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From 92a9a816dd93a361ad2e0751e503c5e12accf38b Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 10 Oct 2018 20:22:03 +0100
Subject: [PATCH 37/49] block-backend: Add .drained_poll callback

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20181010202213.7372-25-kwolf@redhat.com>
Patchwork-id: 82614
O-Subject: [RHEL-8 qemu-kvm PATCH 34/44] block-backend: Add .drained_poll callback
Bugzilla: 1637976
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Thomas Huth <thuth@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>
(cherry picked from commit fe5258a503a87e69be37c9ac48799e293809386e)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@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 3554b7e..dffc6f0 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,
@@ -2198,6 +2200,13 @@ 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