drm/i915: Refactor duplicate object vmap functions

We now have two implementations for vmapping a whole object, one for
dma-buf and one for the ringbuffer. If we couple the mapping into the
obj->pages lifetime, then we can reuse an obj->mapping for both and at
the same time couple it into the shrinker. There is a third vmapping
routine in the cmdparser that maps only a range within the object, for
the time being that is left alone, but will eventually use these routines
in order to cache the mapping between invocations.

v2: Mark the failable kmalloc() as __GFP_NOWARN (vsyrjala)
v3: Call unpin_vmap from the right dmabuf unmapper

v4: Rename vmap to map as we don't wish to imply the type of mapping
involved, just that it contiguously maps the object into kernel space.
Add kerneldoc and lockdep annotations

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460113874-17366-4-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>

4 files changed, 84 insertions, 72 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 542401659013..c262d5184e12 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2169,10 +2169,7 @@ struct drm_i915_gem_object {
 		struct scatterlist *sg;
 		int last;
 	} get_page;
-
-	/* prime dma-buf support */
-	void *dma_buf_vmapping;
-	int vmapping_count;
+	void *mapping;
 
 	/** Breadcrumb of last rendering to the buffer.
 	 * There can only be one writer, but we allow for multiple readers.
@@ -2988,12 +2985,44 @@ static inline void i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
 	BUG_ON(obj->pages == NULL);
 	obj->pages_pin_count++;
 }
+
 static inline void i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
 {
 	BUG_ON(obj->pages_pin_count == 0);
 	obj->pages_pin_count--;
 }
 
+/**
+ * i915_gem_object_pin_map - return a contiguous mapping of the entire object
+ * @obj - the object to map into kernel address space
+ *
+ * Calls i915_gem_object_pin_pages() to prevent reaping of the object's
+ * pages and then returns a contiguous mapping of the backing storage into
+ * the kernel address space.
+ *
+ * The caller must hold the struct_mutex.
+ *
+ * Returns the pointer through which to access the backing storage.
+ */
+void *__must_check i915_gem_object_pin_map(struct drm_i915_gem_object *obj);
+
+/**
+ * i915_gem_object_unpin_map - releases an earlier mapping
+ * @obj - the object to unmap
+ *
+ * After pinning the object and mapping its pages, once you are finished
+ * with your access, call i915_gem_object_unpin_map() to release the pin
+ * upon the mapping. Once the pin count reaches zero, that mapping may be
+ * removed.
+ *
+ * The caller must hold the struct_mutex.
+ */
+static inline void i915_gem_object_unpin_map(struct drm_i915_gem_object *obj)
+{
+	lockdep_assert_held(&obj->base.dev->struct_mutex);
+	i915_gem_object_unpin_pages(obj);
+}
+
 int __must_check i915_mutex_lock_interruptible(struct drm_device *dev);
 int i915_gem_object_sync(struct drm_i915_gem_object *obj,
 			 struct intel_engine_cs *to,
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 339d183f05b0..55ad50bc3921 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2232,6 +2232,11 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
 	 * lists early. */
 	list_del(&obj->global_list);
 
+	if (obj->mapping) {
+		vunmap(obj->mapping);
+		obj->mapping = NULL;
+	}
+
 	ops->put_pages(obj);
 	obj->pages = NULL;
 
@@ -2400,6 +2405,45 @@ i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	return 0;
 }
 
