drm/ttm: use shmem_read_mapping_page

Soon tmpfs will stop supporting ->readpage and read_mapping_page(): once
"tmpfs: add shmem_read_mapping_page_gfp" has been applied, this patch can
be applied to ease the transition.

ttm_tt_swapin() and ttm_tt_swapout() use shmem_read_mapping_page() in
place of read_mapping_page(), since their swap_space has been created with
shmem_file_setup().
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpu/drm/ttm/ttm_tt.c

@@ -31,6 +31,7 @@
 #include <linux/sched.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
+#include <linux/shmem_fs.h>
 #include <linux/file.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
@@ -484,7 +485,7 @@ static int ttm_tt_swapin(struct ttm_tt *ttm)
 	swap_space = swap_storage->f_path.dentry->d_inode->i_mapping;
 
 	for (i = 0; i < ttm->num_pages; ++i) {
-		from_page = read_mapping_page(swap_space, i, NULL);
+		from_page = shmem_read_mapping_page(swap_space, i);
 		if (IS_ERR(from_page)) {
 			ret = PTR_ERR(from_page);
 			goto out_err;
@@ -557,7 +558,7 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistent_swap_storage)
 		from_page = ttm->pages[i];
 		if (unlikely(from_page == NULL))
 			continue;
-		to_page = read_mapping_page(swap_space, i, NULL);
+		to_page = shmem_read_mapping_page(swap_space, i);
 		if (unlikely(IS_ERR(to_page))) {
 			ret = PTR_ERR(to_page);
 			goto out_err;