+/**
+ * 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));