drm/gem: add shmem get/put page helpers

Basically just extracting some code duplicated in gma500, omapdrm, udl,
and upcoming msm driver.
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_gem.c

@@ -358,6 +358,109 @@ int drm_gem_create_mmap_offset(struct drm_gem_object *obj)
 }
 EXPORT_SYMBOL(drm_gem_create_mmap_offset);
 
+/**
+ * drm_gem_get_pages - helper to allocate backing pages for a GEM object
+ * from shmem
+ * @obj: obj in question
+ * @gfpmask: gfp mask of requested pages
+ */
+struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask)
+{
+	struct inode *inode;
+	struct address_space *mapping;
+	struct page *p, **pages;
+	int i, npages;
+
+	/* This is the shared memory object that backs the GEM resource */
+	inode = file_inode(obj->filp);
+	mapping = inode->i_mapping;
+
+	/* We already BUG_ON() for non-page-aligned sizes in
+	 * drm_gem_object_init(), so we should never hit this unless
+	 * driver author is doing something really wrong:
+	 */
+	WARN_ON((obj->size & (PAGE_SIZE - 1)) != 0);
+
+	npages = obj->size >> PAGE_SHIFT;
+
+	pages = drm_malloc_ab(npages, sizeof(struct page *));
+	if (pages == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	gfpmask |= mapping_gfp_mask(mapping);
+
+	for (i = 0; i < npages; i++) {
+		p = shmem_read_mapping_page_gfp(mapping, i, gfpmask);
+		if (IS_ERR(p))
+			goto fail;
+		pages[i] = p;
+
+		/* There is a hypothetical issue w/ drivers that require
+		 * buffer memory in the low 4GB.. if the pages are un-
+		 * pinned, and swapped out, they can end up swapped back
+		 * in above 4GB.  If pages are already in memory, then
+		 * shmem_read_mapping_page_gfp will ignore the gfpmask,
+		 * even if the already in-memory page disobeys the mask.
+		 *
+		 * It is only a theoretical issue today, because none of
+		 * the devices with this limitation can be populated with
+		 * enough memory to trigger the issue.  But this BUG_ON()
+		 * is here as a reminder in case the problem with
+		 * shmem_read_mapping_page_gfp() isn't solved by the time
+		 * it does become a real issue.
+		 *
+		 * See this thread: http://lkml.org/lkml/2011/7/11/238
+		 */
+		BUG_ON((gfpmask & __GFP_DMA32) &&
+				(page_to_pfn(p) >= 0x00100000UL));
+	}
+
+	return pages;
+
+fail:
+	while (i--)
+		page_cache_release(pages[i]);
+
+	drm_free_large(pages);
+	return ERR_CAST(p);
+}
+EXPORT_SYMBOL(drm_gem_get_pages);
+
+/**
+ * drm_gem_put_pages - helper to free backing pages for a GEM object
+ * @obj: obj in question
+ * @pages: pages to free
+ * @dirty: if true, pages will be marked as dirty
+ * @accessed: if true, the pages will be marked as accessed
+ */
+void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
+		bool dirty, bool accessed)
+{
+	int i, npages;
+
+	/* We already BUG_ON() for non-page-aligned sizes in
+	 * drm_gem_object_init(), so we should never hit this unless
+	 * driver author is doing something really wrong:
+	 */
+	WARN_ON((obj->size & (PAGE_SIZE - 1)) != 0);
+
+	npages = obj->size >> PAGE_SHIFT;
+
+	for (i = 0; i < npages; i++) {
+		if (dirty)
+			set_page_dirty(pages[i]);
+
+		if (accessed)
+			mark_page_accessed(pages[i]);
+
+		/* Undo the reference we took when populating the table */
+		page_cache_release(pages[i]);
+	}
+
+	drm_free_large(pages);
+}
+EXPORT_SYMBOL(drm_gem_put_pages);
+
 /** Returns a reference to the object named by the handle. */
 struct drm_gem_object *
 drm_gem_object_lookup(struct drm_device *dev, struct drm_file *filp,

include/drm/drmP.h

@@ -1616,6 +1616,10 @@ void drm_gem_free_mmap_offset(struct drm_gem_object *obj);
 int drm_gem_create_mmap_offset(struct drm_gem_object *obj);
 int drm_gem_create_mmap_offset_size(struct drm_gem_object *obj, size_t size);
 
+struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask);
+void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
+		bool dirty, bool accessed);
+
 struct drm_gem_object *drm_gem_object_lookup(struct drm_device *dev,
 					     struct drm_file *filp,
 					     u32 handle);