[Qemu-devel] [PATCH v3 1/4] block: count bdrv_co_rw_vmstate() requests

[Stefan Hajnoczi <stefanha@redhat.com>]

Call bdrv_inc/dec_in_flight() for vmstate reads/writes.  This seems
unnecessary at first glance because vmstate reads/writes are done
synchronously while the guest is stopped.  But we need the bdrv_wakeup()
in bdrv_dec_in_flight() so the main loop sees request completion.
Besides, it's cleaner to count vmstate reads/writes like ordinary
read/write requests.

The bdrv_wakeup() partially fixes a 'savevm' hang with -object iothread.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/io.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/io.c b/block/io.c
index fdd7485..cc56e90 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1988,17 +1988,24 @@ bdrv_co_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
                    bool is_read)
 {
     BlockDriver *drv = bs->drv;
+    int ret = -ENOTSUP;
+
+    bdrv_inc_in_flight(bs);
 
     if (!drv) {
-        return -ENOMEDIUM;
+        ret = -ENOMEDIUM;
     } else if (drv->bdrv_load_vmstate) {
-        return is_read ? drv->bdrv_load_vmstate(bs, qiov, pos)
-                       : drv->bdrv_save_vmstate(bs, qiov, pos);
+        if (is_read) {
+            ret = drv->bdrv_load_vmstate(bs, qiov, pos);
+        } else {
+            ret = drv->bdrv_save_vmstate(bs, qiov, pos);
+        }
     } else if (bs->file) {
-        return bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
+        ret = bdrv_co_rw_vmstate(bs->file->bs, qiov, pos, is_read);
     }
 
-    return -ENOTSUP;
+    bdrv_dec_in_flight(bs);
+    return ret;
 }
 
 static void coroutine_fn bdrv_co_rw_vmstate_entry(void *opaque)
-- 
2.9.3