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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/18/24 06:59, Ming Lei wrote: > On Sun, Mar 17, 2024 at 09:11:27PM -0600, Jens Axboe wrote: >> On 3/17/24 8:47 PM, Ming Lei wrote: >>> 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 >>>>>>>> Link: https://lore.kernel.org/r/eb08e72e837106963bc7bc7dccfd93d646cc7f36.1710514702.git.asml.silence@gmail.com >>>>>>>> Signed-off-by: Jens Axboe >>>>> >>>>> 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. >> >> Or maybe ublk is doing multiple invocations of task_work completions? I >> added this: > > Yes, your debug log & point does help. > > This patch convert zero flag(!IO_URING_F_UNLOCKED) into IO_URING_F_COMPLETE_DEFER, > and somewhere is easily ignored, and follows the fix, which need to be > folded into patch 2. Thanks, was totally unaware of this chunk. A side note, it's better to be moved to uring_cmd, i'll do the change > diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c > index 5d4b448fdc50..22f2b52390a9 100644 > --- a/io_uring/io_uring.c > +++ b/io_uring/io_uring.c > @@ -3259,7 +3259,8 @@ static bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx, > /* ->sqe isn't available if no async data */ > if (!req_has_async_data(req)) > cmd->sqe = NULL; > - file->f_op->uring_cmd(cmd, IO_URING_F_CANCEL); > + file->f_op->uring_cmd(cmd, IO_URING_F_CANCEL | > + IO_URING_F_COMPLETE_DEFER); > ret = true; > } > } -- Pavel Begunkov