Re: [Qemu-devel] [PATCH v3] blockjob: update nodes head while removing all bdrv

[Max Reitz <mreitz@redhat.com>]

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On 11.09.19 12:03, Max Reitz wrote:
> From: Sergio Lopez <slp@redhat.com>
> 
> block_job_remove_all_bdrv() iterates through job->nodes, calling
> bdrv_root_unref_child() for each entry. The call to the latter may
> reach child_job_[can_]set_aio_ctx(), which will also attempt to
> traverse job->nodes, potentially finding entries that where freed
> on previous iterations.
> 
> To avoid this situation, update job->nodes head on each iteration to
> ensure that already freed entries are no longer linked to the list.
> 
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1746631
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
> v3:
> - Rewrote the loop to make the whole function a bit simpler
>   (Also, remove the node from the job->nodes list before unref'ing it,
>   just to be extra-safe)
> ---
>  blockjob.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)

Thanks Sergio for tracking down the bug’s cause, the original patch, and
the review; I’ve applied the patch to my block branch:

https://git.xanclic.moe/XanClic/qemu/commits/branch/block

Max


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