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Date: Thu, 9 Aug 2012 11:24:54 +0200
From: =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@irqsave.net>
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Subject: Re: [Qemu-devel] [RFC V2 06/10] quorum: Add quorum_aio_writev and
 its dependencies.
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: kwolf@redhat.com, =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@gmail.com>, stefanha@linux.vnet.ibm.com, qemu-devel@nongnu.org, blauwirbel@gmail.com, anthony@codemonkey.ws, pbonzini@redhat.com, eblake@redhat.com, afaerber@suse.de

Le Wednesday 08 Aug 2012 =E0 16:37:13 (+0100), Stefan Hajnoczi a =E9crit =
:
> On Tue, Aug 7, 2012 at 2:44 PM, Beno=EEt Canet <benoit.canet@gmail.com>=
 wrote:
> > +static int quorum_check_ret(QuorumAIOCB *acb)
> > +{
> > +    int i, j;
> > +
> > +    for (i =3D 0, j =3D 0; i <=3D 2; i++) {
> > +        if (acb->aios[0].ret) {
> > +            j++;
> > +        }
> > +    }
> > +
> > +    if (j > 1) {
> > +        return -EIO;
> > +    }
> > +
> > +    return 0;
> > +}
>=20
> Simpler version just scans the return values (also I think
> acb->aios[0].ret should be acb->aios[i].ret):
>=20
> static int quorum_check_ret(QuorumAIOCB *acb)
> {
>     int i;
>     for (i =3D 0; i <=3D 2; i++) {
>         if (acb->aios[i].ret) {
>             return -EIO; /* or acb->aios[i].ret */
>         }
>     }
>     return 0;
> }

I am wondering what is the best code to return.
There is some potential case like a filer containing a particular
image (or a image on the network) going down where the user probably
don't want to get an -EIO.

The=20
if (j > 1) {
    return -EIO;
}
part was about detecting an error count greater dans the threshold (2).

>=20
> > +
> > +static void quorum_aio_bh(void *opaque)
> > +{
> > +    QuorumAIOCB *acb =3D opaque;
> > +
> > +    qemu_bh_delete(acb->bh);
> > +    acb->common.cb(acb->common.opaque, quorum_check_ret(acb));
> > +    if (acb->finished) {
> > +        *acb->finished =3D true;
> > +    }
> > +    qemu_aio_release(acb);
> > +}
> > +
> > +static QuorumAIOCB *quorum_aio_get(BlockDriverState *bs,
> > +                                 QEMUIOVector *qiov,
> > +                                 int64_t sector_num,
> > +                                 int nb_sectors,
> > +                                 BlockDriverCompletionFunc *cb,
> > +                                 void *opaque)
> > +{
> > +    QuorumAIOCB *acb =3D qemu_aio_get(&quorum_aio_pool, bs, cb, opaq=
ue);
> > +    int i;
> > +
> > +    acb->qiov =3D qiov;
> > +    acb->bh =3D NULL;
> > +    acb->count =3D 0;
> > +    acb->sector_num =3D sector_num;
> > +    acb->nb_sectors =3D nb_sectors;
> > +    acb->vote =3D NULL;
> > +    acb->vote_ret =3D 0;
>=20
> acb->finished =3D NULL;
>=20