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Date: Mon, 23 May 2011 14:17:18 +0100
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From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [RFC/PATCH] virtio-9p: Add Read only support for
	9p export.
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To: mohan@in.ibm.com
Cc: rlandley@parallels.com, qemu-devel@nongnu.org

On Mon, May 23, 2011 at 12:49 PM, M. Mohan Kumar <mohan@in.ibm.com> wrote:
> On Mon, May 23, 2011 at 11:08:34AM +0100, Stefan Hajnoczi wrote:
>> On Mon, May 23, 2011 at 8:58 AM, M. Mohan Kumar <mohan@in.ibm.com> wrote=
:
>> > A new fsdev parameter "access" is introduced to control accessing 9p e=
xport.
>> > access=3Dro|rw can be used to specify the access type. By default rw a=
ccess
>> > is given to 9p export.
>>
>> It would be consistent with -drive to use readonly=3Don|off (default:
>> off). =A0Do you have any future access modes in mind that require more
>> than readonly on|off?
>
> You mean to use 'readonly=3Don|off' instead of 'access=3Dro|rw' ?

Yes.

>
>>
>> It seems the client does not know ahead of time that the mount is
>> read-only. =A0I wonder if this exposes any weirdness compared to
>> actually mounting ro on the client side (i.e. operations that appear
>> to start okay but then fail with -EROFS at a different point than if
>> you had mounted ro)? =A0It could cause apps to error in new ways.
>>
>
> When a NFS share is exported as read-only, client will come to know about
> that when it does some write operation. IMHO its not an issue.

If it works the same way on NFS then great.

Stefan