block: get rid of bdrv_io_unplugged_begin/end

bdrv_io_plug and bdrv_io_unplug are only called (via their
BlockBackend equivalents) after starting asynchronous I/O.
bdrv_drain is not going to be called while they are running,
because---even if a coroutine runs for some reason---it will
only drain in the next iteration of the event loop through
bdrv_co_yield_to_drain.

So this mechanism is unnecessary, get rid of it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 20161129113334.605-1-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/io.c

@@ -228,9 +228,7 @@ void bdrv_drained_begin(BlockDriverState *bs)
         bdrv_parent_drained_begin(bs);
     }
 
-    bdrv_io_unplugged_begin(bs);
     bdrv_drain_recurse(bs);
-    bdrv_io_unplugged_end(bs);
 }
 
 void bdrv_drained_end(BlockDriverState *bs)
@@ -302,7 +300,6 @@ void bdrv_drain_all_begin(void)
 
         aio_context_acquire(aio_context);
         bdrv_parent_drained_begin(bs);
-        bdrv_io_unplugged_begin(bs);
         aio_disable_external(aio_context);
         aio_context_release(aio_context);
 
@@ -347,7 +344,6 @@ void bdrv_drain_all_end(void)
 
         aio_context_acquire(aio_context);
         aio_enable_external(aio_context);
-        bdrv_io_unplugged_end(bs);
         bdrv_parent_drained_end(bs);
         aio_context_release(aio_context);
     }
@@ -2650,7 +2646,7 @@ void bdrv_io_plug(BlockDriverState *bs)
         bdrv_io_plug(child->bs);
     }
 
-    if (bs->io_plugged++ == 0 && bs->io_plug_disabled == 0) {
+    if (bs->io_plugged++ == 0) {
         BlockDriver *drv = bs->drv;
         if (drv && drv->bdrv_io_plug) {
             drv->bdrv_io_plug(bs);
@@ -2663,7 +2659,7 @@ void bdrv_io_unplug(BlockDriverState *bs)
     BdrvChild *child;
 
     assert(bs->io_plugged);
-    if (--bs->io_plugged == 0 && bs->io_plug_disabled == 0) {
+    if (--bs->io_plugged == 0) {
         BlockDriver *drv = bs->drv;
         if (drv && drv->bdrv_io_unplug) {
             drv->bdrv_io_unplug(bs);
@@ -2674,36 +2670,3 @@ void bdrv_io_unplug(BlockDriverState *bs)
         bdrv_io_unplug(child->bs);
     }
 }
-
-void bdrv_io_unplugged_begin(BlockDriverState *bs)
-{
-    BdrvChild *child;
-
-    if (bs->io_plug_disabled++ == 0 && bs->io_plugged > 0) {
-        BlockDriver *drv = bs->drv;
-        if (drv && drv->bdrv_io_unplug) {
-            drv->bdrv_io_unplug(bs);
-        }
-    }
-
-    QLIST_FOREACH(child, &bs->children, next) {
-        bdrv_io_unplugged_begin(child->bs);
-    }
-}
-
-void bdrv_io_unplugged_end(BlockDriverState *bs)
-{
-    BdrvChild *child;
-
-    assert(bs->io_plug_disabled);
-    QLIST_FOREACH(child, &bs->children, next) {
-        bdrv_io_unplugged_end(child->bs);
-    }
-
-    if (--bs->io_plug_disabled == 0 && bs->io_plugged > 0) {
-        BlockDriver *drv = bs->drv;
-        if (drv && drv->bdrv_io_plug) {
-            drv->bdrv_io_plug(bs);
-        }
-    }
-}

include/block/block.h

@@ -526,8 +526,6 @@ int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
 
 void bdrv_io_plug(BlockDriverState *bs);
 void bdrv_io_unplug(BlockDriverState *bs);
-void bdrv_io_unplugged_begin(BlockDriverState *bs);
-void bdrv_io_unplugged_end(BlockDriverState *bs);
 
 /**
  * bdrv_drained_begin:

include/block/block_int.h

@@ -526,9 +526,8 @@ struct BlockDriverState {
     uint64_t write_threshold_offset;
     NotifierWithReturn write_threshold_notifier;
 
-    /* counters for nested bdrv_io_plug and bdrv_io_unplugged_begin */
+    /* counter for nested bdrv_io_plug */
     unsigned io_plugged;
-    unsigned io_plug_disabled;
 
     int quiesce_counter;
 };