f2fs: fix to restrict mount condition on readonly block device

When we mount an unclean f2fs image in a readonly block device, let's
make mount() succeed only when there is no recoverable data in that
image, otherwise after mount(), file fsyned won't be recovered as user
expected.

Fixes: 938a1842 ("f2fs: give a warning only for readonly partition")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -3966,10 +3966,18 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 		 * previous checkpoint was not done by clean system shutdown.
 		 */
 		if (f2fs_hw_is_readonly(sbi)) {
-			if (!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG))
-				f2fs_err(sbi, "Need to recover fsync data, but write access unavailable");
-			else
-				f2fs_info(sbi, "write access unavailable, skipping recovery");
+			if (!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) {
+				err = f2fs_recover_fsync_data(sbi, true);
+				if (err > 0) {
+					err = -EROFS;
+					f2fs_err(sbi, "Need to recover fsync data, but "
+						"write access unavailable, please try "
+						"mount w/ disable_roll_forward or norecovery");
+				}
+				if (err < 0)
+					goto free_meta;
+			}
+			f2fs_info(sbi, "write access unavailable, skipping recovery");
 			goto reset_checkpoint;
 		}