From: Christoph Hellwig <hch@lst.de>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: "kwolf@redhat.com" <kwolf@redhat.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [Xen-devel] [PATCH] xen_disk: implement BLKIF_OP_FLUSH_DISKCACHE, remove BLKIF_OP_WRITE_BARRIER
Date: Wed, 25 Apr 2012 12:20:24 +0200 [thread overview]
Message-ID: <20120425102024.GA19800@lst.de> (raw)
In-Reply-To: <1335344565.28015.7.camel@zakaz.uk.xensource.com>
On Wed, Apr 25, 2012 at 10:02:45AM +0100, Ian Campbell wrote:
> The blkif spec was recently much improved, you can find it at
> http://xenbits.xen.org/docs/unstable/hypercall/include,public,io,blkif.h.html
>
> TBH I'm not sure it actually answers your questions wrt
> BLKIF_OP_FLUSH_DISKCACHE, if not please let us know and we can see about
> improving it.
That description in there is overly simple, and does not match any of the
implementations known to me on either end.
Talking about those: the mainline Linux blkback backend also implements
different semantics from what mainline Linux blkfront seems to expect,
as well as different from qemu. Looking at these three alone I can't see
how Xen ever managed to get data to disk reliably if using the paravirt
interface.
with the implementations in qemu and the Linux kernel frontend and backends,
which
>
> Ian
>
---end quoted text---
next prev parent reply other threads:[~2012-04-25 10:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-16 17:05 [PATCH] xen_disk: implement BLKIF_OP_FLUSH_DISKCACHE, remove BLKIF_OP_WRITE_BARRIER Stefano Stabellini
2012-04-16 17:10 ` Konrad Rzeszutek Wilk
2012-04-25 8:45 ` Christoph Hellwig
2012-04-25 9:02 ` [Xen-devel] " Ian Campbell
2012-04-25 10:20 ` Christoph Hellwig [this message]
2012-04-25 11:21 ` Stefano Stabellini
2012-04-25 11:17 ` Ian Campbell
2012-04-25 11:23 ` Christoph Hellwig
2012-04-26 15:41 ` Konrad Rzeszutek Wilk
2012-05-09 12:42 ` Stefano Stabellini
2012-12-19 18:46 ` Konrad Rzeszutek Wilk
2013-01-09 18:44 ` Stefano Stabellini
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