From a1a2af075647bb61e1435ce4c78d99e3f36d928b Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 8 Apr 2016 18:26:37 +0200
Subject: [PATCH] block: Cancel jobs first in bdrv_close_all()

So far, bdrv_close_all() first removed all root BlockDriverStates of
BlockBackends and monitor owned BDSes, and then assumed that the
remaining BDSes must be related to jobs and cancelled these jobs.

This order doesn't work that well any more when block jobs use
BlockBackends internally because then they will lose their BDS before
being cancelled.

This patch changes bdrv_close_all() to first cancel all jobs and then
remove all root BDSes from the remaining BBs.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
 block.c                  | 23 ++---------------------
 blockjob.c               | 13 +++++++++++++
 include/block/blockjob.h |  7 +++++++
 3 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/block.c b/block.c
index 45cddd6773..736432f67e 100644
--- a/block.c
+++ b/block.c
@@ -2209,8 +2209,7 @@ static void bdrv_close(BlockDriverState *bs)
 
 void bdrv_close_all(void)
 {
-    BlockDriverState *bs;
-    AioContext *aio_context;
+    block_job_cancel_sync_all();
 
     /* Drop references from requests still in flight, such as canceled block
      * jobs whose AIO context has not been polled yet */
@@ -2219,25 +2218,7 @@ void bdrv_close_all(void)
     blk_remove_all_bs();
     blockdev_close_all_bdrv_states();
 
-    /* Cancel all block jobs */
-    while (!QTAILQ_EMPTY(&all_bdrv_states)) {
-        QTAILQ_FOREACH(bs, &all_bdrv_states, bs_list) {
-            aio_context = bdrv_get_aio_context(bs);
-
-            aio_context_acquire(aio_context);
-            if (bs->job) {
-                block_job_cancel_sync(bs->job);
-                aio_context_release(aio_context);
-                break;
-            }
-            aio_context_release(aio_context);
-        }
-
-        /* All the remaining BlockDriverStates are referenced directly or
-         * indirectly from block jobs, so there needs to be at least one BDS
-         * directly used by a block job */
-        assert(bs);
-    }
+    assert(QTAILQ_EMPTY(&all_bdrv_states));
 }
 
 static void change_parent_backing_link(BlockDriverState *from,
diff --git a/blockjob.c b/blockjob.c
index 0f1bc77b1d..e916b41030 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -331,6 +331,19 @@ int block_job_cancel_sync(BlockJob *job)
     return block_job_finish_sync(job, &block_job_cancel_err, NULL);
 }
 
+void block_job_cancel_sync_all(void)
+{
+    BlockJob *job;
+    AioContext *aio_context;
+
+    while ((job = QLIST_FIRST(&block_jobs))) {
+        aio_context = bdrv_get_aio_context(job->bs);
+        aio_context_acquire(aio_context);
+        block_job_cancel_sync(job);
+        aio_context_release(aio_context);
+    }
+}
+
 int block_job_complete_sync(BlockJob *job, Error **errp)
 {
     return block_job_finish_sync(job, &block_job_complete, errp);
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 30bb2c6fd6..4ac68314ae 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -370,6 +370,13 @@ bool block_job_is_paused(BlockJob *job);
  */
 int block_job_cancel_sync(BlockJob *job);
 
+/**
+ * block_job_cancel_sync_all:
+ *
+ * Synchronously cancels all jobs using block_job_cancel_sync().
+ */
+void block_job_cancel_sync_all(void);
+
 /**
  * block_job_complete_sync:
  * @job: The job to be completed.