f2fs: handle error of f2fs_iget correctly

In recover_orphan_inode, whenever f2fs_iget fail, we will make kernel panic,
but it's not reasonable, because f2fs_iget can fail due to a lot of reasons
including out of memory.

So we change error handling method as below:
a) when finding no entry for the orphan inode, bug_on for catching bugs;
b) for other reasons, report it to caller.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index a79b6b5..4db5cd9 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1245,7 +1245,9 @@
 	f2fs_join_shrinker(sbi);
 
 	/* if there are nt orphan nodes free them */
-	recover_orphan_inodes(sbi);
+	err = recover_orphan_inodes(sbi);
+	if (err)
+		goto free_node_inode;
 
 	/* read root inode and dentry */
 	root = f2fs_iget(sb, F2FS_ROOT_INO(sbi));