drm/msm: Acquire reservation lock in GEM pin/unpin callback

Export msm_gem_pin_pages_locked() and acquire the reservation lock
directly in GEM pin callback. Same for unpin. Prepares for further
changes.

Dma-buf locking semantics require callers to hold the buffer's
reservation lock when invoking the pin and unpin callbacks. Prepare
msm accordingly by pushing locking out of the implementation. A
follow-up patch will fix locking for all GEM code at once.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Dmitry Osipenko <[e-mail]>
Tested-by: Dmitry Osipenko <[e-mail]> # virtio-gpu
Acked-by: Christian König <[e-mail]>
Acked-by: Zack Rusin <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/msm/msm_gem.c

···
 	mutex_unlock(&priv->lru.lock);
 }
 
-struct page **msm_gem_pin_pages(struct drm_gem_object *obj)
+struct page **msm_gem_pin_pages_locked(struct drm_gem_object *obj)
 {
 	struct page **p;
 
-	msm_gem_lock(obj);
+	msm_gem_assert_locked(obj);
+
 	p = msm_gem_get_pages_locked(obj, MSM_MADV_WILLNEED);
 	if (!IS_ERR(p))
 		pin_obj_locked(obj);
-	msm_gem_unlock(obj);
 
 	return p;
 }
 
-void msm_gem_unpin_pages(struct drm_gem_object *obj)
+void msm_gem_unpin_pages_locked(struct drm_gem_object *obj)
 {
-	msm_gem_lock(obj);
+	msm_gem_assert_locked(obj);
+
 	msm_gem_unpin_locked(obj);
-	msm_gem_unlock(obj);
 }
 
 static pgprot_t msm_gem_pgprot(struct msm_gem_object *msm_obj, pgprot_t prot)

drivers/gpu/drm/msm/msm_gem.h

···
 void msm_gem_unpin_iova(struct drm_gem_object *obj,
 		struct msm_gem_address_space *aspace);
 void msm_gem_pin_obj_locked(struct drm_gem_object *obj);
-struct page **msm_gem_pin_pages(struct drm_gem_object *obj);
-void msm_gem_unpin_pages(struct drm_gem_object *obj);
+struct page **msm_gem_pin_pages_locked(struct drm_gem_object *obj);
+void msm_gem_unpin_pages_locked(struct drm_gem_object *obj);
 int msm_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
 		struct drm_mode_create_dumb *args);
 int msm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,

drivers/gpu/drm/msm/msm_gem_prime.c

···
 
 int msm_gem_prime_pin(struct drm_gem_object *obj)
 {
-	if (!obj->import_attach)
-		msm_gem_pin_pages(obj);
-	return 0;
+	struct page **pages;
+	int ret = 0;
+
+	if (obj->import_attach)
+		return 0;
+
+	msm_gem_lock(obj);
+	pages = msm_gem_pin_pages_locked(obj);
+	if (IS_ERR(pages))
+		ret = PTR_ERR(pages);
+	msm_gem_unlock(obj);
+
+	return ret;
 }
 
 void msm_gem_prime_unpin(struct drm_gem_object *obj)
 {
-	if (!obj->import_attach)
-		msm_gem_unpin_pages(obj);
+	if (obj->import_attach)
+		return;
+
+	msm_gem_lock(obj);
+	msm_gem_unpin_pages_locked(obj);
+	msm_gem_unlock(obj);
 }