On Fri, Oct 18, 2019 at 8:16 PM Jens Axboe <axboe@xxxxxxxxx> wrote: > On 10/18/19 12:06 PM, Jann Horn wrote: > > But actually, by the way: Is this whole files_struct thing creating a > > reference loop? The files_struct has a reference to the uring file, > > and the uring file has ACCEPT work that has a reference to the > > files_struct. If the task gets killed and the accept work blocks, the > > entire files_struct will stay alive, right? > > Yes, for the lifetime of the request, it does create a loop. So if the > application goes away, I think you're right, the files_struct will stay. > And so will the io_uring, for that matter, as we depend on the closing > of the files to do the final reap. > > Hmm, not sure how best to handle that, to be honest. We need some way to > break the loop, if the request never finishes. A wacky and dubious approach would be to, instead of taking a reference to the files_struct, abuse f_op->flush() to synchronously flush out pending requests with references to the files_struct... But it's probably a bad idea, given that in f_op->flush(), you can't easily tell which files_struct the close is coming from. I suppose you could keep a list of (fdtable, fd) pairs through which ACCEPT requests have come in and then let f_op->flush() probe whether the file pointers are gone from them...
