Re: [Qemu-devel] [Bug 1336794] Re: 9pfs does not honor open file handles on unlinked files

From: Sean Keeney <seany@seanyseansean.com>
To: Greg Kurz <gkurz@linux.vnet.ibm.com>,
	Server Angels <admin@serverangels.co.uk>
Cc: qemu-devel@nongnu.org,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [Bug 1336794] Re: 9pfs does not honor open file handles on unlinked files
Date: Wed, 25 May 2016 11:51:31 +0000	[thread overview]
Message-ID: <CANdBNa_u2WREL9ZugV4GtvuDCFpXcrOUaPKud2rdVVEeeLC3JQ@mail.gmail.com> (raw)
In-Reply-To: <20160525131419.287982e8@bahia.lab.toulouse-stg.fr.ibm.com>

Apologies - I made the mistake of thinking Ubuntu launchpad was actually
functional, as it is I think they simply throw messages on there back to
the original mailing list!

On Wed, 25 May 2016 at 12:14 Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:

> On Thu, 05 May 2016 20:54:31 -0000
> Server Angels <admin@serverangels.co.uk> wrote:
> > I would appreciate this patch being committed as I *think* it's
> > affecting a system i'm building now.
> >
> > I have a backup host with 2 VMs. For business reasons they need to be
> > network isolated from each other and the host, so each is passed through
> > a physical NIC. Each VM does need access to a variable size datastore on
> > the host so I am using virtfs /9p to expose a mountpoint to each VM.
> >
> > The VMs each backup servers to  their respective mountpoint to this
> > virtfs mount using rsync. Just backing up one server with ~4000 files
> > and 3 large sparse VM images saw the open files on the backup host
> > increase to over *800000* and the rsync progressively get slower.
> > Shutting down these VMs then takes hours as it can't unlock the files it
> > has open on the backup host.
> >
> > I understand rsync does use open-unlink-fstat extensively, hence why I
> > think this is the issue.
> >
> > This is a deal breaker for any production use of virtfs. Does anybody
> > know if this is fixed in other builds of qemu?
> >
> > tl;dr - to recreate this on 16.04 - create a VM with a virtfs/9p mount
> > to the host. Do lots of rsyncs to this mount within the VM, watch 'lsof
> > | wc -l' go higher and higher on the host.
> >
> > Thanks,
> >
> > /Sean
> >
>
> Hi Sean !
>
> I've just stumbled upon this mail... maybe worth to post directly to
> qemu-devel and Cc: 9p maintainers next time :)
>
> "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> (supporter:virtio-9p)
> Greg Kurz <gkurz@linux.vnet.ibm.com> (supporter:virtio-9p)
>
> I'm now catching up on the background for this issue.
>
> Cheers.
>
> --
> Greg
>
>