Re: [Qemu-devel] [PATCH 3/3] blockdev: acquire AioContext in block_set_io_throttle

["Benoît Canet" <benoit.canet@irqsave.net>]

The Wednesday 14 May 2014 à 16:22:47 (+0200), Stefan Hajnoczi wrote :G
> The block_set_io_throttle QMP and HMP commands modify I/O throttling
> limits for block devices.
> 
> Acquire the BlockDriverState's AioContext to protect against race
> conditions with an IOThread that is running I/O for this device.
> 
> Cc: Benoît Canet <benoit.canet@irqsave.net>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  blockdev.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 7810e9f..e0f1978 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1663,6 +1663,7 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
>  {
>      ThrottleConfig cfg;
>      BlockDriverState *bs;
> +    AioContext *aio_context;
>  
>      bs = bdrv_find(device);
>      if (!bs) {
> @@ -1706,6 +1707,9 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
>          return;
>      }
>  
> +    aio_context = bdrv_get_aio_context(bs);
> +    aio_context_acquire(aio_context);
> +
>      if (!bs->io_limits_enabled && throttle_enabled(&cfg)) {
>          bdrv_io_limits_enable(bs);
>      } else if (bs->io_limits_enabled && !throttle_enabled(&cfg)) {
> @@ -1715,6 +1719,8 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
>      if (bs->io_limits_enabled) {
>          bdrv_set_io_limits(bs, &cfg);
>      }
> +
> +    aio_context_release(aio_context);
>  }
>  
>  int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
> -- 
> 1.9.0
> 
Reviewed-by: Benoit Canet <benoit@irqsave.net>