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Date: Mon, 17 Feb 2014 21:30:06 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v13 02/14] block: Introduce op_blockers to
 BlockDriverState
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To: =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@irqsave.net>
Cc: kwolf@redhat.com, rjones@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org, imain@redhat.com, stefanha@redhat.com, pbonzini@redhat.com

On Thu, 02/13 13:24, Beno=EEt Canet wrote:
> The Wednesday 29 Jan 2014 =E0 13:07:29 (+0800), Fam Zheng wrote :
> > +bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error =
**errp)
> > +{
> > +    BdrvOpBlocker *blocker;
> > +    assert((int) op >=3D 0 && op < BLOCK_OP_TYPE_MAX);
> > +    if (!QLIST_EMPTY(&bs->op_blockers[op])) {
> > +        blocker =3D QLIST_FIRST(&bs->op_blockers[op]);
> > +        if (errp) {
> > +            *errp =3D error_copy(blocker->reason);
>=20
> When an operation is blocked the first reason found is returned as **er=
rp.
>=20
> I think that this could lead to some randomization of the error message=
s
> depending on the bdrv_op_block call order.
>=20

This is not randomization IMO.

I think for a program that could fail with more than one reasons, it fail=
s on
and reports the first failure. This behavior is not uncommon. Being verbo=
se
here does not show much more help, but it's still very easy to add later =
when
users asks for it.

Fam