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)
> 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.
--
Dominique Martinet
