[PATCH v3 0/2] bfs: fix null-ptr-deref and possible warning in bfs_move_block() func

https://syzkaller.appspot.com/bug?extid=d98fd19acd08b36ff422

[PATCH v3 1/2] bfs: prevent null pointer dereference in bfs_move_block() v3: Changed the error handling

[PATCH v3 2/2] bfs: ensure buffer is marked uptodate before marking it dirty v3: Replaced the buffer up-to-date check with an error exit by forcefully setting the buffer as up-to-date before call mark_buffer_dirty()