From 79543d4ff66ab2c8f7050e5a5749ea11d1f0c2c0 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 14 Sep 2018 10:55:32 +0200
Subject: [PATCH 41/49] block-backend: Add .drained_poll callback

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20180914105540.18077-35-kwolf@redhat.com>
Patchwork-id: 82190
O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 34/42] block-backend: Add .drained_poll callback
Bugzilla: 1601212
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>

A bdrv_drain operation must ensure that all parents are quiesced, this
includes BlockBackends. Otherwise, callbacks called by requests that are
completed on the BDS layer, but not quite yet on the BlockBackend layer
could still create new requests.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/block-backend.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 2262506..ea85770 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -121,6 +121,7 @@ static void blk_root_inherit_options(int *child_flags, QDict *child_options,
     abort();
 }
 static void blk_root_drained_begin(BdrvChild *child);
+static bool blk_root_drained_poll(BdrvChild *child);
 static void blk_root_drained_end(BdrvChild *child);
 
 static void blk_root_change_media(BdrvChild *child, bool load);
@@ -294,6 +295,7 @@ static const BdrvChildRole child_root = {
     .get_parent_desc    = blk_root_get_parent_desc,
 
     .drained_begin      = blk_root_drained_begin,
+    .drained_poll       = blk_root_drained_poll,
     .drained_end        = blk_root_drained_end,
 
     .activate           = blk_root_activate,
@@ -2217,6 +2219,13 @@ static void blk_root_drained_begin(BdrvChild *child)
     }
 }
 
+static bool blk_root_drained_poll(BdrvChild *child)
+{
+    BlockBackend *blk = child->opaque;
+    assert(blk->quiesce_counter);
+    return !!blk->in_flight;
+}
+
 static void blk_root_drained_end(BdrvChild *child)
 {
     BlockBackend *blk = child->opaque;
-- 
1.8.3.1