cramfs: fix usage on non-MTD device

When both CONFIG_CRAMFS_MTD and CONFIG_CRAMFS_BLOCKDEV are enabled, if
we fail to mount on MTD, we don't try on block device.

Note: this relies upon cramfs_mtd_fill_super() leaving no side
effects on fc state in case of failure; in general, failing
get_tree_...() does *not* mean "fine to try again"; e.g. parsed
options might've been consumed by fill_super callback and freed
on failure.

Fixes: 74f78fc5ef43 ("vfs: Convert cramfs to use the new mount API")

Signed-off-by: Maxime Bizon <[e-mail]>
Signed-off-by: Nicolas Pitre <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/cramfs/inode.c

···
 
 	if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
 		ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
-		if (ret < 0)
-			return ret;
+		if (!ret)
+			return 0;
 	}
 	if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
 		ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);