[PATCH 31/39] drm/i915: Allow page pinning to be in the background

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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@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.c    |  1 +
 drivers/gpu/drm/i915/gem/i915_gem_object.h    |  7 +--
 .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 ++
 drivers/gpu/drm/i915/gem/i915_gem_pages.c     | 53 +++++++++++++++----
 4 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index 1ad53cddd425..588e0ca285e1 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -65,6 +65,7 @@ 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);
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 67d70d144bd9..7ea8013d108f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -234,7 +234,7 @@ 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);
 
@@ -244,6 +244,9 @@ 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)
 {
@@ -267,9 +270,7 @@ i915_gem_object_has_pinned_pages(struct drm_i915_gem_object *obj)
 static inline void
 __i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
 {
-	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
-
 	atomic_dec(&obj->mm.pages_pin_count);
 }
 
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 e87fca4d8194..8f61d7a93078 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 b36ad269f4ea..6bec301cee79 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -73,21 +73,18 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 
 		spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
 	}
+
+	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
@@ -105,7 +102,7 @@ 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);
@@ -121,6 +118,32 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	return err;
 }
 
+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;
+
+	if (IS_ERR(obj->mm.pages)) {
+		err = PTR_ERR(obj->mm.pages);
+		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;
+}
+
 /* Immediately discard the backing storage */
 void i915_gem_object_truncate(struct drm_i915_gem_object *obj)
 {
@@ -201,6 +224,9 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
 
 	GEM_BUG_ON(atomic_read(&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))) {
@@ -227,6 +253,7 @@ 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);
@@ -304,7 +331,7 @@ 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);
@@ -316,7 +343,6 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 		atomic_inc(&obj->mm.pages_pin_count);
 		pinned = false;
 	}
-	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 
 	ptr = page_unpack_bits(obj->mm.mapping, &has_type);
 	if (ptr && has_type != type) {
@@ -334,6 +360,15 @@ 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;
+
+		if (IS_ERR(obj->mm.pages)) {
+			err = PTR_ERR(obj->mm.pages);
+			goto err_unpin;
+		}
+
 		ptr = i915_gem_object_map(obj, type);
 		if (!ptr) {
 			err = -ENOMEM;
-- 
2.20.1

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