[PATCH] fixup! drm/msm: Separate locking of buffer resources from struct_mutex

[Rob Clark <robdclark-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

---
Ok, 2nd fixup to handle vmap shrinking.

 drivers/gpu/drm/msm/msm_gem.c | 44 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 36 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index f5d1f84..3190e05 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -42,6 +42,9 @@ enum {
 	OBJ_LOCK_SHRINKER,
 };
 
+static void msm_gem_vunmap_locked(struct drm_gem_object *obj);
+
+
 static dma_addr_t physaddr(struct drm_gem_object *obj)
 {
 	struct msm_gem_object *msm_obj = to_msm_bo(obj);
@@ -484,6 +487,7 @@ int msm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
 void *msm_gem_get_vaddr(struct drm_gem_object *obj)
 {
 	struct msm_gem_object *msm_obj = to_msm_bo(obj);
+	int ret = 0;
 
 	mutex_lock(&msm_obj->lock);
 
@@ -492,22 +496,35 @@ void *msm_gem_get_vaddr(struct drm_gem_object *obj)
 		return ERR_PTR(-EBUSY);
 	}
 
+	/* increment vmap_count *before* vmap() call, so shrinker can
+	 * check vmap_count (is_vunmapable()) outside of msm_obj->lock.
+	 * This guarantees that we won't try to msm_gem_vunmap() this
+	 * same object from within the vmap() call (while we already
+	 * hold msm_obj->lock)
+	 */
+	msm_obj->vmap_count++;
+
 	if (!msm_obj->vaddr) {
 		struct page **pages = get_pages(obj);
 		if (IS_ERR(pages)) {
-			mutex_unlock(&msm_obj->lock);
-			return ERR_CAST(pages);
+			ret = PTR_ERR(pages);
+			goto fail;
 		}
 		msm_obj->vaddr = vmap(pages, obj->size >> PAGE_SHIFT,
 				VM_MAP, pgprot_writecombine(PAGE_KERNEL));
 		if (msm_obj->vaddr == NULL) {
-			mutex_unlock(&msm_obj->lock);
-			return ERR_PTR(-ENOMEM);
+			ret = -ENOMEM;
+			goto fail;
 		}
 	}
-	msm_obj->vmap_count++;
+
 	mutex_unlock(&msm_obj->lock);
 	return msm_obj->vaddr;
+
+fail:
+	msm_obj->vmap_count--;
+	mutex_unlock(&msm_obj->lock);
+	return ERR_PTR(ret);
 }
 
 void msm_gem_put_vaddr(struct drm_gem_object *obj)
@@ -554,7 +571,7 @@ void msm_gem_purge(struct drm_gem_object *obj)
 
 	put_iova(obj);
 
-	msm_gem_vunmap(obj);
+	msm_gem_vunmap_locked(obj);
 
 	put_pages(obj);
 
@@ -576,10 +593,12 @@ void msm_gem_purge(struct drm_gem_object *obj)
 	mutex_unlock(&msm_obj->lock);
 }
 
-void msm_gem_vunmap(struct drm_gem_object *obj)
+static void msm_gem_vunmap_locked(struct drm_gem_object *obj)
 {
 	struct msm_gem_object *msm_obj = to_msm_bo(obj);
 
+	WARN_ON(!mutex_is_locked(&msm_obj->lock));
+
 	if (!msm_obj->vaddr || WARN_ON(!is_vunmapable(msm_obj)))
 		return;
 
@@ -587,6 +606,15 @@ void msm_gem_vunmap(struct drm_gem_object *obj)
 	msm_obj->vaddr = NULL;
 }
 
+void msm_gem_vunmap(struct drm_gem_object *obj)
+{
+	struct msm_gem_object *msm_obj = to_msm_bo(obj);
+
+	mutex_lock_nested(&msm_obj->lock, OBJ_LOCK_SHRINKER);
+	msm_gem_vunmap_locked(obj);
+	mutex_unlock(&msm_obj->lock);
+}
+
 /* must be called before _move_to_active().. */
 int msm_gem_sync_object(struct drm_gem_object *obj,
 		struct msm_fence_context *fctx, bool exclusive)
@@ -799,7 +827,7 @@ void msm_gem_free_object(struct drm_gem_object *obj)
 
 		drm_prime_gem_destroy(obj, msm_obj->sgt);
 	} else {
-		msm_gem_vunmap(obj);
+		msm_gem_vunmap_locked(obj);
 		put_pages(obj);
 	}
 
-- 
2.9.4

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