Re: [Qemu-devel] [PATCH] blockdev: acquire AioContext in hmp_commit()

["Denis V. Lunev" <den@openvz.org>]

On 10/30/2015 06:57 PM, Stefan Hajnoczi wrote:
> This one slipped through.  Although we acquire AioContext when
> committing all devices we don't for just a single device.
>
> AioContext must be acquired before calling bdrv_*() functions to
> synchronize access with other threads that may be using the AioContext.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   blockdev.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/blockdev.c b/blockdev.c
> index 18712d2..d611779 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1120,6 +1120,9 @@ void hmp_commit(Monitor *mon, const QDict *qdict)
>       if (!strcmp(device, "all")) {
>           ret = bdrv_commit_all();
>       } else {
> +        BlockDriverState *bs;
> +        AioContext *aio_context;
> +
>           blk = blk_by_name(device);
>           if (!blk) {
>               monitor_printf(mon, "Device '%s' not found\n", device);
> @@ -1129,7 +1132,14 @@ void hmp_commit(Monitor *mon, const QDict *qdict)
>               monitor_printf(mon, "Device '%s' has no medium\n", device);
>               return;
>           }
> -        ret = bdrv_commit(blk_bs(blk));
> +
> +        bs = blk_bs(blk);
> +        aio_context = bdrv_get_aio_context(bs);
> +        aio_context_acquire(aio_context);
> +
> +        ret = bdrv_commit(bs);
> +
> +        aio_context_release(aio_context);
>       }
>       if (ret < 0) {
>           monitor_printf(mon, "'commit' error for '%s': %s\n", device,
I like it in general, but could you pls wait a bit before pushing
it up. I am working at the moment on a more generic series.
I am going to attach this patch to it to consider the situation
as a whole.

It would be much trickier than my previous one. There are
several other places discovered.

Den