[PATCH 14/18] drm/i915: Allow page pinning to be in the background

[Chris Wilson]

Assume that pages may be pinned in a background task and use a
completion event to synchronise with callers that must access the pages
immediately.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.c    |  1 +
 drivers/gpu/drm/i915/gem/i915_gem_object.h    |  5 ++-
 .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 ++
 drivers/gpu/drm/i915/gem/i915_gem_pages.c     | 42 +++++++++++++++----
 4 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index e5e707b1a73c..e830609ea6fb 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -98,6 +98,7 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 	obj->mm.madv = I915_MADV_WILLNEED;
 	INIT_RADIX_TREE(&obj->mm.get_page.radix, GFP_KERNEL | __GFP_NOWARN);
 	mutex_init(&obj->mm.get_page.lock);
+	init_completion(&obj->mm.completion);
 
 	i915_gem_info_add_obj(to_i915(obj->base.dev), obj->base.size);
 }
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 7cb1871d7128..0c27dd5bb8a2 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -240,7 +240,7 @@ int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
 int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
 
 static inline int __must_check
-i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
+i915_gem_object_pin_pages_async(struct drm_i915_gem_object *obj)
 {
 	might_lock(&obj->mm.lock);
 
@@ -250,6 +250,9 @@ i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
 	return __i915_gem_object_get_pages(obj);
 }
 
+int __must_check
+i915_gem_object_pin_pages(struct drm_i915_gem_object *obj);
+
 static inline bool
 i915_gem_object_has_pages(struct drm_i915_gem_object *obj)
 {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 9c161ba73558..00835353368a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -7,6 +7,7 @@
 #ifndef __I915_GEM_OBJECT_TYPES_H__
 #define __I915_GEM_OBJECT_TYPES_H__
 
+#include <linux/completion.h>
 #include <linux/reservation.h>
 
 #include <drm/drm_gem.h>
@@ -210,6 +211,8 @@ struct drm_i915_gem_object {
 		 */
 		struct list_head link;
 
+		struct completion completion;
+
 		/**
 		 * Advice: are the backing pages purgeable?
 		 */
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index e53860147f21..6dfaa3ed6937 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -8,6 +8,27 @@
 #include "i915_gem_object.h"
 #include "i915_scatterlist.h"
 
+int i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
+{
+	int err;
+
+	err = i915_gem_object_pin_pages_async(obj);
+	if (err)
+		return err;
+
+	err = wait_for_completion_interruptible(&obj->mm.completion);
+	if (err)
+		goto err_unpin;
+
+	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
+	return 0;
+
+err_unpin:
+	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
+	atomic_dec(&obj->mm.pages_pin_count);
+	return err;
+}
+
 void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 				 struct sg_table *pages,
 				 unsigned int sg_page_sizes)
@@ -59,21 +80,18 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 	spin_lock(&i915->mm.obj_lock);
 	list_add(&obj->mm.link, &i915->mm.unbound_list);
 	spin_unlock(&i915->mm.obj_lock);
+
+	complete_all(&obj->mm.completion);
 }
 
 int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 {
-	int err;
-
 	if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
 		DRM_DEBUG("Attempting to obtain a purgeable object\n");
 		return -EFAULT;
 	}
 
-	err = obj->ops->get_pages(obj);
-	GEM_BUG_ON(!err && !i915_gem_object_has_pages(obj));
-
-	return err;
+	return obj->ops->get_pages(obj);
 }
 
 /* Ensure that the associated pages are gathered from the backing storage
@@ -91,7 +109,7 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	if (err)
 		return err;
 
-	if (unlikely(!i915_gem_object_has_pages(obj))) {
+	if (!obj->mm.pages) {
 		GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 
 		err = ____i915_gem_object_get_pages(obj);
@@ -179,6 +197,9 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
 
 	GEM_BUG_ON(obj->bind_count);
 
+	if (obj->mm.pages == ERR_PTR(-EAGAIN))
+		wait_for_completion(&obj->mm.completion);
+
 	/* May be called by shrinker from within get_pages() (on another bo) */
 	mutex_lock_nested(&obj->mm.lock, subclass);
 	if (unlikely(atomic_read(&obj->mm.pages_pin_count))) {
@@ -205,6 +226,7 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
 	if (!IS_ERR(pages))
 		obj->ops->put_pages(obj, pages);
 
+	reinit_completion(&obj->mm.completion);
 	err = 0;
 unlock:
 	mutex_unlock(&obj->mm.lock);
@@ -282,7 +304,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 	type &= ~I915_MAP_OVERRIDE;
 
 	if (!atomic_inc_not_zero(&obj->mm.pages_pin_count)) {
-		if (unlikely(!i915_gem_object_has_pages(obj))) {
+		if (!obj->mm.pages) {
 			GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 
 			err = ____i915_gem_object_get_pages(obj);
@@ -312,6 +334,10 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 	}
 
 	if (!ptr) {
+		err = wait_for_completion_interruptible(&obj->mm.completion);
+		if (err)
+			goto err_unpin;
+
 		ptr = i915_gem_object_map(obj, type);
 		if (!ptr) {
 			err = -ENOMEM;
-- 
2.20.1