On Thu, Sep 29, 2016 at 12:56:49PM +0000, Anton Altaparmakov wrote: > Hi Al, > > > On 29 Sep 2016, at 13:17, Al Viro <[email protected]> wrote: > > > > On Thu, Sep 29, 2016 at 11:53:21AM +0000, Anton Altaparmakov wrote: > >> Thus if the events happen in this order: > >> > >> evict_inodes() iget_locked() in > >> find_inode_fast() > > > > ... you are buggered, because somebody is trying to grab a reference > > to inode on a filesystem that is being shut down. Look at evict_inode() > > caller... > > But what if that somebody is simply the file system being shutdown trying to > flush some dirty metadata to disk which is stored in a file and thus accessed > via an inode and thus iget on the inode is needed? Surely that is allowed > even during shutdown. Once the write is complete iput() is called which then > immediately evicts the inode as MS_ACTIVE is clear...
If it's a per-superblock inode, just keep it referenced until ->put_super() and be done with that. Besides, the caller has just done sync_filesystem() there, so any dirty metadata would better be already flushed.
