[PATCH] virtio-blk: Convert QEMUBH callback to "bitops.h" API

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

By directly using test_and_clear_bit() from the "bitops.h" API,
we can remove the bitmap[] variable-length array copy on the stack
and the complex manual bit testing/clearing logic.

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index e9050c8987e..25d9b10c02b 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -59,23 +59,12 @@ void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq)
 static void notify_guest_bh(void *opaque)
 {
     VirtIOBlockDataPlane *s = opaque;
-    unsigned nvqs = s->conf->num_queues;
-    unsigned long bitmap[BITS_TO_LONGS(nvqs)];
-    unsigned j;
 
-    memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
-    memset(s->batch_notify_vqs, 0, sizeof(bitmap));
-
-    for (j = 0; j < nvqs; j += BITS_PER_LONG) {
-        unsigned long bits = bitmap[j / BITS_PER_LONG];
-
-        while (bits != 0) {
-            unsigned i = j + ctzl(bits);
+    for (unsigned i = 0; i < s->conf->num_queues; i++) {
+        if (test_and_clear_bit(i, s->batch_notify_vqs)) {
             VirtQueue *vq = virtio_get_queue(s->vdev, i);
 
             virtio_notify_irqfd(s->vdev, vq);
-
-            bits &= bits - 1; /* clear right-most bit */
         }
     }
 }
-- 
2.26.3