drm/exynos: use alloc_page() to allocate pages.

shmem_read_mapping_page_gfp() first tries to allocate pages from page cache
so if pages are allocated from page cache then these pages could have
valid cache line. after that cpu may read garbage data from cache
once gpu operation is completed with allocated pages. so with this patch,
Non-contiguous memory allocation request allocates pages from highmem
through alloc_page() with GFP_HIGHUSER_MOVABLE.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
index acb9f42..47696bb 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
@@ -99,25 +99,17 @@
 struct page **exynos_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 = obj->filp->f_path.dentry->d_inode;
-	mapping = inode->i_mapping;
-
 	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);
+		p = alloc_page(gfpmask);
 		if (IS_ERR(p))
 			goto fail;
 		pages[i] = p;
@@ -127,7 +119,7 @@
 
 fail:
 	while (i--)
-		page_cache_release(pages[i]);
+		__free_page(pages[i]);
 
 	drm_free_large(pages);
 	return ERR_PTR(PTR_ERR(p));
@@ -189,7 +181,7 @@
 		return -EINVAL;
 	}
 
-	pages = exynos_gem_get_pages(obj, GFP_KERNEL);
+	pages = exynos_gem_get_pages(obj, GFP_HIGHUSER_MOVABLE);
 	if (IS_ERR(pages)) {
 		DRM_ERROR("failed to get pages.\n");
 		return PTR_ERR(pages);