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

From: Greg Kurz
Subject: Re: [Qemu-devel] [Bug 1336794] Re: 9pfs does not honor open file handles on unlinked files
Date: Wed, 25 May 2016 13:14:19 +0200

On Thu, 05 May 2016 20:54:31 -0000
Server Angels <address@hidden> 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" <address@hidden> (supporter:virtio-9p)
Greg Kurz <address@hidden> (supporter:virtio-9p)

I'm now catching up on the background for this issue.



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