[v5,10/12] block/io_uring: adds userspace completion polling

Commit Message

Aarushi Mehta June 10, 2019, 1:49 p.m. UTC

Signed-off-by: Aarushi Mehta <[e-mail]>
---
 block/io_uring.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

Comments

Stefan Hajnoczi June 11, 2019, 9:51 a.m. UTC | #1

On Mon, Jun 10, 2019 at 07:19:03PM +0530, Aarushi Mehta wrote:
> +static bool qemu_luring_poll_cb(void *opaque)
> +{
> +    LuringState *s = opaque;
> +    struct io_uring_cqe *cqes;
> +
> +    if (io_uring_peek_cqe(&s->ring, &cqes) == 0) {
> +        if (!cqes) {
> +            qemu_luring_process_completions_and_submit(s);
> +            return true;
> +        }

Is this logic inverted?  We have a completion when cqes != NULL.

Maxim Levitsky June 17, 2019, 2:14 p.m. UTC | #2

On Tue, 2019-06-11 at 10:51 +0100, Stefan Hajnoczi wrote:
> On Mon, Jun 10, 2019 at 07:19:03PM +0530, Aarushi Mehta wrote:
> > +static bool qemu_luring_poll_cb(void *opaque)
> > +{
> > +    LuringState *s = opaque;
> > +    struct io_uring_cqe *cqes;
> > +
> > +    if (io_uring_peek_cqe(&s->ring, &cqes) == 0) {
> > +        if (!cqes) {
> > +            qemu_luring_process_completions_and_submit(s);
> > +            return true;
> > +        }
> 
> Is this logic inverted?  We have a completion when cqes != NULL.

This indeed looks inverted to me.

Best regards,
	Maxim Levitsky

Patch

diff --git a/block/io_uring.c b/block/io_uring.c
index 47e027364a..acfaa48151 100644
--- a/block/io_uring.c
+++ b/block/io_uring.c
@@ -142,6 +142,21 @@  static void qemu_luring_completion_cb(void *opaque)
     qemu_luring_process_completions_and_submit(s);
 }
 
+static bool qemu_luring_poll_cb(void *opaque)
+{
+    LuringState *s = opaque;
+    struct io_uring_cqe *cqes;
+
+    if (io_uring_peek_cqe(&s->ring, &cqes) == 0) {
+        if (!cqes) {
+            qemu_luring_process_completions_and_submit(s);
+            return true;
+        }
+    }
+
+    return false;
+}
+
 static void ioq_init(LuringQueue *io_q)
 {
     QSIMPLEQ_INIT(&io_q->sq_overflow);
@@ -294,7 +309,7 @@  void luring_attach_aio_context(LuringState *s, AioContext *new_context)
     s->aio_context = new_context;
     s->completion_bh = aio_bh_new(new_context, qemu_luring_completion_bh, s);
     aio_set_fd_handler(s->aio_context, s->ring.ring_fd, false,
-                       qemu_luring_completion_cb, NULL, NULL, s);
+                       qemu_luring_completion_cb, NULL, qemu_luring_poll_cb, s);
 }
 
 LuringState *luring_init(Error **errp)