Re: [Qemu-devel] [PATCH] ide: fix double free

[ChenLiang <chenliang88@huawei.com>]

On 2014/7/2 17:04, Paolo Bonzini wrote:

> This is definitely a heavyweight solution, and in fact the bug should 
> not be there in the first place.  See dma_complete:
> 
> static void dma_complete(DMAAIOCB *dbs, int ret)
> {
>     trace_dma_complete(dbs, ret, dbs->common.cb);
> 
>     dma_bdrv_unmap(dbs);
>     if (dbs->common.cb) {
>         dbs->common.cb(dbs->common.opaque, ret);
>     }
>     qemu_iovec_destroy(&dbs->iov);
>     if (dbs->bh) {
>         qemu_bh_delete(dbs->bh);
>         dbs->bh = NULL;
>     }
>     if (!dbs->in_cancel) {
>         /* Requests may complete while dma_aio_cancel is in progress.  In
>          * this case, the AIOCB should not be released because it is still
>          * referenced by dma_aio_cancel.  */
>         qemu_aio_release(dbs);
>     }
> }
> 
> Perhaps something like this?
> 
> diff --git a/dma-helpers.c b/dma-helpers.c
> index 53cbe92..21b70d12 100644
> --- a/dma-helpers.c
> +++ b/dma-helpers.c
> @@ -181,15 +181,15 @@ static void dma_aio_cancel(BlockDriverAIOCB *acb)
>  
>      trace_dma_aio_cancel(dbs);
>  
> +    dbs->in_cancel = true;
>      if (dbs->acb) {
>          BlockDriverAIOCB *acb = dbs->acb;
>          dbs->acb = NULL;
> -        dbs->in_cancel = true;
>          bdrv_aio_cancel(acb);
> -        dbs->in_cancel = false;
>      }
>      dbs->common.cb = NULL;
>      dma_complete(dbs, 0);
> +    qemu_aio_release(dbs);
>  }
>  
>  static const AIOCBInfo dma_aiocb_info = {
> 
> 
> .
> 

acked, thanks

Best regards
Chenliang