Re: [Qemu-devel] [PATCH] xen_disk: fix io accounting

[Stefano Stabellini]

On Thu, 6 Feb 2014, Andreas Färber wrote:
> Am 06.02.2014 16:55, schrieb Olaf Hering:
> > bdrv_acct_done was called unconditional. But in case the ioreq has no
> > segments there is no matching bdrv_acct_start call. This could lead to
> > bogus accounting values.
> > 
> > Found by code inspection.
> > 
> > Signed-off-by: Olaf Hering <address@hidden>
> > ---
> >  hw/block/xen_disk.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> > index 098f6c6..7f0f14a 100644
> > --- a/hw/block/xen_disk.c
> > +++ b/hw/block/xen_disk.c
> > @@ -483,7 +483,18 @@ static void qemu_aio_complete(void *opaque, int ret)
> >      ioreq->status = ioreq->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;
> >      ioreq_unmap(ioreq);
> >      ioreq_finish(ioreq);
> > -    bdrv_acct_done(ioreq->blkdev->bs, &ioreq->acct);
> > +    switch (ioreq->req.operation) {
> > +    case BLKIF_OP_WRITE:
> > +    case BLKIF_OP_FLUSH_DISKCACHE:
> > +        if (!ioreq->req.nr_segments) {
> > +            break;
> > +        }
> 
> This will need a /* fall through */ comment for static analysis tools.
> 

Aside from this, I think that the patch is OK.
Can you please resend it with the comment?

 
> > +    case BLKIF_OP_READ:
> > +        bdrv_acct_done(ioreq->blkdev->bs, &ioreq->acct);
> > +        break;
> > +    default:
> > +        break;
> > +    }
> >      qemu_bh_schedule(ioreq->blkdev->bh);
> >  }
> >  
> > 
> 
> 
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