Patch "block: drop ctx argument from bdrv_root_attach_child" causing crash

[Programmingkid]

After doing some git bisecting I found out a problem I was having with sharing 
a host folder as an USB flash drive on the guest was caused by this patch:

228ca37e12f97788e05bd0c92f89b3e5e4019607 is the first bad commit
commit 228ca37e12f97788e05bd0c92f89b3e5e4019607
Author: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Date:   Wed Apr 28 18:17:34 2021 +0300

    block: drop ctx argument from bdrv_root_attach_child
    
    Passing parent aio context is redundant, as child_class and parent
    opaque pointer are enough to retrieve it. Drop the argument and use new
    bdrv_child_get_parent_aio_context() interface.
    
    Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
    Reviewed-by: Alberto Garcia <berto@igalia.com>
    Reviewed-by: Kevin Wolf <kwolf@redhat.com>
    Message-Id: <20210428151804.439460-7-vsementsov@virtuozzo.com>
    Signed-off-by: Kevin Wolf <kwolf@redhat.com>

 block.c                   | 8 +++++---
 block/block-backend.c     | 4 ++--
 blockjob.c                | 3 +--
 include/block/block_int.h | 1 -
 4 files changed, 8 insertions(+), 8 deletions(-)


With this patch committed the crash can be reproduced like this:

qemu-system-ppc -usb -device usb-storage,drive=fat16 -drive 
file=fat:rw:fat-type=16:"<path of a host folder>",id=fat16,format=raw,if=none

On my system is causes a segment fault.

Thank you.