On 11/20/2019 1:22 PM, Bob Liu wrote: > On 11/20/19 4:44 PM, Pavel Begunkov wrote: >> On 11/20/2019 1:33 AM, Jens Axboe wrote: >>> We currently clear the linked timeout field if we cancel such a timeout, >>> but we should only attempt to cancel if it's the first one we see. >>> Others should simply be freed like other requests, as they haven't >>> been started yet. >>> >>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> >>> >>> --- >>> >>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>> index a79ef43367b1..d1085e4e8ae9 100644 >>> --- a/fs/io_uring.c >>> +++ b/fs/io_uring.c >>> @@ -937,12 +937,12 @@ static void io_fail_links(struct io_kiocb *req) >>> if ((req->flags & REQ_F_LINK_TIMEOUT) && >>> link->submit.sqe->opcode == IORING_OP_LINK_TIMEOUT) { >>> io_link_cancel_timeout(link); >>> - req->flags &= ~REQ_F_LINK_TIMEOUT; >>> } else { >>> io_cqring_fill_event(link, -ECANCELED); >>> __io_double_put_req(link); >>> } >>> kfree(sqe_to_free); >>> + req->flags &= ~REQ_F_LINK_TIMEOUT; >> >> That's not necessary, but maybe would safer to keep. If >> REQ_F_LINK_TIMEOUT is set, than there was a link timeout request, >> and for it and only for it io_link_cancel_timeout() will be called. >> >> However, this is only true if linked timeout isn't fired. Otherwise, >> there is another bug, which isn't fixed by either of the patches. We >> need to clear REQ_F_LINK_TIMEOUT in io_link_timeout_fn() as well. >> >> Let: REQ -> L_TIMEOUT1 -> L_TIMEOUT2 >> 1. L_TIMEOUT1 fired before REQ is completed >> >> 2. io_link_timeout_fn() removes L_TIMEOUT1 from the list: >> REQ|REQ_F_LINK_TIMEOUT -> L_TIMEOUT2 >> >> 3. free_req(REQ) then call io_link_cancel_timeout(L_TIMEOUT2) >> leaking it (as described in my patch). >> >> P.S. haven't tried to test nor reproduce it yet. >> > > Off topic... I'm reading the code regarding IORING_OP_LINK_TIMEOUT. > But confused by what's going to happen if userspace submit a request with IORING_OP_LINK_TIMEOUT but not IOSQE_IO_LINK. > It fails in __io_submit_sqe() with -EINVAL. (see default branch in the switch). As for me, it's better to do it late, as it will generically handle dependant links (e.g. fail them properly). -- Pavel Begunkov