On Thu, Mar 12, 2020 at 10:07:57AM +0000, David Howells wrote: > David Howells <dhowells@xxxxxxxxxx> wrote: > > > Is ext4_dio_read_iter() broken? It calls: > > > > file_accessed(iocb->ki_filp); > > > > at the end of the function - but surely iocb should be expected to have been > > freed when iocb->ki_complete() was called? The iocb is refcounted and only completed when the refcount hits zero, and an extra reference is held until the submission has completed. Take a look at iocb_put(). > I think it's actually worse than that. You also can't call > inode_unlock_shared(inode) because you no longer own a ref on the inode since > ->ki_complete() is expected to call fput() on iocb->ki_filp. the file reference also hold an inode reference. > > Yes, you own a shared lock on it, but unless somewhere along the > fput-dput-iput chain the inode lock is taken exclusively, the inode can be > freed whilst you're still holding the lock. > > Oh - and ext4_dax_read_iter() is also similarly broken. In addition to that DAX never executes asynchronously. > And xfs_file_dio_aio_read() appears to be broken as it touches the inode after > calling iomap_dio_rw() to unlock it. Same as above.
