Hi Al, I'm not sure about the in-tree fs, but in zfsonlinux, it would offload iput to a thread, so this would happen there. And it would wait for the thread in put_super(), so that part is not a problem...
Thanks 2016-07-11 17:46 GMT-07:00 Al Viro <v...@zeniv.linux.org.uk>: > On Mon, Jul 11, 2016 at 05:15:04PM -0700, Chunwei Chen wrote: >> We need to check i_count again with i_lock held, because iput might re-add >> i_count when lazytime is on. Without this check, we could end up with >> double-free or use-after-free. > > Details, please. Ideally - with a reproducer. Who is calling that iput() > at that point of generic_shutdown_super() (has to be another thread) and > just what will happen if the same iput() is delayed until *after* > evict_inodes(), all the way into ->put_super(). At which point there's > no promise whatsoever that the data structures used by ->evict_inode() > hadn't been already freed... >
