Re: [Xen-devel] Fwd: xentop reporting zero written sectors

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2011-10-10 at 17:31 +0100, Konrad Rzeszutek Wilk wrote:
> On Mon, Oct 10, 2011 at 04:16:04PM +0100, Andy Burns wrote:
> > No response in xen-users, asking developers ....
> > 
> > ---------- Forwarded message ----------
> > 
> > Just moving a chunk of files from one filesysstem on xvba to another
> > on xvdb, and was monitoring with xentop as it was taking longer than
> > expected.
> > 
> > The VBD_RD  and VBD_WR counters were both clocking-up as expected, as
> > was the VBD_RSECT counter, but the VBD_WSECT counter was stuck on
> > zero, I toggled on the individual VBD device counters and these showed
> > the same (with the RD and WR counters correctly split between my
> > source and destination disks)
> 
> Huh. Imagine that!
> > 
> > Is this a long standing "feature" that I've never noticed before or a
> > problem that should be reported?
> 
> Must be a feature. We would never write code with bugs. Never :-)
> 
> I think this new "feature" below will fix it for you:
> 
> 
> diff --git a/drivers/block/xen-blkback/blkback.c 
> b/drivers/block/xen-blkback/blkback.c
> index 0bd7143..3e2ca68 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -778,7 +778,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
>  
>       if (operation == READ)
>               blkif->st_rd_sect += preq.nr_sects;
> -     else if (operation == WRITE || operation == WRITE_FLUSH)
> +     else if (operation == WRITE_ODIRECT || operation == WRITE_FLUSH)

Would it be sane to key this off req->operation and BLKIF_OP_* instead
of first encoding them as block layer operations and then decoding back
again? The use of operation here just seems to be adding a layer of
indirection which we don't want or need.

Or maybe (operation & WRITE) instead of == ?

Ian.

>               blkif->st_wr_sect += preq.nr_sects;
>  
>       return 0;
> 
> 
> Thanks for reporting it!
> 
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