+void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj)
+{
+	int ret;
+
+	lockdep_assert_held(&obj->base.dev->struct_mutex);
+
+	ret = i915_gem_object_get_pages(obj);
+	if (ret)
+		return ERR_PTR(ret);
+
+	i915_gem_object_pin_pages(obj);
+
+	if (obj->mapping == NULL) {
+		struct sg_page_iter sg_iter;
+		struct page **pages;
+		int n;
+
+		n = obj->base.size >> PAGE_SHIFT;
+		pages = kmalloc(n*sizeof(*pages), GFP_TEMPORARY | __GFP_NOWARN);
+		if (pages == NULL)
+			pages = drm_malloc_ab(n, sizeof(*pages));
+		if (pages != NULL) {
+			n = 0;
+			for_each_sg_page(obj->pages->sgl, &sg_iter,
+					 obj->pages->nents, 0)
+				pages[n++] = sg_page_iter_page(&sg_iter);
+
+			obj->mapping = vmap(pages, n, 0, PAGE_KERNEL);
+			drm_free_large(pages);
+		}
+		if (obj->mapping == NULL) {
+			i915_gem_object_unpin_pages(obj);
+			return ERR_PTR(-ENOMEM);
+		}
+	}
+
+	return obj->mapping;
+}
+
 void i915_vma_move_to_active(struct i915_vma *vma,
 			     struct drm_i915_gem_request *req)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 616f07830b7e..4e60643ef53a 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -108,51 +108,17 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 {
 	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
 	struct drm_device *dev = obj->base.dev;
-	struct sg_page_iter sg_iter;
-	struct page **pages;
-	int ret, i;
+	void *addr;
+	int ret;
 
 	ret = i915_mutex_lock_interruptible(dev);
 	if (ret)
 		return ERR_PTR(ret);
 
-	if (obj->dma_buf_vmapping) {
-		obj->vmapping_count++;
-		goto out_unlock;
-	}
-
-	ret = i915_gem_object_get_pages(obj);
-	if (ret)
-		goto err;
-
-	i915_gem_object_pin_pages(obj);
-
-	ret = -ENOMEM;
-
-	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
-	if (pages == NULL)
-		goto err_unpin;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
-		pages[i++] = sg_page_iter_page(&sg_iter);
-
-	obj->dma_buf_vmapping = vmap(pages, i, 0, PAGE_KERNEL);
-	drm_free_large(pages);
-
-	if (!obj->dma_buf_vmapping)
-		goto err_unpin;
-
-	obj->vmapping_count = 1;
-out_unlock:
+	addr = i915_gem_object_pin_map(obj);
 	mutex_unlock(&dev->struct_mutex);
-	return obj->dma_buf_vmapping;
 
-err_unpin:
-	i915_gem_object_unpin_pages(obj);
-err:
-	mutex_unlock(&dev->struct_mutex);
-	return ERR_PTR(ret);
+	return addr;
 }
 
 static void i915_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
@@ -161,12 +127,7 @@ static void i915_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
 	struct drm_device *dev = obj->base.dev;
 
 	mutex_lock(&dev->struct_mutex);
-	if (--obj->vmapping_count == 0) {
-		vunmap(obj->dma_buf_vmapping);
-		obj->dma_buf_vmapping = NULL;
-
-		i915_gem_object_unpin_pages(obj);
-	}
+	i915_gem_object_unpin_map(obj);
 	mutex_unlock(&dev->struct_mutex);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index a6e187620c41..41b604e69db7 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2083,35 +2083,13 @@ static int init_phys_status_page(struct intel_engine_cs *engine)
 void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 {
 	if (HAS_LLC(ringbuf->obj->base.dev) && !ringbuf->obj->stolen)
-		vunmap(ringbuf->virtual_start);
+		i915_gem_object_unpin_map(ringbuf->obj);
 	else
 		iounmap(ringbuf->virtual_start);
-	ringbuf->virtual_start = NULL;
 	ringbuf->vma = NULL;
 	i915_gem_object_ggtt_unpin(ringbuf->obj);
 }
 
-static u32 *vmap_obj(struct drm_i915_gem_object *obj)
-{
-	struct sg_page_iter sg_iter;
-	struct page **pages;
-	void *addr;
-	int i;
-
-	pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
-	if (pages == NULL)
-		return NULL;
-
-	i = 0;
-	for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
-		pages[i++] = sg_page_iter_page(&sg_iter);
-
-	addr = vmap(pages, i, 0, PAGE_KERNEL);
-	drm_free_large(pages);
-
-	return addr;
-}
-
 int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 				     struct intel_ringbuffer *ringbuf)
 {
@@ -2129,7 +2107,7 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 		if (ret)
 			goto err_unpin;
 
-		ringbuf->virtual_start = vmap_obj(obj);
+		ringbuf->virtual_start = i915_gem_object_pin_map(obj);
 		if (ringbuf->virtual_start == NULL) {
 			ret = -ENOMEM;
 			goto err_unpin;