On Fri, 9 Dec 2016, Dominique Martinet wrote:
> Nice. I like the idea of async I/Os :)
>
> Stefano Stabellini wrote on Thu, Dec 08, 2016:
> > Add a few fields to struct p9_req_t. Callback is the function which will
> > be called upon requestion completion. offset, rsize, pagevec and kiocb
> > store important information regarding the read or write request,
> > essential to complete the request.
> >
> > Currently not utilized, but they will be used in a later patch.
> >
> > Signed-off-by: Stefano Stabellini <sstabell...@kernel.org>
> > ---
> > include/net/9p/client.h | 8 ++++++++
> > net/9p/client.c | 9 ++++++++-
> > 2 files changed, 16 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/net/9p/client.h b/include/net/9p/client.h
> > index aef19c6..69fc2f0 100644
> > --- a/include/net/9p/client.h
> > +++ b/include/net/9p/client.h
> > @@ -110,6 +110,7 @@ enum p9_req_status_t {
> > *
> > */
> >
> > +struct p9_client;
> > struct p9_req_t {
> > int status;
> > int t_err;
> > @@ -118,6 +119,13 @@ struct p9_req_t {
> > struct p9_fcall *rc;
> > void *aux;
> >
> > + /* Used for async requests */
> > + void (*callback)(struct p9_client *c, struct p9_req_t *req, int status);
> > + size_t offset;
> > + u64 rsize;
> > + struct page **pagevec;
> > + struct kiocb *kiocb;
> > +
> > struct list_head req_list;
> > };
> >
> > diff --git a/net/9p/client.c b/net/9p/client.c
> > index b5ea9a3..bfe1715 100644
> > --- a/net/9p/client.c
> > +++ b/net/9p/client.c
> > @@ -405,6 +405,10 @@ static void p9_free_req(struct p9_client *c, struct
> > p9_req_t *r)
> > int tag = r->tc->tag;
> > p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
> >
> > + r->offset = 0;
> > + r->rsize = 0;
> > + r->kiocb = NULL;
> > + r->callback = NULL;
>
> Probably want to cleanup r->pagevec here too, even if that doesn't seem
> to have any implication short-term (e.g. only looked at if callback is
> not empty from what I've seen)
Thanks, I missed it.
> > r->status = REQ_STATUS_IDLE;
> > if (tag != P9_NOTAG && p9_idpool_check(tag, c->tagpool))
> > p9_idpool_put(tag, c->tagpool);
> > @@ -427,7 +431,10 @@ void p9_client_cb(struct p9_client *c, struct p9_req_t
> > *req, int status)
> > smp_wmb();
> > req->status = status;
> >
> > - wake_up(req->wq);
> > + if (req->callback != NULL)
> > + req->callback(c, req, status);
> > + else
> > + wake_up(req->wq);
> > p9_debug(P9_DEBUG_MUX, "wakeup: %d\n", req->tc->tag);
> > }
> > EXPORT_SYMBOL(p9_client_cb);
>
> Mostly a warning here, but p9_client_cb is called from an interrupt
> context in 9P/RDMA.
> This has been working up till now because we only do a wake_up and
> there's no waiting, but (looking at later patches),
> p9_client_read_complete for example does allocations and possibly other
> unsafe operations from an interrupt context.
>
> I don't know if the way forward is to move p9_client_cb from that
> context or to have the callback be scheduled in a work queue instead;
> but we'll need to fix that later.
Either would work. It might be simpler to have the callback run as a
work queue. I'll make the change. Maybe I'll use kiocb to figure out if
we have to schedule_work.
