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Date: Mon, 22 Sep 2008 21:38:07 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
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Subject: [Qemu-devel] Re: [PATCH 1/3] Only call aio flush handler if set
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To: Ryan Harper <ryanh@us.ibm.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org

Ryan Harper wrote:
> If the aio handler doesn't register an io_flush handler, we'd SEGV; fix that by
> only calling the flush handler if set.  BTW, aio handlers *should* register an
> io_flush routine.
>
> Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
>
> diff --git a/aio.c b/aio.c
> index 687e4be..2bb3ed4 100644
> --- a/aio.c
> +++ b/aio.c
> @@ -105,7 +105,8 @@ void qemu_aio_flush(void)
>          ret = 0;
>
>          LIST_FOREACH(node, &aio_handlers, node) {
> -            ret |= node->io_flush(node->opaque);
> +            if (node->io_flush)
> +                ret |= node->io_flush(node->opaque);
>          }
>   

Just not doing an io_flush is just hiding the real bug--that the user 
didn't register an io_flush handler.  If the inevitable SEGV is not your 
thing, I'd rather see a check added to qemu_aio_set_fd_handler() that 
threw an error and exited if called without an io_flush handler.

Regards,

Anthony Liguori

>          qemu_aio_wait();
>