[Qemu-devel] [PATCH v2 2/3] linux-aio: split processing events function

[Roman Pen <roman.penyaev@profitbricks.com>]

Prepare processing events function to be called from ioq_submit(),
thus split function on two parts: the first harvests completed IO
requests, the second submits pending requests.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
---
 block/linux-aio.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/block/linux-aio.c b/block/linux-aio.c
index 3e29f1d..fae5c82 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -178,20 +178,20 @@ io_getevents_advance_and_peek(io_context_t ctx,
     return io_getevents_peek(ctx, events);
 }
 
-/* The completion BH fetches completed I/O requests and invokes their
- * callbacks.
+/**
+ * qemu_laio_process_completions:
+ * @s: AIO state
+ *
+ * Fetches completed I/O requests and invokes their callbacks.
  *
  * The function is somewhat tricky because it supports nested event loops, for
  * example when a request callback invokes aio_poll().  In order to do this,
- * the completion events array and index are kept in LinuxAioState.  The BH
- * reschedules itself as long as there are completions pending so it will
- * either be called again in a nested event loop or will be called after all
- * events have been completed.  When there are no events left to complete, the
- * BH returns without rescheduling.
+ * indices are kept in LinuxAioState.  Function schedules BH completion so it
+ * can be called again in a nested event loop.  When there are no events left
+ * to complete the BH is being canceled.
  */
-static void qemu_laio_completion_bh(void *opaque)
+static void qemu_laio_process_completions(LinuxAioState *s)
 {
-    LinuxAioState *s = opaque;
     struct io_event *events;
 
     /* Reschedule so nested event loops see currently pending completions */
@@ -220,18 +220,29 @@ static void qemu_laio_completion_bh(void *opaque)
      * own `for` loop.  If we are the last all counters droped to zero. */
     s->event_max = 0;
     s->event_idx = 0;
+}
 
+static void qemu_laio_process_completions_and_submit(LinuxAioState *s)
+{
+    qemu_laio_process_completions(s);
     if (!s->io_q.plugged && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
         ioq_submit(s);
     }
 }
 
+static void qemu_laio_completion_bh(void *opaque)
+{
+    LinuxAioState *s = opaque;
+
+    qemu_laio_process_completions_and_submit(s);
+}
+
 static void qemu_laio_completion_cb(EventNotifier *e)
 {
     LinuxAioState *s = container_of(e, LinuxAioState, e);
 
     if (event_notifier_test_and_clear(&s->e)) {
-        qemu_laio_completion_bh(s);
+        qemu_laio_process_completions_and_submit(s);
     }
 }
 
-- 
2.8.2