From: Paolo Bonzini <pbonzini@redhat.com>
To: Yaowei Bai <baiyaowei@cmss.chinamobile.com>,
fam@euphon.net, dillaman@redhat.com, kwolf@redhat.com,
mreitz@redhat.com
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: COMPARE_AND_WRITE support for rbd driver
Date: Fri, 20 Sep 2019 13:22:02 +0200 [thread overview]
Message-ID: <8a304065-b9ec-8245-09ae-e38724f46645@redhat.com> (raw)
In-Reply-To: <20190919053623.GA19956@byw>
On 19/09/19 07:36, Yaowei Bai wrote:
> baiyaowei@cmss.chinamobile.com
> Bcc:
> Subject: COMPARE_AND_WRITE support for rbd driver
> Reply-To: baiyaowei@cmss.chinamobile.com
>
> Hey guys,
>
> I noticed that COMPARE_AND_WRITE had been supported by CEPH/librbd since
> v12.1.1. And in my company, we use this COMPARE_AND_WRITE support in
> CEPH with the ISCSI protocol. More precisely, we use tgt and CEPH with this
> COMPARE_AND_WRITE support as the SCSI target and export it to the remote
> hosts. And then VMs on remote hosts can use these SCSI targets through ISCSI
> initiator support in QEMU directly or as local SCSI disks. But unfortunately,
> there're some issues with this tgt case. So i think maybe we could also add this
> COMPARE_AND_WRITE support into the rbd driver in QEMU so we can leave the
> ISCSI/tgt alone and use this COMPARE_AND_WRITE support with the
> scsi-disk <--> virtio-scsi <--> rbd driver path. This can also apply to
> the WRITESAME support in CEPH/librbd.
>
> So is it suitable for doing this?
Yes, it would be suitable. In a nutshell you would have to add support
for COMPARE_AND_WRITE to block/io.c (calling into a new BlockDriver
function pointer), block/rbd.c and hw/scsi/scsi-disk.c.
Paolo
next prev parent reply other threads:[~2019-09-20 11:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 5:36 [Qemu-devel] COMPARE_AND_WRITE support for rbd driver Yaowei Bai
2019-09-20 11:22 ` Paolo Bonzini [this message]
2019-09-20 15:26 ` Yaowei Bai
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