On 11/20/19 7:07 PM, Pavel Begunkov wrote: > 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). > I see, thanks. As for me, it may better return -EINVAL in advance so as to skip a lot unnecessary code for those reqs. @@ -3176,6 +3176,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, if (!io_get_sqring(ctx, &req->submit)) { } ... + if (unlikely(req_is_invalid(req))) + return -EINVAL;