From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: James Harper <james.harper@bendigoit.com.au>
Cc: "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: bug when using 4K sectors?
Date: Wed, 5 Sep 2012 16:29:27 -0400 [thread overview]
Message-ID: <20120905202927.GD27814@phenom.dumpdata.com> (raw)
In-Reply-To: <6035A0D088A63A46850C3988ED045A4B299F74F8@BITCOM1.int.sbss.com.au>
On Mon, Aug 13, 2012 at 02:12:58PM +0000, James Harper wrote:
> I notice this code in drivers/block/xen-blkback/common.h
>
> #define vbd_sz(_v) ((_v)->bdev->bd_part ? \
> (_v)->bdev->bd_part->nr_sects : \
> get_capacity((_v)->bdev->bd_disk))
>
> is the value returned by vbd_sz(_v) the number of sectors in the Linux device (eg size / 4096), or the number of 512 byte sectors? I suspect the former which is causing block requests beyond 1/8th the size of the device to fail (assuming 4K sectors are expected to work at all - I can't quite get my head around how it would be expected to work - does Linux do the read-modify-write if required?)
I think you need to instrument it to be sure.. But more interesting, do you actually
have a disk that exposes a 4KB hardware and logical sector? So far I've only found
SSDs that expose a 512kB logical sector but also expose the 4KB hardware.
Never could figure out how that is all suppose to work as the blkback
is filled with << 9 on a bunch of things.
>
> I can't test until tomorrow AEDT, but maybe someone here knows the answer already?
>
> James
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2012-09-05 20:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-13 14:12 bug when using 4K sectors? James Harper
2012-09-05 20:29 ` Konrad Rzeszutek Wilk [this message]
2012-09-05 23:56 ` James Harper
2012-09-06 10:58 ` Konrad Rzeszutek Wilk
2012-09-16 7:00 ` Joseph Glanville
2012-09-16 8:31 ` Keir Fraser
2012-09-16 9:00 ` Joseph Glanville
2012-09-16 10:37 ` James Harper
2012-09-16 11:18 ` Keir Fraser
2012-09-16 11:21 ` James Harper
2012-09-16 11:27 ` Alan Cox
2012-09-16 11:50 ` James Harper
2012-09-16 16:07 ` Alan Cox
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