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Message-ID: <e2167849-8034-4649-9d35-3ab266c8d0d5@gmail.com>
Date: Mon, 18 Mar 2024 02:32:11 +0000
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Subject: Re: [PATCH v2 02/14] io_uring/cmd: fix tw <-> issue_flags conversion
To: Jens Axboe <axboe@kernel.dk>, Ming Lei <ming.lei@redhat.com>
Cc: io-uring@vger.kernel.org, linux-block@vger.kernel.org,
Kanchan Joshi <joshi.k@samsung.com>
References: <cover.1710720150.git.asml.silence@gmail.com>
<c48a7f3919eecbee0319020fd640e6b3d2e60e5f.1710720150.git.asml.silence@gmail.com>
<Zfelt6mbVA0moyq6@fedora> <e987d48d-09c9-4b7d-9ddc-1d90f15a1bfe@kernel.dk>
Content-Language: en-US
From: Pavel Begunkov <asml.silence@gmail.com>
In-Reply-To: <e987d48d-09c9-4b7d-9ddc-1d90f15a1bfe@kernel.dk>
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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@gmail.com>
>>> Link: https://lore.kernel.org/r/eb08e72e837106963bc7bc7dccfd93d646cc7f36.1710514702.git.asml.silence@gmail.com
>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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);
...
}
--
Pavel Begunkov