Re: [Qemu-devel] [RFC V2 06/10] quorum: Add quorum_aio_writev and its dependencies.

["Benoît Canet" <benoit.canet@irqsave.net>]

Le Wednesday 08 Aug 2012 à 16:37:13 (+0100), Stefan Hajnoczi a écrit :
> On Tue, Aug 7, 2012 at 2:44 PM, Benoît Canet <benoit.canet@gmail.com> wrote:
> > +static int quorum_check_ret(QuorumAIOCB *acb)
> > +{
> > +    int i, j;
> > +
> > +    for (i = 0, j = 0; i <= 2; i++) {
> > +        if (acb->aios[0].ret) {
> > +            j++;
> > +        }
> > +    }
> > +
> > +    if (j > 1) {
> > +        return -EIO;
> > +    }
> > +
> > +    return 0;
> > +}
> 
> Simpler version just scans the return values (also I think
> acb->aios[0].ret should be acb->aios[i].ret):
> 
> static int quorum_check_ret(QuorumAIOCB *acb)
> {
>     int i;
>     for (i = 0; i <= 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 
if (j > 1) {
    return -EIO;
}
part was about detecting an error count greater dans the threshold (2).

> 
> > +
> > +static void quorum_aio_bh(void *opaque)
> > +{
> > +    QuorumAIOCB *acb = opaque;
> > +
> > +    qemu_bh_delete(acb->bh);
> > +    acb->common.cb(acb->common.opaque, quorum_check_ret(acb));
> > +    if (acb->finished) {
> > +        *acb->finished = 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 = qemu_aio_get(&quorum_aio_pool, bs, cb, opaque);
> > +    int i;
> > +
> > +    acb->qiov = qiov;
> > +    acb->bh = NULL;
> > +    acb->count = 0;
> > +    acb->sector_num = sector_num;
> > +    acb->nb_sectors = nb_sectors;
> > +    acb->vote = NULL;
> > +    acb->vote_ret = 0;
> 
> acb->finished = NULL;
>