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Date: Fri, 22 Nov 2013 17:20:52 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20131122162052.GD3232@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 2/7] block: Introduce op_blockers to
 BlockDriverState
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To: Fam Zheng <famz@redhat.com>
Cc: kwolf@redhat.com, hbrock@redhat.com, qemu-devel@nongnu.org, rjones@redhat.com, imain@redhat.com, stefanha@redhat.com, pbonzini@redhat.com

On Fri, Nov 22, 2013 at 01:24:49PM +0800, Fam Zheng wrote:
> +bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp)
> +{
> +    BdrvOpBlocker *blocker;
> +    assert(op >=0 && op < BLOCK_OP_TYPE_MAX);
> +    if (!QLIST_EMPTY(&bs->op_blockers[op])) {
> +        blocker = QLIST_FIRST(&bs->op_blockers[op]);
> +        *errp = error_copy(blocker->reason);
> +        return true;
> +    }
> +    return false;
> +}

It's worth following the convention that Error **errp may be NULL:

if (errp) {
    *errp = error_copy(blocker->reason);
}

The bool return value might be enough for some callers who don't need
the full Error.