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

[Vladimir Sementsov-Ogievskiy]

24.05.2021 02:36, Programmingkid wrote:
> 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.

Oops, my fault, thanks for reporting. The problem is that previous commit


commit 3ca1f3225727419ba573673b744edac10904276f
Author: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Date:   Wed Apr 28 18:17:33 2021 +0300

    block: BdrvChildClass: add .get_parent_aio_context handler
    
    Add new handler to get aio context and implement it in all child
    classes. Add corresponding public interface to be used soon.


didn't add .get_parent_aio_context to child_vvfat_qcow


I'll send a patch

--
Best regards,
Vladimir