[PATCH 3/8] virtio_blk_process_queued_requests: always run in a bh

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

This function in virtio_blk_data_plane_start is directly
invoked, accessing the queued requests from the main loop,
while the device has already switched to the iothread context.

The only place where calling virtio_blk_process_queued_requests
from the main loop is allowed is when blk_set_aio_context fails,
and we still need to process the requests.

Since the logic of the bh is exactly the same as
virtio_blk_dma_restart, so rename the function and make it public
so that we can utilize it here too.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 10 +++++++++-
 hw/block/virtio-blk.c           |  4 ++--
 include/hw/virtio/virtio-blk.h  |  1 +
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index f9224f23d2..03e10a36a4 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -234,8 +234,16 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
         goto fail_aio_context;
     }
 
+    blk_inc_in_flight(s->conf->conf.blk);
+    /*
+     * vblk->bh is only set in virtio_blk_dma_restart_cb, which
+     * is called only on vcpu start or stop.
+     * Therefore it must be null.
+     */
+    assert(vblk->bh == NULL);
     /* Process queued requests before the ones in vring */
-    virtio_blk_process_queued_requests(vblk, false);
+    vblk->bh = aio_bh_new(blk_get_aio_context(s->conf->conf.blk),
+                          virtio_blk_restart_bh, vblk);
 
     /* Kick right away to begin processing requests already in vring */
     for (i = 0; i < nvqs; i++) {
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 191f75ce25..29a9c53ebc 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -855,7 +855,7 @@ void virtio_blk_process_queued_requests(VirtIOBlock *s, bool is_bh)
     aio_context_release(blk_get_aio_context(s->conf.conf.blk));
 }
 
-static void virtio_blk_dma_restart_bh(void *opaque)
+void virtio_blk_restart_bh(void *opaque)
 {
     VirtIOBlock *s = opaque;
 
@@ -882,7 +882,7 @@ static void virtio_blk_dma_restart_cb(void *opaque, bool running,
      */
     if (!s->bh && !virtio_bus_ioeventfd_enabled(bus)) {
         s->bh = aio_bh_new(blk_get_aio_context(s->conf.conf.blk),
-                           virtio_blk_dma_restart_bh, s);
+                           virtio_blk_restart_bh, s);
         blk_inc_in_flight(s->conf.conf.blk);
         qemu_bh_schedule(s->bh);
     }
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index d311c57cca..c334353b5a 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -92,5 +92,6 @@ typedef struct MultiReqBuffer {
 
 void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq);
 void virtio_blk_process_queued_requests(VirtIOBlock *s, bool is_bh);
+void virtio_blk_restart_bh(void *opaque);
 
 #endif
-- 
2.31.1