On Sun, Mar 17, 2024 at 08:40:59PM -0600, Jens Axboe wrote: > On 3/17/24 8:32 PM, Pavel Begunkov wrote: > > On 3/18/24 02:25, Jens Axboe wrote: > >> On 3/17/24 8:23 PM, Ming Lei wrote: > >>> On Mon, Mar 18, 2024 at 12:41:47AM +0000, Pavel Begunkov wrote: > >>>> !IO_URING_F_UNLOCKED does not translate to availability of the deferred > >>>> completion infra, IO_URING_F_COMPLETE_DEFER does, that what we should > >>>> pass and look for to use io_req_complete_defer() and other variants. > >>>> > >>>> Luckily, it's not a real problem as two wrongs actually made it right, > >>>> at least as far as io_uring_cmd_work() goes. > >>>> > >>>> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> > >>>> Link: https://lore.kernel.org/r/eb08e72e837106963bc7bc7dccfd93d646cc7f36.1710514702.git.asml.silence@xxxxxxxxx > >>>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> > > > > oops, I should've removed all the signed-offs > > > >>>> --- > >>>> io_uring/uring_cmd.c | 10 ++++++++-- > >>>> 1 file changed, 8 insertions(+), 2 deletions(-) > >>>> > >>>> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c > >>>> index f197e8c22965..ec38a8d4836d 100644 > >>>> --- a/io_uring/uring_cmd.c > >>>> +++ b/io_uring/uring_cmd.c > >>>> @@ -56,7 +56,11 @@ EXPORT_SYMBOL_GPL(io_uring_cmd_mark_cancelable); > >>>> static void io_uring_cmd_work(struct io_kiocb *req, struct io_tw_state *ts) > >>>> { > >>>> struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd); > >>>> - unsigned issue_flags = ts->locked ? 0 : IO_URING_F_UNLOCKED; > >>>> + unsigned issue_flags = IO_URING_F_UNLOCKED; > >>>> + > >>>> + /* locked task_work executor checks the deffered list completion */ > >>>> + if (ts->locked) > >>>> + issue_flags = IO_URING_F_COMPLETE_DEFER; > >>>> ioucmd->task_work_cb(ioucmd, issue_flags); > >>>> } > >>>> @@ -100,7 +104,9 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2, > >>>> if (req->ctx->flags & IORING_SETUP_IOPOLL) { > >>>> /* order with io_iopoll_req_issued() checking ->iopoll_complete */ > >>>> smp_store_release(&req->iopoll_completed, 1); > >>>> - } else if (!(issue_flags & IO_URING_F_UNLOCKED)) { > >>>> + } else if (issue_flags & IO_URING_F_COMPLETE_DEFER) { > >>>> + if (WARN_ON_ONCE(issue_flags & IO_URING_F_UNLOCKED)) > >>>> + return; > >>>> io_req_complete_defer(req); > >>>> } else { > >>>> req->io_task_work.func = io_req_task_complete; > >>> > >>> 'git-bisect' shows the reported warning starts from this patch. > > > > Thanks Ming > > > >> > >> That does make sense, as probably: > >> > >> + /* locked task_work executor checks the deffered list completion */ > >> + if (ts->locked) > >> + issue_flags = IO_URING_F_COMPLETE_DEFER; > >> > >> this assumption isn't true, and that would mess with the task management > >> (which is in your oops). > > > > I'm missing it, how it's not true? > > > > > > static void ctx_flush_and_put(struct io_ring_ctx *ctx, struct io_tw_state *ts) > > { > > ... > > if (ts->locked) { > > io_submit_flush_completions(ctx); > > ... > > } > > } > > > > static __cold void io_fallback_req_func(struct work_struct *work) > > { > > ... > > mutex_lock(&ctx->uring_lock); > > llist_for_each_entry_safe(req, tmp, node, io_task_work.node) > > req->io_task_work.func(req, &ts); > > io_submit_flush_completions(ctx); > > mutex_unlock(&ctx->uring_lock); > > ... > > } > > I took a look too, and don't immediately see it. Those are also the two > only cases I found, and before the patches, looks fine too. > > So no immediate answer there... But I can confirm that before this > patch, test passes fine. With the patch, it goes boom pretty quick. > Either directly off putting the task, or an unrelated memory crash > instead. In ublk, the translated 'issue_flags' is passed to io_uring_cmd_done() from ioucmd->task_work_cb()(__ublk_rq_task_work()). That might be related with the reason. Thanks, Ming
