[Qemu-devel] [RFC PATCH 3/3] rbd: remove aio handler when no requests are pending

[Anthony Liguori]

This allows us to pass NULL for io_flush by removing the aio
event when no requests are pending.

Signed-off-by: Anthony Liguori <aligu...@us.ibm.com>
---
 block/rbd.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/block/rbd.c b/block/rbd.c
index 1a8ea6d..a7c3645 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -407,6 +407,18 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
     g_free(rcb);
 }
 
+static void qemu_rbd_aio_event_reader(void *opaque);
+
+static void qemu_rbd_update_aio_handler(BDRVRBDState *s)
+{
+    if (s->qemu_aio_count > 0) {
+        qemu_aio_set_fd_handler(s->fds[RBD_FD_READ], qemu_rbd_aio_event_reader,
+                                NULL, NULL, s);
+    } else {
+        qemu_aio_set_fd_handler(s->fds[RBD_FD_READ], NULL, NULL, NULL, NULL);
+    }
+}
+
 /*
  * aio fd read handler. It runs in the qemu context and calls the
  * completion handling of completed rados aio operations.
@@ -429,18 +441,12 @@ static void qemu_rbd_aio_event_reader(void *opaque)
                 s->event_reader_pos = 0;
                 qemu_rbd_complete_aio(s->event_rcb);
                 s->qemu_aio_count--;
+                qemu_rbd_update_aio_handler(s);
             }
         }
     } while (ret < 0 && errno == EINTR);
 }
 
-static int qemu_rbd_aio_flush_cb(void *opaque)
-{
-    BDRVRBDState *s = opaque;
-
-    return (s->qemu_aio_count > 0);
-}
-
 static int qemu_rbd_open(BlockDriverState *bs, const char *filename,
                          QDict *options, int flags)
 {
@@ -525,9 +531,8 @@ static int qemu_rbd_open(BlockDriverState *bs, const char 
*filename,
     }
     fcntl(s->fds[0], F_SETFL, O_NONBLOCK);
     fcntl(s->fds[1], F_SETFL, O_NONBLOCK);
-    qemu_aio_set_fd_handler(s->fds[RBD_FD_READ], qemu_rbd_aio_event_reader,
-                            NULL, qemu_rbd_aio_flush_cb, s);
 
+    qemu_rbd_update_aio_handler(s);
 
     return 0;
 
@@ -701,6 +706,7 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
     size = nb_sectors * BDRV_SECTOR_SIZE;
 
     s->qemu_aio_count++; /* All the RADOSCB */
+    qemu_rbd_update_aio_handler(s);
 
     rcb = g_malloc(sizeof(RADOSCB));
     rcb->done = 0;
@@ -736,6 +742,7 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
 failed:
     g_free(rcb);
     s->qemu_aio_count--;
+    qemu_rbd_update_aio_handler(s);
     qemu_aio_release(acb);
     return NULL;
 }
-- 
1.8.0