference to drm_i915_gem_object,
drm_i915_gem_object may hold a reference to intel_memory_region.

Break this loop by dropping region reference counting.

In addition, Have regions with a manager moving fence make sure
that all region objects are released before freeing the region.

v6:
- Fix a code comment.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211122214554.371864-4-thomas.hellstrom@linux.intel.com

5 files changed, 10 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_region.c b/drivers/gpu/drm/i915/gem/i915_gem_region.c
index a016ccec36f3..a4350227e9ae 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_region.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_region.c
@@ -11,7 +11,7 @@
 void i915_gem_object_init_memory_region(struct drm_i915_gem_object *obj,
 					struct intel_memory_region *mem)
 {
-	obj->mm.region = intel_memory_region_get(mem);
+	obj->mm.region = mem;
 
 	mutex_lock(&mem->objects.lock);
 	list_add(&obj->mm.region_link, &mem->objects.list);
@@ -25,8 +25,6 @@ void i915_gem_object_release_memory_region(struct drm_i915_gem_object *obj)
 	mutex_lock(&mem->objects.lock);
 	list_del(&obj->mm.region_link);
 	mutex_unlock(&mem->objects.lock);
-
-	intel_memory_region_put(mem);
 }
 
 struct drm_i915_gem_object *
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index 4a88c89b7a14..cc9fe258fba7 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -664,9 +664,10 @@ static int init_shmem(struct intel_memory_region *mem)
 	return 0; /* Don't error, we can simply fallback to the kernel mnt */
 }
 
-static void release_shmem(struct intel_memory_region *mem)
+static int release_shmem(struct intel_memory_region *mem)
 {
 	i915_gemfs_fini(mem->i915);
+	return 0;
 }
 
 static const struct intel_memory_region_ops shmem_region_ops = {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index ddd37ccb1362..80680395bb3b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -720,9 +720,10 @@ static int init_stolen_smem(struct intel_memory_region *mem)
 	return i915_gem_init_stolen(mem);
 }
 
-static void release_stolen_smem(struct intel_memory_region *mem)
+static int release_stolen_smem(struct intel_memory_region *mem)
 {
 	i915_gem_cleanup_stolen(mem->i915);
+	return 0;
 }
 
 static const struct intel_memory_region_ops i915_region_stolen_smem_ops = {
@@ -759,10 +760,11 @@ err_fini:
 	return err;
 }
 
-static void release_stolen_lmem(struct intel_memory_region *mem)
+static int release_stolen_lmem(struct intel_memory_region *mem)
 {
 	io_mapping_fini(&mem->iomap);
 	i915_gem_cleanup_stolen(mem->i915);
+	return 0;
 }
 
 static const struct intel_memory_region_ops i915_region_stolen_lmem_ops = {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index e9e78ac8f592..6d3d2a558d0f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -997,7 +997,7 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
 	i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags);
 
 	/* Don't put on a region list until we're either locked or fully initialized. */
-	obj->mm.region = intel_memory_region_get(mem);
+	obj->mm.region = mem;
 	INIT_LIST_HEAD(&obj->mm.region_link);
 
 	INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL | __GFP_NOWARN);
@@ -1044,6 +1044,7 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
 
 static const struct intel_memory_region_ops ttm_system_region_ops = {
 	.init_object = __i915_gem_ttm_object_init,
+	.release = intel_region_ttm_fini,
 };
 
 struct intel_memory_region *
diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index 257588b68adc..c69c7d45aabc 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -568,7 +568,7 @@ out_unpin:
 out_put:
 	i915_gem_object_put(obj);
 out_region:
-	intel_memory_region_put(mem);
+	intel_memory_region_destroy(mem);
 	return err;
 }