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: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_gem.c

@@ -99,25 +99,17 @@ static unsigned long roundup_gem_size(unsigned long size, unsigned int flags)
 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 @@ struct page **exynos_gem_get_pages(struct drm_gem_object *obj,
 
 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 @@ static int exynos_drm_gem_get_pages(struct drm_gem_object *obj)
 		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);