Re: [PATCH v2 for-next 3/6] RDMA/rtrs: Fix warning when use poll mode

[Haris Iqbal <haris.iqbal@ionos.com>]

On Sun, Aug 8, 2021 at 1:30 PM Leon Romanovsky <leon@kernel.org> wrote:
>
> On Sun, Aug 08, 2021 at 01:07:29PM +0200, Jack Wang wrote:
> > Leon Romanovsky <leon@kernel.org>于2021年8月8日 周日11:05写道：
> >
> > > On Fri, Aug 06, 2021 at 01:21:09PM +0200, Md Haris Iqbal wrote:
> > > > From: Jack Wang <jinpu.wang@ionos.com>
> > > >
> > > > when test with poll mode, it will fail and lead to warning below:
> > > > echo "sessname=bla path=gid:fe80::2:c903:4e:d0b3@gid:fe80::2:c903:8:ca17
> > > > device_path=/dev/nullb2 nr_poll_queues=-1" |
> > > > sudo tee /sys/devices/virtual/rnbd-client/ctl/map_device
> > > >
> > > > rnbd_client L597: Mapping device /dev/nullb2 on session bla,
> > > > (access_mode: rw, nr_poll_queues: 8)
> > > > WARNING: CPU: 3 PID: 9886 at drivers/infiniband/core/cq.c:447
> > > ib_cq_pool_get+0x26f/0x2a0 [ib_core]
> > > >
> > > > The problem is, when poll_queues are used, there will be more
> > > connections than
> > > > number of cpus; and those extra connections will have ib poll context
> > > set to
> > > > IB_POLL_DIRECT, which is not allowed to be used for shared CQs.
> > > >
> > > > So, in case those extra connections when poll queues are used, use
> > > > ib_alloc_cq/ib_free_cq.
> > > >
> > > > Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
> > > > Reviewed-by: Gioh Kim <gi-oh.kim@ionos.com>
> > > > Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
> > > > ---
> > > >  drivers/infiniband/ulp/rtrs/rtrs-srv.c |  1 +
> > > >  drivers/infiniband/ulp/rtrs/rtrs.c     | 17 ++++++++++++++---
> > > >  2 files changed, 15 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > > index cd9a4ccf4c28..47775987f91a 100644
> > > > --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > > +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > > @@ -1768,6 +1768,7 @@ static struct rtrs_srv_sess *__alloc_sess(struct
> > > rtrs_srv *srv,
> > > >       strscpy(sess->s.sessname, str, sizeof(sess->s.sessname));
> > > >
> > > >       sess->s.con_num = con_num;
> > > > +     sess->s.irq_con_num = con_num;
> > > >       sess->s.recon_cnt = recon_cnt;
> > > >       uuid_copy(&sess->s.uuid, uuid);
> gTgT> > >       spin_lock_init(&sess->state_lock);
> > > > diff --git a/drivers/infiniband/ulp/rtrs/rtrs.c
> > > b/drivers/infiniband/ulp/rtrs/rtrs.c
> > > > index ca542e477d38..9bc323490ce3 100644
> > > > --- a/drivers/infiniband/ulp/rtrs/rtrs.c
> > > > +++ b/drivers/infiniband/ulp/rtrs/rtrs.c
> > > > @@ -228,7 +228,12 @@ static int create_cq(struct rtrs_con *con, int
> > > cq_vector, int nr_cqe,
> > > >       struct rdma_cm_id *cm_id = con->cm_id;
> > > >       struct ib_cq *cq;
> > > >
> > > > -     cq = ib_cq_pool_get(cm_id->device, nr_cqe, cq_vector, poll_ctx);
> > > > +     if (con->cid >= con->sess->irq_con_num)
> > > > +             cq = ib_alloc_cq(cm_id->device, con, nr_cqe, cq_vector,
> > > > +                              poll_ctx);
> > > > +     else
> > > > +             cq = ib_cq_pool_get(cm_id->device, nr_cqe, cq_vector,
> > > poll_ctx);
> > >
> > > I see same "if (con->c.cid >= sess->s.irq_con_num)" checks when calling
> > > to rtrs_cq_qp_create() that will take poll_ctx and convey it to
> > > create_cq().
> > >
> > > Please take a look on nvme_rdma_create_cq() which does the same without
> > > passing poll_ctx.
> > >
> > > Thanks
> >
> > Hi,
> >
> > The reason rtrs needs to have poll_ctx is rtrs-clt and rtrs-srv use
> > different poll_ctx, and they all call into rtrs_cq_qp_create, while
> > nvme_rdma_create_cq is only for host (client) side.
> >
> > I guess you wanted to convert the same if
> > (con->c.cid>=sess->s.irq_con_num), this can be done in a new patch.
>
> I don't want to see code that does something like that:
>  if (a_cond)
>    f(...)
>       if (a_cond)
>         do_X
>        else
>         do_Y
>
> The ideal flow should have minimal number of ifs to make the code
> more clear and readable, and definitely shouldn't have same if()
> checks in various places of the callstack.
>
> In your case, rtrs-srv uses IB_POLL_WORKQUEUE as poll_ctx which doesn't
> look related to the issue stated in the commit message.

Thanks for the inputs Leon.

This patch can be dropped. I will make the changes and send the patchset again.


>
> Thanks
>
> >
> > Thanks
> >
> > >
> > >